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TPS62130 Vout deviation

HM
Intellectual 460 points
Other Parts Discussed in Thread: TPS62130, TPS62090, TPS62085

Hi,

I have a question about Vout deviation of TPS62130.

[Condition]

Vin = 5V

Vout = 1.35V

Iout = 0.08A ~ 2.56A

L = 3.3uH

C = 22uF

Following picture is load transient response from min load(0.08A) to max (2.56A). 

(Ch1:SW, Ch2:Vout)

It shows the Vout deviation is 28.8mVp-p, and it is no problem.

 

 

On the other hand, following picture is load transient response from max load(2.56A) to min (0.08A). 

The Vout deviation is too large (104mVp-p)

 

 

Following picture is load transient response from max load(2.56A) to min (0.08A) with 1.5uH, 22uF. 

The Vout deviation is too large (74.4mVp-p)

 

 

Q1:  Please advise me how to reduce Vout deviation. (where max load to min load)

Q2:  Please let me know about frequency response characteristic for the ripple injection.

 

Best Regards,

Hide

 

  • 0
    TI__Guru**** 191445 points

    I don't directly support TPS62130, but I will comment.  You do not show or specify the current step slew rate, but the easiest approach is to increase the output capacitance.  The TPS62130 supports output capacitance as high as 200 uF.  So long as you stay within the recommended output filter configurations, you should have no issues with stability.

  • 0
    TI__Guru*** 142730 points

    Yes, John is correct.  You should increase the output cap.  As well, you can reduce the inductor value.

    But if you have a 5V input, the TPS62090 or TPS62085 are better options.  They also support 0.47 uH inductors which will give better transient response.

  • 0 in reply to Chris Glaser
    Intellectual 460 points

    Thank you for your information.

    Let me ask one question.

    When load change from Min to Max, I understand it is effective to use a larger capacitance.  But in case of changing load from Max to Min, why the larger capacitance will be effective to reduce Vout deviation?

     

    Best Regards,

    Hide

  • 0 in reply to HM
    TI__Guru**** 191445 points

    It is somewhat symmetrical.  When the load increases, the extra energy must come from Cout.  Higher capacitance means the voltage decrease will be less.  On the load change from max to min, the inductor current cannot change instantly, so the extra current will charge up Cout and increase the output voltage.  Larger Cout will cause the voltage increase to be less.