MAX6699UE34+T - Maxim Integrated Products, Inc.

General Description

The MAX6699 precision multichannel temperature sen-

sor monitors its own temperature and the temperatures

of up to four external diode-connected transistors.

All temperature channels have programmable alert

thresholds. Channels 1 and 4 also have programmable

overtemperature thresholds. When the measured tem-

perature of a channel exceeds the respective thresh-

old, a status bit is set in one of the status registers. Two

open-drain outputs, OVERT and ALERT, assert corre-

sponding to these bits in the status register.

The 2-wire serial interface supports the standard system

management bus (SMBus™) protocols: write byte, read

byte, send byte, and receive byte for reading the tem-

perature data and programming the alarm thresholds.

The MAX6699 is specified for an operating temperature

range of -40°C to +125°C and is available in 16-pin

QSOP and 16-pin TSSOP packages.

Applications

Desktop Computers

Notebook Computers

Workstations

Servers

Features

♦Four Thermal-Diode Inputs

♦Local Temperature Sensor

♦1°C Remote Temperature Accuracy (+60°C to +100°C)

♦Temperature Monitoring Begins at POR for Fail-Safe

System Protection

♦ALERT and OVERT Outputs for Interrupts, Throttling,

and Shutdown

♦Small 16-Pin QSOP and 16-Pin TSSOP Packages

♦2-Wire SMBus Interface

MAX6699

5-Channel Precision Temperature Monitor

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

GND

SMBCLK

SMBDATA

DXN2

DXP2

DXN1

DXP1

VCC

N.C.1

N.C.2DXN4

DXP4

DXN3

DXP3

MAX6699

ALERT

OVERT

2200pF

CPU

0.1µF

TO SYSTEM

SHUTDOWN

INTERRUPT

TO µP

DATA

CLK

4.7kΩ

EACH

+3.3V

Typical Application Circuit

19-3859; Rev 2; 7/07

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

PART TEMP RANGE PIN-

PACKAGE

PKG

CODE

MAX6699EE_ _

-40°C to +125°C 16 QSOP

E16-1

MAX6699UE_ _

-40°C to +125°C 16 TSSOP

U16-1

SMBus is a trademark of Intel Corp.

See the Slave Address section.

Pin Configuration appears at end of data sheet.

MAX6699

5-Channel Precision Temperature Monitor

2 _______________________________________________________________________________________

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.

VCC, SCK, SDA, ALERT, OVERT to GND ................-0.3V to +6V

DXP_ to GND..............................................-0.3V to (VCC + 0.3V)

DXN_ to GND ........................................................-0.3V to +0.8V

SDA, ALERT, OVERT Current .............................-1mA to +50mA

DXN Current .......................................................................±1mA

Continuous Power Dissipation (TA= +70°C)

16-Pin QSOP

(derate 8.30mW/°C above +70°C) ....................727.3mW(E20-1)

16-Pin TSSOP

(derate 9.40mW/°C above +70°C)..................879.1mW(U20-2)

ESD Protection (all pins, Human Body Model) ................±2000V

Operating Temperature Range .........................-40°C to +125°C

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-60°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

ELECTRICAL CHARACTERISTICS

(VCC = +3.0V to +5.5V, TA= -40°C to +125°C, unless otherwise noted. Typical values are at VCC = +3.3V and TA= +25°C.) (Note 1)

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

Supply Voltage VCC 3.0 5.5 V

Standby Supply Current ISS SMBus static 30 µA

Operating Current ICC During conversion

500 1000

µA

Channel 1 only 11

Temperature Resolution Other diode channels 8 Bits

TA = TRJ = +60°C to +100°C -1.0 +1.0

TA = TRJ = 0°C to +125°C

-3.0 +3.0

Remote Temperature Accuracy

VCC = 3.3V

DXN_ grounded,

TRJ = TA = 0°C to +85°C

±2.5

oC

TA = +60°C to +100°C

-2.0 +2.0

Local Temperature Accuracy

VCC = 3.3V

TA = 0°C to +125°C

-3.0 +3.0

oC

Supply Sensitivity of Temperature

Accuracy

±0.2

oC/V

Resistance cancellation on 95

125 156

Remote Channel 1 Conversion

Time tCONV1 Resistance cancellation off

190 250 312

ms

Remote Channels 2 Through 4

Conversion Time tCONV_ 95

125 156

ms

High level 80

100 120

Remote-Diode Source Current IRJ Low level 8 10 12 µA

Undervoltage-Lockout Threshold

UVLO Falling edge of VCC disables ADC

2.30 2.80 2.95

V

Undervoltage-Lockout Hysteresis

90 mV

Power-On Reset (POR) Threshold

VCC falling edge 1.2 2.0 2.5 V

POR Threshold Hysteresis 90 mV

ALERT, OVERT

ISINK = 1mA 0.3

Output Low Voltage VOL ISINK = 6mA 0.5 V

Output Leakage Current 1µA

MAX6699

5-Channel Precision Temperature Monitor

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VCC = +3.0V to +5.5V, TA= -40°C to +125°C, unless otherwise noted. Typical values are at VCC = +3.3V and TA= +25°C.) (Note 1)

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

SMBus INTERFACE (SCL, SDA)

