ZHCSKD0I September 2009 – October 2019 TMP431 , TMP432
PRODUCTION DATA.
The TMP43x allow 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 relates this voltage and temperature.
The value η in Equation 1 is a characteristic of the particular transistor used for the remote channel. When the beta compensation configuration is set to 0111 (beta compensation disabled) or the sensor is diode-connected (base shorted to collector), the η-factor used by the TMP43x is 1.008. When the beta compensation configuration is set to 1000 (beta compensation enabled) and the sensor is GND collector-connected (PNP collector to ground), the η-factor used by the TMP43x is 1. If the η-factor used for the temperature conversion does not match the characteristic of the sensor, then temperature offset is observed. The value in the η-Factor Correction Register can be used to adjust the effective η-factor according to Equation 2 and Equation 3 for disabled beta compensation or a diode-connected sensor. Equation 4 and Equation 5 can be used for enabled beta compensation and a GND collector-connected sensor.
The η-correction value must be stored in twos-complement format, yielding an effective data range from –128 to 127. Table 11 shows the η-factor range for both 1.008 and 1. For the TMP431, the η-correction value can be written to and read from pointer address 18h. For the TMP432, the η-correction value can be written to and read from pointer address 27h. The η-correction value for the second remote channel is read to and written from pointer address 28h. The register power-on reset value is 00h, thus having no effect unless written to.
NADJUST | η = 1.008 | η = 1.000 | ||
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BINARY | HEX | DECIMAL | ||
01111111 | 7F | 127 | 1.747977 | 1.734104 |
00001010 | 0A | 10 | 1.042759 | 1.034483 |
00001000 | 08 | 8 | 1.035616 | 1.027397 |
00000110 | 06 | 6 | 1.028571 | 1.020408 |
00000100 | 04 | 4 | 1.021622 | 1.013514 |
00000010 | 02 | 2 | 1.014765 | 1.006711 |
00000001 | 01 | 1 | 1.011371 | 1.003344 |
00000000 | 00 | 0 | 1.008 | 1 |
11111111 | FF | –1 | 1.004651 | 0.996678 |
11111110 | FE | –2 | 1.001325 | 0.993377 |
11111100 | FC | –4 | 0.994737 | 0.986842 |
11111010 | FA | –6 | 0.988235 | 0.980392 |
11111000 | F8 | –8 | 0.981818 | 0.974026 |
11110110 | F6 | –10 | 0.975484 | 0.967742 |
10000000 | 80 | –128 | 0.706542 | 0.700935 |