TPS54302: TPS54302 ripple waveform

Hi Hardy,

Some questions may need you help to clarify .

1.How to measure the Vout ripple ? with the closest loop ?

2.Any waveform of SW pin ?

3.Any loading change during measurement ?

BRs,

Young

Hi Young,

1. Yes, customer use closest loop to measure ripple waveform.

2. Please see below picture.

3. With1.5A continuous load

Customer is qualifying our 2nd source. They didn't find this phenomenon in TPS56339. Why Vin with a little bit variation will cause Vout ripple obviously change?

Ch1: Vout_ripple; Ch2: SW; Ch3: Vin; Ch4: Vout

Best regards,

Hardy

Hi Hardy,

This may related with 2 items .

1)TPS54302 is integrated with  Frequency spread spectrum to reduce EMI , frequency is varying within 6% corner frequency . 

2) VIN voltage variation will also have effect on output ripple.

Could you help add one larger input cap to stable the VIN voltage and try again?

BRs,

YZ

Hi Young,

We have tried use 3x10uF for Cin and use external DC source. But we still can see stepped ripple on Vout as below picture. Look like this phenomenon is not caused by VIN.

How can we improve Vout ripple?

Best regards,

Hardy

Hi Hardy,

Could you help share the sch for review?

and could you help check on EVM ?

BRS,

Young