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TPS53355 current problem

joset
Prodigy 90 points
Other Parts Discussed in Thread: TPS53355

Hi


I have designed a DC-DC converter using TPS53355 for getting 5v @ 10A using webench design support.

It was getting 5V up to 2A load. If the load is increased above 2A , the  TPS53355 not providing any voltage.


Help me to solve this.3858.webench_design_3907327_6_229207721.pdf

  • 0
    TI__Guru**** 191445 points

    Did you follow the schematic and BOM exactly?  That circuit should current limit at 10.5 A for 12 V input.  Is your input supply current limited?  can you show waveforms at Iout = 2 A and then increase the current slightly above that?   If you are current limiting, you should see the output voltage start to decrease.  When Vout falls below the uVP threshold, the device will shut off and the output voltage go to zero.  Make sure to show LL, VIN and VFB waveforms.

  • 0 in reply to JohnTucker
    Prodigy 90 points

    Hi John Tucker,

     

    I have followed the Schematic and BOM as same. Please find the attached pdf contains the wave forms.

    If the load is increased above 2.7 the LL, VFB, Vout will be nearly zero.  My input power supply have 10A capacity.

    2804.Waveform of TPS53355.pdf2821.TPS53355_layers.pdf

    I have added the layer details3146.TPS53355 Schematic.pdf

    If the PCB layer cause any problems?


    Thanks,

    Anoop Jose

  • 0 in reply to joset
    TI__Guru**** 191445 points

    One thing I notice immediately.  The BOM for the webench design calls for all ceramic capacitors for both input and output filtering.  From your layout, it looks like you are using electrolytic types.  You also do not follow the layout recommendations very closely.  It is important to get the input decoupling caps as close to the VIN and GND connections as possible.  I think you can use one bulk electrolytic type, but the rest need to be ceramic X5R or better.  I would really recommend the output capacitor ground return be a small lop as well.  Se the datasheet example.  In that example, the main power circulating paths are all large copper fill areas on the top side.  Most of the other components are mounted on the bottom, but I think they can easily be placed on the top side.  The inductor should be close to the IC as well.  You want to minimize the copper area for the LL node (but do not make it thin, it needs to be a fill area).  I suspect the current limit circuit is susceptible to noise and the layout is making the noise worse along with the capacitor choice.

  • 0 in reply to JohnTucker
    Prodigy 90 points

    Hi JohnTucker,


    After I replaced all the electrolytic to ceramic capacitors I got these current rating, before that I was getting only 0.5A current rating.


    Is the input capacitor value may cause any problems, in BOM it was 22uF , if I increase to 100uF can I get any benefits.

    Regards,

    Anoop ose