National Semiconductor LM26 Series, Manual

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LM26
SOT-23,
±
3˚C Accurate, Factory Preset Thermostat
General Description
The LM26 is a precision, single digital-output, low-power
thermostat comprised of an internal reference, DAC, tem-
perature sensor and comparator. Utilizing factory program-
ming, 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 −55˚C to +110˚C in 1˚C increments. The LM26 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 tem-
perature shutdown event (OS or OS) or an under tempera-
ture shutdown event (US or US). When preset as an over-
temperature 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
). Simi-
larly, when preprogrammed as an undertemperature shut-
down (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 −10.82mV/˚C output slope.
Available parts are detailed in the ordering information. For
other part options, contact a National Semiconductor Dis-
tributor or Sales Representative for information on minimum
order qualification. The LM26 is currently available in a
5-lead SOT-23 package.
Applications
n
Microprocessor Thermal Management
n
Appliances
n
Portable Battery Powered Systems
n
Fan Control
n
Industrial Process Control
n
HVAC Systems
n
Remote Temperature Sensing
n
Electronic System Protection
Features
n
Internal comparator with pin programmable 2˚C or 10˚C
hysteresis
n
No external components required
n
Open Drain or push-pull digital output; supports CMOS
logic levels
n
Internal temperature sensor with V
TEMP
output pin
n
V
TEMP
output allows after-assembly system testing
n
Internal voltage reference and DAC for trip-point setting
n
Currently available in 5-pin SOT-23 plastic package
n
Excellent power supply noise rejection
Key Specifications
j Power Supply Voltage 2.7V to 5.5V
j Power Supply Current 40µA(max)
20µA(typ)
j Hysteresis Temperature 2˚C or 10˚C(typ)
Temperature Trip Point Accuracy
Temperature Range LM26CIM
−55˚C to +110˚C
±
3˚C (max)
+120˚C
±
4˚C (max)
LM26CIM5-TPA Simplified Block Diagram and Connection Diagram
10132301
The LM26CIM5-TPA has a fixed trip point of 85˚C.
For other trip point and output function availability,
please see ordering information or contact National Semiconductor.
May 2001
LM26
SOT
-23,
±
3˚C
Accurate,
Factory
Preset
Thermostat
© 2003 National Semiconductor Corporation DS101323 www.national.com
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