± ±1°C TemTꢀratꢀTCꢁMonaMꢀCꢂnaꢃ
STꢀnTsCRTsnsarocTC°rocTllranMo
C
AD 746±*
PRODUCT DESCRIPTION
FEATURES
On-chip and remote temperature sensor
0.25°C resolution/1°C accuracy on remote channel
1°C resolution/3°C accuracy on local channel
Automatically cancels up to 3 kΩ (typ) of resistance in series
with remote diode to allow noise filtering
Extended, switchable temperature measurement range 0°C
to +127°C (default) or –55°C to +150°C
Pin and register compatible with ADM1032
2-wire SMBus serial interface with SMBus alert support
Programmable over/under temperature limits
Offset registers for system calibration
The ADT7461 is a dual-channel digital thermometer and
under/over temperature alarm, intended for use in PCs and
thermal management systems. It is pin and register compatible
with the ADM1032. The ADT7461 has three additional features:
series resistance cancellation, where up to 3 kΩ (typical) of
resistance in series with the temperature monitoring diode may
be automatically cancelled from the temperature result, allowing
ALERT
noise filtering; configurable
output; and an extended,
switchable temperature measurement range.
The ADT7461 can measure the temperature of a remote ther-
mal diode accurate to 1ꢀC, and the ambient temperature accu-
rate to 3ꢀC. The temperature measurement range defaults to
0ꢀC to +127ꢀC, compatible with ADM1032, but can be switched
to a wider measurement range, from −55ꢀC to +150ꢀC. The
ADT7461 communicates over a 2-wire serial interface compati-
ble with system management bus (SMBus) standards. An
THERM
Up to 2 overtemperature fail-safe
outputs
Small 8-lead SOIC or MSOP package
170 µA operating current, 5.5 µA standby current
APPLICATIONS
Desktop and notebook computers
Industrial controllers
Smart batteries
ALERT
output signals when the on-chip or remote temperature
THERM
is out of range. The
output is a comparator output that
ALERT
Automotive
allows on/off control of a cooling fan. The
output can
Enbedded systems
Burn-in applications
Instrumentation
THERM
be reconfigured as a second
output if required.
*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.
CONVERSION RATE
ADDRESS POINTER
REGISTER
REGISTER
ON-CHIP
TEMPERATURE
SENSOR
LOCAL TEMPERATURE
LOW LIMIT REGISTER
LOCAL TEMPERATURE
VALUE REGISTER
LOCAL TEMPERATURE
HIGH LIMIT REGISTER
ANALOG
MUX
ADC
REMOTE TEMPERATURE
LOW LIMIT REGISTER
BUSY
RUN/STANDBY
REMOTE TEMPERATURE
HIGH LIMIT REGISTER
D+
D–
REMOTE TEMPERATURE
VALUE REGISTER
2
3
SRC
BLOCK
LOCAL THERM LIMIT
REGISTER
REMOTE OFFSET
REGISTER
EXTERNAL THERM LIMIT
REGISTER
CONFIGURATION
REGISTER
EXTERNAL DIODE OPEN-CIRCUIT
INTERRUPT
STATUS REGISTER
MASKING
ADT7461
SMBus INTERFACE
6
4
1
5
7
8
V
GND
SDATA
SCLK
THERM
ALERT/
DD
THERM2
Figure 1. Functional Block Diagram
Rev. 0
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