ADC

Oscillator

Voltage

Reference

M

U

X

Register

Bank

Serial

Interface

Control

Logic

MUX

5 × I

2 × I

I

6

7

4

8

1

2

5

V+

Local

Thermal BJT

A0

SCL

SDA

DXN

DXP

GND

V+

20 × I

3

A1

Copyright © 2016, Texas Instruments Incorporated

10

TMP421-Q1, TMP422-Q1, TMP423-Q1

SBOS821 – NOVEMBER 2016

www.ti.com

Product Folder Links: TMP421-Q1 TMP422-Q1 TMP423-Q1

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Copyright © 2016, Texas Instruments Incorporated

8 Detailed Description

8.1 Overview

The TMP421-Q1 is a two-channel digital temperature sensor that combines a local die temperature-

measurement channel and a remote-junction temperature-measurement channel, and is available in an 8-pin

SOT-23 package. The TMP422-Q1 (three-channel), and TMP423-Q1 (four-channel) are digital temperature

sensors that combine a local die temperature measurement channel and two or three remote junction

temperature measurement channels, respectively, in a single 8-pin SOT-23 package. These devices are two-

wire- and SMBus interface-compatible and are specified over a temperature range of –40°C to +125°C. The

TMP421-Q1, TMP422-Q1, and TMP423-Q1 each contain multiple registers for holding configuration information

and temperature measurement results.

For proper remote temperature sensing operation, the TMP421-Q1 requires only a transistor connected between

DXP and DXN pins. If the remote channel is not utilized, DXP can be left open or tied to GND.

The TMP422-Q1 requires transistors connected between DX1 and DX2 and between DX3 and DX4. Unused

channels on the TMP422-Q1 must be connected to GND. The TMP423-Q1 requires a transistor connected to

each positive channel (DXP1, DXP2, and DXP3), with the base of each channel tied to the common negative,

DXN. For an unused channel, the TMP423-Q1 DXP pin can be left open or tied to GND.

8.2 Functional Block Diagram

Figure 12. The TMP421-Q1 Supports Multiple Slave Addresses and a Single Remote Diode Input