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TPS61021A: value of input capacitor/loading

Amr Elhadidy
Expert 1005 points
Part Number: TPS61021A
Other Parts Discussed in Thread: TIDA-01385,

Hello,

In reference design TIDA-01385, it was mentioned that TPS61021A when connected to a high input capacitor (e.g. 1mF and up) can't be loaded with a current more than 50mA due to stability issues. May I ask you please what are the stability issues that arise? How to solve them? I intend to insert an input capacitor of about 1mF and connect a load at about 200mA, can this cause any violation of stability margins? What is your suggestion in this case?

Kind Regards,

Amr 

  • 0
    TI__Guru 68655 points

    Hi Amr,

    Thank you for considering the TPS61021A for your applications.  Our experts are currently on holidays until later this week.  I have notified them so you should get their advice in a few days.

    I took a glance through the TIDA-01385, and it mentioned a large C10 may affect the stability,  but not the input capacitor.  Please clarify if I misunderstood you. 

    Thanks,

    Youhao Xi, Applications Engineering

  • 0 in reply to Youhao Xi
    Expert 1005 points

    Hello Youhao,

    Thank you for your reply.

    Well I meant the input capacitor of the boost stage C10 but mentioned it in a general way as it is unclear if it is the same person responsible for the TIDA project also responsible for the disrete parts. The 1mF in the previous message I meant as an example of a higher capacitor value but not C2 in particular. 

    However, wouldn't the 1mF cap C2 be also in parallel with C10,so one can consider both as an input capacitor to the boost stage? (e.g. in times when the supercap not connected to the system).

    Regards,

    Amr

  • 0 in reply to Amr Elhadidy
    TI__Mastermind 34201 points

    Hi Amr,

    Our TI colleague Helen already replied you in another thread about the feedforward capacitor selection question.

    So I'll close this thread. If you have any other question, you can post a new thread.

  • 0 in reply to Zack Liu
    Expert 1005 points

    Hello Zack,

    OK that's fine.

    Thank you.