General Description
The MAX31730 temperature sensor monitors its own tem-
perature and the temperatures of three external diode-
connected transistors. The operating supply voltage is
from 3.0V to 3.6V. Resistance cancellation compensates
for high series resistance in circuit-board traces and the
external thermal diode, while beta compensation corrects
for temperature-measurement errors due to low-beta
sensing transistors.
All temperature channels have programmable temperature
thresholds. When the measured temperature of a channel
crosses the respective threshold, a status bit is set in
the thermal status registers and the open-drain THERM
output asserts. A highest temperature register allows the
master to obtain the temperature of the hottest channel.
The 2-wire serial interface accepts SMBus protocols
(write byte, read byte, send byte, and receive byte) for
reading the temperature data and programming the
temperature thresholds. Any one of eight available slave
addresses can be selected using the address selection
input (ADD), which can be connected to ground or con-
nected to a grounded resistor.
The MAX31730 supports 3.0V to 3.6V operation and is
specified for a -40°C to +125°C operating temperature
range. It is available in a 10-pin µMAX® and a 12-pin,
3mm x 3mm TDFN package.
Benets and Features
● HighestTemperatureRegisterSimplifiesandSpeeds
Overtemperature Notification
● AccurateTemperatureMeasurementHelpsDesigners
Meet Error Budgets
• 12-Bit, 0.0625°C Resolution
• ±1°C Remote Temperature-Measurement Accuracy
(0°C to +100°C)
• -64°C to +150°C Remote Temperature-Measurement
Range
• Resistance Cancellation for Remote Channels
• Compensation for Low Beta Transistors
• Programmable Temperature Thresholds
● IntegrationReducesCost,BoardArea,Power-Supply
Current, and Slave Address Usage
• One Local and Three Remote Temperature-Sensing
Channels
• Eight Selectable Slave Addresses
● FlexibleSMBus/I2C Bus Interfaces to a Variety of
Microcontrollers
For related parts and recommended products to use with this part, refer
to www.maximintegrated.com/MAX31730.related.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
Ordering Information appears at end of data sheet.
VDD
DXP1
DXN
TO MASTER
DXP2
DXP3
IC1
+3.3V
+3.3V
SDA
ADD
THERM
GND
SCL
MAX31730
(10 µMAX)
IC2
VDD
DXP1
DXN1
TO MASTER
DXP2
DXN2
DXP3
DXN3
IC1
+3.3V
+3.3V
SDA
ADD
THERM
GND
SCL
IC2
MAX31730
(12 TDFN)
MAX31730 3-Channel Remote Temperature Sensor
19-6953; Rev 2; 4/15
Typical Application Circuits
EVALUATION KIT AVAILABLE
VDD, SCL, SDA, THERM, ADD ............................-0.3V to +3.7V
All Other Pins ........................................... -0.3V to (VDD + 0.3V)
ESDProtection(AllPins,HumanBodyModel) ....................2kV
Continuous Power Dissipation (TA = +70°C)
µMAX (derate at 8.8mW/°Cabove+70°C) ............707.30mW
TDFN(derate24.4mW/°Cabove+70°C) ...............1951.2mW
Operating Temperature Range ......................... -40°C to +125°C
Junction Temperature ...................................................... +150°C
Storage Temperature Range ............................ -65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) ....................................... +260°C
µMAX
Junction-to-AmbientThermalResistance(θJA) ..... 113.1°C/W
Junction-to-CaseThermalResistance(θJC) ...............36°C/W
TDFN
Junction-to-AmbientThermalResistance(θJA) ..........41°C/W
Junction-to-CaseThermalResistance(θJC) ..............8.5°C/W
(TA = -40°C to +125°C, unless otherwise noted.) (Note 2)
(3.0V≤VDD≤3.6V,TA = -40°C to +125°C, unless otherwise noted)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Voltage Supply VDD (Note 3) 3.0 3.3 3.6 V
Input Logic 0 VIL SDA, SCL (Note 3) -0.3 +0.8 V
Input Logic 1 VIH SDA, SCL (Note 3) 2.2 VDD + 0.3 V
CEXT (between DXP and DXN) βcompensationdisabled 2200 pF
βcompensationenabled 200 pF
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Supply Current IDD
Standby (Note 4) 2.5 7 µA
Operating,βcompensationdisabled 700 1200
Temperature Resolution -0.0625 +0.0625 °C
Remote Temperature Accuracy
TA = 0°C to +70°C,
TRJ = 0°C to +100°C -1 +1
°C
TA = 0°C to +70°C,
TRJ = +100°C to +150°C -2 +2
TA = -40°C to +125°C,
TRJ = -40°C to +125°C -2.5 +2.5
MAX31730 3-Channel Remote Temperature Sensor
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Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
(Note 1)
Package Thermal Characteristics
Recommended Operating Conditions
Electrical Characteristics
(3.0V≤VDD≤3.6V,TA = -40°C to +125°C, timing referenced to VIL(MAX) and VIH(MAX), unless otherwise noted) (Note 6) (Figures 2
and 3)
(3.0V≤VDD≤3.6V,TA = -40°C to +125°C, unless otherwise noted)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Local Temperature Accuracy
TA = 0°C to +70°C -1 +1
°CTA = -20°C to +85°C -1.5 +1.5
TA = -40°C to +125°C -2 +2
TemperatureHysteresis Comparator mode only 2 °C
Conversion Time Per Channel βcompensationdisabled 100 ms
βcompensationenabled 150 ms
Conversion Time for All channels βcompensationdisabled 350 ms
Remote-Diode Source Current IRJ
Highlevel 180 µA
Low level 12
DXN_ Bias Voltage Beta compensation disabled 0.3 V
Beta compensation enabled 0.65
POR Threshold VPOR VDD rising edge 2.65 2.8 V
PORThresholdHysteresis 110 mV
THERM Output Low Voltage VOL
ISINK = 1mA 100 mV
ISINK = 6mA 300
Input Leakage Current ILEAK (Note 5) 0.01 1 µA
OutputHighLeakageCurrent THERM,
SDA 1 µA
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Serial-Clock Frequency fCLK 400 kHz
Bus Free Time Between STOP
and START Condition tBUF fCLK=400kHz 1.3 µs
Repeated START Condition
Setup Time tSU:STA 0.6 µs
START Condition Setup Time 90% of SCL to 90% of SDA,
fCLK=400kHz 0.6 µs
STARTConditionHoldTime tHD:STA 90% of SDA to 90% of SCL,
fCLK=400kHz 0.6 µs
STOP Condition Setup Time tSU:STO
90% of SCL to 90% of SDA,
fCLK=400kHz 0.6 µs
MAX31730 3-Channel Remote Temperature Sensor
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I2C AC Electrical Characteristics
Electrical Characteristics (continued)
Note 2: Limits are 100% production tested at TA = +25°C. Limits over the operating temperature range and
relevantsupplyvoltagerangeareguaranteedbydesignandcharacterization.Typicalvaluesarenotguaranteed.
Note 3: All voltages referenced to ground.
Note 4: SDA = SCL = VDD.
Note 5: Applies to pins SDA, SCL, and ADD.
Note 6: All timing specifications guaranteed by design.
Note 7: A master device must provide a hold time of at least 300ns for the SDA signal to bridge the undefined region of SCL’s
falling edge.
Note 8: HoldingtheSDAlinelowforatimegreaterthantTIMEOUT causes the device to reset SDA to the idle state of the serial-bus
communication (SDA set high).
(3.0V≤VDD≤3.6V,TA = -40°C to +125°C, timing referenced to VIL(MAX) and VIH(MAX), unless otherwise noted) (Note 6) (Figures 2
and 3)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Clock Low Period tLOW 10% to 10% 1 µs
ClockHighPeriod tHIGH 90% to 90% 1 µs
Data-InHoldTime tHD:DAT (Note 7) 0.3 µs
Data-In Setup Time tSU:DAT 100 ns
ReceiveClock/DataRiseTime tR300 ns
ReceiveClock/DataFallTime tF300 ns
Pulse Width of Spike
Suppressed tSP 0 50 ns
Bus Timeout tTIMEOUT (Note 8) 25 45 ms
MAX31730 3-Channel Remote Temperature Sensor
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I2C AC Electrical Characteristics (continued)
(3.0V≤VDD≤3.6V,TA = +25°C, unless otherwise noted.)
400
500
600
700
800
900
1000
-40 10 60 110
ACTIVE CURRENT (µA)
TEMPERATURE (°C)
VDD = 3.6V
ACTIVE CURRENT vs TEMPERATURE
toc01
BETA
COMPENSATION
DISABLED
VDD = 3.3V
VDD = 3.0V
0
1
2
3
4
5
6
-40 10 60 110
STANDBY CURRENT (µA)
TEMPERATURE (°C)
VDD = 3.6V
STANDBY CURRENT vs TEMPERATURE
toc03
VDD = 3.3V
VDD = 3.0V
400
600
800
1000
1200
1400
1600
1800
-40 10 60 110
ACTIVE CURRENT (µA)
TEMPERATURE (°C)
VDD = 3.6V
ACTIVE CURRENT vs TEMPERATURE
toc02
VDD = 3.3V
BETA
COMPENSATION
ENABLED; BETA = 0.1
VDD = 3.0V
-0.25
-0.20
-0.15
-0.10
-0.05
0.00
0.05
0.10
0.15
-40 10 60 110
TEMPERATURE ERROR (°C)
TEMPERATURE (°C)
INTERNAL TEMPERATURE ERROR vs.
TEMPERATURE
toc04
VDD = 3.6V
VDD = 3.3V
VDD = 3.0V
DATA TAKEN IN BATH
LIMITED TO +90°C
MAX31730 3-Channel Remote Temperature Sensor
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Typical Operating Characteristics
10
2
3
4
5
9
8
7
6
SDA
ADD
THERM
GNDDXP3
DXP2
DXN
DXP1
µMAX
TOP VIEW
+
MAX31730
1 SCLVDD
VDD
DXP1
DXN1
DXP2
DXN2
DXP3
SCL
SDA
ADD
GND
DXN3
THERM
MA31730
TOP VIEW
1
+
3 42
TDFN
3mm x 3mm
5 6
11 9 8 71012
PIN NAME FUNCTION
µMAX TDFN
1 1 VDD SupplyVoltageInput.BypasstoGNDwitha0.1µFcapacitor.
