Maxim Integrated MAX31782, User Manual

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MaximIntegrated 6-11
MAX31782 User’s Guide
Revision 0; 8/11
6.2.6ADCExternalTemperatureOffsetRegister(TOEX)
Register Address: M1[1Ah]
The TOEX register contains the temperature offset for the external temperature measurements . The default value of
this register is -273 (Kelvin to Celsius) plus any offset that was calibrated out at the factory . This offset is applied to the
raw data from the ADC prior to the value being stored into the data buffer . The final result stored in the data buffer is
r TOEX, where raw_adc is the converted temperature in Kelvin .
6.2.7ADCVoltageOffsetRegister(ADVOFF)
Register Address: M1[19h]
The ADVOFF register contains the ADC voltage offset for the voltage mode . This is calibrated at the factory to cancel out
any offset that can be present in the ADC . The user can add or subtract any offset that they desire by altering this register .
This offset is applied to the raw data from the ADC prior to the value being stored into the data buffer . The value stored in
the data buffer is r ADVOFF, where raw_adc is the converted voltage without any offset compensation .
6.2.8ADCVoltageScaleTrimRegisters(ADCG1andADCG5)
ADCG1 Register Address: M1[17h]
ADCG5 Register Address: M1[18h]
The ADCG1 and ADCG5 registers are used to adjust the ADC full scale by changing the gain applied to the ADC
reference (internal or external) . These registers are set at the factory to work with the internal reference . The internal
reference voltage is set to 1 .215V and cannot be changed by the user . When using the internal reference, ADCG1 and
ADCG5 are factory calibrated to produce ADC full scale levels of 1 .225V and 5 .5V respectably .
The ADCG1 and ADCG5 registers are provided so the ADC full scale can be adjusted to meet the needs of the targeted
application . Only bits ADCG[14:0] are used to adjust the full scale level . Some basic settings are the following:
• ADCG = 2000h: The full scale is 1x the reference level .
• ADCG = 1000h: The full scale is 2x the reference level .
• ADCG = 0800h: The full scale is 4x the reference level .
It is not recommended that a gain other than 1x, 2x, or 4x be used . This is because the weightings of the ADCG[10:0]
bits are nonlinear . An application specific program needs to be developed that tests the ADC full scale for each pos-
sible code setting until the proper full scale is achieved .
s = special, initial value is dependent on trim settings
s = special, initial value is dependent on trim settings
s = special, initial value is dependent on trim settings
Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Name S S S S 2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
2
-1
2
-2
2
-3
Reset s s s s s s s s s s s s s s s s
Access rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw
Bit
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Name S S S S 2
11
2
10
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
Reset s s s s s s s s s s s s s s s s
Access rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw
Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Name Don’t Care ADCG14 ADCG13 ADCG12 ADCG11 ADCG10 ADCG9 ADCG8 ADCG7 ADCG6 ADCG5 ADCG4 ADCG3 ADCG2 ADCG1 ADCG0
Reset s s s s s s s s s s s s s s s s
Access rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw