UG-1262
Rev. B | Page 65 of 312
When calibrating the gain error for the ADC voltage channels during Analog Devices production testing, the value loaded to the
ADCGAINGN1P5 calibration register is ≥0x4000. To ensure this value, the target ADC result is higher than normal. The factory trim
value for the ADC reference is 1.82 V, but for calibration purposes, the target voltage is 1.835 V.
When calculating a real voltage from an ADC conversion on a channel using the factory gain calibration, the K factor of 1.835 or 1.82
must be taken into account, as shown in Equation 1. If user ADC gain calibration targets a reference voltage of 1.82 V, then the K portion
of Equation 1 is not required.
ADC DIGITAL SIGNAL PROCESSOR (DSP) BUILT IN SELF TEST
It is possible to verify the digital logic blocks on the analog die related to the ADC.
The digital waveform generator can be used to create a digital pattern that is connected directly to the output filters of the ADC,
bypassing the ADC itself. As a new value is outputted from the digital waveform generator block to the sinc3 digital filter, the digital
value is shifted through the calibration block and other digital filter blocks until the digital value reaches the ADC filter result register.
This value can then be fed to the cyclic redundancy check (CRC) accelerator block on the digital die.
By completing the self test for a large number of digital waveform values, the CRC accelerator can compute a final CRC result. By
comparing this CRC result with a known and previously verified CRC result, all of the digital blocks shown in Figure 13 can be checked
for errors. Example code demonstrating how to enable this feature is provided with the
STEP 1: CONFIGURE MUX
TO SELECT WAVEFORM
GENERATOR
SINC3 FILTER
OSR5/4
ADC
GAIN AND
OFFSET
SINC2
FILTER
OSR178
50Hz/60Hz
NOTCH
GAIN
CORRECTION
CRC
(DIGITAL DIE)
SINUSOID
DAC DATA
MMRs
DAC_CORDI
DAC_CORDIC
STEP 3: CONFIGURE WAVEFORM
GENERATOR DATA TYPE
STEP 4: TRIGGER THE DSP BIST
STEP 5: USE SOFTWARE
TO OUTPUT DSP DATA
TO DIGITAL DIE
CRC BLOCK
STEP 6: CHECK THE CRC
RESULT WITH EXPECTED
RESULT WHEN BIST FINISH
STEP 2: CLEAR CRC DATA
166
75-
014
Figure 13. ADC Built In Self Test Feature