ADS7828: ADS7828E/250

Hi Chris,

I can  do some digging internally to see if we have this information available but it is unlikely as this is a relatively old device. What types of signals are you trying to measure and what application is device used in? We can certainly help with some more information on the application.

Regards,

Aaron

Hi Aaron,

Thanks for your help looking into this. I'm planning on taking in multiple analog signals including (temperature, flow rates, pressure...) nothing too high speed but I'm planning to take samples at a rate somewhere between 1KHz to 50KHz and I'm trying to design a signal filter and would like to know the typical input impedance on the input channels seen at these rates to help me choose an appropriate external capacitor to put on the input pins. 

Very Respectfully,

-Chris 

Hi Chris,

With a SAR ADC, it is important that the input is driving appropriately so that the input settles within 0.5LSB by the end of the acquisition time. The use of an external RC filter should help facilitate settling where Cfilt is typically 20x the input capacitance (25pF for ADS7828).

Since the input signals don't seem to be too high speed, perhaps a sample rate of 8kHz would work. When sampling at 8kHz, an external RC filter with R = 1k and C = 500pF should do the trick. 

Regards,
Aaron