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LMG1210: Problem of compatibility with TPS61175-Q1 boost converter - short circuit

Part Number: LMG1210
Other Parts Discussed in Thread: TPS61175-Q1, , LM7171

Hello,
I have some issues with LMG1210RVRR gate driver. Want to use this IC to switch voltages from 15V to 30V at output of
totem pole NMOSFET configuration with bootstrap diode. Because I want to switch to reference of 15V and i don't have
isolated 30 V voltage source I had to connect driver ground to 15 V. I use PWM configuration. 15 V are made from
isolated Murata DC converter. 30 V are made with boost converter TPS61175-Q1. Logical signal at PWM input of
LMG1210 has levels 15 V for logical 0 and 20 V for logical 1.

Problem is that when I solder LMG1210 with all of mentioned components the PCB is short circuited.
I burned like 10 of them already because in first place I thought its my soldering fault.
After I removed the 30V boost converter and powered it from other voltage source short circuit was gone.
But still I couldn't manage to get switching from 15V to 30 V.
My question is: there is possible that LMG1210 is not compatible with TPS61175-Q1? Or I made mistakes
in connections? (schematic below)


About circuit:
15/20V is signal from op amp LM7171 and it works fine without LMG1210
30V is provided from TPS61175-Q1, made gird isolated converter 15V and it works fine without LMG1210
20V is positive signal for EN input
R37,R38 - 150k
C50 - 2.2u
I use this NMOS transistors because I need as low propagation delay from PWM input to HS voltage switch as possible.
This is partial schematic of much advanced circuit.

Thanks for your replies


  • Hi Bartosz,

    Thanks for reaching out on lmg1210.

    Can you share your full schematic and layout of 1210 and tps part.

    Can you take a waveform of HO, LO, and HS to confirm what the issue might be?

    Is the PCB shorted before you power up or is the PCB shorted right after you solder your components on because it could be a soldering issue in this case?

    Thanks,

  • Hi Jeff,

    Before power up of PCB with all components and fresh LMG circuit is not shorted.
    After powering up PCB with TPS and LMG1210, resistance between VIN and VSS of LMG1210 goes down to 2-3 Ohms before that its like 2-3k while it is unsoldered. And it causes short circuit in PCB.

    I think its no problem with soldering as I thought in first place because as I said PCB is not shorted without TPS soldered while LMG is on it.

    I can't show you waveform yet. But without TPS when I provide 30 V from other power supply signals like EN, VDD and LO are on good levels in steady state
    with 15 V at PWM input of LMG. When I switch PWM input voltage to 20 V (yet static with wire) there is no switching between MOSFETs.
    I didn't try to use PWM dynamic signal yet so the bootstrap could work.

    Thank you for your help,
    Bartosz


    7455.schematic.pdf

  • Hi Bartosz,

    Thanks for the update,

    Lmg1210's input can withstand up to 10v max and the VIN pin can withstand up to 20V max.

    This might be what is damaging the device. Can you confirm testing these voltages within the data sheet spec.

    Thanks,

  • In my PCB LMG VSS is tied up to 15 V refered to the PCB GND.
    On VIN pin I have 30 V so LMG sees it as 15 V.
    On input PWM I gave signal 15/20 V so LMG refered to his VSS pin sees it as 0/5 V.
    On input EN I gave 20 V (5 V for LMG).
    So it shouldn't be an issue.




  • Thanks for the update,

    Are you able to provide 1210 input and output waveforms to understand what the issue is more?

    Thanks,