Logic-Input Low Voltage VIL 0.8 V

VCC = 3.0V 2.2 V

Logic-Input High Voltage VIH VCC = 5.0V 2.4 V

Input Leakage Current -1 +1 µA

Output Low Voltage VOL ISINK = 6mA 0.3 V

Input Capacitance CIN 5pF

SMBus-COMPATIBLE TIMING (Figures 3 and 4) (Note 2)

Serial Clock Frequency fSCL (Note 3)

400

kHz

fSCL = 100kHz 4.7

Bus Free Time Between STOP

and START Condition tBUF fSCL = 400kHz 1.6 µs

fSCL = 100kHz 4.7

START Condition Setup Time fSCL = 400kHz 0.6 µs

90% of SCL to 90% of SDA,

fSCL = 100kHz 0.6

Repeat START Condition Setup

Time tSU:STA 90% of SCL to 90% of SDA,

fSCL = 400kHz 0.6

µs

START Condition Hold Time tHD:STA 10% of SDA to 90% of SCL 0.6 µs

90% of SCL to 90% of SDA,

fSCL = 100kHz 4

STOP Condition Setup Time tSU:STO 90% of SCL to 90% of SDA,

fSCL = 400kHz 0.6

µs

10% to 10%, fSCL = 100kHz 1.3

Clock Low Period tLOW 10% to 10%, fSCL = 400kHz 1.3 µs

Clock High Period tHIGH 90% to 90% 0.6 µs

fSCL = 100kHz

300

Data Hold Time tHD:DAT fSCL = 400kHz (Note 4)

900

ns

fSCL = 100kHz

250

Data Setup Time tSU:DAT fSCL = 400kHz

100

ns

fSCL = 100kHz 1

Receive SCL/DSA Rise Time tRfSCL = 400kHz 0.3 µs

Receive SCL/SDA Fall Time tF

300

ns

Pulse Width of Spike Suppressed

tSP 050ns

SMBus Timeout

tTIMEOUT

SDA low period for interface reset 25 37 45 ms

Note 1: All parameters are tested at TA= +25°C. Specifications over temperature are guaranteed by design.

Note 2: Timing specifications are guaranteed by design.

Note 3: The serial interface resets when SCL is low for more than tTIMEOUT.

Note 4: A transition must internally provide at least a hold time to bridge the undefined region (300ns max) of SCL’s falling edge.

MAX6699

5-Channel Precision Temperature Monitor

4 _______________________________________________________________________________________

Typical Operating Characteristics

(VCC = 3.3V, TA= +25°C, unless otherwise noted.)

STANDBY SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX6699 toc01

SUPPLY VOLTAGE (V)

STANDBY SUPPLY CURRENT (µA)

5.34.84.3

3.8

1

2

3

4

5

6

7

8

9

10

11

12

0

3.3

SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX6699 toc02

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (µA)

5.34.8

3.8 4.3

325

330

335

340

350

345

355

360

320

3.3

-4

-2

-3

0

-1

2

1

3

05025 75 100 125

REMOTE TEMPERATURE ERROR

vs. REMOTE-DIODE TEMPERATURE

MAX6699 toc03

REMOTE-DIODE TEMPERATURE (°C)

TEMPERATURE ERROR (°C)

-4

-3

-2

-1

0

1

2

3

4

0 25 50 75 100 125

LOCAL TEMPERATURE ERROR

vs. DIE TEMPERATURE

MAX6699 toc04

DIE TEMPERATURE (°C)

TEMPERATURE ERROR (°C)

REMOTE-DIODE TEMPERATURE ERROR

vs. POWER-SUPPLY NOISE FREQUENCY

MAX6699 toc05

FREQUENCY (MHz)

TEMPERATURE ERROR (°C)

-4

-3

-2

-1

0

1

2

3

4

5

-5

0.1 1

100mVP-P

LOCAL TEMPERATURE ERROR

vs. POWER-SUPPLY NOISE FREQUENCY

MAX6699 toc06

FREQUENCY (MHz)

TEMPERATURE ERROR (°C)

0.10.01

-4

-3

-2

-1

0

1

2

3

4

5

-5

0.001 1

100mVP-P

REMOTE TEMPERATURE ERROR

vs. COMMON-MODE NOISE FREQUENCY

MAX6699 toc07

FREQUENCY (MHz)

TEMPERATURE ERROR (°C)

10.10.01

-4

-3

-2

-1

0

1

2

3

4

5

-5

0.001 10

100mVP-P

MAX6699

5-Channel Precision Temperature Monitor

_______________________________________________________________________________________ 5

REMOTE TEMPERATURE ERROR

vs. COMMON-MODE NOISE FREQUENCY

MAX6699 toc08

FREQUENCY (MHz)

TEMPERATURE ERROR (°C)

10.10.01

-4

-3

-2

-1

0

1

2

3

4

5

-5

0.001 10

100mVP-P

Typical Operating Characteristics (continued)

(VCC = 3.3V, TA= +25°C, unless otherwise noted.)

TEMPERATURE ERROR

vs. DXP-DXN CAPACITANCE

MAX6699 toc09

DXP-DXN CAPACITANCE (nF)

TEMPERATURE ERROR (°C)

10

-4.5

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0

-5.0

1100

Pin Description

PIN NAME FUNCTION

1 DXP1

Combined Current Source and A/D Positive Input for Channel 1 Remote Diode. Connect to the anode

of a remote-diode-connected temperature-sensing transistor. Leave floating or connect to VCC if no

remote diode is used. Place a 2200pF capacitor between DXP1 and DXN1 for noise filtering.

