Maxim Integrated 6-11
MAX31782 User’s Guide
Revision 0; 8/11
6.2.6 ADC External Temperature Offset Register (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
raw_adc + TOEX, where raw_adc is the converted temperature in Kelvin.
6.2.7 ADC Voltage Offset Register (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 raw_adc + ADVOFF, where raw_adc is the converted voltage without any offset compensation.
6.2.8 ADC Voltage Scale Trim Registers (ADCG1 and ADCG5)
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
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