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LM5005: Ripple output voltage

Part Number: LM5005

Dear team

The spec is Vin=56V、Vo=12V

The customer using the LM5005. But they found the output voltage(12V) is not clean, The ripple is about 952mVpp.

They add the output capacitor. but the effect is not obvious.

Could you help to review the schematic? and could you guide us how to resolve this issue or do some experiment?

CH1: output voltage 

CH2: output ripple  

add capacitor => 47uF

capacitor =>100uF

Many thanks

Denny

  • Hi Denny

    Firstly, When testing the Vout ripple, Please make sure minimizing the ground loop created by the probe(using tip and barrel method).And it is typical to specify a 20 MHz bandwidth limit on the oscilloscope channel.

    Can you zoom in the time-scale and see the waveform of Vo_ac and SW? Also, what is the value of C368? Thank you.

    Best regards.