LM57 Temperature Switch
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.

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LM94021 Temperature Sensor
The LM94021 is a precision analog output CMOS integrated circuit temperature sensor that operates at a supply voltage as low as 1.5V. While operating over the wide temperature range of −50°C to +150°C, the LM94021 delivers an output voltage that is inversely proportional to measured temperature. The LM94021's low supply current makes it ideal for battery-powered systems as well as general temperature sensing applications. Two logic inputs, Gain Select 1 (GS1) and Gain Select 0 (GS0), select the gain of the temperature-to-voltage output transfer function. Four slopes are selectable: −5.5mV/°C, −8.2mV/°C, −10.9mV/°C, and −13.6mV/°C. In the lowest gain configuration (GS1 and GS0 both tied low), the LM94021 can operate with a 1.5V supply while measuring temperature over the full −50°C to +150°C operating range. Tying both inputs high causes the transfer function to have the largest gain of −13.6mV/°C for maximum temperature sensitivity. The gain-select inputs can be tied directly to VDD or Ground without any pull-up or pull-down resistors, reducing component count and board area. These inputs can also be driven by logic signals allowing the system to optimize the gain during operation or system diagnostics.

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