We have a product that uses the ADS7812 to acquire data for display on an embedded controller. On occasion the equipment will fault shutting down. Most times this is not a problem but on occasion the ADS7812 starts to pull more current loading down the 5V 100ma regulator to about 3.1V. We clipped the Vcc then measured about 175ma which explains why the regulator is limiting. Vcc is also used to pull INT/EXT high. When this drops the 3.1V the chips stops using the EXT clock to shift out data.
It appears that the 7812 may be locking up due to the fault. It only happens in about 2% and only when a fault in the system occurs. This is a high voltage power supply so a fault typically results in shutting the HV off. The noise may be getting picked up by the ADC.
We have the recommend bypass capacitance Vcc to ground and have followed the design guidelines for grounding and ground plane under the device.
Has anyone seen this before? If so what was the fix?