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Questions of TPS54302

Takahiro Nishizawa
Genius 5575 points
Other Parts Discussed in Thread: TPS54302

We have questions about TPS54302.

We want to change input voltage 24V to 8V or 8V to 24V.

Question 1.

Please tell us the recommended time that output voltage stabilizes by changing input voltage.

(We think that the IC needs waiting time until output voltage stability. )

Question 2.

Please tell us the minimum input voltage.

 1. Vout=3.3V

 2. Vout=5.0V

Question 3.

In datasheet p.13 Figure.15,

Plase tell us the allowable variation of R1~R5 value.

Plase tell us the allowable variation of C1~C5 value.

    Can we use capacitor not recommended value about C1?

    Must we use 22μF*2 about C4 and C5?

    (Are there any problems about using 10μF*4 or 47μF*1?)

Can we use the capacitor  anything other than 75pF about C6?

Question 4.

In datasheet p.17 Table.2,

Is C8 mistake in C6?

Best regards,

Takahiro Nishizawa

  • 0
    TI__Mastermind 23845 points
    Hi,

    Question 1:
    The time should be less than 500us.

    Question 2:
    Based on the datasheet reference design, seems like 8V should be ok with 3A load. It all depends on dropout and efficiency of the converter at a specific frequency.

    Question 3:
    R1-R5 variation +/- 1% should be ok
    C1-C5 variation +/- 10% should be ok

    Yes you can use 10uF *4 as for 47uF *1 please make sure that the value does not derate with voltage.
    Yes you can use capacitor other than 75pF depended upon how your bode plot looks like

    Question 4:
    Yes the C8 should be C6

    Thanks
    -Arief
  • 0 in reply to Arief Hernadi
    Genius 5575 points
    Thank you for your answer!


    We have questions.

    About changing input voltage,

    Can we instantaneously change the input voltage from 24 V to 8 V?
    It means that the time to change from 24 V to 8 V is very short time.
    Are there any problems by changing instantaneously?
    Does this IC need the time that input voltage changes?


    500μs is the time that output voltage stabilizes by changing input voltage.
    Is this understanding correct?

    We think that input capacitor(C1) is used to stabilize the input.
    Can we use capacitor not recommended value about C1?

    Best regards,


    Takahiro Nishizawa
  • 0 in reply to Takahiro Nishizawa
    TI__Mastermind 23845 points
    Hi,

    Yes you can change the input voltage 24V to 8V. In terms of "short time" it is pretty relative. You might have to test it on your board to see the effect. Changing instantaneously on the VIN could have some undershoot, etc especially if you have long wires in your test setup, etc. Therefore just be aware of that and you probably need some dampening bulk capacitor at the front end.

    Yes 500us is an approximate but the output should be settled by then.

    As for capacitor C1, you might need some input bulk capacitor to stabilize the input
    www.ti.com/.../snva538.pdf

    The reason being is that your leads is inductive and if you dont have a correct dampening capacitor with some ESR, there is ringing that might damage your input.

    Thanks and i hope that helps
    -Arief