2 2 DXP1
Combined Current Source and ADC Positive Input for Channel 1 Remote Diode. Connect
DXP1 to the anode of a remote-diode-connected, temperature-sensing transistor. Leave
DXP1 unconnected or connect to DXN or DXN1 if the channel 1 remote diode is not
used. Connect a capacitor (see the CEXTspecicationintheElectrical Characteristic
table)betweenDXP1andDXNorDXN1fornoiseltering.
— 3 DXN1
Cathode Input for Channel 1 Remote Diode. Connect the cathode of the channel 1
remote-diode-connected transistor to DXN1. If the channel 1 remote transistor is a
substrate PNP (e.g., on a CPU or ASIC die), connect the base of the PNP to DXN1.
Leave DXN1 unconnected or connect to DXP1 if a remote diode is not used. Connect a
capacitor (see the CEXTspecicationintheElectrical Characteristic table) between DXP1
andDXN1fornoiseltering.
3— DXN
Shared Cathode Input for Remote-Diode Channels. Connect the cathodes of the channel
remote-diode-connected transistors to DXN. If a remote transistor is a substrate PNP
(e.g., on a CPU or ASIC die), connect the base of the PNP to DXN. Connect a capacitor
(see the CEXTspecicationintheElectrical Characteristic table) between DXP_ and DXN
fornoiseltering.
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Pin Description
Pin Congurations
PIN NAME FUNCTION
µMAX TDFN
4 4 DXP2
Combined Current Source and ADC Positive Input for Channel 2 Remote Diode. Connect
DXP2 to the anode of a remote-diode-connected, temperature-sensing transistor. Leave
DXP2 unconnected or connect to DXN or DXN2 if a remote diode is not used. Connect a
capacitor (see the CEXTspecicationintheElectrical Characteristic table) between DXP2
andDXNorDXN2fornoiseltering.
— 5 DXN2
Cathode Input for Channel 2 Remote Diode. Connect the cathode of the channel 2
remote-diode-connected transistor to DXN2. If the channel 2 remote transistor is a
substrate PNP (e.g., on a CPU die), connect the base of the PNP to DXN2. Leave DXN2
unconnected or connect to DXP2 if a remote diode is not used. Connect a capacitor (see
the CEXTspecicationintheElectrical Characteristic table) between DXP2 and DXN2 for
noiseltering.
5 6 DXP3
Combined Current Source and ADC Positive Input for Channel 3 Remote Diode. Connect
DXP3 to the anode of a remote-diode-connected, temperature-sensing transistor. Leave
DXP3 unconnected or connect to DXN or DXN3 if a remote diode is not used. Connect a
capacitor (see the CEXTspecicationintheElectrical Characteristic table) between DXP3
andDXNorDXN3fornoiseltering.
— 7 DXN3
Cathode Input for Channel 3 Remote Diode. Connect the cathode of the channel 3
remote-diode-connected transistor to DXN3. If the channel 3 remote transistor is a
substrate PNP (e.g., on a CPU die), connect the base of the PNP to DXN3. Leave DXN3
unconnected or connect to DXP3 if a remote diode is not used. Connect a capacitor (see
the CEXTspecicationintheElectrical Characteristic table) between DXP3 and DXN3 for
noiseltering.
6 8 GND Ground
7 9 THERM
Active-Low,Open-DrainOver/UndertemperatureOutput.CanalsobeusedasaSMBus
alertoutputbysettingthedevicetointerruptmodeusingtheCongurationregister.
When enabled, THERM asserts low when the temperature of any channel goes beyond a
programmed threshold.
8 10 ADD Address-Select Input. Sampled at power-up. One of eight possible addresses can be
selectedbyconnectingADDtoGND,orconnectingADDtoagroundedresistor.
911 SDA I2C/SMBusSerial-DataInput/Output.ConnectSDAtoapullupresistor.
10 12 SCL I2C/SMBusSerial-ClockInput.ConnectSCLtoapullupresistor.
MAX31730 3-Channel Remote Temperature Sensor
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Pin Description (continued)
Detailed Description
The MAX31730 is a precision temperature monitor that
features one local and three remote temperature-sensing
channels, with programmable temperature thresholds for
each channel. Communication with the device is achieved
through the SMBus/I2C-compatible serial interface and
over/undertemperature-detection output (THERM). The
THERM output asserts if the software-programmed tem-
perature thresholds are exceeded. THERM normally
operates in comparator mode and can be connected to
a fan, system shutdown, or other thermal-management
circuitry. It can also operate in interrupt mode to serve as
a SMBus alert interrupt.
ADC Conversion Sequence
The device starts the conversion sequence by measuring
the temperature on remote channel 1, followed by remote
channel 2, remote channel 3, and the local channel. The
conversion result for each enabled channel is stored in
the corresponding temperature data register. No conver-
sion is performed on any remote channel that does not
have a diode connected, whose DXP_ - DXN_ inputs are
shorted together, or that has a short between DXP_ and
VDD,DXP_andGND,orDXN_andVDD, or if the chan-
nel is not enabled in the Highest Temperature Enable
register. See the Register 36h: Diode Fault Status section
for additional details.
VDD
SCL SDA ADD GND
MUX
REF
SMBus/I2C INTERFACE
ADC
+
-
CURRENT
SOURCE
REGISTER BANK
CONFIGURATION BYTES
REMOTE TEMPERATURES
LOCAL TEMPERATURES
THERM
SMBus ALERT THRESHOLD
LOCAL
TEMPERATURE THERMAL THRESHOLDS
ALERT RESPONSE ADDRESS
ALARM
MAX31730
DXN1
DXP1
DXN2
DXP2
DXN3
DXP3
MAX31730 3-Channel Remote Temperature Sensor
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Block Diagram
Series-Resistance Cancellation
Some thermal diodes on high-power ICs have excessive
series resistance that can cause temperature-measure-
ment errors when used with conventional remote temper-
ature sensors. External channels 1–3 of the device have
a series-resistance cancellation feature that eliminates
the effect of diode series resistance and interconnection
resistance. The cancellation range is from 0 to 300Ω.
Series-resistance cancellation is always enabled.
Low-Power Standby Mode
Enter software-standby mode by setting the STOP bit to
1 in the Configuration register. Software-standby mode
disables the ADC and reduces the supply current to
approximately 2.5µA. During software standby, data is
retained in memory and the bus interface is active and
listening for commands. If a START condition is
recognized,activityonthebuscausesthesupplycurrent
to increase. If a standby command is received while a
conversion is in progress, the conversion cycle is finished,
then the device enters shutdown, and the temperature
registers are updated.
SMBus Digital Interface
The device is SMBus 2.0 compatible and supports four
standard SMBus protocols: write byte, read byte, send
byte, and receive byte, as well as multibyte reads and
writes (Figure 1). The shorter receive-byte protocol
allows quicker transfers, provided that the correct register
was previously selected by a read-byte instruction. Use
caution with the shorter protocols in multimaster systems,
since a second master could overwrite the register byte
without informing the first master. Figure 2 is the SMBus
write timing diagram and Figure 3 is the SMBus read
timing diagram.
The write-byte format consists of the master transmitting
the slave address, followed by the address for the target
register, followed by the 8 bits of data to be written to
the target register. To write multiple bytes to two or more
contiguous registers, write a new byte after each ACK.
The register address then increments after each byte is
written. End the transaction with a STOP condition.
The read-byte format consists of the master transmitting
the slave address followed by the address for the register
to be read. The master then begins a new transaction
by sending the slave address again, after which the
slave returns the data from the selected register. To read
multiple bytes from two or more contiguous registers,
continue reading after each ACK. The register address
then increments after each byte is read. Conclude the
overall transaction with a NACK and a STOP condition.
When the first byte of a 2-byte temperature value is
read, the device prevents updates of the second byte’s
contents until the second byte has been read. If the
second byte has not been read within a SMBus timeout
period (nominally 35ms), it is again allowed to update.
The send-byte format can be used to transmit a regis-
ter address without a transfer of data. It consists of the
master transmitting the slave address followed by the
address of the target register.
The receive-byte format can be used to read data from
a register that was previously selected. It consists of the
master transmitting the slave address, after which the
slave returns the data from the register that was previous-
ly selected. After this command completes, the address
pointer does not increment.
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Figure 1. I2C/SMBus Format
S ADDRESS WR ACK ACK PDATA ACKREGISTER
7 BITS 18 BITS8 BITS
SLAVE ADDRESS: EQUIVALENT
TO CHIP-SELECT LINE OF
A 3-WIRE INTERFACE
DATA BYTE: DATA GOES INTO THE REGISTER
SET BY THE REGISTER BYTE
WRITE-BYTE FORMAT
S ADDRESSADDRESS WR ACK ACK PS RD ACK ///DATAREGISTER
7 BITS 7 BITS 8 BITS8 BITS
READ-BYTE FORMAT
SLAVE ADDRESS: EQUIVALENT
TO CHIP SELECT LINE
REGISTER BYTE: SELECTS
WHICH REGISTER YOU ARE
READING FROM
S PADDRESS WR ACK ACKREGISTER
7 BITS 8 BITS
SEND-BYTE FORMAT
REGISTER BYTE: SENDS REGISTER
ADDRESS WITH NO DATA.
S PADDRESS RD ACK ///DATA
7 BITS 8 BITS
RECEIVE-BYTE FORMAT
DATA BYTE: READS DATA FROM
THE REGISTER COMMANDED
BY THE LAST READ-BYTE OR
WRITE-BYTE TRANSMISSION;
ALSO USED FOR SMBus ALERT
RESPONSE RETURN ADDRESS
SLAVE ADDRESS: REPEATED
DUE TO CHANGE IN DATA-
FLOW DIRECTION
DATA BYTE: READS FROM
THE REGISTER SET BY THE
REGISTER BYTE
S = START CONDITION
P = STOP CONDITION
SHADED = SLAVE TRANSMISSION
/// = NOT ACKNOWLEDGED
MULTIPLE WRITE-BYTE FORMAT
STOP///
SADDRESSADDRESS WR ACK ACK S RD ACK ...
...
REGISTER
7 BITS 7 BITS8 BITS
DATA DATAACK ACK DATA
...
...
...
...
8 BITS 8 BITS 8 BITS
MULTIPLE READ-BYTE FORMAT
STOP
SADDRESS WR ACK ACK ACKDATA ...
...
REGISTER
7 BITS 8 BITS 8 BITS
DATA DATAACK ACK ACKDATA
...
...
...
...
8 BITS 8 BITS 8 BITS
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Alert Response Address (ARA)
The SMBus alert response interrupt pointer provides
quick fault identification for simple slave devices that lack
the complex logic necessary to be a bus master. Upon
receiving an interrupt signal, the host master can broad-
cast a receive-byte transmission to the alert response
slave address (19h). Then, any slave device that gener-
ated an interrupt attempts to identify itself by putting its
own address on the bus. The alert response can activate
several different slave devices simultaneously, similar to
the I2C general call.
