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LM5113-Q1: High side driver/bootstrap not working

Robbe Willaert
Prodigy 20 points
Part Number: LM5113-Q1

Tool/software:

When using the LM5113-Q1 I cant seem to get my bootstrap working.
It works for a short while in the beginning of the pulse but then just stops.
Below is the circuit I use. It might not be that visible but VSS is connected to GND.

When hooking it up to an O-scope without a load connected i get this.
Blue is V_gate and magenta is V_source. As you can see there is only a slight difference of 2V in the beginning. It should be 5V.

When connecting a transformer to link the secondary side of my converter I get this as  a differential signal Vgs.

The absolute V_gate with a load looks like this.

I already made the Bootstrap resistor smaller (10 ohm) and changed the C_boot to 150nF but nothing changed.
The Vbus is 12V and the frequency is 100kHz


  • 0
    TI__Prodigy 710 points

    Hi Robbe,

    Thank you for reaching out. It seems that the bootstrap capacitor is not fully charging. Could you provide the HB-HS, HO-HS, LO and HS waveforms using tip and barrel method at the pins of the driver? These waveforms will help us verify if LO is switching properly and allowing Cboot to charge. Additionally, if possible, sharing IN and VDD waveforms would be helpful to rule out any input/supply issues. For future reference, the LM5113-Q1 Schematic Review Template can be found on the product page. 

    Thanks,
    Annabelle

  • 0 in reply to Annabelle Alemand
    TI__Prodigy 710 points

    Hi Robbe,

    I am going to go ahead and close this thread due to inactivity. If further support is needed, please open a new thread.

    Thanks,

    Annabelle