PMP9256: Output Ripple

Ch Ramakrishna

Part Number: PMP9256

Dear Sir,

The output Ripple is around 160 to 140 mV with 20 MHZ band limited Scope.

Is there any suggested ripple suppression filter or any other circuit modification such that the ripple can be reduced to a level of 10mV.

over 6 years ago

0 Robert Taylor1 over 6 years ago

TI__Expert 6620 points

Hi,

A second stage LC could be added to the output to reduce the ripple level. You need to take specific care to make sure that the stability of the converter is not affected. Please refer to the following reference material

Power Tips: Designing a two-stage LC filter

Many applications require low-noise power supplies, including laser-diode drivers and optical modules. Even with low equivalent series resistance (ESR) ceramic output capacitors, it is often impractical…

By Ryan Manack over 10 years ago in Technical articles > Power management

Thanks,

Robert

0 Ch Ramakrishna over 6 years ago in reply to Robert Taylor1

Prodigy 240 points

Dear Sir,

Thank you for your response..

As we are not expert in power supply design we have directly adopted the PMP9256 design and made the board.

For second stage ripple filter for this particular board is there any suggested filter design with indicated values to achieve ripple of order 10 mV.

Please suggest the values and we will work around with the available components.

thank you..

0 Robert Taylor1 over 6 years ago in reply to Ch Ramakrishna

TI__Expert 6620 points

Hi,

You can try to add a 1uH inductor and move the ceramic capacitors to after this inductor. This should provide enough attenuation to get to 10mV. Also the frequency of the LC will be high enough to not cause problems for the loop stability.

Thanks,
Robert

0 Ch Ramakrishna over 6 years ago in reply to Robert Taylor1

Prodigy 240 points

Hi Robert,
thank you for your immediate response..
As per my understanding w.r.t schematic diagram, the output from X1_B transformer Pin4 to be connected with 1microH inductor after that the capacitors Cout1 to Cout4 should be connected.
Whether my understanding is inline with your solution?

0 Robert Taylor1 over 6 years ago in reply to Ch Ramakrishna

TI__Expert 6620 points

Hi,

No I think it is best to connect the inductor to the VOUT terminal after the capacitors. Then place the other additional capacitors after the inductor. Connect the load after this point.

thanks,
Robert

0 Ch Ramakrishna over 6 years ago in reply to Robert Taylor1

Prodigy 240 points

Thank you Robert, we will proceed as per your suggestion..

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PMP9256: Output Ripple