9.1.2.5 Clipping and Over-Range

The ADC31JB68 device has two regions of signal clipping: code clipping (over-range) and ESD clipping. When the input signal amplitude exceeds the full-scale reference range, code clipping occurs during which the digital output codes saturate. If the signal amplitude increases beyond the absolute maximum rating of the analog inputs, ESD clipping occurs due to the activation of ESD diodes.

Code clipping may be monitored via the SDO/OVR pin, which can be configured to output an quick detect over-range signal. The over-range threshold is programmable via the SPI. An over-range hold feature is also available to extend the time duration of the indicator longer than the over-range event itself to accommodate the case that a device monitoring the over-range signal cannot process at the rate of the ADC sampling clock.

ESD clipping and activation of the ESD diodes at the analog input should be avoided to prevent damage or shortened life of the device. This clipping may be avoided by selecting an ADC driver with an appropriate saturating output voltage, by placing insertion loss between the driver and ADC, by limiting the maximum amplitude earlier in the signal path at the system level, or by using a dedicated differential signal limiting device such as a clamp. Any signal swing limiting device must be chosen carefully to prevent added distortion to the signal.