Features • Trip temperature set by external resistors • External resistor tolerance contributes zero error • Push-pull and open-drain temperature switch outputs • Wide operating temperature and trip-temperature range of −50°C to 150°C • Very linear analog VTEMP temperature sensor output • Analog and digital outputs are short-circuit protected • TRIP-TEST pin allows in-system testing • Latching function for the digital outputs • Very small 2.5 mm by 2.5 mm 8-Pin LLP package Description 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 0.02°C in still air. Key Specification Supply voltage 2.4V to 5.5V Supply current 24 μA (typ) Temperature switch accuracy ±1.5°C Analog (VTEMP) Accuracy ±0.7°C Operating temperature −50°C to 150°C Hysteresis magnitude 5°C, 10°C Applications • Cell phones • Wireless transceivers • Digital cameras • Personal digital assistants (PDA's) • Battery management • Automotive • Disk drives • Games • Appliances

LM57 Typical Application MY BRIEFCASE                                       Click any "Briefcase" icon to add an item

Typical Application click for larger image LM57 Typical Application	Block Diagram click for larger image LM57 Block Diagram
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Datasheet

Title		Size	Date	Other Language
	LM57 Resistor-Programmable Temperature Switch and Analog Temperature Sensor	555 Kbytes	5-Oct-09

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