cmos_ajay
Full Member level 2
Hello, I have a unity gain buffer connected to a switch and a big capacitor of 5uF. It supplies a 2.5V to a capacitive DAC array in a SAR A/D converter. When the most significant capacitor (MSB) in the DAC array is switched at a certain frequency, the voltage at node A keeps falling by a few uV every clock cycle. I would expect the voltage to remain stable at around 2.5V always.
But if I remove the switch and replace it with a short, the voltage at node A remains stable for all clock cycles .
* I believe the switch resistance is causing the capacitor C to discharge by a few uV with every clock cycle .
Is there any solution for this since I need to use a switch in my design ??
Please see attached picture.
But if I remove the switch and replace it with a short, the voltage at node A remains stable for all clock cycles .
* I believe the switch resistance is causing the capacitor C to discharge by a few uV with every clock cycle .
Is there any solution for this since I need to use a switch in my design ??
Please see attached picture.