TI LM57 电阻可编程温度开关型模拟温度传感器参考设计方案

TI公司的LM57是一款集成模拟传感器的精确双路输出温度开关器件，温度阀值可通过两个外部1%精度电阻进行设置。LM57通过外部电阻设置可以实现256种不同温度阀值设置，同时内嵌等比例负温度系数传感器通过VTEMP引脚输出模拟量。本文首先介绍芯片的简介、特性、内部框图及应用领域，并给出相应设计方案的设计原理图、元器件列表及PCB元件布局图。
The LM57 is a precision, dual-output, temperature switch with integrated analog temperature sensor. The trip temperature (TTRIP) is programmable by using two external 1% resistors. Using extremely small packaged resistors (0.5 mm x 1 mm), the LM57 can be programmed to any of 256 trip temperatures while consuming very little board space. The VTEMP output delivers an analog output voltage which is proportional with a negative temperature coefficient (NTC) to the measured temperature.
Built-in temperature hysteresis (THYST) keeps the output stable in an environment of thermal oscillation. The digital temperature switch outputs will go active when the die temperature exceeds TTRIP and will release when the temperature falls below a temperature equal to TTRIP minus THYST. One of the digital outputs, TOVER, is active-high with a push-pull structure. The other digital output, TOVER, is active-low with an open-drain structure.
Driving the TRIP-TEST input high will make the digital outputs active. A processor can read the logic level of the temperature switch outputs, confirming that they changed to their active state. This allows for in-situ verification that the comparator and output circuitry are functional after system assembly. When the TRIP-TEST pin is high, the trip-level reference voltage appears at the Vtemp pin. The system could then use this voltage to calibrate the sensor for even tighter accuracy. Tying TOVER to TRIP-TEST will latch the output after it trips. It can be cleared by forcing TRIP-TEST low or powering off the LM57.
As it draws only 28µA max from its supply, it has very low self-heating, about ...