May 2006 1 MIC184
MIC184 Micrel
MIC184
Local/Remote Thermal Supervisor
General Description
The MIC184 is a versatile digital thermal supervisor capable
of measuring temperature using either its own internal sensor
or an inexpensive external sensor. A 2-wire serial interface is
provided to allow communication with either I2C or SMBus
masters. This device is a pin-for-pin and software compatible
upgrade for the industry standard LM75.
Additional features include remote temperature measurement
capability, and interrupt status and mask bits in the chip’s
configuration register for software polling. The open-drain
interrupt output pin can be used as either an overtemperature
alarm or thermostatic control signal. Three programmable ad-
dress pins permit users to multidrop up to 8 devices along the
2-wire bus, allowing simple distributed temperature sensing
networks. Superior performance, low power and small size
makes the MIC184 an excellent choice for the most demand-
ing thermal management applications.
Typical Application
DATA
1
2
3
8
4
5
6
7
FROM
SERIAL BUS
HOST
OPTIONAL
REMOTE
TEMPERATURE
SENSOR
2200pF
MIC184
CLK
INT
Data
3.0V to 3.6V
VDD
Clock
Interrupt
VDD
3 ×
10k A2/T1
A1
A0
GND
0.1µF
ceramic
2-Channel SMBus Temperature Measurement System
Features
• Measures local and remote temperatures
• Pin and software backward compatible to LM75
• 9-bit sigma-delta ADC
• 2-wire I2C/SMBus compatible interface
• Programmable thermostatic settings for either internal or
external zone
• Open-drain comparator/interrupt output pin
• Interrupt mask and status bits
• Low-power shutdown mode
• Fail-safe response to diode faults
• 2.7V to 5.5V power supply range
• Up to 8 devices may share the same bus
• 8-Lead SOP and MSOP Packages
Applications
• Desktop, Server and Notebook Computers
• Printers and Copiers
• Test and measurement equipment
• Consumer electronics
Ordering Information
Part Number Temperature Range Package Pb-FREE
MIC184BM -55°C to +125°C 8-lead SOIC
MIC184BMM -55°C to +125°C 8-lead MSOP
MIC184YM -55°C to +125°C 8-lead SOIC X
MIC184YMM -55°C to +125°C 8-lead MSOP X
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
MIC184 Micrel
MIC184 2 May 2006
Pin Description
Pin Number Pin Name Pin Function
1 DATA Data (Digital I/O): Open-drain. Serial data input/output.
2 CLK Clock (Digital Input): The host provides the serial bit clock on this input.
3 INT Interrupt (Digital Output): Open-drain. Interrupt or thermostat output.
4 GND Ground: Power and signal return for all IC functions.
5 A2/T1 Address Bit 2 (Digital Input): Slave address selection input. See “Slave Ad-
dress Truth Table.”
Temperature Sensor 1 (Analog Input): Input from remote temperature sensor
(diode junction).
6 A1 Address Bit 1 (Digital Input): Slave address selection input. See “Slave Ad-
dress Truth Table.”
7 A0 Address Bit 0 (Digital Input): Slave address selection input. See “Slave Ad-
dress Truth Table.”
8 VDD Supply (Analog Input): Power supply input to the IC.
Pin Configuration
1DATA
CLK
INT
GND
8 VDD
A0
A1
A2/T1
7
6
5
2
3
4
May 2006 3 MIC184
MIC184 Micrel
Absolute Maximum Ratings (Note 1)
Power Supply Voltage, VDD .......................................... 6.0V
Voltage on Any Pin ................................–0.3V to VDD+0.3V
Current Into Any Pin ................................................... ±6mA
Power Dissipation, TA = +125°C ................................ 30mW
Junction Temperature .............................................. +150°C
Storage Temperature ................................ –65°C to +150°C
ESD Ratings (Note 3)
Human Body Model .....................................................700V
Machine Model ............................................................ 100V
Soldering
Vapor Phase (60 sec.) .............................. +220°C +5⁄–0°C
Infrared (15 sec.) ...................................... +235°C +5⁄–0°C
Operating Ratings (Note 2)
Power Supply Voltage, VDD ......................... +2.7V to +5.5V
Ambient Temperature Range (TA) ............. -55°C to +125°C
Package Thermal Resistance (θJA)
SOP .................................................................+152°C/W
MSOP ..............................................................+206°C/W
Electrical Characteristics
2.7V ≤ VDD ≤ 5.5; TA = +25°C, bold values indicate –55°C ≤ TA ≤ +125°C, Note 4; unless noted.
Symbol Parameter Condition Min Typ Max Units
Power Supply
IDD Supply Current INT open, A2, A1, A0 = VDD or GND, 340 500 µA
CLK = DATA = high, normal mode
shutdown mode, CLK = 100kHz 2.5 µA
INT open, A2, A1, A0 = VDD or GND, 1 10 µA
CLK = DATA = high, shutdown mode
tPOR Power-On Reset Time VDD > VPOR 15 100 µs
VPOR Power-On Reset Voltage all registers reset to default values, 2.0 2.7 V
A/D conversions initiated
VHYST Power-On Reset
Hysteresis Voltage 250 mV
Temperature-to-Digital Converter Characteristics
Accuracy—Local Temperature 0°C ≤ TA ≤ +100°C, INT open, ±1 ±2 °C
Note 5, 6 3V ≤ VDD ≤ 3.6V
