LM27A Datasheet | National Semiconductor

Description This datasheet applies to the LM27A, which is the die form of the LM27. The LM27 is available in the SOT23-5 package. Please refer to the LM27 datasheet for detailed specifications pertaining to the packaged part. The LM27A is a precision, single digital-output, low-power thermostat prised of an internal reference, DAC, temperature sensor and parator. Utilizing factory programming, it can be manufactured with different trip points as well as different digital output functionality. The trip point (TOS) can be preset at the factory to any temperature in the range of +120°C to +150°C in 1°C increments. The LM27A has two digital output pads, one digital input (HYST) and one analog output (VTEMP). One digitial output is an active-high, push-pull output and the other is an active-low, open-drain output. Either of the outputs (but not both) are available. The LM27A is available in either an overtemperature shutdown or an undertemperature shutdown option. An LM27A with overtemperature shutdown is configured so that its thermostat outputs (OS and OS) will go active when a rising temperature crosses the trip point and the hysteresis will apply to a falling temperature. The thermostat outputs of an LM27A with an undertemperature shutdown (US and US) will trip on a falling temperature and hysteresis will apply on a rising temperature. For example, when the LM27A is preset as an overtemperature shutdown, the active-high output (OS) will go HIGH and the active-low output (OS) will go LOW to indicate that the die temperature is over the internally preset TOS . The outputs will reset to their normal states when the temperature goes below (TOS- THYST). Similarly, when preprogrammed as an undertemperature shutdown the activehigh output (US) will go HIGH and the active-low output (US) will go LOW to indicate that the temperature is below TUS . The outputs will reset when the temperature is above (TUS+THYST). The typical hysteresis, THYST, can be set to 2°C or 10°C and is...