Datasheet

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General Description

The MAX6642 precise, two-channel digital temperature

sensor accurately measures the temperature of its own

die and a remote PN junction and reports the tempera-

ture data over a 2-wire serial interface. The remote PN

junction is typically a substrate PNP transistor on the

die of a CPU, ASIC, GPU, or FPGA. The remote PN

junction can also be a discrete diode-connected small-

signal transistor.

The 2-wire serial interface accepts standard system

management bus (SMBus™), Write Byte, Read Byte,

Send Byte, and Receive Byte commands to read the

temperature data and to program the alarm thresholds.

To enhance system reliability, the MAX6642 includes an

SMBus timeout. The temperature data format is 10 bit

with the least significant bit (LSB) corresponding to

+0.25°C. The ALERT output asserts when the local or

remote overtemperature thresholds are violated. A fault

queue may be used to prevent the ALERT output from

setting until two consecutive faults have been detected.

Measurements can be done autonomously or in a sin-

gle-shot mode.

Remote accuracy is ±1°C maximum error between

+60°C and +100°C. The MAX6642 operates from -40°C

to +125°C, and measures remote temperatures

between 0°C and +150°C. The MAX6642 is available in

a 6-pin TDFN package with an exposed pad.

Applications

Desktop Computers

Notebook Computers

Servers

Thin Clients

Test and Measurement

Workstations

Graphic Cards

Features

o Dual Channel: Measures Remote and Local

Temperature

o +0.25°C Resolution

o High Accuracy ±1°C (max) (Remote) and

±2°C (Local) from +60°C to +100°C

o Measures Remote Temperature Up to +150°C

o Programmable Overtemperature Alarm

Temperature Thresholds

o SMBus/I

C-Compatible Interface

o Tiny TDFN Package with Exposed Pad

MAX6642

±1°C, SMBus-Compatible Remote/Local

Temperature Sensor with Overtemperature Alarm

________________________________________________________________

Maxim Integrated Products

Ordering Information

19-2920; Rev 3; 10/09

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.

EVALUATION KIT

AVAILABLE

PART TEMP RANGE PIN-PACKAGE

MAX6642ATT90-T -40°C to +125°C 6 TDFN-EP*

MAX6642ATT92-T -40°C to +125°C 6 TDFN-EP*

MAX6642ATT94-T -40°C to +125°C 6 TDFN-EP*

MAX6642ATT96-T -40°C to +125°C 6 TDFN-EP*

MAX6642ATT98-T -40°C to +125°C 6 TDFN-EP*

MAX6642ATT9A-T -40°C to +125°C 6 TDFN-EP*

MAX6642ATT9C-T -40°C to +125°C 6 TDFN-EP*

MAX6642ATT9E-T -40°C to +125°C 6 TDFN-EP*

MAX6642

2200pF

0.1μF

μP

DXP

GND

SDA

SCLK

ALERT

DATA

CLOCK

INTERRUPT TO μP

47Ω

10kΩ EACH

3.3V

Typical Operating Circuit

PART

MEASURED TEMP RANGE

TOP

MARK

MAX6642ATT90-T 0°C to +150°C

AFC

MAX6642ATT92-T 0°C to +150°C

AFD

MAX6642ATT94-T 0°C to +150°C

AFE

MAX6642ATT96-T 0°C to +150°C

AFF

MAX6642ATT98-T 0°C to +150°C

AEW

MAX6642ATT9A-T 0°C to +150°C

AFG

MAX6642ATT9C-T 0°C to +150°C

AFH

MAX6642ATT9E-T 0°C to +150°C AFI

Selector Guide

T = Tape and reel.

EP = Exposed pad.

Pin Configuration and Functional Diagram appear at end of

data sheet.

SMBus is a trademark of Intel Corp.

Summary of content (14 pages)