–55°C ≤ TA ≤ +125°C, INT open, ±2 ±3 °C
3V ≤ VDD ≤ 3.6V
Accuracy—Remote Temperature 0°C ≤ TD ≤ +100°C, INT open, ±1 ±3 °C
Note 5, 6, 7 3V ≤ VDD ≤ 3.6V, 0°C ≤ TA ≤ +85°C
–55°C ≤ TD ≤ +125°C, INT open, ±2 ±5 °C
3V ≤ VDD ≤ 3.6V, 0°C ≤ TA ≤ +85°C
tCONV Conversion Time, Note 5 local temperature 100 160 ms
remote temperature 200 320 ms
Remote Temperature Input (T1)
IF Current to External Diode high level 224 400 µA
Note 5 low level 7.5 14 µA
Address Inputs (A2/T1, A1, A0)
VIL Low Input Voltage 2.7V ≤ VDD ≤ 5.5V 0.6 V
VIH High Input Voltage 2.7V ≤ VDD ≤ 5.5V 2.0 V
CIN Input Capacitance 10 pF
ILEAK Input Current ±0.01 ±1 µA
IPD Pulldown Current on A2/T1 A2 = VDD, flows for tPOR at power-up 25 µA
MIC184 Micrel
MIC184 4 May 2006
Symbol Parameter Condition Min Typ Max Units
Serial Data I/O Pin (DATA)
VOL Low Output Voltage IOL = 3mA 0.4 V
IOL = 6mA 0.8 V
VIL Low Input Voltage 2.7V ≤ VDD ≤ 5.5V 0.3VDD V
VIH High Input Voltage 2.7V ≤ VDD ≤ 5.5V 0.7VDD V
CIN Input Capacitance 10 pF
ILEAK Input current ±0.01 ±1 µA
Serial Clock Input (CLK)
VIL Low Input Voltage 2.7V ≤ VDD ≤ 5.5V 0.3VDD V
VIH High Input Voltage 2.7V ≤ VDD ≤ 5.5V 0.7VDD V
CIN Input Capacitance 10 pF
ILEAK Input current ±0.01 ±1 µA
Status Output (INT)
VOL Low Output Voltage, IOL = 3mA 0.4 V
Note 8 IOL = 6mA 0.8 V
tINT Interrupt Propagation Delay, from TEMP > T_SET, FQ = 00 to INT < VOL,
tCONV+1
µs
Note 5 RPULLUP = 10kΩ; POL bit = 0
tnINT Interrupt Reset Propagation Delay, from any register read to INT > VOH, 1 µs
Note 5 RPULLUP = 10kΩ; POL bit = 0
T_SET Default T_SET Value tPOR after VDD > VPOR, Note 9 80 80 80 °C
HYST Default HYST Value tPOR after VDD > VPOR, Note 9 75 75 75 °C
Serial Interface Timing (Note 5)
t1 CLK (Clock) Period 2.5 µs
t2 Data In Setup Time to CLK High 100 ns
t3 Data Out Stable After CLK Low 0 ns
t4 DATA Low Setup Time to CLK Low start condition 100 ns
t5 DATA High Hold Time stop condition 100 ns
After CLK High
Note 1. Exceeding the absolute maximum rating may damage the device.
Note 2. The device is not guaranteed to function outside its operating rating.
Note 3. Devices are ESD sensitive. Handling precautions recommended.
Human body model: 1.5k in series with 100pF. Machine model: 200pF, no series resistance.
Note 4. Final test on outgoing product is performed at TA = TBD°C.
Note 5. Guaranteed by design over the operating temperature range. Not 100% production tested.
Note 6. Accuracy specification does not include quantization noise, which may be as great as ±1⁄2LSB (±1⁄4°C).
Note 7. TD is the temperature of the remote diode junction. Testing is performed using a single unit of one of the transistors listed in Table 5.
Note 8. Current into the INT pin will result in self-heating of the MIC184. INT pin current should be minimized for best accuracy.
Note 9. This is the decimal representation of a binary data value.
Timing Diagram
t1
t2
t5
t4
t3
SCL
SDA Input
SDA Output
Serial Interface Timing
May 2006 5 MIC184
MIC184 Micrel
Typical Characteristics
-3
-2
-1
0
1
2
3
-60
-40
-20
0
20
40
60
80
100
120
140
MESUREMENT ERROR (°C)
LOCAL DIODE TEMERATURE (°C)
L oc al T emperature
Meas urement E rror
VDD = 3.3V
-5
-4
-3
-2
-1
0
1
2
3
4
5
-60
-40
-20
0
20
40
60
80
100
120
140
MESUREMENT ERROR (°C)
REMOTE DIODE TEMERATURE (°C)
R emote T emperature
Meas urement E rror
VDD = 3.3V
0
50
100
150
200
250
300
350
400
450
500
-60
-40
-20
0
20
40
60
80
100
120
140
SUPPLY CURRENT (µA)
TEMPERATURE (°C)
Operating IDD
vs . Temperature
VDD = 3.3V
VDD = 5.0V
fC LOC K = 0Hz
0
1
2
3
4
5
6
7
8
9
0 50 100 150 200 250 300 350 400
SHUTDOWN CURRENT (µA)
CLOCK FREQUENCY (kHz)
S hutdown IDD
vs . F requenc y
VDD = 3.0V
VDD = 5.0V
0
0.5
1
1.5
2
2.5
3
3.5
-60
-40
-20
0
20
40
60
80
100
120
140
SHUTDOWN CURRENT (µA)
TEMPERATURE (°C)
S hutdown Mode IDD
vs . Temperature
VDD = 5.0V
VDD = 3.3V
fC LOC K = 0Hz
0
50
100
150
200
250
300
350
400
0246
SUPPLY CURRENT (µA)
SUPPLY VOLTAGE (V)
S upply C urrent
vs . S uppl
y
Voltage
0
20
40
60
80
100
120
140
0 5 10 15
MEASURED LOCAL TEMPERATURE (°C)
TIME (Sec)
R es pons e to Immers ion in
125°C F luid B a th
S O IC -8
MS O P -8
-30
-25
-20
-15
-10
-5
0
5
1x10 61x10 71x10 81x10 9
MEASUREMENT ERROR (°C)
RESISTANCE FROM T1(Ω)
Meas urement E rror vs .
P C B L eak age to +5V/+3.3V /G ND
G ND
3.3V
5.0V
-12
-10
-8
-6
-4
-2
0
012345678910
MEASURMENT ERROR (°C)
CAPACITANCE (nF)
Meas urment E rror vs .
C apcitanc e on T1
MIC184 Micrel
MIC184 6 May 2006
Functional Description
Pin Descriptions
VDD
Power supply input. See electrical specifications.
GND
Ground return for all MIC184 functions.
CLK
Clock input to the MIC184 from the two-wire serial bus. The
clock signal is provided by the bus host and is shared by all
devices on the bus.
DATA
Serial data I/O pin that connects to the two-wire serial bus.
DATA is bidirectional and has an open-drain output driver.
An external pull-up resistor or current source somewhere in
the system is necessary on this line. This line is shared by
all devices on the bus.
