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TPS65320D-Q1: Load transient optimzied

Perry Wang
Prodigy 140 points
Part Number: TPS65320D-Q1
Other Parts Discussed in Thread: TPS65320-Q1

Dears

Currently we are using one TI power IC(TPS65320-Q1) in our product, But we are facing a problem in our degin:

This power regulator output 3V3 & 1V8 rail, and there is one power 1V0 (high load(Up to 7.5A on limited case)) is converted from 3V3, When power down our system, There is a spike（around 300mV） appear on 3V3 output regulation as attached picture below,

We suspect it is due to the power IC transient perfermance is not very good,  We have tried to add more capacitors (E.G,Add PC15  = 47uF) on output but it doesn't work. our design please refer to below:

We want to fix the spike if any good idea or suggestion please advise,

Any questions please let me know, Thanks!

  • 0
    TI__Mastermind 33140 points

    Hi Perry,

      Both outputs 3V3 & 1V8 rails have sourcing current not sinking current capability; any OV (Over Voltage) spike caused by their load can't be regulated.

      If the 300mV spike can't be accepted during system power down, a schottky diode can be used from the 3.3V output to the input of the 1.0V convertor; and then the spike should be seen on the negative side the diode instead of on the positive side which is on the 3.3V rail. 

    Thanks!

    Phil 

  • 0
    Prodigy 140 points

    Dear Phil

    Thanks for your answer, I will try to test add the diode,The diode (cathode) should be connect to the 3V3 output,  the diode (anode) should be connect to the input of the 1.0V convertor, Right?

    While from my understand the spike is due to the power IC poor transient perfermance, Is there any good advise how to optimize the spike? E.G add capacitors or adjust some component value?

    Thanks and waiting for feedback

  • 0 in reply to Perry Wang
    TI__Mastermind 33140 points

    Hi Perry,

      The diode's anode should be connect to the 3V3 output, the diode's cathode should be connect to the input of the 1.0V convertor to make the current from 3.3V to the 1.0V convertor.

      Yes; adding capacitance can improve transient performance. If the spike happens when the system is powering off, the power IC may be out of its normal regulation; and then the spike may be still there. Can you try power off the 3.3V first before turning of its input power supply? 

    Thanks!

    Phil

  • 0 in reply to Phil Yi40
    Prodigy 140 points

    OK， I misunderstand that the diode need to be in serial intead of in parallel from 3V3 output to input od the 1.0v convertor. But it is not easy to find the type diode to meet the high current from 3.3V to the 1.0v converter,

    The power sequence can not be changed according to the load (SoC) requirement. So the only optimized to improve the spike is to add more capacitors on the 3v3 output power rail?

    Thanks for your answer.

  • 0 in reply to Perry Wang
    TI__Mastermind 33140 points

    Hi Perry,

      What's the exact part number? is it TPS65320-Q1 or TPS65320B/C/D-Q1? 

    Thanks!

    Phil

  • 0 in reply to Phil Yi40
    Prodigy 140 points

    Hi, Yi40,

    The expected PN: TPS65320DQPWPRQ1 which can be found from the SCH.

    Thanks

  • 0 in reply to Perry Wang
    TI__Mastermind 33140 points

    Hi Perry,

      Can you try using another 3A resistor load to replace the 1.0V convertor and check if the spike is still there? 

    Thanks!

    Phil