Hi experts:
My customer is designing with ADS1120. To filter out the noise they use a serial 220ohm resistor between 3.3V supply and DVDD pin. The DVDD voltage is initially 3.3V after power up and before configuration the device, however, once the SCLK is pulsed (with 5MHz frequency), they found the DVDD voltage dropped to about 2V. That means the DVDD voltage is in fact 1.3V/220ohn = 6mA, while the datasheet spec is only 95uA for IDVDD. Why?
Here is the schematic:
The device seems function properly. They have tried to short the 220ohm resistor and ADC works properly. I have also confirmed with engineer that the filtered out, 3VISO1 is only used to drive DVDD pin and 1M pull up resistor, no other load on it.
Question is why the DVDD current of device is so high?
Thank you!
John