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PTN78020WAH (Spike observed 10ms before the module turn on)

SIYUAN ZHANG
Prodigy 30 points
Other Parts Discussed in Thread: PTN78020W

Is anyone who could give me some proposals to reduce the spike? Thanks very much. 

  • 0
    TI__Mastermind 38230 points

    SIYUAN:

    Can you send  me your exact schematic with input and output capacitors  including ceramic capacitors. What is the input voltage  and output voltage , and output current.?  It appears the ± pulse is directly  coupled from other  power circuitry to the PTN78020W out put bus. I  suggest you add a small resistive load  on Vout pins  of PTN78020W. 50-100 ohms.

    Tom

  • 0 in reply to Tom Guerin
    Prodigy 30 points

    I configured the DC-DC converter the same way as what the data sheet required. The input voltage was 15V from bench supply and the output voltage was 2.5V to diode load. I think that you are correct that -+pulse was coupled from other power circuitry which the bench supply's switch bouncing. Could you tell me please where to add the recommended resistor?Across the converter's output to gnd or in series with my diode load? Also, why you think add a resistor will possibly make it better?

    Thank you very much.

    Best,

    Siyuan 

  • 0 in reply to Tom Guerin
    Prodigy 30 points
    I configured the DC-DC converter the same way as what the data sheet required. The input voltage was 15V from bench supply and the output voltage was 2.5V to diode load. I think that you are correct that -+pulse was coupled from other power circuitry which the bench supply's switch bouncing. Could you tell me please where to add the recommended resistor?Across the converter's output to gnd or in series with my diode load? Also, why you think add a resistor will possibly make it better?

    Thank you very much.

    Best,

    Siyuan
  • 0 in reply to SIYUAN ZHANG
    TI__Mastermind 38230 points

    SIYUAN:

    I would add the resistor directly across the Vout power trace to ground.

    This will likely introduce an low impedance path  to ground  before PTN78020W initiates normal power -up.

    Tom