TPS560200: There is a lot of noise in power supply

Hi Amal:
first pls check when you test the 3V3,whether you scope and its GND close to Vo and GND as close and as possible. otherwise, the scope will pick in some noise.
second, pls make sure the scope bandwidth is 20Mhz, higher bandwidth will inevitable pick in high frequency noise(much higher than Fsw) .

thrid, if the noise is coming from the power supply, if it is low frequency, adding choke with ceramic cap may helpful.

if the noise is high frequency, you can use bead with smaller ceramic capacitor to avoiding the noise go through Dc/Dc power stage coming to you output.

it is better you can provide some waveform which may help us identify what kind of noise you are dealing with.

hope this suggestion is helpful.

Thanks

Daniel Li

hai,

Sorry for late reply,

I have added an image of the noise level in my 3v3 supply.Please analyze the image.

Hi,

Please set the coupling to AC and zoom in the waveform, it is normal there is output ripple. If the ripple is not too large, it is okay.

Shawn

Hai Shawn,
Actually the power supply is used to power an MCU and i have trouble reading my adc. The variation is affecting my adc reading values a lot.Am not able to get linearity in ADC measurement due to this.I need help regarding this issue

Hi,

As I mentioned, please test the output ripple first to know how much it is, and what is your expect value for the ripple?

Shawn

Yaa let me first test that and i will inform you that.

hey what is the expected dc resistance of the Inductor in the design?