ADT7421ARMZ-2RL View Datasheet(PDF) - ON Semiconductor

Part Name

Description

MFG CO.

ADT7421ARMZ-2RL

Precision Temperature Sensor with Beta Compensation (for <45 nm Geometries)

ON Semiconductor 

ADT7421

Another feature of the ADT7421 is Series Resistance

Cancellation, where up to 50 W (typical) of resistance in

series with the temperature monitoring transistor can be

automatically cancelled from the temperature result,

allowing noise filtering.

The combination of Beta cancellation and series

resistance cancellation provides critical high accuracy

temperature sensing on 45 nm CPU’s and GPU’s.

The ADT7421 can measure the temperature of a remote

thermal transistor accurate to ±1°C and the ambient

temperature accurate to ±1°C. The temperature measurement

range defaults to 0°C to +125°C, compatible with the

ADM1032, but it can be switched to a wider measurement

range of −40°C to +125°C.

The ADT7421 has a configurable ALERT output and an

extended, switchable temperature measurement range.

The ADT7421 communicates over a 2−wire serial

interface, compatible with system management bus

(SMBus) standards. The default SMBus address of the

ADT7421 is 0x4C. An ADT7421−2 is available with a

SMBus address of 0x4D. This is useful if more than one

ADT7421 is used on the same SMBus.

An ALERT output signals when the on−chip or remote

temperature is out of range. 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.

ON−CHIP

TEMPERATURE

SENSOR

CONVERSION RATE

REGISTER

LOCAL TEMPERATURE

VALUE REGISTER

D+ 2

D– 3

ANALOG

MUX

A−TO−D

CONVERTER

BUSY RUN/STANDBY

REMOTE TEMPERATURE

VALUE REGISTER

REMOTE OFFSET

REGISTER

EXTERNAL DIODE OPEN−CIRCUIT

ADT7421

1

VDD

5

GND

STATUS REGISTER

ADDRESS POINTER

REGISTER

LOCAL TEMPERATURE

LOW−LIMIT REGISTER

LOCAL TEMPERATURE

HIGH−LIMIT REGISTER

REMOTE TEMPERATURE

LOW−LIMIT REGISTER

REMOTE TEMPERATURE

HIGH−LIMIT REGISTER

LOCAL THERM LIMIT

REGISTERS

EXTERNAL THERM LIMIT

REGISTERS

CONFIGURATION

REGISTERS

INTERRUPT

MASKING

SMBus INTERFACE

7

SDATA

8

SCLK

Figure 1. Block Diagram

6 ALERT/THERM2

4 THERM

PIN ASSIGNMENT

Pin No.

Mnemonic

1

VDD

2

D+

3

D−

4

THERM

5

GND

6

ALERT / THERM2

7

SDATA

8

SCLK

Description

Positive Supply, 3.0 V to 3.6 V.

Positive Connection to Remote Temperature Sensor. (Anode)

Negative Connection to Remote Temperature Sensor. (Cathode)

Open-Drain Output. Can be used to turn a fan on/off or throttle a CPU clock in the event of an

overtemperature condition. Requires pullup resistor.

Supply Ground Connection.

Open-Drain Logic Output Used as Interrupt or SMBus ALERT. This can also be configured as a

second THERM output. Requires pullup resistor.

Logic Input/Output, SMBus Serial Data. Open-Drain Output. Requires pullup resistor.

Logic Input, SMBus Serial Clock. Requires pullup resistor.

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