A2/T1, A1, A0
These inputs set the three least significant bits of the MIC184’s
7-bit slave address. Each MIC184 will only respond to its own
unique slave address, allowing the use of up to eight MIC184s
on a single bus. A match between the MIC184’s address and
Functional Diagram
2:1
MUX
TEMPERATURE-TO-DIGITAL
CONVERTER
1-Bit
DAC
A2/T1
A1
A0
DATA
MIC184
CLK
INT
2-Wire
Serial Bus
Interface
Pointer
Register
Temperature
Hysteresis
Register
State
Machine
and
Digital
Comparator
Digital Filter
and
Control
Logic
Thermostat
Output
Configuration
Register
Bandgap
Sensor
and
Reference
Result
Register
Temperature
Setpoint
Register
the address specified in the serial bit stream must be made
to initiate communication. A1 and A0 should be connected
directly to VDD or ground. When A2/T1 is used as an address
bit input, it should also be tied to VDD or ground. A2/T1 can
alternatively connect to a remote temperature sensor. When
A2/T1 is used for temperature measurements, an off-chip di-
ode junction must be connected between A2/T1 and ground. In
this case, internal circuitry will detect A2 as logic low, leaving
four possible slave addresses. See “Temperature Measure-
ment” and “Power On” for more information. A2/T1, A1, and
A0 determine the slave address as shown in Table 1.
INT
Temperature events are indicated to external circuitry via this
output. INT may be configured as active-low or active-high
by the host. Operation of the INT output is controlled by the
MODE and POL bits in the MIC184’s configuration register.
See “Comparator and Interrupt Modes” below. This output
is open-drain and may be wire-ORed with other open-drain
signals. Most systems will require a pull-up resistor or current
source on this pin. If the IM bit in the configuration register
is set, it prevents the INT output from sinking current. In
I2C and SMBus systems, the IM bit is therefore an interrupt
mask bit.
May 2006 7 MIC184
MIC184 Micrel
stupnI sserddAevalS481CIM
1T/2A 1A 0A yraniB xeH
000 0001001 b84 h
0 0 1 1001001 b94 h
0 1 0 0101001 bA4 h
0 1 1 1101001 bB4 h
1 0 0 0011001 bC4 h
1 0 1 1011001 bD4 h
1 1 0 0111001 bE4 h
1 1 1 1111001 bF4 h
edoid 0 0 0001001 b84 h
edoid 0 1 1001001 b94 h
edoid 1 0 0101001 bA4 h
edoid 1 1 1101001 bB4 h
Table 1. MIC184 Slave Address Settings
Temperature Measurement
The temperature-to-digital converter for both internal and
external temperature data is built around a switched current
source and a 9-bit analog-to-digital converter. The tem-
perature is calculated by measuring the forward voltage of a
diode junction at two different bias current levels. An internal
multiplexer directs the current source’s output to either an
internal or external diode junction.
The MIC184 uses two’s-complement data to represent
temperatures. If the MSB of a temperature value is 0, the
temperature is ≥ 0°C. If the MSB is 1, the temperature is <
0°. More detail on this is given in “Temperature Data For-
mat” below. A temperature event results if the value in the
temperature result register (TEMP) is greater than the value
in the overtemperature setpoint register (T_SET), or if it is
less than the value in the temperature hysteresis register
(T_HYST).
The value of the ZONE bit in the configuration register deter-
mines whether readings are taken from the on-chip sensor
or from the A2/T1 input. At power-up, the ZONE bit of the
configuration register is set to zero. The MIC184 therefore
monitors its internal temperature and compares the result
against the contents of T_SET and T_HYST. Setting the ZONE
bit in CONFIG will result in the MIC184 acquiring temperature
data from an external diode connected to the A2/T1 pin. This
diode may be embedded in an integrated circuit (such as a
CPU, ASIC, or graphics processor), or it may be a diode-con-
nected discrete transistor. Once the new value is written to
CONFIG, the A/D converter will begin a new conversion and
return temperature data from the external zone. This data
will be compared against T_SET, T_HYST, and the state of
the Fault_Queue (described below). The internal status bit
(STS) and the INT output will then be updated accordingly.
See “Applications Information” for more details on switching
between zones.
Diode Faults
The MIC184 is designed to respond in a fail-safe manner to
hardware faults in the external sensing circuitry. If the con-
nection to the external diode is lost, or the sense line (A2/T1)
is shorted to VDD or ground, the temperature data reported
by the A/D converter will be forced to its full-scale value
(+127.5°C). This will cause an overtemperature event to oc-
cur whenever T_SET ≤ +127.0°C (0 1111 1110b). An interrupt
will be generated if so enabled. The temperature reported for
the external zone will remain 0 1111 1111b = +127.5°C until
the fault condition is cleared. This fault detection requires
that the MIC184 complete the number of conversion cycles
specified by Fault_Queue. The MIC184 may therefore require
one or more conversion cycles following power-on or a transi-
tion from shutdown to normal operation before reporting an
external diode fault.
Serial Port Operation
The MIC184 uses standard SMBus WRITE_BYTE, READ_
BYTE, WRITE_WORD, and READ_WORD operations for
communication with its host. The SMBus WRITE_BYTE and
WRITE_WORD operations involve sending the device’s slave
address (with the R/W bit low to signal a write operation),
followed by a command byte and one or two data bytes. The
SMBus READ_BYTE operation is similar, but is a composite
write and read operation: the host first sends the device’s
slave address followed by the command byte, as in a write
operation. A new “start” bit must then be sent to the MIC184,
followed by a repeat of the slave address with the R/W bit
(LSB) set to the high (read) state. The data to be read from
etyB_dnammoC retsigeRtegraT
yraniB xeH lebaL noitpircseD
00000000 b00 hPMET tlusererutarepmetderusaem
10000000 b10 hGIFNOC retsigernoitarugifnoc
01000000 b20 hTSYH_T siseretsyherutarepmet
11000000 b30 hTES_T tniopteserutarepmetrevo
00100000 b40 h
devreser esutonod
·
·
·
·
·
·
11111111 bFF h
Table 2. MIC184 Register Addresses
MIC184 Micrel
MIC184 8 May 2006
Figure 1. WRITE_BYTE Protocol
Figure 2. READ_BYTE Protocol
Figure 3. WRITE_WORD Protocol
Figure 4. READ_WORD Protocol
S 1 0 0 1
A2 A1 A0
1 A A
D4D5D6 D3 D2 D1 D0D7D8
/A PX X X X X X X
MIC184 Slave Address
DATA
CLK
High-Order Byte from MIC184
Low-Order Byte from MIC184
START
STOP
R/W = READ
ACKNOWLEDGE ACKNOWLEDGE
NOT ACKNOWLEDGE
Master-to-slave transmission Slave-to-master response
Figure 5. RECEIVE_DATA from a 16-Bit Register
May 2006 9 MIC184
MIC184 Micrel
S 1 0 0 1
A2 A1 A0
A X1 X X X X X X X A
MIC184 Slave Address
First Byte of Transaction
START
ACKNOWLEDGE ACKNOWLEDGE
R/W = WRITE
/A PXX X X X X X X
Last Byte of Transaction
A/D Converter�
in Standby
Conversion�
in Progress
New Conversion�
in Progress
New Conversion
Begins
Conversion Interrupted
By MIC184 Acknowledge
Result�
Ready
tCONV
STOP
NOT ACKNOWLEDGE
…
Figure 6. A/D Converter Timing
A
S S1 0 0 0
A2 A1 A0 A2 A1 A0
0 A 0 0 0 0 0 0 0 1 A 1 0 10 0 XX X X X X X X /A P
MIC184 Slave Address
TEMP exceeds T_SET or falls below T_HYST
MIC184 Slave Address
DATA
INT*
Command Byte = 01h = CONFIG
CONFIG Value**
START
START
STOP
R/W = WRITE
ACKNOWLEDGE
ACKNOWLEDGE
ACKNOWLEDGE
R/W = READ
NOT ACKNOWLEDGE
Master-to-slave transmission Slave-to-master response
t
n/INT
t
/INT
* Assumes INT Polarity is active low.
