Detailed Description

The MAX6680/MAX6681 are temperature sensors designed

to work in conjunction with a microprocessor or other

intelligence in thermostatic, process-control, or monitoring

applications. Communication with the MAX6680/MAX6681

occurs through the SMBus serial interface and dedicated

alert pin. The overtemperature alarm

OVERT is asserted if

the software or hardware programmed temperature thresh-

olds are exceeded.

OVERT can be connected to a fan,

system shutdown, or other thermal management circuitry.

The MAX6680/MAX6681 convert temperatures at a pro-

grammed rate or a single conversion. Legacy mode

conversions have a 1°C resolution. Legacy resolution

represents temperature as 7 bits + sign bit and allows

for faster autonomous conversion rates at 8Hz. The

remote diode temperature can also be represented in

extended-resolution mode. Extended resolution repre-

sents temperature as 10 bits + sign bit and is available

for autonomous conversions that are 4Hz or slower and

single-shot conversions.

The MAX6680/MAX66681 default low-temperature mea-

surement limit is 0 °C. The device temperature measure-

ment can be placed in extended temperature range by

setting bit 3 of the Configuration register to 1. In extend-

ed temperature range, the remote and local temperature

measurement range is extended down to -64°C.

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-

±1°C Fail-Safe Remote/Local Temperature

Sensors with SMBus Interface

6

_______________________________________________________________________________________

RESET

CIRCUITRY

MUX

REMOTE

LOCAL

ADC

2

CONTROL

LOGIC

SMBus

READ

WRITE

8

8

ADDRESS

DECODER

7

S

R

Q

DIODE

FAULT

DXP

DXN

ADD0

SMBCLK

SMBDATA

ADD1

REGISTER BANK

COMMAND BYTE

REMOTE TEMPERATURE

LOCAL TEMPERATURE

ALERT THRESHOLD

ALERT RESPONSE ADDRESS

OVERT THRESHOLD (EXT)

OVERT THRESHOLD (INT)

CRIT0

CRIT1

INT_SEL

STBY

RESET

S

R

Q

OVERT

ALERT

SENS_SEL

MAX6680

MAX6681

Figure 1. MAX6680/MAX6681 Functional Diagram