Other Parts Discussed in Thread: TPS62816EVM-140, TPS62913
I'm currently evaluating the TPS62816-Q1 part with the evaluation board TPS62816EVM-140. In our application it should supply noise sensitive ADC/DAC supplies. I made a ripple and FFT measurement of the output voltage which raised some questions. Please check the scope screen shot below.
The output voltage on the eval. board shows a peak-to-peak ripple of appr. 1.1mV (corresponding to the -69dBVrms peak at 2.225MHz). For our application we'll need to further reduce the output ripple by adding a second stage filter. Now the questions:
1) In the second screen shot you can see the waveform of the output voltage and the FFT. The signal shows some low frequency noise/ripple with appr. 2mVpp. It's also visible in the FFT below 1MHz. What causes this noise? Is it already wideband noise / flicker noise / etc. as described on the following references?
2) Is there a way to reduce this noise or is it caused by the converter and it's internal circuitry itself?
Thanks in advance for any help!