If more than one slave attempts to respond, bus arbitra-
tion rules apply, and the device with the lower address
code wins. The losing device does not generate an
acknowledgment and continues to hold the THERM pin
low until cleared (the conditions for clearing an alert
vary depending on the type of slave device). Successful
completion of the alert response protocol clears the
output latch. If the condition that caused the alert still
exists, the device reasserts the interrupt at the end of the
next conversion. The device responds to the ARA only
when in interrupt mode.
Interrupt Mode
Thermal interrupts occur when the local or remote
temperature reading crosses a user-programmable high
thermal limit or a low thermal limit. The THERM interrupt
output signal can be cleared by reading the status register
associated with the fault or by successfully responding
to an ARA transmission by the master. In both cases,
the thermal fault is cleared but is reasserted at the end
of the next conversion if the fault condition still exists.
The interrupt does not halt automatic conversions. The
THERM output is open drain so that multiple devices can
share a common interrupt line. All thermal interrupts can
be masked using the THERM Mask register. Interrupt
mode can be selected by writing bit 4 in the Configuration
register to a 0.
Figure 2. SMBus/I2C Write Timing Diagram
Figure 3. SMBus/I2C Read Timing Diagram
SCL
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
A B C D EF G H I J
SDA
tSU:STA tHD:STA
tLOW tHIGH
tBUF
L MK
E = SLAVE PULLS SDA LINE LOW
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO SLAVE
H = LSB OF DATA CLOCKED INTO SLAVE
I = SLAVE PULLS SDA LOW
J = ACKNOWLEDGE CLOCKED INTO MASTER
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION
M = NEW START CONDITION
tSU:DAT
tSU:STO
SCL
A B C D EF G H I
SDA
tSU:STA tHD:STA
tLOW tHIGH
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SDA LINE LOW
JK
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO MASTER
H = LSB OF DATA CLOCKED INTO MASTER
I = ACKNOWLEDGE CLOCK PULSE
J = STOP CONDITION
K = NEW START CONDITION
tSU:DAT tHD:DAT
tBUF
tSU:STO
MAX31730 3-Channel Remote Temperature Sensor
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Comparator Mode
Selecting comparator mode in the Configuration register
causes the THERM output to assert based on a tempera-
ture measurement exceeding a trip threshold value, just
asininterruptmode.However,incomparatormode,the
output deasserts automatically when the temperature
crosses the threshold back into the acceptable range. A
2°C hysteresis is applied in comparator mode, so clearing
the THERM output in this mode requires the temperature
to be 2°C less than the high thermal limit and 2°C greater
than the low thermal limit.
Temperature Register Format
Temperature data is stored in the temperature, limit, and
reference temperature registers. The temperature data
format is 12 bits, two’s complement, and the register is
read out in 2 bytes: an upper byte and a lower byte. Bits
D[15:0] contain the temperature data, with the LSB repre-
senting 0.0625°C and the MSB representing the sign bit
(see Table 1). The MSB is transmitted first.
In addition to the normal two’s-complement temperature
data format, the device offers an optional extended data
format that allows temperatures equal to or greater than
+127.9375°C to be read. In the extended format (selected
by bit 1 of the Configuration register, 13h), the measured
temperature is the value in the temperature register plus
64°C, as shown in Table 2. Note: when the extended
format is selected, all limit and reference temperature
registers must be written in this format. They are not auto-
matically translated by toggling the extended format bit.
Table 1. Temperature, Reference Temperature, Thermal-Limit Register Definition
Table 2. Temperature Register Data Format
UPPER BYTE LOWER BYTE
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Sign
bit
MSB
64°C
26
32°C
25
16°C
24
8°C
23
4°C
22
2°C
21
1°C
20
0.5°C
2-1
0.25°C
2-2
0.125°C
2-3
0.0625
2-4 0000
ACTUAL
TEMPERATURE (°C)
NORMAL FORMAT EXTENDED FORMAT
BINARY HEX BINARY HEX
+150 0111 1111 1111 0000 0x7FF0 0101 0110 0000 0000 0x5600
+128 0111 1111 1111 0000 0x7FF0 0100 0000 0000 0000 0x4000
+127 0111 1111 0000 0000 0x7F00 0011 1111 0000 0000 0x3F00
+125 0111 1101 0000 0000 0x7D00 0011 1101 0000 0000 0x3D00
+64 0100 0000 0000 0000 0x4000 0000 0000 0000 0000 0x0000
+25 0001 1001 0000 0000 0x1900 1101 1001 0000 0000 0xD900
+0.5 0000 0000 1000 0000 0x0080 1100 0000 1000 0000 0xC080
0 0000 0000 0000 0000 0x0000 1100 0000 0000 0000 0xC000
-0.5 1111 1111 1000 0000 0xFF80 1011 1111 1000 0000 0xBF80
-25 1110 0111 0000 0000 0xE700 1010 0111 0000 0000 0xA700
-55 1100 1001 0000 0000 0xC900 1000 1001 0000 0000 0x8900
-64 1100 0000 0000 0000 0xC000 1000 0000 0000 0000 0x8000
Diode Fault 0000 0000 0000 0000 0x0000 0000 0000 0000 0000 0x0000
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Temperature Channel Enable Register
The Temperature Channel Enable register selects which
temperature-sensing channels are enabled. Channels not
selected are skipped during the temperature-conversion
cycle and diode fault detection is not performed on them.
If a channel is deselected while a thermal or diode fault is
indicated in the corresponding fault register, the fault bit(s)
remain asserted until the register contents are read, and
then do not reassert until the channel is again enabled
and a fault detected.
Highest Temperature Registers
The Highest Temperature registers (10h and 11h) work
with the Reference Temperature registers’ (40h through
47h) value for each temperature channel. The Reference
Temperature registers can effectively serve as an offset
temperature margin, or their contents can simply be set
tozero.
After each temperature conversion, the Reference
Temperature value is subtracted from the measured tem-
perature for the corresponding channel (e.g., remote 2 tem-
perature minus remote 2 reference temperature), and the
result is compared to the most recent results for the other
channels. The highest of all these values is loaded into
the Reference Temperature register.
Highest Temperature Enable Register
The Highest Temperature Enable register selects the
temperature channels from which the contents of the
HighestTemperatureregisterareobtained(seeTable 4).
Table 3. Temperature Channel Enable Register (35h)
Table 4. Highest Temperature Enable Register (12h)
BIT NAME POR VALUE FUNCTION
7 (MSB) Reserved 0 Reserved.
6 Reserved 0 Reserved.
5 Reserved 0 Reserved.
4 Reserved 0 Reserved.
3 Remote 3 1 Channel 3 Enable Bit. Set this bit to logic 1 to enable temperature conversions and
diode fault detection for remote channel 3.
2 Remote 2 1 Channel 2 Enable Bit. Set this bit to logic 1 to enable temperature conversions and
diode fault detection for remote channel 2.
1 Remote 1 1 Channel 1 Enable Bit. Set this bit to logic 1 to enable temperature conversions and
diode fault detection for remote channel 1.
0 Local 1 Local Temperature Channel Enable Bit. Set this bit to logic 1 to enable temperature
conversions for the local channel.
BIT NAME POR VALUE FUNCTION
7 (MSB) Reserved 1 Reserved.
6 Reserved 1 Reserved.
5 Reserved 1 Reserved.
4 Reserved 1 Reserved.
3 Remote 3 1 Channel 3 Select Bit. Set to logic 1 to use remote channel 3 in determining the highest
temperature.
2 Remote 2 1 Channel 2 Select Bit. Set to logic 1 to use remote channel 2 in determining the highest
temperature.
1 Remote 1 1 Channel 1 Select Bit. Set to logic 1 to use remote channel 1 in determining the highest
temperature.
0 Local 1 Local Select Bit. Set to logic 1 to use local channel in determining the highest
temperature.
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Thermal-Limit Registers
The Thermal Limit registers (20h through 27h) store over-
temperature and undertemperature thermal-threshold
values. Access to these registers is provided through
the I2C/SMBus-compatibleinterface.Alarmsaremasked
at power-up. If a threshold is crossed, a bit is set in the
Thermal Status registers (40h through 47h) to indicate the
thermal fault. The THERM pin is also asserted unless the
channel is masked using the THERM Mask register.
Conguration Register
The Configuration register (Table 5) has several functions.
Bit 7 (MSB) is used to put the device either in software-
standby mode (stop) or continuous-conversion mode.
In standby mode, the ADC is shut down and the supply
current reduced. The bus remains active. Bit 6 resets all
registers to their POR conditions and then clears itself. Bit
5 disables the bus timeout function. Bit 4 selects whether
the THERM output functions as an interrupt or as a
comparator. Bits 2 and 3 enable the fault queue, which sets
the number of consecutive thermal faults required before
asserting the thermal status bits and the THERM output.
Bit 1 selects the extended range temperature data format
(Table 2), which allows reading temperature values of
127.9375°C or greater. When set to 1, bit 0 begins a single
conversion on all enabled temperature channels. This one-
shot function can be enabled only when in stop mode.
Table 5. Configuration Register (13h)
BIT NAME POR VALUE FUNCTION
7 (MSB) STOP 0 Standby-Mode Control Bit. Setting STOP to 1 disables the ADC and reduces
supply current to 2.5µA.
6 POR 0 Power-On-Reset Bit. Set to logic 1 to enter the power-on state. This bit is
self-clearing.
5 TIMEOUT 0 Timeout Enable Bit. Set to logic 0 to enable SMBus timeout.
4INTERRUPT/
COMPARATOR 1Interrupt/ComparatorMode-SelectBit.Settologic1toselectcomparatormode
for the THERM output.
3FAULT QUEUE 0Selects the number of consecutive faults needed to assert the Thermal Status bits
and THERM output. 00 = 1; 01 = 2; 10 = 4; 11 = 6.
2 0
1EXTRANGE 0
Extended-Range Enable Bit. Set bit 1 to logic 1 to set the temperature, limit, and
reference data range to maximum reportable temperature of +127.9375°C. Set
bit 1 to logic 0 to set the data range to a maximum reportable temperature of
+191.9375°C.
0ONESHOT 0
Writing 1 to this bit initiates a single cycle of temperature conversions. All other bits
intheCongurationregisterareignored,andbit0automaticallyresetsto0.ONE
SHOTcanonlybeenabledinstopmode.
