Rainbow Electronics LM95221 - Manual

LM95221
Dual Remote Diode Digital Temperature Sensor with
SMBus Interface
General Description
The LM95221 is a dual remote diode temperature sensor in
an 8-lead MSOP package. The 2-wire serial interface of the
LM95221 is compatible with SMBus 2.0. The LM95221 can
sense three temperature zones, it can measure the tempera-
ture of its own die as well as two diode connected transis-
tors. The diode connected transistors can be a thermal diode
as found in Pentium and AMD processors or can simply be a
diode connected MMBT3904 transistor. The LM95221 reso-
lution format for remote temperature readings can be pro-
grammed to be 10-bits plus sign or 11-bits unsigned. In the
unsigned mode the LM95221 remote diode readings can
resolve temperatures above 127˚C. Local temperature read-
ings have a resolution of 9-bits plus sign.
The temperature of any ASIC can be accurately determined
using the LM95221 as long as a dedicated diode (semicon-
ductor junction) is available on the target die. The LM95221
remote sensor accuracy of
± 1˚C is factory trimmed for a
series resistance of 2.7 ohms and 1.008 non-ideality factor.
Features
n Accurately senses die temperature of remote ICs or
diode junctions
n Remote diode fault detection
n On-board local temperature sensing
n Remote temperature readings:
— 0.125 ˚C LSb
— 10-bits plus sign or 11-bits programmable resolution
— 11-bits resolves temperatures above 127 ˚C
n Local temperature readings:
— 0.25 ˚C
— 9-bits plus sign
n Status register support
n Programmable conversion rate allows user optimization
of power consumption
n Shutdown mode one-shot conversion control
n SMBus 2.0 compatible interface, supports TIMEOUT
n 8-pin MSOP package
Key Specifications
j Local Temperature Accuracy
T
A
=0˚C to 85˚C ± 3.0 ˚C (max)
j Remote Diode Temperature Accuracy
T
A
=30˚C to 50˚C, T
D
=45˚C to 85˚C ± 1.0 ˚C (max)
T
A
=0˚C to 85˚C, T
D
=25˚C to 140˚C ± 3.0 ˚C (max)
j Supply Voltage 3.0 V to 3.6 V
j Supply Current 2 mA (typ)
Applications
n Processor/Computer System Thermal Management
(e.g. Laptop, Desktop, Workstations, Server)
n Electronic Test Equipment
n Office Electronics
Simplified Block Diagram
20094301
Pentium ™ is a trademark of Intel Corporation.
May 2004
LM95221
Dual
Remote
Diode
Digital
T
emperature
Sensor
with
SMBus
Interface
© 2004 National Semiconductor Corporation DS200943 www.national.com