Hi Shinichi
In the ADC08D1000, ADC08D500 and ADC08D1500, if the On-Command calibration is done when the ADC is set in Auto DES Mode, the internal clock duty cycle correction circuitry can become unstable and the internal clock will stop. The only way to recover from this state is to power-cycle the ADC.
For this reason, the device must first be set to non-DES mode, then calibrated, then set back to Auto DES mode.
I hope this is helpful.
Best regards,
Jim B