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TPS548A20: Some Solution Schematic Review Request

MINGKUN HE
Prodigy 60 points
Part Number: TPS548A20
Other Parts Discussed in Thread: TPS54326, TPS54620

Can someone here help me with schematic review of the TPS548A20, TPS54326, TPS54620? 

/cfs-file/__key/communityserver-discussions-components-files/196/TI-Power.pdf

  • 0
    TI__Expert 4795 points

    Hi Mingkun,

    Our US team will feedback to you after holiday. Thanks.

  • 0 in reply to Vincent Zhang(BSR)
    TI__Mastermind 35185 points

    Hi Mingkun,

    I have checked the TPS54620 and have one comment. Did you intend for C999 to be a high frequency input bypass capacitor like C810? It is good to include a 0.1µF high frequency input bypass capacitor and place it as close as possible to the PVIN and GND pins. Suggest using the same component that is being used for the BOOT-PH capacitor.

    How were the component values selected? Do you have any targets for output ripple or transient response?

  • 0 in reply to Anthony F
    Prodigy 60 points

    Anthony,

    Thanks for your reply.

    As the schematic, I used 22uF on C999. Thanks for your suggestion, it's right and I will add an additional 0.1uF placing it as close as possible to the PVIN and GND pins.

    Yes I have targets for output ripple and transient response. Output ripple pk-pk limits 2% of output voltage and transient response max limits 3%.

  • 0 in reply to MINGKUN HE
    TI__Mastermind 35185 points

    Hi Mingkun,

    Thanks for the ripple and transient response targets. What is the assumed load step size for the transient response? How were the external components selected in order to meet those targets? If you didn't already use it, WEBENCH works well for this.

    I should also mention the apps engineers who support the remaining parts on this schematic are out of the office until next week for the holiday.

    Anthony

  • 0 in reply to Anthony F
    Prodigy 60 points

    Hi Anthony,

    Thanks for your reply.

    I will use a DC electronic load to test transient response. The load step size is about 50% and current ramp slew rate is 5A/us. And I already drawn the schemitic by referring WEBENCH. 

    It's all right. I will wait for further more suggestion about this schemetic viewing.

    Mingkun

  • 0 in reply to MINGKUN HE
    TI__Mastermind 26820 points

    Hi Mingkun,

    TPS54326 designs look fine to me except the output capacitor is on the higher side than what is recommended in the datasheet. I see most designs have 47uFx2 and 4x22uF caps whereas max datasheet recommended is a nominal of 68uF. DC bias will lower the effective cap value but I suggest you to evaluate stability and load transient performance with the capacitors you have on these designs and change as required.

    Thanks,

    Amod

  • 0 in reply to MINGKUN HE
    TI__Mastermind 23985 points

    Mingkun,

    For the TPS548A20,  change the L3 to 1uH.     The remaining components are reasonable are similar to the webench calculation.

    R680, R686, R679 should connect to a quiet ground.  See Figure 40 in datasheet for the ground connections. 

    Review Figure 50 for the recommended pcb layout notice the connection of the

    power stage ground and the quiet ground. .