** Status bits in CONFIG are cleared to zero following this operation.
Figure 7. Responding to Interrupts
MIC184 Micrel
MIC184 10 May 2006
the MIC184 may then be clocked out. There is one excep-
tion to this rule: If the location latched in the pointer register
from the last write operation is known to be correct (i.e.,
points to the desired register), then the “RECEIVE_DATA”
procedure may be used. To perform a RECEIVE_DATA, the
host sends an address byte to select the slave MIC184, and
then retrieves the appropriate number (one or two) of data
bytes. Figures 1 through 5 show the formats for these data
read and data write procedures.
The command byte is 8 bits (1 byte) wide. This byte carries
the address of the MIC184 register to be operated upon, and
is stored in the MIC184’s pointer register. The pointer register
is a write-only register, which is implemented for backward
compatibility to the National Semiconductor LM75 and similar
devices. The command byte (pointer register) values corre-
sponding to the various MIC184 register addresses are shown
in Table 2. Command byte values other than 0000 00XXb =
00h through 03h are reserved, and should not be used.
The CONFIG register is 8 bits (1 byte) wide. Therefore, com-
munications with the CONFIG register will at a minimum require
a READ_BYTE, WRITE_BYTE, or a RECEIVE_BYTE.
The TEMP, T_HYST, and T_SET registers are logically
nine bits wide. Note, though, that these registers are physi-
cally two bytes (one SMBus word) wide within the MIC184.
Properly communicating with the MIC184 involves a 16-bit
READ_WORD or RECEIVE_WORD from, or WRITE_WORD
to, these registers. This is a requirement of the I2C/SMBus
serial data protocols, which only allow data transfers to occur
in multiples of eight bits.
Temperature Data Format
The LSB of each 9-bit logical register represents 0.5°C. The
values are in a two’s complement format, wherein the most
significant bit (D8) represents the sign: “0” for positive tem-
peratures and “1” for negative temperatures. The seven least
significant bits of each 16-bit physical register are undefined.
Therefore, physical bits D6 through D0 of the data read
from these registers must be masked off, and the resulting
binary value right justified before using the data received.
It is also possible to read only the first byte of any of these
three registers, sacrificing 0.5°C of resolution in exchange
for somewhat simpler data handling. However, all writes
to the T_SET and T_HYST registers must be in the 16-bit
WRITE_WORD format. Table 3 shows examples of the data
format used by the MIC184 for temperatures.
A/D Converter Timing
Whenever the MIC184 is not in its low power shutdown mode,
the internal A/D converter (ADC) attempts to make continuous
conversions unless interrupted by a bus transaction accessing
the MIC184. When the MIC184 is accessed, the conversion
in progress will be halted, and the partial result discarded.
When the access of the MIC184 is complete the ADC will
begin a new conversion cycle, with results valid tCONV after
that. Figure 6 shows this behavior. tCONV is twice as long for
external conversions as it is for internal conversions. This al-
lows the use of a filter capacitor on the A2/T1 input without a
loss of accuracy due to the resulting longer settling times.
Power-On
When power is initially applied, the MIC184’s internal registers
are set to default states which make the MIC184 completely
backward compatible with the LM75. Also at this time, the
levels on the address inputs A2, A1, and A0 are read to es-
tablish the device’s slave address. The MIC184’s power-up
default state can be summarized as follows:
• Normal-mode operation
(MIC184 not in shutdown)
• ZONE is set to internal
(on-chip temperature sensing)
• INT function is set to comparator mode
• INT output is set to active-low operation
• Fault_Queue depth = 1
• Interrupts are enabled (IM = 0)
• T_SET = +80°C; T_HYST = +75°C
In order to accommodate the use of A2/T1 as a dual-purpose
input, there is a weak pulldown on A2/T1 that will attempt to
sink ≈25µA from the pin to ground for tPOR following power-
up of the MIC184. This allows the MIC184 to pull A2/T1 to a
low state when a diode junction is connected from that pin
to ground, and latch a zero as the A2 address value. If A2 is
not to be used as a diode connection, it should be connected
to VDD or ground. Note that a fault in the external tempera-
ture sensor (if used) may not be reported until one or more
conversion cycles have been completed following power-on.
See DIODE FAULTS.
Shutdown Mode
Setting the SHDN bit in the configuration register halts the
otherwise continuous conversions by the A/D converter. The
erutarepmeT yraniBwaR yraniBdeksaM xeHdeksaM
C°521+ XXXXXXX010111110 010111110 bAF0 h
C°52+ XXXXXXX010011000 010011000 b230 h
C°5.0+ XXXXXXX100000000 100000000 b100 h
C°0 XXXXXXX000000000 000000000 b000 h
C°5.0– XXXXXXX111111111 111111111 bFF1 h
C°52– XXXXXXX011100111 011100111 bEC1 h
C°04– XXXXXXX000011011 000011011 b0B1 h
C°55– XXXXXXX010010011 010010011 b291 h
Table 3. Digital Temperature Format
May 2006 11 MIC184
MIC184 Micrel
MIC184’s power consumption drops to 1µA typical in shutdown
mode. All registers may be read from, or written to, while in
shutdown mode. Serial bus activity will slightly increase the
MIC184’s power consumption.
