Tip / Sign in to post questions, reply, level up, and achieve exciting badges. Know more

cross mob
Level 4
Level 4
Good day,

If some data availible regarding ADC sensitivity to supply ripples (PSRR)?
(Power Supply Rejection Ratio = PSRR = 20*log(Vout/Vin)

Say, in XMC4500 Relax Lite Kit-V1 both: VDDA(35) & VAREF(33) pins connected to
3.3V supply line through BLM18PG600 EMI filters (60Om@100MHz).
As well decoupling capacitors 0.1uF used.

This NW is quite effective @100MHz, providing 70dB PSRR.
But, it is not effective at 330kHz - 1MHz,
where most of modern DC/DC working.

Assuming 12 bit resolution (4096 points) and 3.3V span, 1 bit will be 3300mV/4095 = 0.8mV approximately. So, if DC/DC has 20mVp-p ripples, we need supress it to level of 0.2mV or better.
Consequently, we need PSRR 40dB @330kHz or better.

So, if additional filtering shall be done, to avoid degrading performance of ADC, in case XMC4500 powered from DC/DC?

Best Regards,
0 Replies