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APPLICATION INFORMATION

0.1 F

m

10kW

(typ)

10kW

(typ)

TMP421

DXP

DXN

V+

8

7

6

5

2

1

R

S

(2)

R

S

(2)

C

DIFF

(3)

C

DIFF

(3)

R

S

(2)

R

S

(2)

GND

SCL

SDA

+5V

SMBus

Controller

Diode-connectedconfiguration

:

(1)

SeriesResistance

Transistor-connectedconfiguration

:

(1)

A1

A0

4

3

TMP421

TMP422

TMP423

SBOS398B – JULY 2007 – REVISED MARCH 2008

The TMP421 (two-channel), TMP422 (three-channel),

The TMP422 requires transistors connected between

and TMP423 (four-channel) are digital temperature

DX1 and DX2 and between DX3 and DX4. Unused

sensors

that

combine

a

local

die

temperature

channels on the TMP422 must be connected to GND.

measurement channel and one, two, or three remote

The TMP423 requires a transistor connected to each

junction temperature measurement channels in a

positive channel (DXP1, DXP2, and DXP3), with the

single

SOT23-8

package.

These

devices

are

base of each channel tied to the common negative,

two-wire- and SMBus interface-compatible and are

DXN. For an unused channel, the TMP423 DXP pin

specified over a temperature range of –40

°C to

can be left open or tied to GND.

+125

°C. The TMP421/22/23 each contain multiple

The TMP421/22/23 SCL and SDA interface pins each

registers for holding configuration information and

require pull-up resistors as part of the communication

temperature measurement results.

bus. A 0.1

µF power-supply bypass capacitor is

For proper remote temperature sensing operation, the

recommended for local bypassing. Figure 11 shows a

TMP421

requires

only

a

transistor

connected

typical configuration for the TMP421; Figure 12

between DXP and DXN pins. If the remote channel is

illustrates a typical application for the TMP422.

not utilized, DXP can be left open or tied to GND.

Figure 13 illustrates a typical application for the

TMP423.

(1) Diode-connected configuration provides better settling time. Transistor-connected configuration provides better series resistance

cancellation.

Figure 6, Remote Temperature Error vs Differential Capacitance.

Figure 11. TMP421 Basic Connections

8

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Product Folder Link(s): TMP421 TMP422 TMP423