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20

TMP451-Q1

SLOS877B – OCTOBER 2014 – REVISED JUNE 2019

www.ti.com

Product Folder Links: TMP451-Q1

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Copyright © 2014–2019, Texas Instruments Incorporated

7.6.1.5 Conversion Rate Register

The conversion rate register (read address 04h, write address 0Ah) controls the rate at which temperature

conversions are performed. This register adjusts the idle time between conversions but not the conversion time

itself, thereby allowing the TMP451-Q1 power dissipation to be balanced with the temperature register update

rate. Table 7 lists the conversion rate options and corresponding time between conversions. The default value of

the register is 08h, which gives a default rate of 16 conversions per second.

Table 7. Conversion Rate

VALUE

CONVERSIONS PER SECOND

TIME (SECONDS)

00h

0.0625

16

01h

0.125

8

02h

0.25

4

03h

0.5

2

04h

1

1

05h

2

0.5

06h

4

0.25

07h

8

0.125

08h

16 (default)

0.0625 (default)

09h

32

0.03125

7.6.1.6 One-Shot Start Register

When the TMP451-Q1 device is in shutdown mode (SD = 1 in the configuration register), a single conversion is

started by writing any value to the one-shot start register, pointer address 0Fh. This write operation starts one

conversion and comparison cycle on both the local and the remote sensors. The TMP451-Q1 device returns to

shutdown mode when the cycle completes. The value of the data sent in the write command is irrelevant and is

not stored by the TMP451-Q1 device.

7.6.1.7 η-Factor Correction Register

The TMP451-Q1 device allows for a different η-factor value to be used for converting remote channel

voltage measurement to determine the temperature of the remote transistor. Equation 1 shows this voltage and

temperature.

(1)

The value η in Equation 1 is a characteristic of the particular transistor used for the remote channel. The power-

on reset value for the TMP451-Q1 device is η = 1.008. The value in the η-factor correction register may be used

to adjust the effective η-factor according to Equation 2 and Equation 3.

(2)

(3)

The η-factor correction value must be stored in twos complement format, yielding an effective data range from

–128 to 127. The η-factor correction value is written to and read from pointer address 23h. The register power-on

reset value is 00h, thus having no effect unless a different value is written to it.

Table 8. η-Factor Range

η

BINARY

HEX

DECIMAL

0111 1111

7F

127

0.950198

0000 1010

0A

10

1.003195