Dual Channel Temperature Sensor

and Overtemperature Alarm

ADT7482

Rev. 0

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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

Automatically cancels up to 1.5 kΩ (typ) of resistance in

series with the remote sensors

Extended, switchable temperature measurement range 0°C

to +127°C (default) or −55°C to +150°C

2-wire SMBus serial interface with SMBus alert support

Programmable overtemperature/undertemperature limits

Offset registers for system calibration

Up to 2 overtemperature fail-safe THERM outputs

Small, 10-lead MSOP package

240 μA operating current, 5 μA standby current

APPLICATIONS

Desktop and notebook computers

Industrial controllers

Smart batteries

Automotive

Embedded systems

Burn-in applications

Instrumentation

GENERAL DESCRIPTION

The ADT74821 is a three-channel digital thermometer and

undertemperature/overtemperature alarm for PCs and thermal

management systems. It can measure the temperature in two

remote locations, such as in the remote thermal diode in a CPU

or GPU, or using a discrete diode connected transistor. This

device also measures its own ambient temperature.

One feature of the ADT7482 is series resistance cancellation

where up to 1.5 kΩ (typical) of resistance in series with each of

the temperature monitoring diodes can be automatically

cancelled from the temperature result, allowing noise filtering.

The temperature of the remote thermal diodes and ambient

temperature can be measured accurate to ±1°C. The tempera-

ture measurement range, which defaults to 0°C to 127°C, can be

switched to a wider measurement range of from −55°C to +150°C.

The ADT7482 communicates over a 2-wire serial interface

compatible with system management bus (SMBus) standards.

The default address of the ADT7482 is 0x4C. 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 on/off control of a cooling fan. The ALERT output can

be reconfigured as a second THERM output if required.

6,133,753, 6,169,442, 7,010,440, other patents pending.

FUNCTIONAL BLOCK DIAGRAM

11-BIT ADC

RUN/STANDBY

BUSY

SRC

STATUS REGISTERS

INTERRUPT

MASKING

LOCAL TEMPERATURE

VALUE REGISTER

ON-CHIP

TEMPERATURE

SENSOR

ANALOG

MUX

EXTERNAL DIODES OPEN-CIRCUIT

SMBus INTERFACE

ADT7482

6

7

10

1

5

9

GND

SDATA

SCLK

8

D2+

D2–

3

2

D1+

D1–

ALERT/THERM2

CONFIGURATION

REGISTERS

LOCAL TEMPERATURE

HIGH-LIMIT REGISTER

LOCAL TEMPERATURE

LOW-LIMIT REGISTER

LOCAL TEMPERATURE

THERM-LIMIT REGISTER

CONVERSION RATE

REGISTER

ONE-SHOT

REGISTER

ADDRESS POINTER

REGISTER

4

THERM

REMOTE 1 AND 2 TEMP

VALUE REGISTERS

REMOTE 1 AND 2 TEMP

THERM-LIMIT REGISTERS

REMOTE 1 AND 2 TEMP

LOW-LIMIT REGISTERS

REMOTE 1 AND 2 TEMP

HIGH-LIMIT REGISTERS

REMOTE 1 AND 2 TEMP

VALUE REGISTERS

Figure 1.