Entering shutdown mode will not affect the state of INT when
the device is in comparator mode (MODE = 0). However, If
the device is shut down while in interrupt mode, the INT pin
will be deasserted and the internal latch (STS) holding the
interrupt status will be cleared. Therefore, no interrupts will
be generated while the MIC184 is in shutdown mode, and
the interrupt status will not be retained. It is important to
note, however, that the cause of the last temperature event
will be retained in the MIC184. This is described further in
“Comparator and Interrupt Modes” below. The diode fault
detection mechanism (see “Diode Faults”) requires one or
more A/D conversion cycles to detect external sensor faults.
Hence, no diode faults will be detected while the device is
in shutdown.
Comparator and Interrupt Modes
Depending on the setting of the MODE bit in the configura-
tion register, the INT output will behave either as an interrupt
request signal or a thermostatic control signal. Thermostatic
operation is known as comparator mode. The INT output is
asserted whenever the measured temperature, as reported
in the TEMP register, exceeds the threshold programmed in
the T_SET register for the number of conversions specified by
Fault_Queue (described below). In comparator mode, INT will
remain asserted unless and until the measured temperature
falls below the value in the T_HYST register for Fault_Queue
conversions. No action on the part of the host is required for
operation in comparator mode. Note that entering shutdown
mode will not affect the state of INT when the device is in
comparator mode.
In interrupt mode, once a temperature event has caused STS
to be set, and the INT output to be asserted, they will not be
automatically deasserted when the measured temperature
falls below T_HYST. They can only be deasserted by reading
any of the MIC184's internal registers or by putting the device
into SHUTDOWN mode. If the most recent temperature event
was an overtemperature condition, STS will not be set again,
and INT cannot be reasserted, until the device has detected
that TEMP < T_HYST. Similarly, if the most recent temperature
event was an undertemperature condition, STS will in be set
again, and INT cannot be reasserted, until the device has
detected that TEMP > T_SET. This keeps the internal logic of
the MIC184 backward compatible with that of the LM75 and
similar devices. There is a software override for this: while
the MIC184 is operating in interrupt mode, the part can be
unconditionally set to monitor for an overtemperature condi-
tion, regardless of what caused the last temperature event.
This is done by clearing the MODE bit, and then immediately
resetting it to 1. Following this sequence the next temperature
event detected will be an overtemperature condition, regard-
less of whether the last temperature event was the result of
an overtemperature or undertemperature condition.
In both modes, the MIC184 will be responsive to overtem-
perature events upon power up.
Fault_Queue
A Fault_Queue (programmable digital filter) is provided in the
MIC184 to prevent false tripping due to thermal or electrical
noise. Two bits, CONFIG[4:3], set the depth of Fault_Queue.
Fault_Queue then determines the number of consecutive
temperature events (TEMP > T_SET or TEMP < T_HYST)
which must occur in order for the condition to be considered
valid. As an example, assume the MIC184 is in comparator
mode, and CONFIG[4:3] is programmed with 10b. Then the
measured temperature would have to exceed T_SET for four
consecutive A/D conversions before INT would be asserted
or the status bit set. Similarly, TEMP would have to be less
than T_HYST for four consecutive conversions before INT
would be reset.
Like any filter, the Fault_Queue function also has the effect of
delaying the detection of temperature events. In this example,
it would take 4 × tCONV to detect a temperature event. The
depth of Fault_Queue vs. D[4:3] of the configuration register
is shown in Table 4.
Handling Interrupts
The MIC184 may be either polled by the host, or request the
host’s attention via the INT pin. In the case of polled opera-
tion, the host periodically reads the contents of CONFIG to
check the state of the status bit. The act of reading CONFIG
clears the status bit, STS. If more than one event that sets
the status bit occurs before the host polls the MIC184, only
the fact that at least one such event has occurred will be
apparent to the host.
If TEMP < T_HYST or TEMP > T_SET for Fault_Queue con-
versions, the status bit STS will be set in the CONFIG register.
This action cannot be masked. However, a temperature
event will only generate an interrupt signal on INT if inter-
rupts from the MIC184 are enabled (IM = 0 and MODE = 1
in the configuration register). Reading any register following
an interrupt will cause INT to be deasserted, and will clear
STS. The host should read the contents of the configuration
register after receiving an interrupt to confirm that the MIC184
was the source of the interrupt. This is shown in Figure 7.
As noted above, putting the device into shutdown mode will
also deassert INT and clear STS. Therefore, this usually
should not be done before completing the appropriate inter-
rupt service routine(s).
Since temperature-to-digital conversions continue while INT
is asserted, it is possible that temperature could change be-
tween the MIC184’s assertion of its INT output and the host’s
response to the interrupt. It is good practice when servicing
interrupts for the host to read the current temperature to confirm
that the condition that caused the interrupt still exists.
]3:4[GIFNOC htpeDeueuQ_tluaF
00 *noisrevnoc1
10 snoisrevnoc2
01 snoisrevnoc4
11 snoisrevnoc6
gnittestluafeD*
Table 4. Fault_Queue Depth Settings
MIC184 Micrel
MIC184 12 May 2006
Interrupt Polarity Selection
The INT output can be programmed to behave as an active-
low signal or an active-high signal. The default is active-low.
INT polarity is selected by programming the appropriate value
into the polarity bit (POL) in the CONFIG register. Clearing
POL selects active-low interrupts; setting POL selects ac-
tive-high interrupts. INT is an open-drain digital output and
may be wire-ORed with other open-drain logic signals. Most
applications will require a pull-up resistor on this pin.
Whether the CONFIG register’s POL bit is set to provide a
current-sinking (low) or high-Z (high) state at the INT pin when
STS is high, writing a one to IM will put the INT pin into a high-
Z state. This meets the requirement of an active-low interrupt
for the SMBus, while making IM available as an INT-forcing
bit for those applications which employ an active-high INT
output (for example, software fan-control routines).
LM75 Compatibility
The MIC184 can be used interchangeably with the LM75 in
existing applications. The MIC184 offers several advantages
over the LM75:
• Ability to monitor a second, remote temperature
• Interrupt masking capability
• Status bit for software polling routines
• Lower quiescent current
• Supports single-byte reads from 16-bit registers
• No “inadvertent 8-bit read” bus lock-up issues
The three MSB’s of the configuration register (which power
up as zeroes) are used to access the MIC184’s additional
functions. These are reserved bits according to the LM75
specification and, for the LM75, must always be written as
zeroes. The MSB of the MIC184’s status register is a status
flag that does not exist in the LM75. This bit will be set to one
whenever an overtemperature event occurs. This bit would
never be set by an LM75. Software should not depend on this
bit being zero when using the MIC184 as an LM75 upgrade. If
at power-up the measured temperature is higher than T_SET,
the status bit will be set following the first conversion by the
A/D. See “Applications Information” for a method by which
host software can use this fact to differentiate between an
MIC184 and an LM75.