2 DXN1 Cathode Input for Channel 1 Remote Diode. Connect the cathode of the channel 1 remote-diode-

connected transistor to DXN1.

3 DXP2

Combined Current Source and A/D Positive Input for Channel 2 Remote Diode. Connect to the anode

of a remote-diode-connected temperature-sensing transistor. Leave floating or connect to VCC if no

remote diode is used. Place a 2200pF capacitor between DXP2 and DXN2 for noise filtering.

4 DXN2 Cathode Input for Channel 2 Remote Diode. Connect the cathode of the channel 2 remote-diode-

connected transistor to DXN2.

5 DXP3

Combined Current Source and A/D Positive Input for Channel 3 Remote Diode. Connect to the anode

of a remote-diode-connected temperature-sensing transistor. Leave floating or connect to VCC if no

remote diode is used. Place a 2200pF capacitor between DXP3 and DXN3 for noise filtering.

6 DXN3 Cathode Input for Channel 3 Remote Diode. Connect the cathode of the channel 1 remote-diode-

connected transistor to DXN3.

MAX6699

Detailed Description

The MAX6699 is a precision multichannel temperature

monitor that features one local and four remote temper-

ature-sensing channels with a programmable alert

threshold for each temperature channel and a program-

mable overtemperature threshold for channels 1 and 4

(see Figure 1). Communication with the MAX6699 is

achieved through the SMBus serial interface and a

dedicated alert pin. The alarm outputs, OVERT and

ALERT, assert if the software-programmed temperature

thresholds are exceeded. ALERT typically serves as an

interrupt, while OVERT can be connected to a fan, sys-

tem shutdown, or other thermal-management circuitry.

ADC Conversion Sequence

In the default conversion mode, the MAX6699 starts the

conversion sequence by measuring the temperature on

channel 1, followed by 2, 3, and local channel 4. The

conversion result for each active channel is stored in

the corresponding temperature data register.

In some systems, one of the remote thermal diodes may

be monitoring a location that experiences temperature

changes that occur much more rapidly than in the other

channels. If faster temperature changes must be moni-

tored in one of the temperature channels, the MAX6699

allows channel 1 to be monitored at a faster rate than

the other channels. In this mode (set by writing a 1 to bit

4 of the configuration 1 register), measurements of

channel 1 alternate with measurements of the other

channels. The sequence becomes channel 1, channel

2, channel 1, channel 3, channel 1, etc. Note that the

time required to measure all five channels is consider-

ably greater in this mode than in the default mode.

Low-Power Standby Mode

Standby mode reduces the supply current to less than

15µA by disabling the internal ADC. Enter standby by

setting the STOP bit to 1 in the configuration 1 register.

During standby, data is retained in memory, and the

SMBus interface is active and listening for SMBus com-

mands. The timeout is enabled if a start condition is rec-

ognized on SMBus. Activity on the SMBus causes the

supply current to increase. If a standby command is

received while a conversion is in progress, the conver-

sion cycle is interrupted, and the temperature registers

are not updated. The previous data is not changed and

remains available.

5-Channel Precision Temperature Monitor

6 _______________________________________________________________________________________

PIN NAME FUNCTION

7 DXP4

Combined Current Source and A/D Positive Input for Channel 4 Remote Diode. Connect to the anode

of a remote-diode-connected temperature-sensing transistor. Leave floating or connect to VCC if no

remote diode is used. Place a 2200pF capacitor between DXP4 and DXN4 for noise filtering.

8 DXN4 Cathode Input for Channel 4 Remote Diode. Connect the cathode of the channel 1 remote-diode-

connected transistor to DXN4.

9, 10 N.C._ No Connection. Must be connected to ground.

11 OVERT Overtemperature Active-Low, Open-Drain Output. OVERT asserts low when the temperature of

channels 1 and 4 exceeds the programmed threshold limit.

12 VCC Supply Voltage Input. Bypass to GND with a 0.1µF capacitor.

13 ALERT SMBus Alert (Interrupt), Active-Low, Open-Drain Output. ALERT asserts low when the temperature of

any channel exceeds the programmed ALERT threshold.

14

SMBDATA

SMBus Serial-Data Input/Output. Connect to a pullup resistor.

15 SMBCLK SMBus Serial-Clock Input. Connect to a pullup resistor.

16 GND Ground

Pin Description (continued)

SMBus Digital Interface

From a software perspective, the MAX6699 appears as

a series of 8-bit registers that contain temperature-mea-

surement data, alarm threshold values, and control bits.

A standard SMBus-compatible 2-wire serial interface is

used to read temperature data and write control bits

and alarm threshold data. The same SMBus slave

address also provides access to all functions.

The MAX6699 employs four standard SMBus protocols:

write byte, read byte, send byte, and receive byte

(Figure 2). The shorter receive-byte protocol allows

quicker transfers, provided that the correct data regis-

ter was previously selected by a read byte instruction.

Use caution with the shorter protocols in multimaster

systems, since a second master could overwrite the

command byte without informing the first master. Figure

3 is the SMBus write timing diagram, and Figure 4 is

the SMBus read timing diagram.

