Datasheet

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General Description

The MAX6646/MAX6647/MAX6649 are precise, two-

channel digital temperature sensors. The devices accu-

rately measure the temperature of their own die and a

remote PN junction, and report the temperature in digital

form using a 2-wire serial interface. The remote PN junc-

tion is typically the emitter-base junction of a common-

collector PNP on a CPU, FPGA, or ASIC.

The 2-wire serial interface accepts standard system man-

agement 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 MAX6646/MAX6647/MAX6649

include an SMBus timeout. A fault queue prevents the

ALERT and OVERT outputs from setting until a fault has

been detected one, two, or three consecutive times

(programmable).

The MAX6646/MAX6647/MAX6649 provide two system

alarms: ALERT and OVERT. ALERT asserts when any of

four temperature conditions are violated: local overtem-

perature, remote overtemperature, local undertempera-

ture, or remote undertemperature. OVERT asserts when

the temperature rises above the value in either of the two

OVERT limit registers. The OVERT output can be used to

activate a cooling fan, or to trigger a system shutdown.

Measurements can be done autonomously, at the pro-

grammed conversion rate, or in a single-shot mode. The

adjustable conversion rate allows optimizing supply cur-

rent and temperature update rate to match system needs.

Remote accuracy is ±1°C maximum error between +60°C

and +145°C with no calibration needed. The MAX6646/

MAX6647/MAX6649 operate from -55°C to +125°C, and

measure temperatures between 0°C and +145°C. The

MAX6646/MAX6647/MAX6649 are available in an 8-pin

μMAX

package.

Applications

Features

♦ Dual Channel: Measures Remote and Local

Temperature

♦ 0.125°C Resolution

♦ High Accuracy ±1°C (max) from +60°C to +145°C

(Remote), and ±2°C (max) from +60°C to +100°C

(Local)

♦ Measures High-Ideality Thermal Diodes Up to

+170°C (Apparent)

+145°C (Real)

♦ Two Alarm Outputs: ALERT and OVERT

♦ Programmable Under/Overtemperature Alarm

Temperature Thresholds

♦ Programmable Conversion Rate

♦ SMBus-Compatible Interface

♦ SMBus Timeout

MAX6646/MAX6647/MAX6649

+145°C Precision SMBus-Compatible Remote/

Local Sensors with Overtemperature Alarms

Ordering Information

DXP

DXN

10kΩ EACH

CLOCK

TO FAN DRIVER OR

SYSTEM SHUTDOWN

3.3V

DATA

INTERRUPT TO μP

200Ω

0.1μF

SDA

SCLK

ALERT

GND

2200pF

μP

MAX6646

MAX6647

MAX6649

OVERT

Typical Operating Circuit

19-2540; Rev 4; 7/12

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

MEASURED

TEMP RANGE

MAX6646MUA+

-55°C to

+125°C

8 μMAX 0°C to +145°C

MAX6647MUA+

-55°C to

+125°C

8 μMAX 0°C to +145°C

MAX6649MUA+

-55°C to

+125°C

8 μMAX 0°C to +145°C

Selector Guide, Pin Configurations, and Functional Diagram

appear at end of data sheet.

Denotes a lead(Pb)-free/RoHS-compliant package.

μMAX is a registered trademark of Maxim Integrated Products, Inc.

Graphics Processors

Desktop Computers

Notebook Computers

Servers

Thin Clients

Workstations

Test and Measurement

Multichip Modules

Summary of content (16 pages)

