TMP468 datasheet(31/49 Pages) TI2

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Processor, FPGA, or ASIC

TMP468

D+

D-

CDIFF

(3)

(2)

PNP Transistor-Connected Configuration

(1)

PNP Diode-Connected Configuration

(1)

Series Resistance

(2)

NPN Diode-Connected Configuration

(1)

Series Resistance

(2)

Integrated PNP Transistor-Connected Configuration

(1)

Internal and PCB

Series Resistance

(2)

TMP468

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SBOS762B – NOVEMBER 2016 – REVISED JUNE 2017

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Typical Application (continued)

Figure 23. TMP468 Remote Transistor Configuration Options

8.2.1 Design Requirements

The TMP468 device is designed to be used with either discrete transistors or substrate transistors built into

processor chips, field programmable gate arrays (FPGAs), and application-specific integrated circuits (ASICs) ;

see Figure 23. Either NPN or PNP transistors can be used, as long as the base-emitter junction is used as the

remote temperature sensor. NPN transistors must be diode-connected. PNP transistors can either be transistor-

or diode-connected (see Figure 23).

Errors in remote temperature sensor readings are typically the consequence of the ideality factor (η-factor) and

current excitation used by the TMP468 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 TMP468 uses 7.5 μA (typical) for ILOW and 120 μA (typical) for IHIGH.

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

an ideal diode. The TMP468 allows for different η-factor values; see the η-Factor Correction Register section.

The η-factor for the TMP468 device is trimmed to 1.008. For transistors that have an ideality factor that does not

match the TMP468 device, Equation 4 can be used to calculate the temperature error.

TMP468 Datasheet(PDF) 31 Page - Texas Instruments

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