1FEATURES
2• 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
• 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

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

KEY SPECIFICATIONS
• 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)

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 Table 1. For other part options, contact a Texas
Instruments Distributor or Sales Representative for information on minimum order qualification. The
LM27 is currently available in a 5-lead SOT-23
package.