May 2006 13 MIC184
MIC184 Micrel
Register Set and Programmer’s Model
Internal Register Set
emaN noitpircseD etyBdnammoC noitarepO tluafeDpU-rewoP
PMET erutarepmetderusaem 00 hylnodaertib-9 000000000 bC°0 )1(
GIFNOC retsigernoitarugifnoc 10 hetirw/daertib-8 00000000 b)2etoN(
TSYH_T siseretsyh 20 hetirw/daertib-9 011010010 bC°57+
TES_T tniopteserutarepmet 30 hetirw/daertib-9 000001010 bC°08+
Detailed Register Descriptions
)etirW/daeRtiB-8(GIFNOC
]7[D ]6[D ]5[D ]4[D ]3[D ]2[D ]1[D ]0[D
ylnodaer etirw/daer etirw/daer etirw/daer etirw/daer etirw/daer etirw/daer
tpurretni
sutats
)STS(
tpurretni
ksam )3(
)MI(
pmet
tceles
)ENOZ(
eueuqtluaf
htped
)Q_F(
tni
ytiralop
)LOP(
TNI/PMC
edom
)EDOM(
nwodtuhS
)NDHS(
stiB noitcnuF noitarepO
STS )ylnodaer(sutatstpurretni enon=0,deruccotpurretni=1
MI ksamtpurretni delbasid=1,delbane=0
ENOZ noitceleserutarepmetetomer/lanretni lanretni=0,etomer=1
Q_F htpedeueuQ_tluaF ,snoisrevnoc2=10,noisrevnoc1=00
snoisrevnoc6=11,snoisrevnoc4=01
LOP noitcelesytiraloptuptuoTNI wolevitca=0,hgihevitca=1
EDOM tpurretni/rotarapmoc
nipTNIrofnoitcelesedom
,edomtpurretni=1
edomrotarapmoc=0
NDHS nwodtuhs/lamron
noitcelesedomgnitarepo
,nwodtuhs=1
lamron=0
Power-Up Default Value: 0000 0000b = 00h(4)
• not in shutdown mode
• comparator mode
• INT = active low
• Fault_Queue depth = 1
• local temperature zone
• interrupts enabled.
CONFIG Command Byte Address: 0000 0001b = 01h
(1) TEMP will contain measured temperature data for the selected
zone after the completion of one conversion.
(2) After the first Fault_Queue conversions are complete, the
status bit will be set if TEMP < T_HYST or TEMP > T_SET.
(3) Setting IM forces the open-drain INT output into its high-Z
state. See “INT Polarity Selection.”
(4) After the first Fault_Queue conversions are completed, the
status bit will be set if TEMP < T_HYST or TEMP > T_SET.
MIC184 Micrel
MIC184 14 May 2006
T_SET Power-Up Default Value: 0 1010 0000b (+80°C)
T_SET Command Byte Address: 0000 0011b = 03h
* The value in T_SET is 9 logical bits in width, but due to the
conventions of I2C/SMBus, it is represented by 16 serial bits.
System software should ignore undefined bits D[6:0] during
register reads. Bits [6:0] should be set to zero during register
writes. See Serial Port Operation" and “Temperature Data
Format” for more details.
Temperature Setpoint Register
)etirW/daeRtiB-9(TES_T
]51[D ]41[D ]31[D ]21[D ]11[D ]01[D ]9[D ]8[D ]7[D ]6[D ]5[D ]4[D ]3[D ]2[D ]1[D ]0[D
BSM 7tib 6tib 5tib 4tib 3tib 2tib 1tib BSL X X X X X X X
tniopteserutarepmetrevo
stiB noitcnuF noitarepO
]7:51[D tnioptesrotarapmocerutarepmetrevo *etirw/daer
T_HYST Power-Up Default Value: 0 1001 0110b (+75°C)
T_HYST Command Byte Address: 0000 0010b = 02h
* The value in T_HYST is 9 logical bits in width, but due to the
conventions of I2C/SMBus, it is represented by 16 serial bits.
System software should ignore undefined bits D[6:0] during
register reads. Bits [6:0] should be set to zero during register
writes. See "Serial Port Operation" and “Temperature Data
Format” for more details.
Hysteresis Register
)etirW/daeRtiB-9(TSYH_T
]51[D ]41[D ]31[D ]21[D ]11[D ]01[D ]9[D ]8[D ]7[D ]6[D ]5[D ]4[D ]3[D ]2[D ]1[D ]0[D
BSM 7tib 6tib 5tib 4tib 3tib 2tib 1tib BSL X X X X X X X
gnittessiseretsyherutarepmet
stiB noitcnuF noitarepO
]7:51[D gnittessiseretsyherutarepmet *etirw/daer
Temperature Result Register
)ylnOdaeRtiB-9(PMET
]51[D ]41[D ]31[D ]21[D ]11[D ]01[D ]9[D ]8[D ]7[D ]6[D ]5[D ]4[D ]3[D ]2[D ]1[D ]0[D
BSM 7tib 6tib 5tib 4tib 3tib 2tib 1tib BSL X X X X X X X
CDAmorfataderutarepmet
stiB noitcnuF noitarepO
]7:51[D ataderutarepmetderusaem
enozdetcelesrof *ylnodaer
Power-Up Default Value: 0 0000 0000b = 0°C†
TEMP Command Byte Address: 0000 0000b = 00h
* The value in TEMP is 9 logical bits in width, but due to the
conventions of I2C/SMBus, it is represented by 16 serial bits.
System software should ignore undefined bits D[6:0]. See
“Serial Port Operation" and "Temperature Data Format” for
more details.
† TEMP will contain measured temperature data for the selected
zone after the completion of one conversion.
May 2006 15 MIC184
MIC184 Micrel
Applications Information
Switching Zones
The recommended procedure for switching between the
internal and external zones is as follows:
1. Disable interrupts (if used)
by setting the IM bit in CONFIG.
2. Read the CONFIG register to:
a) Verify no masked interrupt was pending
(D[7] = 0)
b) Clear STS prior to switching zones
c) Hold the settings of CONFIG register for the
current zone
3. Write the appropriate values to
T_SET and T_HYST for the new zone.