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THERM Mask Register
The THERM Mask register functions are described in
Table 6. Bits [3:0] are used to mask the THERM pin
output. Bit 0 masks assertion of THERM due to the local
channel thermal faults and the remaining bits mask the
remote thermal faults. The power-up state of this register
is 0000 0000 (00h).
Status Register Functions
The status registers indicate temperature or diode fault
status. The Thermal High Status register indicates
whether a measured local or remote temperature has
exceeded the associated threshold limit set in the
associated Thermal High Status register. The Thermal
Low Status register indicates whether the measured
temperature has fallen below the threshold limit set in
the Thermal Low Status register for the local or remote-
sensing diodes. The Diode Fault Status register indicates
whether there is a diode fault (open or short) in any of the
remote-sensing channels.
Bits in the Thermal Status registers are cleared by a
successful read, but set again after the next conversion
unless the fault is corrected, either by a change in the
measured temperature or by a change in the threshold
temperature. When in comparator mode, reading the
status registers has no effect on the THERM output state;
the state depends on the current temperature, threshold,
and mask values. Similarly, bits in the Diode Fault Status
register are cleared by a successful read, but set again
after the next conversion if the fault is still in effect.
In interrupt mode, the THERM output follows the status
bits for all unmasked channels. Once the THERM out-
put is asserted while in interrupt mode, it can be deas-
serted either by reading the thermal status register or by
successfully responding to an ARA. In both cases, the
THERM pin is cleared even if the fault condition remains
in effect, but the THERM output reasserts at the end of
the next conversion if the fault condition is still present.
Table 6. THERM Mask Register (34h)
BIT NAME POR VALUE FUNCTION
7(MSB) Reserved 0 Reserved.
6 Reserved 0 Reserved.
5 Reserved 0 Reserved.
4 Reserved 0 Reserved.
3 Remote 3 0 Channel 3 Remote Mask Bit. Set to logic 1 to mask assertion of THERM due to remote
channel 3 thermal fault.
2 Remote 2 0 Channel 2 Remote Mask Bit. Set to logic 1 to mask assertion of THERM due to remote
channel 2 thermal fault.
1 Remote 1 0 Channel 1 Remote Mask Bit. Set to logic 1 to mask assertion of THERM due to remote
channel 1 thermal fault.
0 Local 0 Local Mask Bit. Set to logic 1 to mask assertion of THERM due to local sensor
thermal fault.
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Table 7. Thermal High Status Register (32h)
Table 8. Thermal Low Status Register (33h)
BIT NAME POR VALUE FUNCTION
7 (MSB) Reserved 0 Reserved.
6 Reserved 0 Reserved.
5 Reserved 0 Reserved.
4 Reserved 0 Reserved.
3 Remote 3 0
Channel3Remote-DiodeHighThermalBit.Thisbitissettologic1whenthechannel
3remote-diodetemperatureexceedsthethresholdintheRemote3ThermalHigh
Limit registers.
2 Remote 2 0
Channel2Remote-DiodeHighThermalBit.Thisbitissettologic1whenthechannel
2remote-diodetemperatureexceedsthethresholdintheRemote2ThermalHigh
Limit registers.
1 Remote 1 0
Channel1Remote-DiodeHighThermalBit.Thisbitissettologic1whenthechannel
1remote-diodetemperatureexceedsthethresholdintheRemote1ThermalHigh
Limit registers.
0 Local 0 LocalChannelHighThermalBit.Thisbitissettologic1whenthelocaltemperature
exceedsthethresholdintheLocalThermalHighLimitregisters.
BIT NAME POR VALUE FUNCTION
7 (MSB) Reserved 0 Reserved.
6 Reserved 0 Reserved.
5 Reserved 0 Reserved.
4 Reserved 0 Reserved.
3 Remote 3 0
Channel 3 Remote-Diode Low Thermal Bit. This bit is set to logic 1 when the channel
3 remote-diode temperature is less than the threshold in the Thermal Low Limit
registers.
2 Remote 2 0
Channel 2 Remote-Diode Low Thermal Bit. This bit is set to logic 1 when the channel
2 remote-diode temperature is less than the threshold in the Thermal Low Limit
registers.
1 Remote 1 0
Channel 1 Remote-Diode Low Thermal Bit. This bit is set to logic 1 when the channel
1 remote-diode temperature is less than the threshold in the Thermal Low Limit
registers.
0 Local 0 Local Channel Low Thermal Bit. This bit is set to logic 1 when the local temperature is
less than the threshold in the Thermal Low Limit registers.
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Diode Fault Detection
If a remote channel’s DXP_ and DXN_ inputs are uncon-
nected or are shorted to each other, to ground, or to the
supply voltage, the device detects a diode fault. A diode
fault does not cause THERM to assert and does not allow
an overtemperature or undertemperature event to be
detected for the affected channel. A bit in the Diode Fault
Status register (36h) corresponding to the channel is set
to 1 and the temperature data for the channel is stored as
0°C (0000h in normal format).
A period of approximately 3ms at the beginning of each
channel’s temperature conversion cycle is dedicated to
diode fault detection. Once a diode fault is detected, the
temperature conversion for that channel is abandoned
and fault detection/temperature conversion begins on
the next channel in the conversion sequence. See the
Register 36h: Diode Fault Status section.
Effect of Ideality Factor
The accuracy of the remote temperature measurements
depend on the ideality factor (n) of the remote “diode”
(actually a diode-connected transistor). The default value
for the MAX31730 is n = 1.008 (channels 1–3). A thermal
diode on the substrate of an external IC is normally a PNP,
with the base and emitter brought out and the collector
grounded. DXP_ must be connected to the anode (emit-
ter) and DXN_ must be connected to the cathode (base)
of this PNP. If a sense transistor with an ideality factor
other than 1.008 is used, the output data will be different
from the data obtained with the optimum ideality factor. If
necessary, a different ideality factor value can be chosen
using the Custom Ideality Factor register (Table 9). The
Custom Ideality Enable register (Table 10) allows each
channel to have the default ideality of 1.008 or the value
selected in the Custom Ideality Factor register. Note that
any change in the ideality selections occur on subsequent
conversions; current temperature register values do not
change until a new conversion has completed.
Table 9. Custom Ideality Factor Register (14h)
SELECTION (HEX) IDEALITY FACTOR
0x00 0.9844
0x01 0.9853
0x02 0.9863
0x03 0.9873
0x04 0.9882
0x05 0.9892
0x06 0.9902
0x07 0.991
0x08 0.9921
0x09 0.9931
0x0A 0.9941
0x0B 0.9950
0x0C 0.9960
0x0D 0.9970
0x0E 0.9980
0x0F 0.9990
0x10 1.0000
0x11 1.0010
0x12 1.0020
0x13 1.0030
0x14 1.0040
0x15 1.0050
SELECTION (HEX) IDEALITY FACTOR
0x16 1.0060
0x17 1.0070
0x18 (default) 1.0080
0x19 1.0090
0x1A 1.0100
0x1B 1.0110
0x1C 1.0120
0x1D 1.0130
0x1E 1.0141
0x1F 1.0151
0x20 1.0161
0x21 1.0171
0x22 1.0182
0x23 1.0192
0x24 1.0202
0x25 1.0213
0x26 1.0223
0x27 1.0233
0x28 1.0244
0x29 1.0254
0x2A 1.0265
0x2B 1.0275
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Table 9. Custom Ideality Factor Register (14h) (continued)
Table 10. Custom Ideality Enable Register (15h)
SELECTION (HEX) IDEALITY FACTOR
0x2C 1.0286
0x2D 1.0296
0x2E 1.0307
0x2F 1.0317
0x30 1.0328
0x31 1.0338
0x32 1.0349
0x33 1.0360
0x34 1.0370
0x35 1.0381
0x36 1.0392
SELECTION (HEX) IDEALITY FACTOR
0x37 1.0402
0x38 1.0413
0x39 1.0424
0x3A 1.0435
0x3B 1.0445
0x3C 1.0456
0x3D 1.0467
0x3E 1.0478
0x3F 1.0489
≥0x40 Not Valid
BIT NAME POR VALUE FUNCTION
7 (MSB) Reserved 0 Reserved.
6 Reserved 0 Reserved.
5 Reserved 0 Reserved.
4 Reserved 0 Reserved.
3 Remote 3 0
Channel 3 Remote-Diode Custom Ideality Enable Bit. Write 0 to this bit to select
ideality factor = 1.008 for this channel. Write 1 to this bit to select ideality factor
determined by the Custom Ideality Factor register.
2 Remote 2 0
Channel 2 Remote-Diode Custom Ideality Enable Bit. Write 0 to this bit to select
ideality factor = 1.008 for this channel. Write 1 to this bit to select ideality factor
determined by the Custom Ideality Factor register.
1 Remote 1 0
Channel 1 Remote-Diode Custom Ideality Enable Bit. Write 0 to this bit to select
ideality factor = 1.008 for this channel. Write 1 to this bit to select ideality factor
determined by the Custom Ideality Factor register.
0 Reserved 0 Reserved.
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Beta Compensation
Beta compensation corrects for errors caused by low
beta-sensing transistors. Note: it applies only to PNP
transistors with their collectors grounded and their bases
and emitters connected to DXN_ and DXP_, respectively
(see Figure 4). Select the remote channels for which beta
compensation are active using the Beta Compensation
Enable register (Table 11). Note that any changes to this
register do not change the results currently in the tem-
perature registers or temperature conversion in progress;
changes affect subsequent conversion results.
Before beginning a temperature measurement with beta
compensation enabled, the device first measures the
beta of the target transistor, and then adjusts the drive
current level to produce accurate collector current ratios.
The beta value registers (Table 12) for the three remote
channels contain the minimum beta values for the corre-
sponding transistors.
If a target transistor has a beta less than 0.09, tempera-
ture measurement does not work reliably and a tempera-
ture measurement is not initiated for that transistor. The
diode fault bit is set for the corresponding channel and the
temperature registers updated with 0000h. If an attempt
at temperature measurement is desired for that remote
channel, set the associated Beta Compensation Enable
bit to 0. Note that if beta compensation is enabled, the
seriesresistanceinthediodepathmustbeminimizedas
the series resistance cancellation circuitry will interfere
with the beta compensation.
Noise Filter
In noisy environments, it can be useful to average the
results of multiple temperature conversion results. Use
the Filter Enable register (Table 13) to average the previ-
ous four conversions to determine the value stored in the
temperature registers. Even when enabled, averaging
occurs when performing a one-shot conversion sequence
(selected by bit 0 in the Configuration register), so caution
should be exercised when long delays occur between one-
shot conversions. Note that filtering begins after enabling
the filter; the current register contents do not change.