The remote diode 1 measurement channel provides 11

bits of data (1 LSB = 0.125°C). All other temperature-

measurement channels provide 8 bits of temperature

data (1 LSB = 1°C). The 8 most significant bits (MSBs)

can be read from the local temperature and remote

temperature registers. The remaining 3 bits for remote

diode 1 can be read from the extended temperature

register. If extended resolution is desired, the extended

resolution register should be read first. This prevents

the most significant bits from being overwritten by new

MAX6699

5-Channel Precision Temperature Monitor

_______________________________________________________________________________________ 7

Figure 1. Internal Block Diagram

DXP1

DXN1

DXP2

DXN2

DXP3

DXN3

DXP4

DXN4

INPUT

BUFFER

10/100µA

VCC

REF

COUNT

COUNTER

COMMAND BYTE

REMOTE TEMPERATURES

LOCAL TEMPERATURES

REGISTER BANK

ALERT THRESHOLD

OVERT THRESHOLD

ALERT RESPONSE ADDRESS

ALARM

ALU

ADC

SMBus

INTERFACE

MAX6699

SCL SDA

OVERT

AVERT

MAX6699

conversion results until they have been read. If the

most significant bits have not been read within an

SMBus timeout period (nominally 37ms), normal updat-

ing continues. Table 1 shows the main temperature

register (high byte) data format, and Table 2 shows the

extended resolution register (low byte) data format.

Diode Fault Detection

If a channel’s input DXP_ and DXN_ are left open, the

MAX6699 detects a diode fault. An open diode fault does

not cause either ALERT or OVERT to assert. A bit in the sta-

tus register for the corresponding channel is set to 1 and

the temperature data for the channel is stored as all 1s

(FFh). It takes approximately 4ms for the MAX6699 to

detect a diode fault. Once a diode fault is detected, the

MAX6699 goes to the next channel in the conversion

sequence. Depending on operating conditions, a shorted

5-Channel Precision Temperature Monitor

8 _______________________________________________________________________________________

Write Byte Format

Read Byte Format

Send Byte Format Receive Byte Format

Slave Address: equiva-

lent to chip-select line of

a 3-wire interface

Command Byte: selects to

which register you are writing

Data Byte: data goes into the register

set by the command byte (to set

thresholds, configuration masks, and

sampling rate)

Slave Address: equiva-

lent to chip-select line

Command Byte: selects

from which register you

are reading

Slave Address: repeated

due to change in data-

flow direction

Data Byte: reads from

the register set by the

command byte

Command Byte: sends com-

mand with no data, usually

used for one-shot command

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

S = Start condition Shaded = Slave transmission

P = Stop condition /// = Not acknowledged

SADDRESS RD ACK DATA /// P

7 bits 8 bits

WRSACK COMMAND ACK P

8 bits

ADDRESS

7 bits

P

1

ACKDATA

8 bits

ACKCOMMAND

8 bits

ACKWRADDRESS

7 bits

S

SADDRESS WR ACK COMMAND ACK SADDRESS

7 bits8 bits7 bits

RD ACK DATA

8 bits

/// P

Figure 2. SMBus Protocols

TEMP (°C) DIGITAL OUTPUT

>127 0111 1111

127 0111 1111

126 0111 1110

25 0001 1001

0.00 0000 0000

<0.00 0000 0000

Diode fault (open) 1111 1111

Diode fault (short) 1111 1111 or 1110 1110

Table 1. Main Temperature Register

(High Byte) Data Format

TEMP (°C) DIGITAL OUTPUT

0 000X XXXX

+0.125 001X XXXX

+0.250 010X XXXX

+0.375 011X XXXX

+0.500 100X XXXX

+0.625 101X XXXX

+0.725 110X XXXX

+0.875 111X XXXX

Table 2. Extended Resolution Temperature

Register (Low Byte) Data Format

diode may or may not cause ALERT or OVERT to assert,

so if a channel will not be used, disconnect its DXP and

DXN inputs.

Alarm Threshold Registers

There are 9 alarm threshold registers that store over-

temperature ALERT and OVERT threshold values.

Seven of these registers are dedicated to store one

local alert temperature threshold limit and six remote

alert temperature threshold limits (see the

ALERT

Interrupt Mode section). The remaining two registers

are dedicated to remote channels 1 and 4 to store

overtemperature threshold limits (see the

OVERT

Overtemperature Alarm section). Access to these regis-

ters is provided through the SMBus interface.

ALERT

Interrupt Mode

An ALERT interrupt occurs when the internal or external

temperature reading exceeds a high-temperature limit

(user programmable). The ALERT interrupt output signal

can be cleared by reading the status register(s) associ-

ated with the fault(s) or by successfully responding to an

alert response address transmission by the master. In

both cases, the alert 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 ALERT output is open drain so that multiple devices

can share a common interrupt line. All ALERT interrupts

can be masked using the configuration 3 register. The

POR state of these registers is shown in Table 3.

