Features • 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 VTEMP output pin • VTEMP 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 Description 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 (TOS) 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 (VTEMP). 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 TOS and go HIGH when the temperature goes below (TOS-THYST). Similarly, when preprogrammed as an undertemperature shutdown (US) it will go HIGH to indicate that the temperature is below TUS and go LOW when the temperature is above (TUS+THYST). The typical hysteresis, THYST, can be set to 2°C or 10°C and is controlled by the state of the HYST pin. A VTEMP 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. Key Specification Power Supply Voltage 2.7V to 5.5V Power Supply Current 40µA(max) 15µA(typ) Hysteresis Temperature 2°C or 10°C(typ) Temperature Trip Point Accuracy ±3°C (max) Applications • Microprocessor Thermal Management • Appliances • Portable Battery Powered Systems • Fan Control • Industrial Process Control • HVAC Systems • Electronic System Protection

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Datasheet

Title		Size	Date	Other Language
	LM27 SOT-23, ±3°C Accurate, 120°C-150°C Factory Preset Thermostat	586 Kbytes	5-Oct-06	日本語

Featured Application Notes

Title		Size	Date	Other Language
	AN-1202: Application Note 1202 LM2698 Demoboard	217 Kbytes	10-May-04

More Application Notes

Title		Size	Date	Other Language
	AN-1256: Application Note 1256 Tiny Temperature Sensors for Portable Systems	66 Kbytes	1-Oct-02

Reliability Metrics

Part Number	Process	EFR Reject	EFR Sample Size	PPM	LTA Rejects	LTA Device Hours	FITS	MTTF (Hours)
LM27-2PL MDA	CMOS7	0	18406	0	0	1089000	4	309006723
LM27CIM5-1HJ	CMOS7	0	18406	0	0	1089000	4	309006723
LM27CIM5-2HJ	CMOS7	0	18406	0	0	1089000	4	309006723
LM27CIM5-ZHJ	CMOS7	0	18406	0	0	1089000	4	309006723

Note: The Early Failure Rates (EFR) were calculated as point estimate PPM based on rejects and sample size for EFR. The Long Term Failure Rates were calculated at 60% confidence using the Arrhenius equation at 0.7eV activation energy and derating the assumed stress temperature of 150°C to an application temperature of 55°C.

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