13

TMP421-Q1, TMP422-Q1, TMP423-Q1

www.ti.com

SBOS821 – NOVEMBER 2016

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

Submit Documentation Feedback

Copyright © 2016, Texas Instruments Incorporated

(1)

Resolution is 0.0625°C/count. All possible values are shown.

Both local and remote temperature data use two bytes for data storage. The high byte stores the temperature

with 1°C resolution. The second or low byte stores the decimal fraction value of the temperature and allows a

higher measurement resolution, as shown in Table 2. The measurement resolution for the both the local and

remote channels is 0.0625°C, and is not adjustable.

Table 2. Decimal Fraction Temperature Data Format (Local and Remote Temperature Low Bytes)

TEMPERATURE

(°C)

TEMPERATURE REGISTER LOW BYTE VALUE

(0.0625°C RESOLUTION)(1)

STANDARD AND EXTENDED BINARY

HEX

0

0000 0000

00

0.0625

0001 0000

10

0.1250

0010 0000

20

0.1875

0011 0000

30

0.2500

0100 0000

40

0.3125

0101 0000

50

0.3750

0110 0000

60

0.4375

0111 0000

70

0.5000

1000 0000

80

0.5625

1001 0000

90

0.6250

1010 0000

A0

0.6875

1011 0000

B0

0.7500

1100 0000

C0

0.8125

1101 0000

D0

0.8750

1110 0000

E0

0.9385

1111 0000

F0

8.3.2 Remote Sensing

The TMP421-Q1, TMP422-Q1, and TMP423-Q1 are designed to be used with either discrete transistors or

substrate transistors built into processor chips and 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 20, Figure 21, and

Figure 22).

8.3.3 Series Resistance Cancellation

Series resistance in an application circuit that typically results from printed circuit board (PCB) trace resistance

and remote line length is automatically cancelled by the TMP421-Q1, TMP422-Q1, and TMP423-Q1, preventing

what would otherwise result in a temperature offset. A total of up to 3 k

Ω of series line resistance is cancelled by

the TMP421-Q1, TMP422-Q1, and TMP423-Q1, eliminating the need for additional characterization and

temperature offset correction. See the two Remote Temperature Error vs Series Resistance typical characteristic

curves (Figure 5 and Figure 6) for details on the effects of series resistance and power-supply voltage on sensed

remote temperature error.

8.3.4 Differential Input Capacitance

The TMP421-Q1, TMP422-Q1, and TMP423-Q1 tolerate differential input capacitance of up to 1000 pF with

minimal change in temperature error. The effect of capacitance on sensed remote temperature error is illustrated

in Figure 7, Remote Temperature Error vs Differential Capacitance.