The LM27 is a precision, single digital-output, low-powerthermostat comprised of an internal reference, DAC, temperaturesensor and comparator. Utilizing factory programming,it can be manufactured with different trip points as wellas different digital output functionality. The trip point (TOS)can be preset at the factory to any temperature in the rangeof +120°C to +150°C in 1°C increments. The LM27 has onedigital output (OS/OS/US/US), one digital input (HYST) andone analog output (VTEMP). The digital output stage can bepreset as either open-drain or push-pull. In addition, it can befactory programmed to be active HIGH or LOW. The digitaloutput can be factory programmed to indicate an over temperatureshutdown event (OS or OS) or an under temperatureshutdown event (US or US). When preset as an overtemperatureshutdown (OS) it will go LOW to indicate thatthe die temperature is over the internally preset TOS and goHIGH when the temperature goes below (TOS–THYST). Similarly,when preprogrammed as an undertemperature shutdown(US) it will go HIGH to indicate that the temperature isbelow TUS and go LOW when the temperature is above(TUS+THYST). The typical hysteresis, THYST, can be set to2°C or 10°C and is controlled by the state of the HYST pin. AVTEMP analog output provides a voltage that is proportionalto temperature and has a −10.7mV/°C output slope.
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