I design a board .on my board there is a ATmega88pa and a 24bit ADC.
because of adc low stability i suspect to power supply and watch it by oscilloscope .
for watching noise i set the oscilloscope on AC mode .the result was really strange .
This is what i have on my Vcc and Gnd pins .
the pick to pick voltage is approximately 400m/volt
and when i set the mcu into sleep mode (power Down) it reduced to 2 m/volt.
why muc generate such a noise ?
Sorry for low quality