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TPS62050 output cap

Joris Van Dyck
Prodigy 20 points
Other Parts Discussed in Thread: TPS62050, TPS61030, TPS5410, TPS54140

Dear,

Is the TPS62050 step-down IC stable with an output capactor in the 3300 - 5600 uF range (electrolytic capacitor with low-ESR, eg Panasonic FM/FC/FK).

Also, is the load completely disconnected from the supply in shutdown mode?

Thanks for your answers.

Kind regards,

 

  • 0
    TI__Mastermind 36110 points

    The TPS62050 is not designed to operate with the amount of load capacitance you require.  I expect the design to be unstable and oscillate.  You should use the recommended capacitor values stated in the datasheet.

    If you have a pulsed load, you may be able to isolate your large capacitance from the acutal TPS62050 output capacitance with some resistance.  I do not have a closed form equation to calculate the required resistance as a function of capacitance, so you will need to find a value through experimentation.  Your other option is to use a power supply controller that allows you to select you output capacitance and then design the proper compensation values to make your power supply stable.  Texas Instruments has many TPS54xxx supplies that may be a better fit for your application.

  • 0 in reply to Matthew Day
    Prodigy 20 points

    Thanks for your kind reply.

    I once had a similar problem in step-up fashion using a TPS61030 and got it stable putting a 560 pF cap between the output and fb pins.

    Are you stating this kind of compensation is impossible with the mentioned TPS62050? (and that it would be possible with a TPS5410 for example?)

  • 0 in reply to Joris Van Dyck
    TI__Mastermind 36110 points

    You can adjust the compensation by adjusting the Cff capacitor (capacitor between Vout and FB), however I do not think you can make it stable with the capacitance you will be using.  I would not recommend the TPS5410 either because you do not have access to any compensation components.  A device like the TPS54140 might be more suitable to your application.