SCL

V+

D+

D±

GND

A0

SMBus

Controller

Host Processor

A1

Overtemperature

Shutdown

SDA

GND

GND

1.7 V to 3.6 V

1.7 V to 3.6 V

GND

Built-in

Thermal

Transistor

or Diode

FPGA, ADC,

DAC, or ASIC

THERM

ALERT/

THERM2

TMP461-SP

1

2

3

4

5

6

7

8

9

10

Copyright © 2017, Texas Instruments Incorporated

TL1431-SP

or

LM4050QML-SP

TL1431-SP

or

LM4050QML-SP

Vbatt

Vbatt

24

TMP461-SP

SBOS876B – SEPTEMBER 2017 – REVISED FEBRUARY 2020

www.ti.com

Product Folder Links: TMP461-SP

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Copyright © 2017–2020, Texas Instruments Incorporated

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

8.1 Application Information

The TMP461-SP device requires only a transistor connected between the D+ and D– pins for remote

temperature measurement. Tie the D+ pin to D– or GND if the remote channel is not used and only the local

temperature is measured. The SDA, ALERT, and THERM pins (and SCL, if driven by an open-drain output)

require pullup resistors as part of the communication bus. A 0.1-µF power-supply decoupling capacitor is

recommended for local bypassing. Figure 18 illustrates the typical configurations for the TMP461-SP device.

8.2 Typical Application

Figure 18. TMP461-SP Basic Connections Using a Processor Built-In Remote Transistor

8.2.1 Design Requirements

The TMP461-SP device is designed to be used with either discrete transistors or substrate transistors built into

processor chips and application-specific integrated circuits (ASICs). Either NPN or PNP transistors can be used,

as long as the base-emitter junction is used as the remote temperature sense. NPN transistors must be diode-

connected. PNP transistors can either be transistor- or diode-connected (see Figure 18).

Errors in remote temperature sensor readings are typically the consequence of the ideality factor and current

excitation used by the TMP461-SP device versus the manufacturer-specified operating current for a given

transistor. Some manufacturers specify a high-level and low-level current for the temperature-sensing substrate

transistors. The TMP461-SP device uses 7.5 μA for ILOW and 120 μA for IHIGH.

The ideality factor (η) is a measured characteristic of a remote temperature sensor diode as compared to an

ideal diode. The TMP461-SP allows for different η-factor values; see the η-Factor Correction Register section.