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TPS65132L Vpos Output capacitor

tateo yamashiro
Guru 10890 points
Other Parts Discussed in Thread: TPS65132L

Hi,

My customer has questions about TPS65132L.
Could you tell me about questoins?

[Question]
 - How much is the maximum recommended Vpos output capacitor value?
   My customer considers to use max 30uF. Is there any problem?

 - How much is variation of Vpos soft start time?

 - How much is the Vpos inrush current capability?
   When the Vpos output capacitor is 30uF, input current is peak 700mA at Vin=3.3V, Vpos=5.4V.
   So Vpos LDO peak output current may be over 200mA.
   My customer concern LDO inrush current capability.

Best Regards
tateo

  • 0
    TI__Expert 8010 points

    Hello Tateo,

    Is this device used in tablet or smart phone mode?

    Regards,
    Ilona

  • 0 in reply to Ilona
    Guru 10890 points
    Thank you for your reply.

    The device is used in smart phone mode.

    Best Regards,
    tateo
  • 0 in reply to tateo yamashiro
    TI__Expert 8010 points
    Hello Tateo,

    In smartphone- mode the minimum effective capacitance would be 2.35uF (considering dc-bias, temperature). Why would the customer apply such a high output capacitor? I would not see any problem with this higher capacitance although it is rather redundant.
    What is the output current?
    Thank you,
    Best Regards,
    Ilona
  • 0 in reply to Ilona
    Guru 10890 points

    Thank you for your reply.

    The panel has input capacitor. So the device total output capacitor is 30uF. And the output current is max 40mA.

    The device should use high output capacitance. Could you help us?

    Best regards,

    tateo

  • 0 in reply to tateo yamashiro
    TI__Expert 8010 points
    Hello Tateo,

    The start-up of the LDO is independent of the output- capacitor. In Version L the start-up time has been increased to 500 us and therefore the inrush current has been reduced (factor 3)
    As long as the output current is within the range (40mA are within the range) you don't need to be concerned about the LDO.

    Regards,
    Ilona
  • 0 in reply to Ilona
    TI__Expert 8010 points
    Hello Tateo,
    To add more facts on this: The LDO follows a start-up ramp for min. 500 us, which is clamped at 200mA. That means, if the output cap cannot deliver the current, then the start-up time will increase. In your case (assumption: dc-bias --> eff. output cap ~ 20uF) the start-up time would be roughly
    t_start = (20 uF * 5.4 V)/200 mA = 540 us.Is that more clear to you?
    Best Regards,Ilona