Table 11. Beta Compensation Enable Register (19h)
Figure 4. PNP Configuration for use with Beta Compensation.
BIT NAME POR VALUE FUNCTION
7 (MSB) Reserved 0 Reserved.
6 Reserved 0 Reserved.
5 Reserved 0 Reserved.
4 Reserved 0 Reserved.
3 Remote 3 0
Channel 3 Beta Compensation Enable Bit. Set this bit to logic 1 to enable
beta compensation for remote channel 3. Set this bit to logic 0 to disable beta
compensation.
2 Remote 2 0
Channel 2 Beta Compensation Enable Bit. Set this bit to logic 1 to enable
beta compensation for remote channel 2. Set this bit to logic 0 to disable beta
compensation.
1 Remote 1 0
Channel 1 Beta Compensation Enable Bit. Set this bit to logic 1 to enable
beta compensation for remote channel 1. Set this bit to logic 0 to disable beta
compensation.
0 Reserved 0 Reserved.
DXP
DXN
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Table 12. Beta Compensation Values (Registers 1Ah, 1Bh, and1Ch) (Read Only)
Table 13. Filter Enable Register (18h)
VALUE (HEX) BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 BETA (MIN)
0 (default) Reserved Reserved Reserved Reserved 0 0 0 0 0.67
1 Reserved Reserved Reserved Reserved 0 0 0 1 0.50
2 Reserved Reserved Reserved Reserved 0 0 1 0 0.36
3 Reserved Reserved Reserved Reserved 0 0 1 1 0.30
4 Reserved Reserved Reserved Reserved 0 1 0 0 0.25
5 Reserved Reserved Reserved Reserved 0 1 0 1 0.20
6 Reserved Reserved Reserved Reserved 0 1 1 0 0.15
7 Reserved Reserved Reserved Reserved 0 1 1 1 0.13
8 Reserved Reserved Reserved Reserved 1 0 0 0 0.11
9 Reserved Reserved Reserved Reserved 1 0 0 1 0.09
F Reserved Reserved Reserved Reserved 1 1 1 1 Low B Fault
BIT NAME POR VALUE FUNCTION
7 (MSB) Reserved 0 Reserved.
6 Reserved 0 Reserved.
5 Reserved 0 Reserved.
4 Reserved 0 Reserved.
3 Remote 3 0 Channel3FilterEnableBit.Setthisbittologic1toenablelterforremotechannel3.
Setthisbittologic0todisablelter.
2 Remote 2 0 Channel2FilterEnableBit.Setthisbittologic1toenablelterforremotechannel2.
Setthisbittologic0todisablelter.
1 Remote 1 0 Channel1FilterEnableBit.Setthisbittologic1toenablelterforremotechannel1.
Setthisbittologic0todisablelter.
0 Reserved 0 Reserved.
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Offset Registers
If desired, an offset value can be applied to the data in
any selected temperature channel. Select the offset value
using the Custom Offset register (Table 14). The resolu-
tion of the custom offset value is 0.125°C, and the MSB
is 16°C. The temperature offset is calculated using the
following equation:
-14.875°C+b[7:0]/8=TemperatureOffset
The resulting offset range is -14.875°C to +17°C. With a
default power-on value of 77h, the device has a default
temperature offset of 0°C.
Choose the temperature channels to which custom off-
set is applied using the Custom Offset Enable register
(Table 15). The offset value does not affect the value in
the highest temperature registers.
Table 14. Custom Offset Register (16h)
Table 15. Custom Offset Enable Register (17h)
BIT NAME POR STATE FUNCTION
7 (MSB) 16°C 0 Digital offset (weighted).
6 8°C 1 Digital offset (weighted).
5 4°C 1 Digital offset (weighted).
4 2°C 1 Digital offset (weighted).
3 1°C 0 Digital offset (weighted).
2 0.5°C 1 Digital offset (weighted).
1 0.25°C 1 Digital offset (weighted).
0 0.125°C 1 Digital offset (weighted).
BIT NAME POR STATE FUNCTION
7 (MSB) Reserved 0 Reserved.
6 Reserved 0 Reserved.
5 Reserved 0 Reserved.
4 Reserved 0 Reserved.
3 Remote 3 0 Remote 3 Offset Enable Bit. Set to logic 1 to enable offset in the Custom Offset register.
2 Remote 2 0 Remote 2 Offset Enable Bit. Set to logic 1 to enable offset in the Custom Offset register.
1 Remote 1 0 Remote 1 Offset Enable Bit. Set to logic 1 to enable offset in the Custom Offset register.
0 Reserved 0 Reserved.
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Register Map
REGISTER ADDRESS
(HEX)
POR
VALUE
(HEX)
READ/
WRITE DESCRIPTION
Local Temperature MSB 00 00 R Read local temperature MSB
Local Temperature LSB 01 00 R Read local temperature LSB
Remote 1 Temperature MSB 02 00 R Read channel 1 remote temperature MSB
Remote 1 Temperature LSB 03 00 R Read channel 1 remote temperature LSB
Remote 2 Temperature MSB 04 00 R Read channel 2 remote temperature MSB
Remote 2 Temperature LSB 05 00 R Read channel 2 remote temperature LSB
Remote 3 Temperature MSB 06 00 R Read channel 3 remote temperature MSB
Remote 3 Temperature LSB 07 00 R Read channel 3 remote temperature LSB
HighestTemperatureMSB 10 00 R
HighestcurrenttemperaturevalueMSB.Valueinhighest
temperature register is the greater of all (temperature
channel value minus the channel reference temperature
value).
HighestTemperatureLSB 11 00 R
HighestcurrenttemperaturevalueLSB.Valueinhighest
temperature register is the greater of all (temperature
channel value minus the channel reference temperature
value).
HighestTemperatureEnable 12 0F R/W Selects which channels are used in determining contents
of highest temperature registers.
Conguration 13 10 R/W Standby,POR,timeout,extendedrange,comparator/
interruptmode,one-shot,andlter.
Custom Ideality Factor 14 18 R/W Select a custom ideality factor for remote-sensing
diodes.
Custom Ideality Enable 15 00 R/W Select the nominal ideality (1.008) or the custom ideality
for each remote channel.
Custom Offset 16 77 R/W
Select an offset value for temperature measurement.
The device default is -14.875°C, with a programmed
value of +14.875°C, which leaves a summed offset of
0°Cdefaultfromfactory/POR.
Custom Offset Enable 17 00 R/W Enable/disablethecustomoffsettemperaturevaluefor
each channel.
MAX31730 3-Channel Remote Temperature Sensor
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Register Map (continued)
REGISTER ADDRESS
(HEX)
POR
VALUE
(HEX)
READ/
WRITE DESCRIPTION
Filter Enable 18 00 R/W Enable/disablelterforeachremotechannel(shouldbe
disabled when not in constant conversion mode).
Beta Compensation
Enable 19 00 R/W Enable/disablebetacompensationforeachremote
channel.
Beta Value Channel 1 1A 00 R Contains the beta compensation value for channel 1.
Beta Value Channel 2 1B 00 R Contains the beta compensation value for channel 2.
Beta Value Channel 3 1C 00 R Contains the beta compensation value for channel 3.
LocalThermalHighLimit
MSB 20 7F R/W Read/writelocalthermalhigh-temperaturethreshold
limit MSB.
LocalThermalHighLimit
LSB 21 00 R/W Read/writelocalthermalhigh-temperaturethreshold
limit LSB.
Remote1ThermalHigh
Limit MSB 22 7F R/W Read/writeremotechannel1thermalhigh-temperature
threshold limit MSB.
Remote1ThermalHigh
Limit LSB 23 00 R/W Read/writeremotechannel1thermalhigh-temperature
threshold limit LSB.
Remote2ThermalHigh
Limit MSB 24 7F R/W Read/writeremotechannel2thermalhigh-temperature
threshold limit MSB.
Remote2ThermalHighLimit
LSB 25 00 R/W Read/writeremotechannel2thermalhigh-temperature
threshold limit LSB.
Remote3ThermalHighLimit
MSB 26 7F R/W Read/writeremotechannel3thermalhigh-temperature
threshold limit MSB.
Remote3ThermalHighLimit
LSB 27 00 R/W Read/writeremotechannel3thermalhigh-temperature
threshold limit LSB.
Thermal Low Limit (All
Channels) MSB 30 C9 R/W Read/writethermallow-temperaturethresholdMSB
(shared by all channels).
Thermal Low Limit (All
Channels) LSB 31 00 R/W Read/writethermallow-temperaturethresholdLSB
(shared by all channels).
ThermalStatus,High
Temperature 32 00 R Read the high-temperature thermal status for each
channel.
Thermal Status, Low
Temperature 33 00 R Read the low-temperature thermal status for each
channel.
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Register Map (continued)
Register 00h: Local Temperature MSB
REGISTER ADDRESS
(HEX)
POR
VALUE
(HEX)
READ/
WRITE DESCRIPTION
THERM Mask 34 00 R/W Mask faults from asserting the THERM pin for each
channel.
Temperature Channel Enable 35 0F R/W Read/writetemperaturechannelenable.
Diode Fault Status 36 00 R Read diode fault status for each channel.
Local Reference Temperature
MSB 40 00 R/W MSB of local reference temperature for determining
content of the highest temperature registers.
Local Reference Temperature
LSB 41 00 R/W LSB of local reference temperature for determining
content of the highest temperature registers.
Remote 1 Reference
Temperature MSB 42 00 R/W MSB of remote channel 1 reference temperature for
determining content of the highest temperature registers.
Remote 1 Reference
Temperature LSB 43 00 R/W LSB of remote channel 1 reference temperature for
determining content of the highest temperature registers.
Remote 2 Reference
Temperature MSB 44 00 R/W MSB of remote channel 2 reference temperature for
determining content of the highest temperature registers.
Remote 2 Reference
Temperature LSB 45 00 R/W LSB of remote channel 2 reference temperature for
determining content of the highest temperature registers.
Remote 3 Reference
Temperature MSB 46 00 R/W MSB of remote channel 3 reference temperature for
determining content of the highest temperature registers.
Remote 3 Reference
Temperature LSB 47 00 R/W LSB of remote channel 3 reference temperature for
determining content of the highest temperature registers.
Manufacturer ID 50 4D R Read manufacturer ID.
Revision Code 51 01 R Read die revision.
