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

www.ti.com

SBOS398C – JULY 2007 – REVISED MAY 2012

APPLICATION INFORMATION

The TMP421 is a two-channel digital temperature

For proper remote temperature sensing operation, the

sensor that combines a local die temperature-

TMP421

requires

only

a

transistor

connected

measurement

channel

and

a

remote-junction

between DXP and DXN pins. If the remote channel is

temperature-measurement channel, and is available

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

in SOT23-8 and DSBGA-8 packages. The TMP422

The TMP422 requires transistors connected between

(three-channel),

and

TMP423

(four-channel)

are

DX1 and DX2 and between DX3 and DX4. Unused

digital temperature sensors that combine a local die

channels on the TMP422 must be connected to GND.

temperature measurement channel and two or three

The TMP423 requires a transistor connected to each

remote junction temperature measurement channels,

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

respectively, in a single SOT23-8 package. These

base of each channel tied to the common negative,

devices

are

two-wire-

and

SMBus

interface-

DXN. For an unused channel, the TMP423 DXP pin

compatible and are specified over a temperature

can be left open or tied to GND.

range of –40°C to +125°C. The TMP421/22/23 each

contain multiple registers for holding configuration

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

information and temperature measurement results.

require pull-up resistors as part of the communication

bus. A 0.1

μF power-supply bypass capacitor is

recommended

for

local

bypassing.

Figure

11,

Figure 12, and Figure 13 show typical configurations

for the TMP421, TMP422, and TMP423, respectively.

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

cancellation.

(2) RS (optional) should be < 1.5kΩ in most applications. Selection of RS depends on application; see the Filtering section.

(3) CDIFF (optional) should be < 1000pF in most applications. Selection of CDIFF depends on application; see the Filtering section and

Figure 6, Remote Temperature Error vs Differential Capacitance.

Figure 11. TMP421 Basic Connections

Copyright © 2007–2012, Texas Instruments Incorporated

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Product Folder Link(s): TMP421 TMP422 TMP423