4. Write to CONFIG as follows:
a) To toggle the ZONE bit (1 = remote, 0 =
internal)
b) If interrupts are being used, step 4 should
also clear MODE
5. If interrupts are being used, MODE must then be
set to 1 and IM reset to 0
At the conclusion of the serial bus transaction for step 4, the
A/D converter will begin a conversion cycle using the new
zone setting. The next conversion cycle completed after
the serial bus transaction for step 5 will result in the state of
the INT output being updated (if enabled) for the new zone.
Generally the MIC184’s A/D converter operates continuously,
but it will be halted and reset each time the part recognizes
its slave address on the serial bus. Interrupted conversions
will remain halted until the end of the host’s communication
with the MIC184. After the completion of step 5 and a delay
of tCONV x Fault_Queue, STS and INT will contain the results
for the new zone. The above routine is extremely unlikely
to miss a temperature event, as even one A/D conversion is
typically much slower than the I2C/SMBus transactions that
control the MIC184. See Figure 6: A/D Converter Timing.
Step 2(c) is recommended because the MIC184 has only
one CONFIG register, corresponding to the active zone. In
order to preserve data integrity for both zones, 2(c) allows
the host to create a virtual CONFIG register for the inactive
zone by dedicating one byte of memory to that purpose.
Additional virtual registers may be created as needed by
inserting additional reads as steps 2(d), 2(e), etc. These
could for example correspond to the values in T_SET and
T_HYST immediately prior to switching zones. Steps 4(b) and
5 ensure that the MIC184 will enter the new zone searching
for an overtemperature event.
Identifying an MIC184 by Software Test
The MIC184 and the LM75 each have an eight-bit CON-
FIG register. In LM75-type parts, no more than seven of
the eight bits of this register are used, and at least one bit
(the MSB) will always return a zero. The MIC184 uses all
eight bits of the CONFIG register: the MSB is the part’s
status bit (STS). A simple test by which the host can
determine whether a system has an MIC184 installed, or
is using a legacy LM75-type device, is to create a situation
which will set the MSB in the MIC184’s CONFIG register
and then determine if the MSB is in fact set. Two examples
of how this can be done are outlined below. The first is in-
terrupt-driven, the second uses software polling. Note that
both procedures generate one or more spurious interrupts.
The code for these tests should therefore temporarily dis-
able any affected interrupt routines.
{START Interrupt-Driven Test and Initialization
Routine}
1. Disable the host’s overtemperature and under-
temperature interrupt handling routine. Redirect
interrupts from the part under test to a handler
for the interrupt that will be generated in steps
(4) and (7) of this routine.
2. Write 0000 0010b (02h) to the CONFIG register.
(The assumption is made that the host is an I2C
or SMBus part, and therefore responds to an ac-
tive-low interrupt request.)
3. Write 1100 1000 1000 0000b = C880h to T_SET
and T_HYST. This corresponds to -55.5°C.
4. When the part has finished its first A/D conver-
sion, INT will be asserted.
5. Read out the contents of the CONFIG register:
a) If the part is an MIC184, the MSB will be set
to one (CONFIG = 1000 0010b = 82h).
b) If the part is a conventional LM75-type part,
the MSB will be zero (CONFIG = 0000
0010b = 02h).
6.Write 0111 1111 1000 0000b = 7F80h to T_SET
and T_HYST. This corresponds to +127.5°C.
7.When the part has finished its next A/D conver-
sion, INT will be asserted a second time.
8.Read CONFIG again, to clear the interrupt re-
quest from step (7). This will also clear STS, if
the part under test is an MIC184.
9.Based on the results of the test in step (4), do the
following within 50ms total:
a) Set the CONFIG register as required.
b) Load T_HYST with its operational value.
c) Load T_SET with its operational value.
d) Set the host’s interrupt handling routine back
to overtemperature and undertemperature
mode.
{END}
{START Polling-Based Test and Initialization Rou-
tine}
1. Temporarily disable the host’s interrupt input
MIC184 Micrel
MIC184 16 May 2006
from the device under test.
2. Write 0000 0010b (02h) to the CONFIG register.
3. Write 1100 1000 1000 0000b = C880h to T_SET
and T_HYST. This corresponds to -55.5°C.
4. Wait tconv (160ms max.) for the part to finish at
least one A/D conversion.
5. Read the contents of the CONFIG register:
a) If the part is an MIC184, the MSB will be set
to one (CONFIG = 82h).
b) If the part is a conventional LM75-type part,
the MSB will be zero (CONFIG = 02h).
6. Write 0111 1111 1000 0000b = 7F80h to T_SET
and T_HYST. This corresponds to +127.5°C.
7. Wait an additional tconv for the part to finish a
second conversion.
8. Read CONFIG again, to clear the interrupt
request from step (7). This will also clear STS, if
the part under test is an MIC184.
9. Based on the results of the test in step (4), do
the following four steps within 50ms total:
a) Set the CONFIG register as required.
b) Load T_HYST with its operational value.
c) Load T_SET with its operational value.
d) Re-enable the host’s interrupt handling input
from the part under test.
{END}
These routines force the device under test to generate an
overtemperature fault (steps 3 and 4), followed by an under-
temperature fault (steps 6 through 8). This sequence causes
the device under test to exit the routine prepared to respond
to an overtemperature condition. If being immediately pre-
pared to detect an undertemperature condition upon exit is
desired, swap steps 3 and 6 in each routine.
Remote Diode Selection
Most small-signal PNP transistors with characteristics similar
to the JEDEC 2N3906 will perform well as remote tempera-
ture sensors. Table 3 lists several examples of such parts.
Micrel has tested those marked with a bullet for use with the
MIC184.
Minimizing Errors
Self-Heating
One concern when using a part with the temperature accuracy
and resolution of the MIC184 is to avoid errors induced by
self-heating (VDD × IDD). In order to understand what level of
error this might represent, and how to reduce that error, the
dissipation in the MIC184 must be calculated, and its effects
examined as a temperature error.
