Detailed Description

The MAX6657/MAX6658/MAX6659 are temperature

sensors designed to work in conjunction with a micro-

processor or other intelligence in thermostatic,

process-control, or monitoring applications. Com-

munication with the MAX6657/MAX6658/MAX6659

occurs through the SMBus serial interface and dedicat-

ed alert pins. Two independent overtemperature alarms

(OVERT1 and OVERT2) are asserted if their software

programmed temperature thresholds are exceeded.

OVERT1 and OVERT2 can be connected to fans, a sys-

tem shutdown, or other thermal management circuitry.

The MAX6657/MAX6658/MAX6659 convert tempera-

tures to digital data either at a programmed rate or a

single conversion. Conversions have a 0.125°C resolu-

tion (extended resolution) or 1°C resolution (legacy res-

olution). Extended resolution represents temperature as

10 bits + sign bit and is available for autonomous con-

versions that are 4Hz and slower and single-shot con-

versions. Legacy resolution represents temperature as

7 bits + sign bit and allows for faster autonomous con-

version rates of 8Hz and 16Hz.

ADC and Multiplexer

The averaging ADC integrates over a 60ms period

(each channel, typically, in the 7-bit + sign legacy

mode). Using an averaging ADC attains excellent noise

rejection.

The multiplexer automatically steers bias currents

through the remote and local diodes. The ADC and

associated circuitry measure each diode’s forward volt-

age and compute the temperature based on this volt-

age. If the remote channel is not used, connect DXP to

DXN. Do not leave DXP and DXN unconnected. When a

conversion is initiated, both channels are converted

6

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MUX

REMOTE

LOCAL

ADC

2

CONTROL

LOGIC

SMBus

READ

WRITE

8

8

ADDRESS

DECODER

7

S

R

Q

S

R

Q

S

R

Q

DIODE

FAULT

DXP

DXN

(ADD)

SMBCLK

SMBDATA

REGISTER BANK

COMMAND BYTE

REMOTE TEMPERATURE

LOCAL TEMPERATURE

ALERT THRESHOLD

ALERT RESPONSE

ADDRESS

OVERT1 THRESHOLD

(OVERT2 THRESHOLD)

( ) ARE FOR MAX6659 ONLY

MAX6659 ONLY

MAX6657

MAX6658

MAX6659

(STBY)

ALERT

OVERT1

(OVERT2)

Functional Diagram

±1°C, SMBus-Compatible Remote/Local Temperature

Sensors with Overtemperature Alarms