ADJUST

eff

1.008

2088

N

2088

§

·

u

¨

¸

©

¹

eff

ADJUST

1.008

2088

2088

N

§

·

u

¨

¸

©

¹

=

V

V

BE2

BE1

-

hkT

q

ln

I

2

I

1

TMP451

www.ti.com

SBOS686 – JUNE 2013

η-Factor Correction Register

The TMP451 allows for a different

η-factor value to be used for converting remote channel measurements to

measurement to determine the temperature of the remote transistor. Equation 1 describes 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 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 7.

η-Factor Range

BINARY

HEX

DECIMAL

η

0111 1111

7F

127

0.950198

0000 1010

0A

10

1.003195

0000 1000

08

8

1.004152

0000 0110

06

6

1.005111

0000 0100

04

4

1.006072

0000 0010

02

2

1.007035

0000 0001

01

1

1.007517

0000 0000

00

0

1.008

1111 1111

FF

–1

1.008483

1111 1110

FE

–2

1.008967

1111 1100

FC

–4

1.009935

1111 1010

FA

–6

1.010905

1111 1000

F8

–8

1.011877

1111 0110

F6

–10

1.012851

1000 0000

80

–128

1.073837

Offset Register

The offset register allows the TMP451 to store any system offset compensation value that might be observed

from precision calibration. The value in the register is stored in the same format as the temperature result, and is

added to the remote temperature result upon every conversion. Combined with the

η-factor correction, this

function allows for very accurate system calibration over the entire temperature range.

Copyright © 2013, Texas Instruments Incorporated

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