We are testing a fabricated chip with expected output current of around 4mA which is then used to charge a button cell. The input is from a PV cell. However, when we attach an oscilloscope probe onto one of the pin outs of the chip (i.e. the ring oscillator and the clock), we detect a significant current drop at the output, from 4mA to around 1mA. The current from the PV cell also drops.
what would be the cause of this current drop?
We tried with a different oscilloscope, and still detected a drop in current, albeit of a different value.
Attached is the block diagram of the DUT.
implemented in 65nm CMOS
note: the buffer is connected to the rectifier through offchip capacitors.