10 – adc voltage offset register (advoff), Ds4830a user’s guide – Maxim Integrated DS4830A Optical Microcontroller User Manual
Page 62
DS4830A User’s Guide
62
7.2.10 – ADC Voltage Offset Register (ADVOFF)
Bit
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Name
S
S
S
2
12
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
s = special, initial value is dependent on trim settings
This register contains the ADC voltage offset for the voltage mode. This is calibrated for ADCG1 at the factory to
cancel out any offset that may 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 will be raw_adc + ADVOFF, where raw_adc is the converted voltage
without any offset compensation.
7.2.11 – ADC Voltage Scale Trim Registers (ADCG1, ADCG2, ADCG3 and ADCG4)
Bit
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Name
ADCG[15:0]
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
s = special, initial value is dependent on trim settings
These registers are used to adjust the ADC full scale by changing the gain applied to the ADC reference (internal).
These registers are set at the factory to work with the internal reference. The internal reference voltage is set to
1.2V and cannot be changed by the user.
These gain registers are provided so the ADC full scale can be adjusted to meet the needs of the targeted
application. Only bits ADCG[15:2] are used to adjust the full scale level. Some approximate settings are:
• ADCGx = 32A8h: The full scale is ~1X the reference level
• ADCGx = 1960h: The full scale is ~2X the reference level
• ADCGx = 0B90h: The full scale is ~4X the reference level
• ADCGx = 0328h: The full scale is ~6X the reference level
It is not recommended that a gain other than 1X, 2X, 4X or 6X be used. This is because the weightings of the
ADCGx [15:0] bits are non-linear. An application specific program needs to be developed that tests the ADC full
scale for each possible code setting until the proper full scale is achieved. It is recommended that the user should
not change ADCG1. The ADC controller uses ADCG1 (not user selectable) for Sample and Hold.