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R R R R R R R R
00h D15 D14 D13 D12 D11 D10 D9 D8
ºC Sign 26252423222120
Bit 7 Bit 0
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Register 01h: Local Temperature LSB
Register 02h: Remote 1 Temperature MSB
Register 03h: Remote 1 Temperature LSB
Register 04h: Remote 2 Temperature MSB
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R R R R R R R R
01h D7 D6 D5 D4 D3 D2 D1 D0
ºC 2-1 2-2 2-3 2-4 0000
Bit 7 Bit 0
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R R R R R R R R
02h D15 D14 D13 D12 D11 D10 D9 D8
ºC Sign 26252423222120
Bit 7 Bit 0
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R R R R R R R R
03h D7 D6 D5 D4 D3 D2 D1 D0
ºC 2-1 2-2 2-3 2-4 0000
Bit 7 Bit 0
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R R R R R R R R
04h D15 D14 D13 D12 D11 D10 D9 D8
ºC Sign 26252423222120
Bit 7 Bit 0
MAX31730 3-Channel Remote Temperature Sensor
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HighestcurrenttemperaturevalueMSB.Valueinthehighesttemperatureregisteristhegreaterofall(thetemperature
channel value minus the channel reference temperature value).
Register 06h: Remote 3 Temperature MSB
Register 07h: Remote 3 Temperature LSB
Register 10h: Highest Temperature MSB
Register 05h: Remote 2 Temperature LSB
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R R R R R R R R
05h D7 D6 D5 D4 D3 D2 D1 D0
ºC 2-1 2-2 2-3 2-4 0000
Bit 7 Bit 0
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R R R R R R R R
06h D15 D14 D13 D12 D11 D10 D9 D8
ºC Sign 26252423222120
Bit 7 Bit 0
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R R R R R R R R
07h D7 D6 D5 D4 D3 D2 D1 D0
ºC 2-1 2-2 2-3 2-4 0000
Bit 7 Bit 0
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R R R R R R R R
10h D15 D14 D13 D12 D11 D10 D9 D8
ºC Sign 26252423222120
Bit 7 Bit 0
MAX31730 3-Channel Remote Temperature Sensor
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Highest current temperature value LSB. Value in the highest temperature register will be the greater of all (the
temperature channel value minus the channel reference temperature value).
Selects which channels are used in determining the contents of the highest temperature register.
Register 12h: Highest Temperature Enable
Register 11h: Highest Temperature LSB
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R R R R R R R R
11h D7 D6 D5 D4 D3 D2 D1 D0
ºC 2-1 2-2 2-3 2-4 0000
Bit 7 Bit 0
Factory Default Value: 0Fh
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
12h Reserved Reserved Reserved Reserved Remote 3 Remote 2 Remote 1 Local
Bit 7 Bit 0
Bit 7 Reserved Powers on with a value of 0.
Bit 6 Reserved Powers on with a value of 0.
Bit 5 Reserved Powers on with a value of 0.
Bit 4 Reserved Powers on with a value of 0.
Bit 3 Remote 3
Channel3HighestTemperatureSelectBit.
0 = Do not use channel 3 in determining the highest temperature.
1 = Use channel 3 in determining the highest temperature (default).
Bit 2 Remote 2
Channel2HighestTemperatureSelectBit.
0 = Do not use channel 2 in determining the highest temperature.
1 = Use channel 2 in determining the highest temperature (default).
Bit 1 Remote 1
Channel1HighestTemperatureSelectBit.
0 = Do not use channel 1 in determining the highest temperature.
1 = Use channel 1 in determining the highest temperature (default).
Bit 0 Local
LocalChannelHighestTemperatureSelectBit.
0 = Do not use the local channel in determining the highest temperature.
1 = Use the local channel in determining the highest temperature (default).
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Register 13h: Conguration
Register 14h: Customer Ideality Factor
Factory Default Value: 10h
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
13h STOP POR TIMEOUT INTERRUPT/
COMPARATOR
FAULT
QUEUE
FAULT
QUEUE EXTRANGE ONESHOT
Bit 7 Bit 0
Bit 7 STOP
Standby-Mode Control Bit. Setting STOP to 1 disables the ADC and reduces supply current
to 2.5µA.
0 = ADC enabled (default).
1 = ADC disabled.
Bit 6 POR Power-On-Reset Bit. Write this bit to logic 1 to enter the power-on state. This bit is self-
clearing. Power-on default value is 0.
Bit 5 TIMEOUT
Timeout Enable Bit. Set to logic 0 to enable SMBus timeout.
0 = SMBus timeout enabled (default).
1 = SMBus timeout disabled.
Bit 4 INTERRUPT/
COMPARATOR
Interrupt/ComparatorMode-SelectBit.
0 = Interrupt mode.
1 = Comparator mode (default).
Bit 3 FAULT QUEUE
Selects the number of consecutive faults needed to assert a thermal fault.
00 = 1 (default)
01 = 2
10 = 4
11 = 6
Bit 2
Bit 1 EXTRANGE
Extended-Range Enable Bit.
0 = Set maximum reportable temperature value to +127.9375ºC (default).
1 = Set maximum reportable temperature value to +191.9375ºC.
Bit 0 ONESHOT
Default state is 0. Write this bit to a 1 to initiate a single cycle of temperature conversions.
AllotherbitsintheCongurationregisterareignored.Aftertheconversion,thebit
automaticallyresetsto0.ONESHOTcanonlybeenabledwithinstopmode.
Factory Default Value: 18h
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
14h D7 D6 D5 D4 D3 D2 D1 D0
See Table 8
Bit 7 Bit 0
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The temperature offset is calculated using the following equation:
-14.875°C+b[7:0]/8=temperatureoffset
The resulting offset range is -14.875°C to +17°C. With a default power-on value of 77h, the device has a default
temperature offset of 0°C.
Register 16h: Custom Offset
Register 15h: Custom Ideality Enable
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access N/A N/A N/A N/A R/W R/W R/W N/A
15h Reserved Reserved Reserved Reserved Remote 3 Remote 2 Remote 1 Reserved
Bit 7 Bit 0
Bit 7 Reserved Reserved.
Bit 6 Reserved Reserved.
Bit 5 Reserved Reserved.
Bit 4 Reserved Reserved.
Bit 3 Remote 3
Channel 3 Remote-Diode Ideality Enable Bit.
0 = Sets ideality factor to 1.008 (default).
1 = Sets the ideality factor to the value from the Custom Ideality Factor register (14h).
Bit 2 Remote 2
Channel 2 Remote-Diode Ideality Enable Bit.
0 = Sets ideality factor to 1.008 (default).
1 = Sets the ideality factor to the value from the Custom Ideality Factor register (14h).
Bit 1 Remote 1
Channel 1 Remote-Diode Ideality Enable Bit.
0 = Sets ideality factor to 1.008 (default).
1 = Sets the ideality factor to the value from the Custom Ideality Factor register (14h).
Bit 0 Reserved Reserved.
Factory Default Value: 77h
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
16h D7 D6 D5 D4 D3 D2 D1 D0
ºC 24232221202-1 2-2 2-3
Bit 7 Bit 0
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Selects the temperature channels to which the custom offset is applied. The offset value does not affect the value in the
highest temperature register.
Register 17h: Custom Offset Enable
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access N/A N/A N/A N/A R/W R/W R/W N/A
17h Reserved Reserved Reserved Reserved Remote 3 Remote 2 Remote 1 Reserved
Bit 7 Bit 0
Bit 7 Reserved Reserved.
Bit 6 Reserved Reserved.
Bit 5 Reserved Reserved.
Bit 4 Reserved Reserved.
Bit 3 Remote 3
Remote Channel 3 Offset Enable Bit:
0 = Offset not enabled (default).
1 = Offset enabled.
Bit 2 Remote 2
Remote Channel 2 Offset Enable Bit:
0 = Offset not enabled (default).
1 = Offset enabled.
Bit 1 Remote 1
Remote Channel 1 Offset Enable Bit:
0 = Offset not enabled (default).
1 = Offset enabled.
Bit 0 Reserved Reserved.
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Register 18h: Filter Enable
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access N/A N/A N/A N/A R/W R/W R/W N/A
1Ch Reserved Reserved Reserved Reserved Remote 3 Remote 2 Remote 1 Reserved
Bit 7 Bit 0
Bit 7 Reserved Reserved.
Bit 6 Reserved Reserved.
Bit 5 Reserved Reserved.
Bit 4 Reserved Reserved.
Bit 3 Remote 3
Channel 3 Noise Filter Select Bit.
0=Noiselteringdisabled(default).
1=Noiselteringenabled.
Bit 2 Remote 2
Channel 2 Noise Filter Select Bit.
0=Noiselteringdisabled(default).
1=Noiselteringenabled.
Bit 1 Remote 1
Channel 1 Noise Filter Select Bit.
0=Noiselteringdisabled(default).
1=Noiselteringenabled.
Bit 0 Reserved Reserved.
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Register 19h: Beta Compensation Enable
Register 1Ah: Beta Value Channel 1
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access N/A N/A N/A N/A R/W R/W R/W N/A
19h Reserved Reserved Reserved Reserved Remote 3 Remote 2 Remote 1 Reserved
Bit 7 Bit 0
Bit 7 Reserved Reserved.
Bit 6 Reserved Reserved.
Bit 5 Reserved Reserved.
Bit 4 Reserved Reserved.
Bit 3 Remote 3
Channel 3 Beta Compensation Enable Bit.
0 = Beta compensation disabled (default).
1 = Beta compensation enabled.
Bit 2 Remote 2
Channel 2 Beta Compensation Enable Bit.
0 = Beta compensation disabled (default).
1 = Beta compensation enabled.
Bit 1 Remote 1
Channel 1 Beta Compensation Enable Bit.
0 = Beta compensation disabled (default).
1 = Beta compensation enabled.
Bit 0 Reserved Reserved.
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access N/A N/A N/A N/A R R R R
1Ah Reserved Reserved Reserved Reserved Beta Value Beta Value Beta Value Beta Value
Bit 7 Bit 0
Bits [7:4] Reserved The bits in these locations are reserved.
Bits [3:0] Beta Value Reports the amount of beta compensation applied for the remote-diode channel 1 if enabled from
the register (see Table 12).
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When the extended format is selected, all limit and reference temperature registers must be written in this format. They
are not automatically translated by toggling the extended format bit.