PAGE 1
9-2540; Rev 4; 7/12 +145°C Precision SMBus-Compatible Remote/ Local Sensors with Overtemperature Alarms Features The MAX6646/MAX6647/MAX6649 are precise, twochannel digital temperature sensors. The devices accurately measure the temperature of their own die and a remote PN junction, and report the temperature in digital form using a 2-wire serial interface. The remote PN junction is typically the emitter-base junction of a commoncollector PNP on a CPU, FPGA, or ASIC.
PAGE 2
MAX6646/MAX6647/MAX6649 +145°C Precision SMBus-Compatible Remote/ Local Sensors with Overtemperature Alarms ABSOLUTE MAXIMUM RATINGS ESD Protection (all pins, Human Body Model) ................±2000V Junction Temperature ......................................................+150°C Operating Temperature Range .........................-55°C to +125°C Storage Temperature Range .............................-65°C to +150°C Soldering Temperature (reflow) .......................................
PAGE 3
+145°C Precision SMBus-Compatible Remote/ Local Sensors with Overtemperature Alarms (VCC = 3.0V to 5.5V, TA = -55°C to +125°C, unless otherwise specified. Typical values are at VCC = 3.3V and TA = +100°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS ALERT, OVERT Output Low Voltage Output High Leakage Current I SINK = 1mA 0.4 I SINK = 4mA 0.6 VOH = 5.5V 1 μA 0.8 V V SMBus-COMPATIBLE INTERFACE (SCLK AND SDA) Logic Input Low Voltage Logic Input High Voltage VIL VIH VCC = 3.0V 2.
PAGE 4
Typical Operating Characteristics (VCC = 3.3V, TA = +25°C, unless otherwise noted.) 4.0 3.5 3.0 1.5 TEMPERATURE ERROR (°C) OPERATING SUPPLY CURRENT (μA) 4.5 2.0 MAX6649 toc02 400 MAX6649 toc01 300 200 100 1.0 0.5 0 -0.5 -1.0 TA = +85°C FAIRCHILD 2N3906 -1.5 2.5 -2.0 0 3.5 4.0 4.5 5.5 5.0 0.63 0.13 0.25 0.50 1.00 50 75 100 125 CONVERSION RATE (Hz) TEMPERATURE (°C) LOCAL TEMPERATURE ERROR vs. DIE TEMPERATURE TEMPERATURE ERROR vs.
PAGE 5
+145°C Precision SMBus-Compatible Remote/ Local Sensors with Overtemperature Alarms PIN NAME 1 VCC Supply Voltage Input, 3V to 5.5V. Bypass VCC to GND with a 0.1μF capacitor. A 200 series resistor is recommended but not required for additional noise filtering. 2 DXP Combined Remote-Diode Current Source and A/D Positive Input for Remote-Diode Channel. DO NOT LEAVE DXP UNCONNECTED; connect DXP to DXN if no remote diode is used. Place a 2200pF capacitor between DXP and DXN for noise filtering.
PAGE 6
MAX6646/MAX6647/MAX6649 +145°C Precision SMBus-Compatible Remote/ Local Sensors with Overtemperature Alarms The DXP-DXN differential input voltage range is 0.25V to 0.95V. Excess resistance in series with the remote diode causes +0.5°C (typ) error per ohm. Remote Temperature Measurement Range The MAX6646/MAX6647/MAX6649 measure remote temperatures significantly above the +120°C limit of many temperature sensors.
PAGE 7
+145°C Precision SMBus-Compatible Remote/ Local Sensors with Overtemperature Alarms MAX6646/MAX6647/MAX6649 Write Byte Format S ADDRESS WR ACK COMMAND 7 bits ACK DATA 8 bits Slave Address: equivalent to chip-select line of a 3-wire interface ACK P 8 bits Command Byte: selects which register you are writing to 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
PAGE 8
MAX6646/MAX6647/MAX6649 +145°C Precision SMBus-Compatible Remote/ Local Sensors with Overtemperature Alarms A tLOW B tHIGH C D E F G H I J K L M SMBCLK SMBDATA tSU:STA tHD:STA tSU:DAT 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 tHD:DAT 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
PAGE 9
+145°C Precision SMBus-Compatible Remote/ Local Sensors with Overtemperature Alarms BIT 7 6 to 3 NAME RFU RFU POR STATE FUNCTION 1 Reserved. Always write 1 to this bit. 0 Reserved. Always write zero to this bit. 2 FQ1 1 Fault queue-length control bit (see Table 4). 1 FQ0 1 Fault queue-length control bit (see Table 4). 0 RFU 0 Reserved. Always write zero to this bit. The alert response can activate several different slave devices simultaneously, similar to the I2C general call.
PAGE 10
MAX6646/MAX6647/MAX6649 +145°C Precision SMBus-Compatible Remote/ Local Sensors with Overtemperature Alarms Table 5.
PAGE 11
+145°C Precision SMBus-Compatible Remote/ Local Sensors with Overtemperature Alarms BIT NAME POR STATE 7 (MSB) BUSY 0 A/D is busy converting when 1. FUNCTION 6 LHIGH 0 Local (internal) high-temperature alarm has tripped when 1; cleared by POR or readout of the status byte if the fault condition no longer exists. 5 LLOW 0 Local (internal) low-temperature alarm has tripped when 1; cleared by POR or readout of the status byte if the fault condition no longer exists.
PAGE 12
MAX6646/MAX6647/MAX6649 +145°C Precision SMBus-Compatible Remote/ Local Sensors with Overtemperature Alarms Applications Information μV Ω = 0. 453 °C μV Ω 198. 6 °C 90 Remote-Diode Selection The MAX6646/MAX6647/MAX6649 can directly measure the die temperature of CPUs and other ICs that have on-board temperature-sensing diodes (see Typical Operating Circuit ), or they can measure the temperature of a discrete diode-connected transistor.
PAGE 13
+145°C Precision SMBus-Compatible Remote/ Local Sensors with Overtemperature Alarms 10 MILS 10 MILS DXP MINIMUM 10 MILS DXN 10 MILS GND Figure 4. Recommended DXP-DXN PC Traces 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 PC board layout and proper external noise filtering.
PAGE 14
MAX6646/MAX6647/MAX6649 +145°C Precision SMBus-Compatible Remote/ Local Sensors with Overtemperature Alarms When measuring the temperature of a CPU or other IC with an on-chip sense junction, thermal mass has virtually no effect; the measured temperature of the junction tracks the actual temperature within a conversion cycle. When measuring temperature with discrete remote sensors, smaller packages, such as SC70s or SOT23s, yield the best thermal response times.
PAGE 15
+145°C Precision SMBus-Compatible Remote/ Local Sensors with Overtemperature Alarms POR VALUES ALERT ASSERTED WHILE DIODE OPEN PART ADDRESS EXTERNAL OVERT LIMIT (°C) EXTERNAL ALERT THIGH LIMIT (°C) MAX6646 1001 101 +125 +95 MAX6647 1001 110 +125 +95 No MAX6649 1001 100 +85 +85 Yes No Pin Configuration Chip Information PROCESS: BiCMOS TOP VIEW Package Information VCC 1 DXP 2 DXN 3 OVERT 4 + MAX6646 MAX6647 MAX6649 μMAX 8 SCLK 7 SDA 6 ALERT 5 GND For the latest packag
PAGE 16
MAX6646/MAX6647/MAX6649 +145°C Precision SMBus-Compatible Remote/ Local Sensors with Overtemperature Alarms Revision History REVISION NUMBER 4 REVISION DATE DESCRIPTION PAGES CHANGED 7/12 Updated the Ordering Information table to include lead-free packages; added the soldering temperature value to the Absolute Maximum Ratings section; added the Package Information table; updated the Electrical Characteristics table for the following: 1) Removed the START Condition Setup Time parameter 2) Changed tSU: