LM57

GND

TRIP TEST

TEMP SENSOR

(negative temp

coefficient)

+

-

TRIP

TEST = 1

TRIP

TEST = 0

SENSE1

SENSE2

DAC

GAIN

LM57-Q1

SNIS191A – JULY 2015 – REVISED JULY 2015

www.ti.com

7 Detailed Description

7.1 Overview

The LM57-Q1 is a precision, dual-output, temperature switch with analog temperature sensor output. The trip

analog output provides a voltage that is proportional to temperature. The LM57-Q1 includes an internal reference

DAC, analog temperature sensor and analog comparator. The reference DAC is connected to one of the

the SENSE pins. The resistance value sets one of 16 "logic" levels at the SENSE pins. These "logic" levels are

then decoded and applied to the DAC input, thus the actual resistance tolerance does not directly affect the

threshold level accuracy. The result of the reference DAC voltage and the temperature sensor output comparison

The gain setting is dependent on the trip point selected by resistance applied to the SENSE pins.

an open-drain structure. There are two different hysteresis options available that are factory preset. The preset

hysteresis can be selected by purchasing the proper order number as described in Device Comparison Table .

that the comparator and output circuitry are functional after system assembly. When the TRIP-TEST pin is high,

trips. It can be cleared by forcing TRIP-TEST low or powering off the LM57-Q1.

7.2 Functional Block Diagram

12

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