August 15, 2008
LM95235/LM95235Q
Precision Remote Diode Temperature Sensor with SMBus
Interface and TruTherm™ Technology
Diode Model Selection Bit - MMBT3904 or 65/90 nm
processor diodes
Two Formats: −128°C to 127.875°C and
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General Description
The LM95235 is an 11-bit digital temperature sensor with a
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2-wire System Management Bus (SMBus) interface and
0°C to 255.875°C
TruTherm technology that can monitor the temperature of a
remote diode as well as its own temperature. The LM95235
Digital filter for remote channel
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Programmable TCRIT and OS thresholds
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can be used to very accurately monitor the temperature of
external devices such as microprocessors, graphics proces-
sors, or a diode-connected MMBT3904 transistor. For auto-
motive applications the LM95235Q is available that is AEC-
Q100 Grade3 compliant and is manufactured on an
Automotive Grade Flow. TruTherm BJT (transistor) beta com-
pensation technology allows the LM95235 to precisely mon-
itor thermal diodes found in 90 nm and smaller geometry
processes. LM95235 reports temperature in two different for-
mats for +127.875°C/-128°C range and 0°C/255°C range.
The LM95235 T_CRIT and OS outputs are asserted when
either unmasked channel exceeds its programmed limit and
can be used to shutdown the system, to turn on the system
fans, or as a microcontroller interrupt function. The current
status of the T_CRIT and OS pins can be read back from the
status registers via the SMBus interface. All limits have a
shared programmable hysteresis register.
Programmable shared hysteresis register
Diode Fault Detection
Mask, Offset, and Status Registers
SMBus 2.0 compatible interface, supports TIMEOUT
Programmable conversion rate for best power
consumption
Three-level address pin
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Standby mode one-shot conversion control
Pin-for-pin compatible with the LM86/LM89
8-pin MSOP package
Key Specifications
3.0 V to 3.6 V
350 µA (typ)
■ꢀSupply Voltage
The remote temperature channel of the LM95235 has a pro-
grammable digital filter. The LM95235 contains a diode model
selection bit to select between a typical Intel® processor on
a 65 nm or 90 nm process or MMBT3904, as well as an offset
register for maximum flexibility and best accuracy.
■ꢀSupply Current, Conv. Rate = 1 Hz
■ꢀRemote Diode Temperature Accuracy
ꢀTA = 25°C to 85°C; TD = 60°C to 100°C
ꢀTA = 25°C to 85°C; TD = 40°C to 125°C
■ꢀLocal Temperature Accuracy
ꢀTA = 25°C to 100°C
±0.75°C (max)
±1.5°C (max)
The LM95235 has a three-level address pin to connect up to
3 devices to the same SMBus master, that is shared with the
OS output. The LM95235 has a programmable conversion
rate register and a standby mode to save power. One con-
version can be triggered in standby mode by writing to the
one-shot register.
±2.0°C (max)
16 to 0.4 Hz
■ꢀConversion Rate, Both Channels
Applications
Processor/Computer System Thermal Management
(e.g. Laptops, Desktops, Workstations, Servers)
Features
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Remote and Local temperature channels
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Electronic Test Equipment and Office Electronics
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TruTherm BJT beta compensation technology
LM95235Q is AEC-Q100 Grade 3 compliant and is
manufactured on an Automotive Grade Flow
Connection Diagram
MSOP-8
20174902
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TruTherm™ is a trademark of National Semiconductor Corporation.
Intel® is a registered trademark of Intel Corporation.
Pentium® is a registered trademark of Intel Corporation.
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