[FAQ] ADS7138: ADS7xx8 and ADS7xx8-Q1 product family input bias / leakage currents

Hello,

The maximum input leakage current of the analog inputs when not converting is roughly 1uA across the full temperature range.  This current will be less at 25C, likely in the 10's of nA range. 

The other, likely more significant effects on driving the device without a low impedance source will be the charge required during the acquisition period of the conversion process.  For more information there's a great video linked here about all of the effects and design considerations when driving these devices without an input buffer:  https://training.ti.com/ti-precision-labs-driving-sar-without-amplifiers