TPS62827: how to measure jitter for DCS-control

Hi Ann,

Usually, you would set the oscilloscope to persistence mode and look at the SW node.  Triggering on the rising edge, the width of the falling edge would be the jitter.

Did you have a specific design or a need for measuring jitter?

Chris

Hello Chris,

Please kindly see below three waveform, is there any waveform is correct measurement for jitter? My question is the hysteresis control which is non-linear control, it should not be fixed frequency operation. Why do we measure single pulse rather than measure two pulse for it? Thanks!

1-->

2-->

3-->

Best regards,

Ann Lien

Hi Ann,

Any of these can be correct, depending on what you want to do.  Why do you measure the jitter?

The second and third waveform are more showing the variation in switching frequency.  This is not usually what is meant by jitter.

You can measure the loop response on this device, if you are trying to measure stability.

Chris

Hello Chris,

For customer, it is report needed. And for me, the meaning of jitter is to check the system stability. The second one should be the DCAP jitter measure way, right? Thanks!

Best regards,

Ann Lien

Hi Ann,

If the customer requested the measurement, they should be able to explain what they want measured.

The more common way to measure stability is with a load transient and/or bode plot.  These are both valid stability tests for the TPS62827.

TPS62827 does not use DCAP, though its DCS-Control is similar.

Chris