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LM5101A: Half Bridge Driver using LM5101A not working

Part Number: LM5101A
Other Parts Discussed in Thread: CSD19502Q5B,

Tool/software:

I have not been able to get this circuit to work properly and convincingly with many MOSFET models.

VDD=10V VLI and VHI are complementary square wave inputs of 10 MHz frequency of 3.3V amplitude.

I expect the output to be a square wave switching from 0 to 20V. I have tried it with a few different MOSFET

models. The load is a capacitance of 26 pF (100 pF max).

  • Hi Subhajit,

    We are currently investigating the cause for this model issue following your previous question about the same model. We will provide you with an update as soon as possible.

    Best,

    Amy

  • Hi Subhajit, 

    We were able to investigate this model and were able to replicate the issue you were seeing. The model itself appears to be compatible with certain model types. I have it working with the CSD19502Q5B model, you may consider using this. We are planning to update this model soon.

    Best,

    Amy

  • This N-channel MOSEFT (CSD19502Q5B ) does not appear to be in the library of MOSFETS in the TINA Spice library I have installed

    Most of them have prefixes 2N and IRF under model type Level-3. Pls. let me know how to incorporate this MOSFET into my test bench. Kindly also

    send me the model parameters for this MOSFET if available.

    With my thanks & regards,

    Subhajit

  • Hey Subhajit, 

    I pulled the model into TINA and found the 2N6755 works with the LM5101A model. When you see it is not working correctly with certain models, does the output waveform always look like the screenshot sent above?

    When measuring the signal on HO, please be sure to measure between HO-HS. HS acts as a floating ground, that is why the waveform does not appear to accurately switch between the desired voltages. 

    Furthermore, bootstrap capacitor should be at least 10 times greater than the gate capacitance of the high-side FET. In my model, I am able to get the FET model to work well with a 100nF capacitor. 

    I see that your switching frequency is also very high. In my own testing, I noticed this can result in strange behavior of the simulator. I would decrease the switching frequency as see if this leads to more desirable behavior with certain FETs. 

    For more information about sizing of components please see this application note: Bootstrap Circuitry Selection for Half-Bridge Configurations. We also recommend the use of the LM5101A Schematic Review Template for guidance. 

    Best,

    Amy