• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 62 subscribers
  • Views 744 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.

The output capacitor of TPS2042B

takahiko yokota
Mastermind 7135 points
Other Parts Discussed in Thread: TPS2042B

Hi

TPS2042B is recommended the electrolytic capacitor as Cout when the output load is heavy in datasheet.
Is there the concrete value that Cout should be the electrolytic capacitor?
Best regards
Yokota
  • 0
    TI__Mastermind 42795 points

    Hi Yokota-san,

    Please point me to the datasheet page/section that you are referring to.

  • 0 in reply to Eric Wright
    Mastermind 7135 points

    Hi Eric-san

    The sentence is written  in "
    10.2.1.2.1 Power-Supply Considerations" of datasheet p.22 (follow sentence).
    10.2.1.2.1 Power-Supply Considerations
    TI recommends placing a 0.01-µF to 0.1-µF ceramic bypass capacitor between IN and GND, close to the device.
    When the output load is heavy, TI recommends placing a high-value electrolytic capacitor on the necessary
    output pins. This precaution reduces power-supply transients that may cause ringing on the input. Additionally,
    bypassing the output with a 0.01-μF to 0.1-μF ceramic capacitor improves the immunity of the device to short-
    circuit transients.
    Best regards,
    Yokota
  • 0 in reply to takahiko yokota
    Mastermind 7135 points

    Hi Eric-san

    Let me ask you a question in addition.
    TPS2042B requires high-value electrolytic capacitor on output pin when the output load is heavy.
    Can I change  electrolytic capacitor to ceramic capacitor?
    Best regards,
    Yokota

  • 0 in reply to takahiko yokota
    TI__Mastermind 42795 points

    Hi Yokota-san,

    The datasheet paragraph refers mostly to the transient nature of the output load with respect to capacitor value and type. For example, if you only have 0.1uF at the output then transient currents which exceed the Ios of TPS2042B for short periods may cause the switch to react quickly and remove the output voltage. This is usually undesirable and by putting larger values of capacitance the transient nature of the load can be masked allowing output voltage to remain stable during those short periods.

    The other consideration is the input supply. Of course the input supply will be able to source currents above the Ios of the TPS2042B so that it is TPS2042B Ios which sets the port capacity. Input and output capacitance can also help mask transients which might otherwise ripple through the switch from being detected by the input supply (causing OC foldback and port turn off).

    So, with the transient current of your load known, you can choose appropriate IN and OUT capacitors to help the supply and switch ride through those transients. there is an online PSPICE model for the load switch and you can adjust IN and OUT capacitance as well as set up the transient behavior of your load.

    You can use ceramic capacitors and they can provide better transient performance than electrolytics because of the lower ESR.