May 2006
LM95235
Precision Remote Diode Temperature Sensor with
™
SMBus Interface and TruTherm Technology
n Two Formats: −128˚C to +127.875˚C and 0˚C to 255˚C
n Digital filter for remote channel
General Description
The LM95235 is an 11-bit digital temperature sensor with a
2-wire System Management Bus (SMBus) interface and Tru-
Therm technology that can monitor the temperature of a
remote diode as well as its own temperature. The LM95235
can be used to very accurately monitor the temperature of
external devices such as microprocessors, graphics proces-
sors, or a diode-connected MMBT3904 transistor. TruTherm
technology allows the LM95235 to precisely monitor thermal
diodes found in 90 nm and smaller geometry processes.
LM95235 reports temperature in two different formats 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.
n Programmable TCRIT and OS thresholds
n Programmable shared hysteresis register
n Diode Fault Detection
n Mask, Offset, and Status Registers
n SMBus 2.0 compatible interface, supports TIMEOUT
n Programmable conversion rate for best power
consumption
n Three-level address pin
n Standby mode one-shot conversion control
n Pin-for-pin compatible with the LM86/LM89
n 8-pin MSOP package
Key Specifications
j
j
j
Supply Voltage
3.0 V to 3.6 V
350 µA (typ)
Supply Current, Conv. Rate = 1 Hz
Remote Diode Temperature Accuracy
The remote temperature channel of the LM95235 has a
programmable digital filter. The LM95235 contains a diode
model selection bit to select between a typical Intel® proces-
sor on a 65 nm or 90 nm process or MMBT3904, as well as
an offset register for maximum flexibility and best accuracy.
TA = 25˚C to 85˚C; TD = 60˚C to 100˚C
TA = 25˚C to 85˚C; TD = 40˚C to 120˚C
0.75˚C (max)
1.5˚C (max)
j
Local Temperature Accuracy
TA = 25˚C to 100˚C
2.0˚C (max)
16 to 0.4 Hz
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.
j
Conversion Rate, Both Channels
Applications
n Processor/Computer System Thermal Management
(e.g. Laptops, Desktops, Workstations, Servers)
n Electronic Test Equipment
Features
n Office Electronics
n Remote and Local temperature channels
n Diode Model Selection Bit - MMBT3904 or 65/90 nm
processor diodes
Connection Diagram
MSOP-8
20174902
TOP VIEW
™
TruTherm is a trademark of National Semiconductor Corporation.
Intel® is a registered trademark of Intel Corporation.
Pentium® is a registered trademark of Intel Corporation.
Intel® Core Duo is a trademark of Intel Corporation.
™
Intel® Core Solo is a trademark of Intel Corporation.
™
© 2006 National Semiconductor Corporation
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