LM27  Product Folder

The LM27 is a precision, single digital-output, low-power thermostat comprised of an internal reference, DAC, temperature sensor and comparator. Utilizing factory programming, it can be manufactured with different trip points as well as different digital output functionality. The trip point (T_OS) can be preset at the factory to any temperature in the range of +120°C to +150°C in 1°C increments. The LM27 has one digital output (OS/OS#/US/US#), one digital input (HYST) and one analog output (V_TEMP). The digital output stage can be preset as either open-drain or push-pull. In addition, it can be factory programmed to be active HIGH or LOW. The digital output can be factory programmed to indicate an over temperature shutdown event (OS or OS#) or an under temperature shutdown event (US or US#). When preset as an overtemperature shutdown (OS#) it will go LOW to indicate that the die temperature is over the internally preset T_OS and go HIGH when the temperature goes below (T_OS-T_HYST). Similarly, when preprogrammed as an undertemperature shutdown (US) it will go HIGH to indicate that the temperature is below T_US and go LOW when the temperature is above (T_US+T_HYST). The typical hysteresis, T_HYST, can be set to 2°C or 10°C and is controlled by the state of the HYST pin. A V_TEMP analog output provides a voltage that is proportional to temperature and has a -10.7mV/°C output slope.

Currently, there are several standard parts available, see ordering information for details. For other part options, contact a National Semiconductor Distributor or Sales Representative for information on minimum order qualification. The LM27 is currently available in a 5-lead SOT-23 package.

• Internal comparator with pin selectable 2°C or 10°C hysteresis
• No external components required
• Open-drain or push-pull digital output; supports CMOS logic levels
• Internal temperature sensor with V_TEMP output pin
• V_TEMP output allows after-assembly system testing
• Internal voltage reference and DAC for trip-point setting
• Currently available in 5-pin SOT-23 plastic package
• Excellent power supply noise rejection

• Microprocessor Thermal Management
• Appliances
• Portable Battery Powered Systems
• Fan Control
• Industrial Process Control
• HVAC Systems
• Electronic System Protection