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LMG1025-Q1: LMG1025-Q1 Technical Query

Manimuthu Vel
Prodigy 10 points
Part Number: LMG1025-Q1

Dear team,

We have procured the GanFET driver “LMG1025QDEETQ1” to drive the GanFET “GS61004B-MR”.

We required some technical data of the GanFET driver.

Before getting into query, please refer the “Drive pulse characteristics” and “Parasitic components of GanFET “GS61004B-MR””

You recommended to use at least a 2-Ω resistor at each OUTH and OUTL to avoid voltage over stress due to inductive ringing.

For our application, suggest the minimum and maximum gate resistance value.

Drive pulse characteristics :

Rise time/Fall time = ~1nsec.

Pulse-ON time(Max) = 20nsec

Pulse repetition time = 1msec

Pulse shape = square pulse

Parasitic components of GanFET “GS61004B-MR” :

Lds (drain to source inductance in ON state) = 1.3nH

Ls (source inductance) = 450pH

Lg_loop (gate loop inductance) = 1.2nH

Internal gate resistance = 0.9 Ohm

Awaiting for your valuable response.

Regards,

Manimuthu

  • 0
    TI__Genius 13445 points

    Hello Manimuthu,

    Thanks for your interest in our driver.

    The 2-Ohms gate resistance recommendation in the datasheet is not one-size-fit-all but rather case-by-case scenario tailored for each application's needs.

    As you probably noticed from the driver's datasheet, LMG1025-Q1 is a 7-A/5-A source/sink current driver with a gate drive voltage capability of up to 5.25V.

    From the GaN FET datasheet, it seems the load seen by the driver at the gate is 6.2nC typ. Assuming your application requires 1ns rise/fall times at the gate, 

    you will need the gate driver IC to source/sink Ipk = dQg/dt = 6.2nC / 1ns = ~6.2-A which is within the driver's capability.

    In this scenario, I would advise to start off with very little gate resistance 0 to 1-Ohm to meet the (assumed/desired) rise/fall time at the gate. As you know, higher gate resistor will slow the rise/fall time at the gate and consequently slow the fall/rise at the Vds. If the 0 to 1-Ohm induce significant overshoot or too fast of dv/dt at the gate, you may tune this value to the appropriate rise/fall time at the gate.

    Keeping in mind, resistor on OUTL will influence Vgs fall time while OUTH resistor will impact rise time.   

    The link below further discusses gate resistance selection guide and its impact on the gate drive portion.

    https://www.ti.com/lit/an/slla385a/slla385a.pdf

    Regards,

    -Mamadou