MAX6699

5-Channel Precision Temperature Monitor

_______________________________________________________________________________________ 9

SMBCLK

A = START CONDITION

B = MSB OF ADDRESS CLOCKED INTO SLAVE

C = LSB OF ADDRESS CLOCKED INTO SLAVE

D = R/W BIT CLOCKED INTO SLAVE

AB CD

EFG HIJ

SMBDATA

tSU:STA tHD:STA

tLOW tHIGH

tSU:DAT tSU:STO tBUF

LMK

E = SLAVE PULLS SMBDATA LINE LOW

F = ACKNOWLEDGE BIT CLOCKED INTO MASTER

G = MSB OF DATA CLOCKED INTO SLAVE

H = LSB OF DATA CLOCKED INTO SLAVE

I = MASTER PULLS DATA LINE LOW

J = ACKNOWLEDGE CLOCKED INTO SLAVE

K = ACKNOWLEDGE CLOCK PULSE

L = STOP CONDITION

M = NEW START CONDITION

Figure 3. SMBus Write Timing Diagram

SMBCLK

AB CD

EFG H

IJK

SMBDATA

tSU:STA tHD:STA

tLOW tHIGH

tSU:DAT tHD:DAT tSU:STO tBUF

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 SMBDATA LINE LOW

LM

F = ACKNOWLEDGE BIT CLOCKED INTO MASTER

G = MSB OF DATA CLOCKED INTO MASTER

H = LSB OF DATA CLOCKED INTO MASTER

I = MASTER PULLS DATA LINE LOW

J = ACKNOWLEDGE CLOCKED INTO SLAVE

K = ACKNOWLEDGE CLOCK PULSE

L = STOP CONDITION

M = NEW START CONDITION

Figure 4. SMBus Read Timing Diagram

MAX6699

5-Channel Precision Temperature Monitor

10 ______________________________________________________________________________________

REGISTER ADDRESS

(HEX)

POR STATE

(HEX)

READ/

WRITE

DESCRIPTION

Local 07 00 R Read local temperature register

Remote 1 01 00 R Read channel 1 remote temperature register

Remote 2 02 00 R Read channel 2 remote temperature register

Remote 3 03 00 R Read channel 3 remote temperature register

Remote 4 04 00 R Read channel 4 remote temperature register

Reserved 05 00 R —

Reserved 06 00 R —

Configuration 1 41 00 R/W Read/write configuration register 1

Configuration 2 42 00 R/W Read/write configuration register 2

Configuration 3 43 00 R/W Read/write configuration register 3

Status1 44 00 R Read status register 1

Status2 45 00 R Read status register 2

Status3 46 00 R Read status register 3

Local ALERT High Limit 17 5A R/W

Read/write local alert high-temperature threshold limit register

Remote 1 ALERT High Limit

11 6E R/W Read/write channel 1 remote-diode alert high-temperature

threshold limit register

Remote 2 ALERT High Limit

12 7F R/W Read/write channel 2 remote-diode alert high-temperature

threshold limit register

Remote 3 ALERT High Limit

13 64 R/W Read/write channel 3 remote-diode alert high-temperature

threshold limit register

Remote 4 ALERT High Limit

14 64 R/W Read/write channel 4 remote-diode alert high-temperature

threshold limit register

Reserved 15 64 R/W —

Reserved 16 64 R/W —

Remote 1 OVERT High Limit

21 6E R/W Read/write channel 1 remote-diode overtemperature threshold

limit register

Remote 4 OVERT High Limit

24 7F R/W Read/write channel 4 remote-diode overtemperature threshold

limit register

Reserved 25 5A R/W —

Reserved 26 5A R/W —

Remote 1 Extended

Temperature 09 00 R Read channel 1 remote-diode extended temperature register

Manufacturer ID 0A 4D R Read manufacturer ID

Table 3. Command Byte Register Bit Assignment

MAX6699

5-Channel Precision Temperature Monitor

______________________________________________________________________________________ 11

ALERT

Response Address

The SMBus alert response interrupt pointer provides

quick fault identification for simple slave devices that

lack the complex logic needed to be a bus master.

Upon receiving an interrupt signal, the host master can

broadcast a receive byte transmission to the alert

response slave address (see the Slave Addresses sec-

tion). Then, any slave device that generated an inter-

rupt 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 ALERT line

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 MAX6699 reasserts the ALERT

interrupt at the end of the next conversion.

OVERT

Overtemperature Alarms

The MAX6699 has two overtemperature registers that

store remote alarm threshold data for the OVERT output.

OVERT is asserted when a channel’s measured temper-

ature is greater than the value stored in the correspond-

ing threshold register. OVERT remains asserted until the

temperature drops below the programmed threshold

minus 4°C hysteresis. An overtemperature output can

be used to activate a cooling fan, send a warning, initi-

ate clock throttling, or trigger a system shutdown to pre-

vent component damage. See Table 3 for the POR state

of the overtemperature threshold registers.

Command Byte Functions

The 8-bit Command Byte register (Table 3) is the mas-

ter index that points to the various other registers within

the MAX6699. This register’s POR state is 0000 0000.

Configuration Bytes Functions

There are three Read-Write Configuration registers

(Tables 4, 5, and 6) that can be used to control the

MAX6699’s operation.

Configuration 1 Register

The Configuration 1 register (Table 4) has several func-

tions. Bit 7(MSB) is used to put the MAX6699 either in

software standby mode (STOP) or continuous conversion

mode. Bit 6 resets all registers to their power-on reset

conditions and then clears itself. Bit 5 disables the

SMBus timeout. Bit 4 enables more frequent conversions

on channel 1, as described in the ADC Conversion

Sequence section. Bit 3 enables resistance cancellation

on channel 1. See the Series Resistance Cancellation

section for more details. The remaining bits of the

Configuration 1 register are not used. The POR state of

this register is 0000 0000 (00h).

