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

23

TMP461-SP

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SBOS876B – SEPTEMBER 2017 – REVISED FEBRUARY 2020

Product Folder Links: TMP461-SP

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Copyright © 2017–2020, Texas Instruments Incorporated

7.6.1.9 η-Factor Correction Register

The TMP461-SP device allows for a different η-factor value to be used for converting remote channel

measurements to temperature. The remote channel uses sequential current excitation to extract a differential VBE

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 TMP461-SP device is η = 1.008. The value in the η-factor correction register can 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. The resolution of the η-factor

register is 0.000483.

Table 10. η-Factor Range

NADJUST

η

BINARY

HEX

DECIMAL

0111 1111

7F

127

0.950205

0000 1010

0A

10

1.003195

0000 1000

08

8

1.004153

0000 0110

06

6

1.005112

0000 0100

04

4

1.006073

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

1.008966

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

1.073829

7.6.1.10 Remote Temperature Offset Register

The offset register allows the TMP461-SP device to store any system offset compensation value that may result

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.

7.6.1.11 Manufacturer Identification Register

The TMP461-SP device allows for the two-wire bus controller to query the device for manufacturer and device

IDs to enable software identification of the device at the particular two-wire bus address. The manufacturer ID is

obtained by reading from pointer address FEh. The TMP461-SP device reads 55h for the manufacturer code.