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LMZ31704 Bootstrap Circuit

Other Parts Discussed in Thread: LMZ31704


My customer has question about LMZ31704.
Could you tell me about questoin?

 How is the internal circuit of Bootstrap circuit?
 My customer has problem at start-up.
 Wave form is below.

 My customer is thinking that the reason is that the device can't charge Bootstrap capacitor.
 So he wants to know internal Bootstrap circuit.

Best Regards,

  • The bootstrap capacitor is internal to the device between pins 9 (DNC) & pin 10 (PH). Pin 10 must be connected to other PH pins to ensure the boot cap charges. From the waveforms it looks like the bootstrap circuit is operating as expected because VOUT is regulating after the initial glitch. Can you send me the schematic of this design? You can send it to me directly at

    Is there any circuit applied to the INH pin? Are they setting UVLO externally? Are they controlling the SS/TR with any external circuit?

    Thanks, Jason