JAJSFC6C May 2015 – April 2018 ADS52J90
PRODUCTION DATA.
The auto offset calculation module can be used to calculate the channel offset that is then subtracted from the ADC output. To enable the auto offset correction mode, set the OFFSET_REMOVAL_SELF bit and DIG_OFFSET_EN bit to 1.
In auto offset correction mode the dc component of the ADC output (assumed to be the channel offset) is estimated using a digital accumulator. The ADC output sample set used by the accumulator is determined by a start time or first sample and number of samples to be used. A high pulse on the TX_TRIG pin or setting the OFFSET_REMOVAL_START_MANUAL register can be used to determine the first sample to the accumulator. To set the number of samples, the AUTO_OFFSET_REMOVAL_ACC_CYCLES register must be programmed according to Table 7.
If a pulse on the TX_TRIG pin is used to set the first sample, additional flexibility in setting the first sample is provided. A programmable delay between the TX_TRIG pulse and the first sample can be set by writing to the OFFSET_CORR_DELAY_FROM_TX_TRIG register.
The determined offset value can be read out for each channel. Set the channel number in the AUTO_OFFSET_REMOVAL_VAL_RD_CH_SEL register and read the offset value for the corresponding channel in the AUTO_OFFSET_REMOVAL_VAL_RD register. Note that the offset estimation is done separately for the odd and even data streams of each of the 16 ADCs and results in 32 sets of offset estimates that can be read out.
AUTO_OFFSET_REMOVAL_ACC_CYCLES (Bits 3-0) | NUMBER OF SAMPLES USED FOR OFFSET VALUE EVALUATION |
---|---|
0 | 2047 |
1 | 127 |
2 | 255 |
3 | 511 |
4 | 1023 |
5 | 2045 |
6 | 4095 |
7 | 8191 |
8 | 16383 |
9 | 32767 |
10 to 15 | 65535 |