PAGE 1
9-2920; Rev 3; 10/09 KIT ATION EVALU E L B AVAILA ±1°C, SMBus-Compatible Remote/Local Temperature Sensor with Overtemperature Alarm The MAX6642 precise, two-channel digital temperature sensor accurately measures the temperature of its own die and a remote PN junction and reports the temperature data over a 2-wire serial interface. The remote PN junction is typically a substrate PNP transistor on the die of a CPU, ASIC, GPU, or FPGA.
PAGE 2
MAX6642 ±1°C, SMBus-Compatible Remote/Local Temperature Sensor with Overtemperature Alarm ABSOLUTE MAXIMUM RATINGS All Voltages Referenced to GND VCC ...........................................................................-0.3V to +6V DXP.............................................................-0.3V to (VCC + 0.3V) SCLK, SDA, ALERT ..................................................-0.3V to +6V SDA, ALERT Current ...........................................
PAGE 3
±1°C, SMBus-Compatible Remote/Local Temperature Sensor with Overtemperature Alarm (VCC = +3.0V to +5.5V, TA = -40°C to +125°C, unless otherwise specified. Typical values are at VCC = +3.3V and TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 0.8 V +1 µA SMBus-COMPATIBLE INTERFACE (SCLK and SDA) Logic Input Low Voltage VIL Logic Input High Voltage VIH Input Leakage Current ILEAK Output Low Sink Current IOL Input Capacitance CIN VCC = 3.0V 2.2 VIN = GND or 5.
PAGE 4
Typical Operating Characteristics (VCC = 3.3V, TA = +25°C, unless otherwise noted.) STANDBY SUPPLY CURRENT vs. CLOCK FREQUENCY 4.0 3.5 3.0 2.5 2.0 1 0.1 1 10 0 100 100 125 TEMPERATURE ERROR vs. POWER-SUPPLY NOISE FREQUENCY TEMPERATURE ERROR (°C) 1.5 -1 -2 25 50 75 100 REMOTE ERROR 1.0 LOCAL ERROR 0.5 0 -0.5 -1.0 -3 VIN = 100mVP-P SQUARE WAVE APPLIED TO VCC WITH NO BYPASS CAPACITOR -1.5 0.0001 0.001 125 MAX6642 toc04 2.0 MAX 6642 toc03 0 0.01 0.
PAGE 5
±1°C, SMBus-Compatible Remote/Local Temperature Sensor with Overtemperature Alarm PIN NAME FUNCTION Supply Voltage Input, +3V to +5.5V. Bypass VCC to GND with a 0.1µF capacitor. A 47Ω series resistor is recommended but not required for additional noise filtering. 1 VCC 2 GND Ground 3 DXP Combined Remote-Diode Current Source and ADC Input for Remote-Diode Channel. Place a 2200pF capacitor between DXP and GND for noise filtering. 4 SCLK SMBus Serial-Clock Input. May be pulled up to +5.
PAGE 6
MAX6642 ±1°C, SMBus-Compatible Remote/Local Temperature Sensor with Overtemperature Alarm WRITE BYTE FORMAT S ADDRESS WR ACK COMMAND 7 BITS ACK DATA 8 BITS ACK P 8 BITS SLAVE ADDRESS: EQUIVALENT TO CHIP-SELECT LINE OF A 3-WIRE INTERFACE 1 DATA BYTE: DATA GOES INTO THE REGISTER SET BY THE COMMAND BYTE (TO SET THRESHOLDS, CONFIGURATION MASKS, AND SAMPLING RATE) READ BYTE FORMAT S ADDRESS WR ACK COMMAND 7 BITS ACK S SLAVE ADDRESS: EQUIVALENT TO CHIP SELECT LINE ADDRESS RD ACK DATA
PAGE 7
±1°C, SMBus-Compatible Remote/Local Temperature Sensor with Overtemperature Alarm register was previously selected by a Write Byte instruction. Use caution when using the shorter protocols in multimaster systems, as a second master could overwrite the command byte without informing the first master. Read temperature data from the read internal temperature (00h) and read external temperature (01h) registers.
PAGE 8
MAX6642 ±1°C, SMBus-Compatible Remote/Local Temperature Sensor with Overtemperature Alarm Table 3.
PAGE 9
±1°C, SMBus-Compatible Remote/Local Temperature Sensor with Overtemperature Alarm Command Byte Functions The 8-bit command byte register (Table 3) is the master index that points to the various other registers within the MAX6642. The register’s POR state is 0000 0000, so a Receive Byte transmission (a protocol that lacks the command byte) that occurs immediately after POR returns the current local temperature data.
PAGE 10
MAX6642 ±1°C, SMBus-Compatible Remote/Local Temperature Sensor with Overtemperature Alarm III. A thermal diode on the substrate of an IC is normally a PNP with its collector grounded. Connect the anode (emitter) to DXP and the cathode to GND of the MAX6642. 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.
PAGE 11
±1°C, SMBus-Compatible Remote/Local Temperature Sensor with Overtemperature Alarm ADC Noise Filtering The integrating ADC used has good noise rejection for low-frequency signals such as 60Hz/120Hz power-supply hum. In noisy environments, high-frequency noise reduction is needed for high-accuracy remote measurements. The noise can be reduced with careful PCB layout and proper external noise filtering. High-frequency EMI is best filtered at DXP with an external 2200pF capacitor.
PAGE 12
MAX6642 ±1°C, SMBus-Compatible Remote/Local Temperature Sensor with Overtemperature Alarm Cable resistance also affects remote-sensor accuracy. For every 1Ω of series resistance, the error is approximately 1/2°C. Thermal Mass and Self-Heating When sensing local temperature, this device is intended to measure the temperature of the PCB to which it is soldered. The leads provide a good thermal path between the PCB traces and the die.
PAGE 13
±1°C, SMBus-Compatible Remote/Local Temperature Sensor with Overtemperature Alarm VCC 2 MUX REMOTE DXP CONTROL LOGIC ADC LOCAL DIODE FAULT SMBus 8 ALERT S 8 Q R SDA READ SCLK WRITE REGISTER BANK COMMAND BYTE 7 REMOTE TEMPERATURE MAX6642 LOCAL TEMPERATURE ALERT THRESHOLD ADDRESS DECODER ALERT RESPONSE ADDRESS Pin Configuration Chip Information PROCESS: BiCMOS TOP VIEW MAX6642 Package Information VCC 1 6 ALERT GND 2 5 SDA DXP 3 4 SCLK EP* For the latest package outline inf
PAGE 14
MAX6642 ±1°C, SMBus-Compatible Remote/Local Temperature Sensor with Overtemperature Alarm Revision History PAGES CHANGED REVISION NUMBER REVISION DATE 0 8/03 Initial release 1 10/08 Added missing EP description to Ordering Information and Pin Description, removed the transistor count on page 12, and corrected some minor style issues 2 7/09 Corrected errors in Figures 2 and 3 6, 7 3 10/09 Corrected error in Package Information table 13 DESCRIPTION — 1, 5, 9, 10, 12 Maxim cannot assume res