In most applications, the INT output will be low for at most a
few milliseconds before the host sets it back to the high state,
making its duty cycle low enough that its contribution to self-
heating of the MIC184 is negligible. Similarly, the DATA pin
will in all likelihood have a duty cycle of substantially below
25% in the low state. These considerations, combined with
more typical device and application parameters, allow the
following calculation of typical device self-heating in inter-
rupt-mode:
PD = (IDD(typ.) 3.3V + 25% IOL(data)0.3V +
1% IOL(int)0.3V)
PD = (0.3mA × 3.3V + 25% × 1.5mA × 0.3V +
1% × 1.5mA × 0.3V)
ΔTJ = 1.11mW × 206°C/W
ΔTJ relative to TA is 0.23°C
If the part is to be used in comparator mode, calculations
similar to those shown above (accounting for the expected
value and duty cycle of IOL(int)) will give a good estimate of
the device’s self-heating error.
In any application, the best test is to verify performance
against calculation in the final application environment. This
is especially true when dealing with systems for which some
of the thermal data, (for example, PC board thermal conduc-
tivity and/or ambient temperature), may be poorly defined or
unavailable except by empirical means.
Series Resistance
The operation of the MIC184 depends upon sensing the
ΔVCB-E of a diode-connected PNP transistor ("diode") at
two different current levels. For remote temperature mea-
surements, this is done using an external diode connected
between A2/T1 and ground.
Since this technique relies upon measuring the relatively small
voltage difference resulting from two levels of current through
the external diode, any resistance in series with the external
diode will cause an error in the temperature reading from the
MIC184. A good rule of thumb is this: for each ohm in series
with the external transistor, there will be a 0.9°C error in the
MIC184's temperature measurement. It is not difficult to keep
the series resistance well below an ohm (typically 0.1Ω), so
Vendor Part Number Package Tested
Fairchild MMBT3906 SOT-23
On Semiconductor MMBT3906L SOT-23
Phillips Semiconductor PMBT3906 SOT-23
Rohm Semiconductor SST3906 SOT-23
Samsung KST3906-TF SOT-23
Zetex FMMT3906 SOT-23
Table 5. Transistors Suitable for Remote Temperature Sensing Use
May 2006 17 MIC184
MIC184 Micrel
in most systems this will not be an issue.
Filter Capacitor Selection
When using a remote diode for temperature sensing, it is
sometimes desirable to use a filter capacitor between the
A2/T1 and GND pins of the MIC184. The use of this capaci-
tor is recommended in environments with a significant high
frequency noise (such as digital switching noise), or if long
wires are used to connect to the remote diode. The maximum
recommended total capacitance from the A2/T1 pin to GND
is 2700pF. This usually suggests the use of a 2200pF NP0
or C0G ceramic capacitor with a 10% tolerance.
If the remote diode is to be at a distance of more than 6" ~
12" from the MIC184, using a shielded cable (solid foil shield
microphone cable is a good choice) for the connections to the
diode can significantly help reduce noise pickup. Remember
to subtract the cable's conductor-to-shield capacitance from
the 2700pF maximum total capacitance.
Layout Considerations
Local Mode Only Applications:
If the MIC184 is not going to be used with an external diode,
the best layout is one which keeps it thermally coupled to the
subsystem(s) whose temperature it must monitor, while avoid-
ing any strong sources of EMI, RFI, or electrostatically coupled
noise. Two of the most common examples of such sources
are switching power supply transformers and CRTs.
Remote Mode Applications:
1. If the remote sensing capability of the
MIC184 will be used in an application, place the
MIC184 as close to the remote diode as pos-
sible, while taking care to avoid severe noise
sources (high frequency power transformers,
CRTs, memory and data busses, and the like).
2. Since any conductance from the various volt-
ages on the PC Board and the A2/T1 pin can
induce serious errors, it is good practice to guard
the remote diode’s emitter trace with a pair of
ground traces. These ground traces should be
returned to the MIC184’s own ground pin. They
should not be grounded at any other part of their
run. However, it is highly desirable to use these
guard traces to carry the diode’s own ground
return back to the ground pin of the MIC184,
thereby providing a Kelvin connection for the
base of the diode. See Figure 8.
3. When using the MIC184 to sense the tempera-
ture of a processor or other device which has an
integral on-board “diode” (e.g., Intel’s Pentium®
III), connect the emitter and base of the remote
sensor to the MIC184 using the guard traces
and Kelvin return shown in Figure 8. The col-
lector of the remote “diode” is inaccessible to
the user on these types of chips. To allow for
this, the MIC184 has superb rejection of noise
appearing from collector to GND, as long as the
base to ground connection is relatively quiet.
4. Due to the small currents involved in the mea-
surement of the remote diode’s ΔVBE, it is
important to adequately clean the PC board after
soldering. This is most likely to show up as an
issue in some situations where water-soluble
soldering fluxes are used.
5. In general, wider traces for the ground and
A2/T1 pins will help reduce susceptibility to radi-
ated noise (wider traces are less inductive). Use
trace widths and spacing of 10 mils wherever
possible. Wherever possible, place a ground
plane under the MIC184, and under the connec-
tions from the MIC184 to the remote diode. This
will help guard against stray noise pickup.
6. Always place a good quality VDD bypass ca-
pacitor directly adjacent to, or underneath, the
MIC184. This part should be a 0.1µF ceramic
capacitor. Surface-mount parts provide the best
bypassing because of their low inductance.
7. When the MIC184 is being powered from par-
ticularly noisy power supplies, or from supplies
which may have sudden high-amplitude spikes
appearing on them, it can be helpful to add ad-
ditional power supply filtering. This should be
implemented as a 100Ω resistor in series with
the part’s VDD pin, and a 4.7µF, 6.3V electrolytic
capacitor from VDD to GND. See Figure 9.
MIC184 Micrel
MIC184 18 May 2006
REMOTE DIODE (A2/T1)
GUARD/RETURN
1
2
3
DATA
CLK
INT
GND
8
7
6
54
VDD
A0
A1
A2/T1
GUARD/RETURN
Figure 8. Guard Traces/Kelvin Ground Returns
DATA
1
2
3
8
4
5
6
7
FROM
SERIAL BUS
HOST
2N3906
2200pF
MIC184
CLK
INT
VDD
100
3.0V to 3.6V
10k Pull-ups
A2/T1
A1
A0
GND
4.7µF0.1F
Figure 9. VDD Decoupling for Very Noisy Supplies
May 2006 19 MIC184
MIC184 Micrel
Package Information
8-Lead SOIC (M)
8-Lead MSOP (MM)

























MIC184 Micrel
MIC184 20 May 2006
MICREL INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com
This information furnished by�
Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not�
reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into
the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's
use or sale of Micrel Pr�
Micrel for any damages resulting from such use or sale.
© 2005 Micrel Incorporated