ADS7828 REF_IN current requirements & power-on sequence

Hi Thomas,

Unfortunately, we don't have this maximum reference current specification in datasheet. The current required by the reference is dynamic, and it is required to settle the signal and also for bits judgement during conversion time, the most significant bit (MSB) hold the most charge and require the most current during the conversion time, but no current is drawn during acquisition time. The value of the current required by the ADC reference pin is a nonlinear function of the analog input signal, also this dynamic current is a function of both the SAR ADC throughput rate and the internal clock that controls the bit trials. Here is a link for a good article to simulate its behavior.   www.ti.com/lit/pdf/slyy097

The datasheet doesn't show the detailed information for power sequence, but it's always a good practice to power up analog power supply (AVDD) before reference and analog input signal are available, in case the analog core powers up in a probable latch-up state, the current through AVDD can be much higher than the specification in the datasheet and cause ADC to be pretty hot or damaged.

Thanks.

Regards

Dale Li