Configuration 2 Register

The Configuration 2 register functions are described in

Table 5. Bits [6:0] are used to mask the ALERT interrupt

output. Bit 6 masks the local alert interrupt and bit 5

through bit 2 mask the remote alert interrupts. The

power-up state of this register is 0000 0000 (00h).

Configuration 3 Register

Table 6 describes the Configuration 3 register. Bits 3

and 0 mask the OVERT interrupt output for channels 4

and 1. The remaining bits, 7, 6, 5, 4, 2, and 1, are

reserved. The power-up state of this register is 0000

0000 (00h).

Status Registers Functions

Status registers 1, 2, and 3 (Tables 7, 8, and 9) indicate

which (if any) temperature thresholds have been

exceeded and if there is an open-circuit or short-circuit

fault detected with the external sense junctions. Status

register 1 indicates if the measured temperature has

exceeded the threshold limit set in the ALERT registers

for the local or remote-sensing diodes. Status register 2

indicates if the measured temperature has exceeded

the threshold limit set in the OVERT registers. Status

register 3 indicates if there is a diode fault (open or

short) in any of the remote-sensing channels.

Bits in the Alert Status register clear by a successful

read, but set again after the next conversion unless the

fault is corrected, either by a drop in the measured tem-

perature or an increase in the threshold temperature.

The ALERT interrupt output follows the status flag bit.

Once the ALERT output is asserted, it can be deassert-

ed by either reading Status register 1 or by successfully

responding to an alert response address. In both

MAX6699

cases, the alert is cleared even if the fault condition

exists, but the ALERT output reasserts at the end of the

next conversion. The bits indicating the fault for the

OVERT interrupt output clear only on reading the Status

2 register even if the fault conditions still exist. Reading

the Status 2 register does not clear the OVERT interrupt

output. To eliminate the fault condition, either the mea-

sured temperature must drop below the temperature

threshold minus the hysteresis value (4°C), or the trip

temperature must be set at least 4°C above the current

temperature.

Applications Information

Remote-Diode Selection

The MAX6699 directly measures the die temperature of

CPUs and other ICs that have on-chip temperature-

sensing diodes (see the Typical Application Circuit), or

it can measure the temperature of a discrete diode-

connected transistor.

Effect of Ideality Factor

The accuracy of the remote temperature measurements

depends on the ideality factor (n) of the remote diode

(actually a transistor). The MAX6699 is optimized for

n = 1.008. A thermal diode on the substrate of an IC is

normally a pnp with the base and emitter brought out

the collector (diode connection) grounded. DXP_ must

be connected to the anode (emitter), 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 is different from the data

obtained with the optimum ideality factor. Fortunately,

the difference is predictable. Assume a remote-diode

5-Channel Precision Temperature Monitor

12 ______________________________________________________________________________________

BIT NAME POR

STATE FUNCTION

7(MSB) STOP 0 Standby Mode Control Bit. If STOP is set to logic 1, the MAX6699 stops

converting and enters standby mode.

6POR0

Reset Bit. Set to logic 1 to put the device into its power-on state. This bit is self-

clearing.

5TIMEOUT 0 Timeout Enable Bit. Set to logic 0 to enable SMBus timeout.

4 Fast remote 1 0 Channel 1 Fast Conversion Bit. Set to logic 1 to enable fast conversion of

channel 1.

3Resistance

cancellation 0Resistance Cancellation Bit. When set to logic 1, the MAX6699 cancels series

resistance in the channel 1 thermal diode.

2 Reserved 0 —

1 Reserved 0 —

0 Reserved 0 —

Table 4. Configuration 1 Register

Table 5. Configuration 2 Register

BIT NAME POR

STATE FUNCTION

7(MSB) Reserved 0

6

Mask Local ALERT

0 Local Alert Mask. Set to logic 1 to mask local channel ALERT.

5 Reserved 0 —

4 Reserved 0 —

3 Mask ALERT 4 0 Channel 4 Alert Mask. Set to logic 1 to mask channel 4 ALERT.

2 Mask ALERT 3 0 Channel 3 Alert Interrupt Mask. Set to logic 1 to mask channel 3 ALERT.

1 Mask ALERT 2 0 Channel 2 Alert Mask. Set to logic 1 to mask channel 2 ALERT.

0 Mask ALERT 1 0 Channel 1 Alert Mask. Set to logic 1 to mask channel 1 ALERT.

sensor designed for a nominal ideality factor nNOMINAL

is used to measure the temperature of a diode with a

different ideality factor n1. The measured temperature

TMcan be corrected using:

where temperature is measured in Kelvin and

nNOMIMAL for the MAX6699 is 1.008. As an example,

assume you want to use the MAX6699 with a CPU that

has an ideality factor of 1.002. If the diode has no

series resistance, the measured data is related to the

real temperature as follows:

For a real temperature of +85°C (358.15K), the mea-

sured temperature is +82.87°C (356.02K), an error of

-2.13°C.

