ADT7481 Datasheet, PDF (1/24 Pages) Analog Devices – Dual Channel Temperature Sensor and Over Temperature Alarm

Dual Channel Temperature Sensor
and Over Temperature Alarm
ADT7481
FEATURES
1 local and 2 remote temperature sensors
0.25°C resolution/1°C accuracy on remote channels
1°C resolution/1°C accuracy on local channel
Extended, switchable temperature measurement range 0°C
to 127°C (default) or –64°C to +191°C
2-wire SMBus serial interface with SMBus ALERT support
Programmable over/under temperature limits
Offset registers for system calibration
Up to 2 over temperature fail-safe THERM outputs
Small 10-lead MSOP package
240 μA operating current, 5 μA standby current
GENERAL DESCRIPTION
The ADT7481¹ is a 3-channel digital thermometer and under/
over temperature alarm, intended for use in PCs and thermal
management systems. It can measure its own ambient temperature
or the temperature of two remote thermal diodes. These thermal
diodes can be located in a CPU or GPU, or they can be discrete
diode connected transistors. The ambient temperature, or the
temperature of the remote thermal diode, can be accurately
measured to ±1°C. The temperature measurement range defaults
to 0°C to +127°C, compatible with ADM1032, but can be
switched to a wider measurement range from −64°C to +191°C.
APPLICATIONS
Desktop and notebook computers
Industrial controllers
Smart batteries
Automotive
Embedded systems
Burn-in applications
Instrumentation
The ADT7481 communicates over a 2-wire serial interface
compatible with system management bus (SMBus) standards.
The SMBus address of the ADT7481 is 0x4C. An ADT7481-1
with an SMBus address of 0x4B is also available.
An ALERT output signals when the on-chip or remote
temperature is outside the programmed limits. The THERM
output is a comparator output that allows, for example, on/off
control of a cooling fan. The ALERT output can be reconfigured
as a second THERM output if required.
FUNCTIONAL BLOCK DIAGRAM
D1+ 2
D1– 3
D2+ 7
D2– 8
ON-CHIP TEMP
SENSOR
CONVERSION RATE
REGISTER
LOCAL TEMPERATURE
VALUE REGISTER
ANALOG
MUX
11-BIT A-TO-D
CONVERTER
BUSY RUN/STANDBY
REMOTE 1 AND 2 TEMP
VALUE REGISTERS
REMOTE 1 AND 2 TEMP
OFFSET REGISTERS
EXTERNAL DIODES OPEN-CIRCUIT
ADT7481
STATUS REGISTERS
SMBUS INTERFACE
ADDRESS POINTER
REGISTER
ONE-SHOT
REGISTER
LOCAL TEMPERATURE
THERM LIMIT REGISTER
LOCAL TEMPERATURE
LOW LIMIT REGISTER
LOCAL TEMPERATURE
HIGH LIMIT REGISTER
REMOTE 1 AND 2 TEMP
THERM LIMIT REGISTER
REMOTE 1 AND 2 TEMP
LOW LIMIT REGISTERS
REMOTE 1 AND 2 TEMP
HIGH LIMIT REGISTERS
CONFIGURATION
REGISTERS
INTERRUPT
MASKING
8 _ALERT/THERM2
1
V_DD
6
GND
9
SDATA
10
SCLK
Figure 1.
4
THERM
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. 0
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