• State Resolved
  • Locked Locked
  • Replies 8 replies
  • Subscribers 64 subscribers
  • Views 264 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

TPS7A7002: Load Capacitance larger than larger than 47uF

TPS7A7002: Load Capacitance larger than 200uF

Emanuele Pellegrini
Prodigy 20 points
Part Number: TPS7A7002

Hi Team:

in my application I should use a load capacitance of 660uF (330uF tantalium + 330uF electrolytic), and with a feedforward capacitor of 4.7nF the TPS7A7002 and the device is working well.

Since in the datasheet of TPS7A7002 the max recommended load capacitance is 200uF, could I meet a functional and/or reliability problem?

Thanks,

Emanuele

  • 0
    TI__Mastermind 44665 points

    Hi Emanuele,

    The device likely just wasn't characterized beyond 200uF on the output. The risk with doing this is that there may be some operating point over temperature and load (and also with process variation) where the device becomes unstable, and since there is no characterization data we can't assess the likelihood of this happening or where it could happen. Is this a mass production application? 

    Regards,

    Nick

  • 0 in reply to Nick Butts
    Prodigy 20 points

    Hi Nick,

    thanks for the quick reply. Supposing to receive a feedback like yours, just yesterday I've tested 3 samples of my application with only the 330uF tantalium cap (removed 330uF e-cap) and a 2.2nF feedforward capacitor, and they works well too. What do you think about the setup above? Could I have reduced the risks you mentioned? Since this is a mass production application for 2024, could you suggest me a similar LDO without the load capacitance limit (or larger than 200uF)?

    Thanks and Best Regards,

    Emanuele

  • 0 in reply to Emanuele Pellegrini
    TI__Mastermind 44665 points

    Hi Emanuele,

    It's hard to say because testing a small number of units at room temperature does not speak very much to how it can vary with process variation and temperature. Does your application require the large caps?

    I can suggest a different device is you provide me some more application requirements. What are the VIN, VOUT, IOUT, and any other key care-abouts (e.g. PSRR, noise, transient performance, cost, EN functionality, etc.)?

    Regards,

    Nick

  • 0 in reply to Nick Butts
    Prodigy 20 points

    Hi Nick,

    I understand what you mean, and my application needs 330uF tantalium cap as recommended in its application note.

    My application specs are: Vin=5V, Vout=3.8V, Iout_max=2.2A, Iout_avg=700mA, ENABLE pin, Load & Line reg.<2%, SMT package.

    Thanks for any suggestion. Best Regards.

    Emanuele

  • 0 in reply to Emanuele Pellegrini
    TI__Mastermind 44665 points

    Hi Emanuele,

    What is your max ambient temperature? 1.2V headroom at 2.2A is 2.64W, and most devices will struggle thermally with this much power dissipation. Is the 2.2A a transient current or is that an expected steady-state current?

    Regards,

    Nick

  • 0 in reply to Nick Butts
    Prodigy 20 points

    Hi Nick,

    max amb temperature is 80°C.

    The 2.2A is the steady state current of a square waveform for only 600uSec with a duty of 12%, so is not a thermal issue.

    Regards,

    Emanuele

  • +1 in reply to Emanuele Pellegrini
    TI__Mastermind 44665 points

    Hi Emanuele,

    Got it. Check out TPS7A53. I think it meets all of your requirements and is spec'd to 3000uF output cap. It has a BIAS rail but with VIN = 5 V you do not need a separate BIAS supply.

    Regards,

    Nick

  • 0 in reply to Nick Butts
    Prodigy 20 points

    Hi Nick,

    thank you for the suggestion. Looking the datasheet seem it comply with my application spec.

    Best Regards

    Emanuele