Series Resistance Cancellation

Some thermal diodes on high-power ICs can have

excessive series resistance, which can cause tempera-

ture-measurement errors with conventional remote tem-

perature sensors. Channel 1 of the MAX6699 has a

series resistance cancellation feature (enabled by bit 3

of the Configuration 1 register) that eliminates the effect

of diode series resistance. Set bit 3 to 1 if the series

resistance is large enough to affect the accuracy of

channel 1. The series resistance cancellation function

increases the conversion time for channel 1 by 125ms.

This feature cancels the bulk resistance of the sensor

and any other resistance in series (wire, contact resis-

tance, etc.). The cancellation range is from 0 to 100Ω.

Discrete Remote Diodes

When the remote-sensing diode is a discrete transistor,

its collector and base must be connected together.

Table 10 lists examples of discrete transistors that are

appropriate for use with the MAX6699. 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, and at

the lowest expected temperature, the forward voltage

must be less than 0.95V at 100µA. Large power transis-

tors must not be used. Also, ensure that the base resis-

tance is less than 100Ω. Tight specifications for forward

current gain (50 < ß <150, for example) 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 is normally not

a problem since good-quality discrete transistors tend to

have ideality factors that fall within a relatively narrow

range. A variety of discrete transistors have variations in

remote temperature readings of less than ±2°C. Still, it is

good design practice to verify good consistency of tem-

perature readings with several discrete transistors from

any manufacturer under consideration.

TT

n

nTT

ACTUAL M NOMINAL MM

=×

⎛

⎝

⎜

⎞

⎠

⎟=×

⎛

⎝

⎜⎞

⎠

⎟=

1

1 008

1 002 1 00599

.

.(. )

TT n

n

M ACTUAL NOMINAL

=⎛

⎝

⎜

⎞

⎠

⎟

1

MAX6699

5-Channel Precision Temperature Monitor

______________________________________________________________________________________ 13

Table 6. Configuration 3 Register

BIT NAME POR

STATE FUNCTION

7(MSB) Reserved 0 —

6 Reserved 0 —

5 Reserved — —

4 Reserved — —

3 Mask OVERT 4 0 Channel 4 Remote-Diode OVERT Mask Bit. Set to logic 1 to mask channel 4

OVERT.

2 Reserved 0 —

1 Reserved 0 —

0 Mask OVERT 1 0 Channel 1 Remote-Diode OVERT Mask Bit. Set to logic 1 to mask channel 1

OVERT.

MAX6699

Unused Diode Channels

If one or more of the remote diode channels is not

needed, the DXP and DXN inputs for that channel

should either be unconnected, or the DXP input should

be connected to VCC. 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 Configuration 2 and Configuration 3 regis-

ters. This will prevent unused channels from causing

ALERT# or OVERT# to assert.

Thermal Mass and Self-Heating

When sensing local temperature, the MAX6699 mea-

sures the temperature of the printed-circuit board

(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 compar-

ison, making air temperature measurements impracti-

cal. Because the thermal mass of the PCB is far greater

than that of the MAX6699, the device follows tempera-

ture changes on the PCB with little or no perceivable

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 conver-

sion 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 significantly affect measurement accuracy.

Remote-sensor self-heating due to the diode current

source is negligible.

5-Channel Precision Temperature Monitor

14 ______________________________________________________________________________________

Table 7. Status 1 Register

BIT NAME POR

STATE FUNCTION

7(MSB) Reserved 0 —

6 Local ALERT 0

Local Channel High-Alert Bit. This bit is set to logic 1 when the local

temperature exceeds the temperature threshold limit in the local ALERT high-

limit register.

5 Reserved — —

4 Reserved — —

3 Remote 4 ALERT 0

Channel 4 Remote-Diode High-Alert Bit. This bit is set to logic 1 when the

channel 4 remote-diode temperature exceeds the temperature threshold limit

in the remote 4 ALERT high-limit register.

2 Remote 3 ALERT 0

Channel 3 Remote-Diode High-Alert Bit. This bit is set to logic 1 when the

channel 3 remote-diode temperature exceeds the programmed temperature

threshold limit in the remote 3 ALERT high-limit register.

1 Remote 2 ALERT 0

Channel 2 Remote-Diode High-Alert Bit. This bit is set to logic 1 when the

channel 2 remote-diode temperature exceeds the temperature threshold limit

in the remote 2 ALERT high-limit register.

0 Remote 1 ALERT 0

Channel 1 Remote-Diode High-Alert Bit. This bit is set to logic 1 when the

channel 1 remote-diode temperature exceeds the temperature threshold limit

in the remote 1 ALERT high-limit register.

MAX6699

5-Channel Precision Temperature Monitor

______________________________________________________________________________________ 15

BIT NAME POR

STATE FUNCTION

7(MSB) Reserved 0 —

6 Reserved 0 —

5 Reserved — —

4 Reserved — —

3 Remote 4 OVERT 0

Channel 4 Remote Diode Overtemperature Status Bit. This bit is set to logic 1

when the channel 4 remote-diode temperature exceeds the temperature

threshold limit in the remote 4 OVERT high-limit register.

2 Reserved 0 —

1 Reserved 0 —

0 Remote 1 OVERT 0

Channel 1 Remote-Diode Overtemperature Status Bit. This bit is set to logic 1

when the channel 1 remote-diode temperature exceeds the temperature

threshold limit in the remote 1 OVERT high-limit register.