Register 1Bh: Beta Value Channel 2
Register 20h: Local Thermal High Limit MSB
Register 1Ch: Beta Value Channel 3
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access N/A N/A N/A N/A R R R R
1Bh Reserved Reserved Reserved Reserved Beta Value Beta Value Beta Value Beta Value
Bit 7 Bit 0
Bits [7:4] Reserved The bits in these locations are reserved.
Bits [3:0] Beta Value Reports the amount of beta compensation applied for the remote-diode channel 2 if enabled from
the Beta Compensation Enable register (see Table 12).
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access N/A N/A N/A N/A R R R R
1Ch Reserved Reserved Reserved Reserved Beta Value Beta Value Beta Value Beta Value
Bit 7 Bit 0
Bits [7:4] Reserved The bits in these locations are reserved.
Bits [3:0] Beta Value Reports the amount of beta compensation applied for the remote-diode channel 3 if enabled from
the Beta Compensation Enable register (see Table 12).
Factory Default Value: 7Fh
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
20h D15 D14 D13 D12 D11 D10 D9 D8
ºC Sign 26252423222120
Bit 7 Bit 0
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When the extended format is selected, all limit and reference temperature registers must be written in this format. They
are not automatically translated by toggling the extended format bit.
When the extended format is selected, all limit and reference temperature registers must be written in this format. They
are not automatically translated by toggling the extended format bit.
When the extended format is selected, all limit and reference temperature registers must be written in this format. They
are not automatically translated by toggling the extended format bit.
Register 21h: Local Thermal High Limit LSB
Register 23h: Remote 1 Thermal High Limit LSB
Register 22h: Remote 1 Thermal High Limit MSB
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
21h D7 D6 D5 D4 D3 D2 D1 D0
ºC 2-1 2-2 2-3 2-4 0 0 0 0
Bit 7 Bit 0
Factory Default Value: 7Fh
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
22h D15 D14 D13 D12 D11 D10 D9 D8
ºC Sign 26252423222120
Bit 7 Bit 0
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
23h D7 D6 D5 D4 D3 D2 D1 D0
ºC 2-1 2-2 2-3 2-4 0 0 0 0
Bit 7 Bit 0
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When the extended format is selected, all limit and reference temperature registers must be written in this format. They
are not automatically translated by toggling the extended format bit.
When the extended format is selected, all limit and reference temperature registers must be written in this format. They
are not automatically translated by toggling the extended format bit.
When the extended format is selected, all limit and reference temperature registers must be written in this format. They
are not automatically translated by toggling the extended format bit.
Register 25h: Remote 2 Thermal High Limit LSB
Register 24h: Remote 2 Thermal High Limit MSB
Register 26h: Remote 3 Thermal High Limit MSB
Factory Default Value: 7Fh
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
24h D15 D14 D13 D12 D11 D10 D9 D8
ºC Sign 26252423222120
Bit 7 Bit 0
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
25h D7 D6 D5 D4 D3 D2 D1 D0
ºC 2-1 2-2 2-3 2-4 0 0 0 0
Bit 7 Bit 0
Factory Default Value: 7Fh
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
26h D15 D14 D13 D12 D11 D10 D9 D8
ºC Sign 26252423222120
Bit 7 Bit 0
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When the extended format is selected, all limit and reference temperature registers must be written in this format. They
are not automatically translated by toggling the extended format bit.
When the extended format is selected, all limit and reference temperature registers must be written in this format. They
are not automatically translated by toggling the extended format bit.
When the extended format is selected, all limit and reference temperature registers must be written in this format. They
are not automatically translated by toggling the extended format bit.
Register 27h: Remote 3 Thermal High Limit LSB
Register 30h: Thermal Low Limit (All Channels) MSB
Register 31h: Thermal Low Limit (All Channels) LSB
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
27h D7 D6 D5 D4 D3 D2 D1 D0
ºC 2-1 2-2 2-3 2-4 0 0 0 0
Bit 7 Bit 0
Factory Default Value: C9h
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
30h D15 D14 D13 D12 D11 D10 D9 D8
ºC Sign 26252423222120
Bit 7 Bit 0
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
31h D7 D6 D5 D4 D3 D2 D1 D0
ºC 2-1 2-2 2-3 2-4 0 0 0 0
Bit 7 Bit 0
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Register 32h: Thermal Status, High Temperature
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access N/A N/A N/A N/A R R R R
32h Reserved Reserved Reserved Reserved Remote 3 Remote 2 Remote 1 Local
Bit 7 Bit 0
Bits [7:4] Reserved Reserved.
Bit 3 Remote 3
Channel3Remote-DiodeHighThermalBit.
0 = Default value.
1 = Indicates that the temperature sensed on the channel 3 remote diode exceeds the selected
temperature threshold limit stored in the channel 3 thermal high limit register.
Bit 2 Remote 2
Channel2Remote-DiodeHighThermalBit.
0 = Default value.
1 = Indicates that the temperature sensed on the channel 2 remote diode exceeds the selected
temperature threshold limit stored in the channel 2 thermal high limit register.
Bit 1 Remote 1
Channel1Remote-DiodeHighThermalBit.
0 = Default value.
1 = Indicates that the temperature sensed on the channel 1 remote diode exceeds the selected
temperature threshold limit stored in the channel 1 thermal high limit register.
Bit 0 Local
LocalHighThermalBit.
0 = Default value.
1 = Indicates that the temperature sensed on the local channel exceeds the selected temperature
threshold limit stored in the local thermal high limit register.
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Register 33h: Thermal Status, Low Temperature
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access N/A N/A N/A N/A R R R R
33h Reserved Reserved Reserved Reserved Remote 3 Remote 2 Remote 1 Local
Bit 7 Bit 0
Bits [7:4] Reserved Reserved.
Bit 3 Remote 3
Channel 3 Remote-Diode Low Thermal Bit.
0 = Default value.
1 = Indicates that the temperature sensed on the channel 3 remote diode is less than the selected
temperature threshold limit stored in the thermal low limit register.
Bit 2 Remote 2
Channel 2 Remote-Diode Low Thermal Bit.
0 = Default value.
1 = Indicates that the temperature sensed on the channel 2 remote diode is less than the selected
temperature threshold limit stored in the thermal low limit register.
Bit 1 Remote 1
Channel 1 Remote-Diode Low Thermal Bit.
0 = Default value.
1 = Indicates that the temperature sensed on the channel 1 remote diode is less than the selected
temperature threshold limit stored in the thermal low limit register.
Bit 0 Local
Local Low Thermal Bit.
0 = Default value.
1 = Indicates that the temperature sensed on the local channel is less than the selected
temperature threshold limit stored in the thermal low limit register.
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Register 34h: THERM Mask
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access N/A N/A N/A N/A R/W R/W R/W R/W
34h Reserved Reserved Reserved Reserved Remote 3 Remote 2 Remote 1 Local
Bit 7 Bit 0
Bits [7:4] Reserved Reserved.
Bit 3 Remote 3
Channel 3 Thermal Mask Bit.
0 = Default value.
1 = Masks the assertion of the THERM pin when a thermal fault on channel 3 occurs.
Bit 2 Remote 2
Channel 2 Thermal Mask Bit.
0 = Default value.
1 = Masks the assertion of the THERM pin when a thermal fault on channel 2 occurs.
Bit 1 Remote 1
Channel 1 Thermal Mask Bit.
0 = Default value.
1 = Masks the assertion of the THERM pin when a thermal fault on channel 1 occurs.
Bit 0 Local
Local Thermal Mask Bit.
0 = Default value.
1 = Masks the assertion of the THERM pin when a thermal fault on the local channel occurs.
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Register 35h: Temperature Channel Enable
Factory Default Value: 0Fh
Memory Type: SRAM, Volatile
Memory Access N/A N/A N/A N/A R/W R/W R/W R/W
35h Reserved Reserved Reserved Reserved Enable 3 Enable 2 Enable 1 Enable
Local
Bit 7 Bit 0
Bits [7:4] Reserved Reserved.
Bit 3 Remote 3
Channel 3 Enable Bit.
0 = Channel 3 is not enabled and is skipped during the temperature conversion cycle. Diode fault
detection is not performed on this channel.
1 = Temperature conversions and diode fault detection are enabled for channel 3 (default).
Bit 2 Remote 2
Channel 2 Enable Bit.
0 = Channel 2 is not enabled is skipped during the temperature conversion cycle. Diode fault
detection is not performed on this channel.
1 = Temperature conversions and diode fault detection are enabled for channel 2 (default).
Bit 1 Remote 1
Channel 1 Enable Bit.
0 = Channel 1 is not enabled, and is skipped during the temperature conversion cycle. Diode fault
detection is not performed on this channel.
1 = Temperature conversions and diode fault detection are enabled for channel 1 (default).
Bit 0 Local
Local Enable Bit.
0 = The Local Channel is not enabled, and will be skipped during the temperature
conversion cycle.
1 = Temperature conversions are enabled for the local channel (default).
MAX31730 3-Channel Remote Temperature Sensor
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MSB of the local reference temperature (used for determining the content of the highest temperature registers).
When the extended format is selected, all limit and reference temperature registers must be written in this format. They
are not automatically translated by toggling the extended format bit.
Register 36h: Diode Fault Status
Register 40h: Local Reference Temperature MSB
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access N/A N/A N/A N/A R/W R/W R/W N/A
36h Reserved Reserved Reserved Reserved Remote 3 Remote 2 Remote 1 Reserved
Bit 7 Bit 0
Bits [7:4] Reserved Reserved.
Bit 3 Remote 3
Channel 3 Diode Fault Bit.
0 = Default value.
1 = Indicates an open or short on the channel 3 remote-diode connection.
Bit 2 Remote 2
Channel 2 Diode Fault Bit.
0 = Default value.
1 = Indicates an open or short on the channel 2 remote-diode connection.
Bit 1 Remote 1
Channel 1 Diode Fault Bit.
0 = Default value.
1 = Indicates an open or short on the channel 1 remote-diode connection.
Bit 0 Reserved Reserved. Always 0.
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
40h D15 D14 D13 D12 D11 D10 D9 D8
ºC Sign 26252423222120
Bit 7 Bit 0
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MSB of the channel 1 reference temperature (used for determining the content of the highest temperature registers).
When the extended format is selected, all limit and reference temperature registers must be written in this format. They
are not automatically translated by toggling the extended format bit.
LSB of the channel 1 reference temperature (used for determining the content of the highest temperature registers).
When the extended format is selected, all limit and reference temperature registers must be written in this format. They
are not automatically translated by toggling the extended format bit.
LSB of the local reference temperature (used for determining the content of the highest temperature registers).
When the extended format is selected, all limit and reference temperature registers must be written in this format. They
are not automatically translated by toggling the extended format bit.
