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TPS7B4253-Q1: Possibility of unstability

na na78
Guru 16770 points
Part Number: TPS7B4253-Q1

Hi

Could you please check following circuit?

Our customer is about to insert resistor at the point in red circle.

The purpose is to suppress peak current generated from load operation.
(The load is a buzzer and LED)

They say this insertion has effect for suppression of peak current.
And they understand the insertion would make some voltage drop for the load.

Question:
Is it likely to make malicious impact for stability by such resister insertion?

(As an aside, this is not for automotive application use.)

I appreciate if you could reply.

BestRegards

  • 0
    TI__Guru 55940 points

    Hi Na,

    In this configuration the resistor will add ESR for the capacitor as well.  As long as the total ESR (5.6 + Coutesr) is within acceptable the ESR range of the regulator, it should not cause a stability issue.

    It should be noted that the load can still pull current from the output capacitor in this configuration.  As such, a better location for the resistor would be after the output capacitor (red arrow below).  In this location the resistor will also help limit current draw from the capacitor.

    If they are only concerned with current coming from their upstream 30 V, supply a better location would be before the regulator IN pin (blue arrow above).  Here you will still suppress the peak current from the 30 V supply; however, you would not have to account for the extra resistor drop.

    Very Respectfully,

    Ryan