Low Cost Microprocessor,
System Temperature Monitor Microcomputer
ADM1021A
FEATURES
PRODUCT DESCRIPTION
Alternative to the ADM1021
On-chip and remote temperature sensing
No calibration necessary
1°C accuracy for on-chip sensor
3°C accuracy for remote sensor
Programmable overtemperature/undertemperature
limits
Programmable conversion rate
2-wire SMBus serial interface
Supports system management bus (SMBus) alert
200 μA max operating current
1 μA standby current
3 V to 5.5 V supply
Small 16-lead QSOP package
The ADM1021A1 is a two-channel digital thermometer and
undertemperature/overtemperature alarm, intended for use
in personal computers and other systems requiring thermal
monitoring and management. The device can measure the
temperature of a microprocessor using a diode-connected
PNP transistor, which can be provided on-chip with the
Pentium® III or similar processors, or can be a low cost discrete
NPN/PNP device, such as the 2N3904/2N3906. A novel
measurement technique cancels out the absolute value of the
transistor’s base emitter voltage so that no calibration is
required. The second measurement channel measures the
output of an on-chip temperature sensor to monitor the
temperature of the device and its environment.
The ADM1021A communicates over a two-wire serial interface
compatible with SMBus standards. Undertemperature and
overtemperature limits can be programmed into the device over
the serial bus, and an ALERT output signals when the on-chip
or remote temperature is out of range. This output can be used
as an interrupt or as an SMBus alert.
APPLICATIONS
Desktop computers
Notebook computers
Smart batteries
Industrial controllers
Telecom equipment
Instrumentation
FUNCTIONAL BLOCK DIAGRAM
ADDRESS POINTER
REGISTER
ONE-SHOT
REGISTER
CONVERSION RATE
REGISTER
ON-CHIP
TEMPERATURE
SENSOR
D+
D–
3
4
BUSY
RUN/STANDBY
REMOTE TEMPERATURE
VALUE REGISTER
LOCAL TEMPERATURE
LOW LIMIT REGISTER
LOCAL TEMPERATURE
HIGH LIMIT REGISTER
REMOTE TEMPERATURE
LOW LIMIT COMPARATOR
A-TO-D
CONVERTER
ANALOG MUX
LOCAL TEMPERATURE
LOW LIMIT COMPARATOR
LOCAL TEMPERATURE
HIGH LIMIT COMPARATOR
LOCAL TEMPERATURE
VALUE REGISTER
REMOTE TEMPERATURE
LOW LIMIT REGISTER
REMOTE TEMPERATURE
HIGH LIMIT REGISTER
REMOTE TEMPERATURE
HIGH LIMIT COMPARATOR
CONFIGURATION
REGISTER
15 STBY
EXTERNAL DIODE OPEN-CIRCUIT
INTERRUPT
MASKING
STATUS REGISTER
1
2
5
VDD
NC
7
8
GND GND
9
13
16
NC
NC
NC
12
14
SDATA
SCLK
10
6
ADD0
ADD1
NC = NO CONNECT
00056-001
SMBUS INTERFACE
ADM1021A
NC
11 ALERT
Figure 1.
1
Protected by U.S. Patents 5,195,827; 5,867,012; 5,982,221; 6,097,239; 6,133,753; 6,169,442; other patents pending.
Rev. F
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infringements of patents or other rights of third parties that may result from its use.
Specifications subject to change without notice. No license is granted by implication
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