The LM57 device is a precision, dual-output, temperature switch with analog temperature sensor output for wide temperature industrial applications. The trip temperature (TTRIP) is selected from 256 possible values in the range of –40°C to +150°C. The VTEMP is a class AB analog voltage output that is proportional to temperature with a programmable negative temperature coefficient (NTC). Two external 1% resistors set the TTRIP and VTEMP slope. The digital and analog outputs enable protection and monitoring of system thermal events.
Built-in thermal hysteresis (THYST) prevents the digital outputs from oscillating. The TOVER and TOVER digital outputs will assert when the die temperature exceeds TTRIP and will de-assert when the temperature falls below a temperature equal to TTRIP minus THYST.
TOVER is active-high with a push-pull structure. TOVER is active-low with an open-drain structure. Tying TOVER to TRIP-TEST will latch the output after it trips. The output can be cleared by forcing TRIP-TEST low. Driving the TRIP-TEST high will assert the digital outputs. A processor can check the state of TOVER or TOVER, confirming they changed to an active state. This allows for in-situ verification that the comparator and output circuitry are functional after system assembly. When TRIP-TEST is high, the trip-level reference voltage appears at the VTEMP pin. The system could then use this voltage to calculate the threshold of the LM57.
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