LM27A Datasheet, PDF (1/10 Pages) National Semiconductor (TI) – ±3°C Accurate, 120°C-150°C Factory Preset Thermostat (LM27 in Die Form)

July 2007
LM27A
±3°C Accurate, 120°C-150°C Factory Preset Thermostat
(LM27 in Die Form)
General 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 comprised of an internal reference, DAC, temper-
ature 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 LM27A has two
digital output pads, one digital input (HYST) and one analog
output (V_TEMP). One digitial output is an active-high, push-pull
output and the other is an active-low, open-drain output. Ei-
ther of the outputs (but not both) are available.
The LM27A is available in either an overtemperature shut-
down or an undertemperature shutdown option. An LM27A
with overtemperature shutdown is configured so that its ther-
mostat outputs (OS and OS) will go active when a rising
temperature crosses the trip point and the hysteresis will ap-
ply 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
T_OS . The outputs will reset to their normal states when the
temperature goes below (T_OS–T_HYST). Similarly, when pre-
programmed as an undertemperature shutdown the active-
high output (US) will go HIGH and the active-low output
(US) will go LOW to indicate that the temperature is below
T_US . The outputs will reset 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. The
V_TEMP analog output provides a voltage that is proportional to
temperature and has a −10.7mV/°C output slope.
Standard parts are available, see ordering information for de-
tails. For other part options, contact a National Semiconductor
Distributor or Sales Representative for information on mini-
mum-order qualification.
Applications
■ ^{Microprocessor Thermal Management}
■ ^Appliances
■ ^{Portable Battery Powered Systems}
■ ^{Fan Control}
■ ^{Industrial Process Control}
■ ^{HVAC Systems}
■ ^{Electronic System Protection}
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 V}_TEMP ^{output pin}
■ ^V_TEMP ^{output allows after-assembly system testing}
■ ^{Internal voltage reference and DAC for trip-point setting}
■ ^{Excellent power supply noise rejection}
■ ^{AEC-Q100 Qualified}
Key Specifications
■ Power Supply Voltage
■ Power Supply Current
■ Hysteresis Temperature
■ Temperature Trip Point Accuracy
2.7V to 5.5V
40µA(max)
15µA(typ)
2°C or 10°C(typ)
±3°C (max)
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