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Original question:

LM74700-Q1： What's output voltage level for LM74700 gate control pin.

LM74700-Q1: LM74700-Q1 Motor Phase ORing

Dario Moscardi
Prodigy 115 points
Part Number: LM74700-Q1
Other Parts Discussed in Thread: LM5060-Q1, LM74800-Q1

Hello, 

I am designing a 48V/500W 3-phase motor control system with an external driver for automotive application. 

I would like to control the rising voltage on every phase with an LM74700-Q1. The voltage rise is expected to reach 60V and I am using an high power TVS per phase to keep it lower than 55V.

The maximum motor speed is 5000rpm, that is nearly 84Hz on the single phase. 

My question is, with the described specifics, what could be the maximum turn-on time for this component if it is supplied from the 48V phase output? Is it better to connect the EN pin to the 48V supply and the Anode to the phase output? Will it reduce the turn-on time?

Is there a more suitable component for this application?

You can find attached the schematic.

Thanks in advance,

Dario Moscardi

  • 0
    TI__Guru** 105361 points

    Hi Dario,

    Thanks for reaching us on E2E.

    Do you want to control rate-of-rise of voltage on every phase of motor winding ? If yes - devices like LM5060-Q1 or LM74800-Q1 are the options.

    Please let me know if I misunderstood your requirement.

    Best Regards, Rakesh

  • 0 in reply to Rakesh
    TI__Guru** 105361 points

    Hi Dario,

    Any update.?

    Best Regards, Rakesh

  • 0 in reply to Rakesh
    Prodigy 115 points

    Hello Rakesh,

    Sorry for the late reply, I've switched to another project, guess I'll be back on it in the next week.

    i have just checked the components you suggested. The problem with them is that they drive a N-Mos. 

    With N-Channel, the motor overvoltage passes through the body diode and sums on the phase driver voltage.

    Then i need to use a P-Mos. 

  • 0 in reply to Dario Moscardi
    Prodigy 115 points

    My need is to open the Mosfet when the voltage on the motor winding is higher than the voltage on the phase driver output (M2 in the picture), then the TVS diode shuts down the overvoltage.

    The problem is that the LM74700-Q1 is intended to work with cotinuous supply, while the motor phase goes ON/OFF according to the motor speed.

    So i have two chances:

    - I can connect the Anode and Enable pins to the 48V supply, and the Cathode to the motor phase winding.

    - I connect Anode and Enable to the 48V supply, but the turn-on time of the IC sould be much lower than the period of the M2 phase.

    Are theese configurations possible?

    Thanks again,

    Dario Moscardi

      

  • 0 in reply to Dario Moscardi
    TI__Guru** 105361 points

    Hi Dario,

    In that case, back-to-back FET configuration with LM74800-Q1 would help. Ideal diode section helps to disconnect the path when Vout > Vin and control FET helps to provide inrush current control.

    Best Regards, Rakesh

  • 0 in reply to Rakesh
    Prodigy 115 points

    Hello Rakesh,

    I reviewed the schematics and according to body diodes polarity I agree with you that a dual fet configuration is needed.

    Thanks again,

    Dario Moscardi

  • 0 in reply to Dario Moscardi
    TI__Guru** 105361 points

    Ok Dario.

    If you don't have any other questions. please close this thread.

    Best regards, Rakesh