Register 41h: Local Reference Temperature LSB
Register 43h: Remote 1 Reference Temperature LSB
Register 42h: Remote 1 Reference Temperature MSB
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
41h D7 D6 D5 D4 D3 D2 D1 D0
ºC 2-1 2-2 2-3 2-4 0 0 0 0
Bit 7 Bit 0
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
42h D15 D14 D13 D12 D11 D10 D9 D8
ºC Sign 26252423222120
Bit 7 Bit 0
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
43h D7 D6 D5 D4 D3 D2 D1 D0
ºC 2-1 2-2 2-3 2-4 0 0 0 0
Bit 7 Bit 0
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LSB of the channel 2 reference temperature (used for determining the content of the highest temperature registers).
When the extended format is selected, all limit and reference temperature registers must be written in this format. They
are not automatically translated by toggling the extended format bit.
MSB of the channel 2 reference temperature (used for determining the content of the highest temperature registers).
When the extended format is selected, all limit and reference temperature registers must be written in this format. They
are not automatically translated by toggling the extended format bit.
MSB of the channel 3 reference temperature (used for determining the content of the highest temperature registers).
When the extended format is selected, all limit and reference temperature registers must be written in this format. They
are not automatically translated by toggling the extended format bit.
Register 46h: Remote 3 Reference Temperature MSB
Register 44h: Remote 2 Reference Temperature MSB
Register 45h: Remote 2 Reference Temperature LSB
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
44h D15 D14 D13 D12 D11 D10 D9 D8
ºC Sign 26252423222120
Bit 7 Bit 0
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
45h D7 D6 D5 D4 D3 D2 D1 D0
ºC 2-1 2-2 2-3 2-4 0 0 0 0
Bit 7 Bit 0
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
46h D15 D14 D13 D12 D11 D10 D9 D8
ºC Sign 26252423222120
Bit 7 Bit 0
MAX31730 3-Channel Remote Temperature Sensor
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LSB of the channel 3 reference temperature (used for determining the content of the highest temperature registers).
When the extended format is selected, all limit and reference temperature registers must be written in this format. They
are not automatically translated by toggling the extended format bit.
Contains the code for the Manufacturer’s ID for the device.
Contains the revision code for the device.
Register 47h: Remote 3 Reference Temperature LSB
Register 51h: Revision Code
Register 50h: Manufacturer ID
Factory Default Value: 00h
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
47h D7 D6 D5 D4 D3 D2 D1 D0
ºC 2-1 2-2 2-3 2-4 0 0 0 0
Bit 7 Bit 0
Factory Default Value: 4Dh
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
50h D7 D6 D5 D4 D3 D2 D1 D0
0 1 0 0 1 1 0 1
Bit 7 Bit 0
Factory Default Value: 01h
Memory Type: SRAM, Volatile
Memory Access R/W R/W R/W R/W R/W R/W R/W R/W
51h D7 D6 D5 D4 D3 D2 D1 D0
0 0 0 0 0 0 0 0
Bit 7 Bit 0
MAX31730 3-Channel Remote Temperature Sensor
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Applications Information
Remote-Diode Selection
The device directly measures the die temperature of CPUs
and other ICs that have on-chip temperature-sensing
diodes (see the Typical Application Circuits), or it can
measure the temperature of a discrete diode-connected
transistor.
Discrete Remote Diodes
When the remote-sensing diode is a discrete transistor,
its collector and base must be connected together; PNP
or npn discrete transistors can be used. Table 16 lists
examples of discrete transistors that are appropriate for
use with this device. The transistor must be a small-signal
type with a relatively high forward voltage; otherwise, the
A/D input voltage range can be violated. The forward
voltage at the highest expected temperature must be
greater than 0.25V at 10µA; at the lowest expected tem-
perature, the forward voltage must be less than 0.95V at
100µA. Large power transistors must not be used. Also,
ensurethatthebaseresistanceislessthan100Ω.Tight
specificationsforforward-currentgain(e.g.,50<β<150)
indicate that the manufacturer has good process controls
and that the devices have consistent VBE characteristics.
Manufacturers of discrete transistors do not normally
specify or guarantee ideality factor. This normally is not
a problem since good-quality discrete transistors tend
to have ideality factors that fall within a relatively narrow
range. Variations in remote temperature readings of less
than ±2°C with a variety of discrete transistors have been
observed. However, it is good design practice to verify
good consistency of temperature readings with several
discrete transistors from any supplier under consideration.
Unused Diode Channels
If one or more of the remote-diode channels is not needed,
disconnect the DXP_ and DXN_ inputs for that channel, or
connect the DXP_ to the corresponding DXN_. The status
register indicates a diode “fault” for this channel and the
channel is ignored during the temperature-measurement
sequence. It is also good practice to mask any unused
channels immediately upon power-up by setting the
appropriate bits in the THERM Mask register. This pre-
vents unused channels from causing THERM to assert.
Thermal Mass and Self-Heating
When sensing local temperature, the device measures
the temperature of the PCB to which it is soldered.
The leads provide a good thermal path between the PCB
traces and the die. As with all IC temperature sensors,
thermal conductivity between the die and the ambient air
is poor by comparison, making air-temperature measure-
ments impractical. Since the thermal mass of the PCB
is far greater than that of the device, the device follows
temperature changes on the PCB with little or no perceiv-
able delay. When measuring the temperature of a CPU,
or other IC with an on-chip sense junction, thermal mass
has virtually no effect; the measured temperature of the
junction tracks the actual temperature within a conversion
cycle. When measuring temperature with discrete remote
transistors, the best thermal-response times are obtained
with transistors in small packages (i.e., SOT23 or SC70).
Take care to account for thermal gradients between
the heat source and the sensor, and ensure that stray
air currents across the sensor package do not interfere
with measurement accuracy. Self-heating does not sig-
nificantly affect measurement accuracy. Remote-sensor
self-heating due to the diode current source is negligible.
Table 16. Remote Sensors Transistor
Suppliers
SUPPLIER PNP MODEL NUMBER
Central Semiconductor Corp.
(USA)
CMPT3906
2N3906
Fairchild Semiconductor
(USA)
MMBT3906
2N3906
Inneon(Germany) SMBT3906
ON Semiconductor
(USA)
MMBT3906
2N3906
ROHMSemiconductor(USA) SST3906
Samsung (Korea) KST3906-TF
Siemens(Germany) SMBT3906
Zetex (England) FMMT3906CT-ND
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ADC Noise Filtering
The integrating ADC has good noise rejection for low-
frequency signals, such as power-supply hum. In envi-
ronments with significant high-frequency EMI, connect
an external 100pF capacitor between DXP_ and DXN_.
Larger capacitor values can be used for added filtering;
however, this can introduce errors due to the rise time
oftheswitchedcurrentsource.Noisecanbeminimized
with careful PCB layout, as discussed in the PCB Layout
section.
Slave Address
Slave addresses can be selected by connecting ADD, as
shown in Table 17.
PCB Layout
Follow the guidelines below to reduce the measurement
error when measuring remote temperature:
1) Place the device as close as possible to the thermal
diode. In noisy environments, such as a computer
motherboard, this distance is typically 10cm to 20cm.
This length can be increased if the worst noise sources
are avoided. Noise sources include displays, clock
generators, memory buses, and PCI buses.
2) Do not route the DXP_ and DXN_ traces across fast
digital signals, which can easily introduce +30°C error,
even with good filtering.
3) Route the DXP_ and DXN_ traces in parallel and in
close proximity to each other. Each parallel pair of trac-
es should go to a thermal diode. Route these traces
away from any higher voltage traces, such as +12VDC.
Leakage currents from PCB contamination must be
dealtwith carefullysincea20MΩleakagepathfrom
DXP_ to ground causes approximately +1°C error. If
high-voltage traces are unavoidable, connect guard
traces to GND on either side of the DXP_ - DXN_
traces (Figure 5).
4) Route through as few vias and crossunders as pos-
sibletominimizecopper/solderthermocoupleeffects.
Use wide traces when possible (5-mil to 10-mil traces
are typical).
Twisted-Pair and Shielded Cables
Use a twisted-pair cable to connect the remote sensor for
remote-sensor distances longer than 20cm or in very noisy
environments. Twisted-pair cable lengths can be between
2m and 4m before noise introduces excessive errors. For
longer distances, the best solution is a shielded twisted
pair, such as those used for audio microphones.
For example, Belden No. 8451 works well for distances
up to 100ft in a noisy environment. At the device,
connect the twisted-pair cables to DXP_ and DXN_ and
the shielded cable to GND. Leave the shielded cable
unconnected at the remote sensor. For very long cable
runs, the cable’s parasitic capacitance often provides
noise filtering; therefore, the 100pF capacitor can often be
removed, or reduced in value.
Table 17. Slave Address Selection
Note: Resistor value tolerence must be ±5% of the listed values. Figure 5. Recommended DXP_ - DXN_ PCB Traces
(The two outer-guard traces are recommended if high-voltage
traces are near the DXN_ and DXP_ traces)
RESISTOR BETWEEN
ADD AND GND
SLAVE ADDRESS
(HEX)
15kΩto39kΩ 0x9E
9.31kΩ 0x9C
6.81kΩ 0x9A
4.75kΩ 0x98
3.01kΩ 0x3E
1.69kΩ 0x3C
750Ω 0x3A
0(<250Ω) 0x38
5–10 mils
5–10 mils
5–10 mils
MINIMUM
5–10 mils
GND
DXP_
DXN_
GND
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+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
*EP = Exposed pad.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
10 µMAX U10+2 21-0061 90-0330
12 TDFN-EP TD1233+1C 21-0664 90-0397
PART TEMP RANGE PIN-PACKAGE
MAX31730AUB+ -40°C to +125°C 10 µMAX
MAX31730AUB+T -40°C to +125°C 10 µMAX
MAX31730ATC+ -40°C to +125°C 12 TDFN-EP*
MAX31730ATC+T -40°C to +125°C 12 TDFN-EP*
MAX31730 3-Channel Remote Temperature Sensor
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Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
thata“+”,“#”,or“-”inthepackagecodeindicatesRoHSstatus
only. Package drawings may show a different suffix character, but
thedrawingpertainstothepackageregardlessofRoHSstatus.
Chip Information
PROCESS: CMOS
Ordering Information
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
03/14 Initial release —
112/14 Updated General Description and Benets and Features sections 1
24/15 Removed future product designation from Ordering Information 47
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
MAX31730 3-Channel Remote Temperature Sensor
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Revision History
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