Table 8. Status 2 Register

BIT NAME POR

STATE FUNCTION

7(MSB) Reserved 0 —

6 Reserved 0 Not Used. 0 at POR, then 1.

5 Reserved 0 Not Used. 0 at POR, then 1.

4 Diode fault 4 0 Channel 4 Remote-Diode Fault Bit. This bit is set to 1 when DXP4 and DXN4

are open circuit or when DXP4 is connected to VCC.

3 Diode fault 3 0 Channel 3 Remote-Diode Fault Bit. This bit is set to 1 when DXP3 and DXN3

are open circuit or when DXP3 is connected to VCC.

2 Diode fault 2 0 Channel 2 Remote-Diode Fault Bit. This bit is set to 1 when DXP2 and DXN2

are open circuit or when DXP2 is connected to VCC.

1 Diode fault 1 0 Channel 1 Remote-Diode Fault Bit. This bit is set to 1 when DXP1 and DXN1

are open circuit or when DXP1 is connected to VCC.

0 Reserved 0 —

Table 9. Status 3 Register

MAX6699

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 2200pF capacitor between DXP_ and

DXN_. Larger capacitor values can be used for added

filtering, but do not exceed 3300pF because it can

introduce errors due to the rise time of the switched

current source. High-frequency noise reduction is

needed for high-accuracy remote measurements.

Noise can be reduced with careful PCB layout as dis-

cussed in the PCB Layout section.

Slave Address

Table 11 shows the MAX6699 slave address.

PCB Layout

Follow these guidelines to reduce the measurement

error when measuring remote temperature:

1) Place the MAX6699 as close as is practical to the

remote diode. In noisy environments, such as a

computer motherboard, this distance can be 4in to

8in (typ). This length can be increased if the worst

noise sources are avoided. Noise sources include

CRTs, clock generators, memory buses, and PCI

buses.

2) Do not route the DXP-DXN lines next to the deflec-

tion coils of a CRT. Also, do not route the traces

across fast digital signals, which can easily intro-

duce +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

traces should go to a remote 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 20MΩleakage

path from DXP to ground causes about +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.

5) Use wide traces when practical.

6) When the power supply is noisy, add a resistor (up

to 47Ω) in series with VCC.

Twisted-Pair and Shielded Cables

Use a twisted-pair cable to connect the remote sensor

for remote-sensor distances longer than 8in or in very

noisy environments. Twisted-pair cable lengths can be

between 6ft and 12ft before noise introduces excessive

errors. For longer distances, the best solution is a

shielded twisted pair like that used for audio micro-

phones. For example, Belden #8451 works well for dis-

tances up to 100ft in a noisy environment. At the

device, connect the twisted pair to DXP and DXN and

the shield to GND. Leave the shield unconnected at the

5-Channel Precision Temperature Monitor

16 ______________________________________________________________________________________

;;@@

5 mils

;;@@

5 mils

;;@@

5 mils

MINIMUM

5 mils

GND

DXP

DXN

GND

Figure 5. Recommended Minimum DXP-DXN PCB Traces

MANUFACTURER MODEL NO.

Central Semiconductor (USA) CMPT3904

Rohm Semiconductor (USA) SST3904

Samsung (Korea) KST3904-TF

Siemens (Germany) SMBT3904

Zetex (England) FMMT3904CT-ND

Table 10. Remote-Sensors Transistor

Manufacturers

Note: Discrete transistors must be diode connected (base

shorted to collector).

PART

SMBus SLAVE ID

PIN-PACKAGE

MAX6699EE34

0011 010 16 QSOP

MAX6699EE38

0011 100 16 QSOP

MAX6699EE99

1001 100 16 QSOP

MAX6699EE9C

1001 110 16 QSOP

MAX6699UE34

0011 010 16 TSSOP

MAX6699UE38

0011 100 16 TSSOP

MAX6699UE99

1001 100 16 TSSOP

MAX6699UE9C

1001 110 16 TSSOP

Table 11. Slave Address

remote sensor. For very long cable runs, the cable’s

parasitic capacitance often provides noise filtering, so

the 2200pF capacitor can often be removed or reduced

in value. Cable resistance also affects remote-sensor

accuracy. For every 1Ωof series resistance, the error is

approximately +1/2°C.

Chip Information

PROCESS: BiCMOS

MAX6699

5-Channel Precision Temperature Monitor

______________________________________________________________________________________ 17

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

GND

SMBCLK

SMBDATA

DXN2

DXP2

DXN1

DXP1

TOP VIEW

VCC

N.C.1

N.C.2DXN4

DXP4

DXN3

DXP3 MAX6699

QSOP/TSSOP

ALERT

OVERT

Pin Configuration

MAX6699

5-Channel Precision Temperature Monitor

18 ______________________________________________________________________________________

Package Information

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,

go to www.maxim-ic.com/packages.)

QSOP.EPS

F

11

21-0055

PACKAGE OUTLINE, QSOP .150", .025" LEAD PITCH

MAX6699

5-Channel Precision Temperature Monitor

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 19

Package Information (continued)

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,

go to www.maxim-ic.com/packages.)

TSSOP4.40mm.EPS

PACKAGE OUTLINE, TSSOP 4.40mm BODY

21-0066

1

I

_____________________Revision History

Pages changed at Rev 2: 1, 3, 5, 6, 8, 9, 11, 14, 15,

16, 19