An Interesting WaveForm on Motor Control Driver

Discussion in 'General Electronics Chat' started by daug, Nov 13, 2009.

  1. daug

    Thread Starter New Member

    Mar 30, 2009
    1.When motor in stop state which means no PWM generate from MCU.The waveform of high side of the B gate of STGF7NC60HD attached below.At this moment the B gate of STGF7NC60HD should be floating, how does this happen? to test the deadtime of both high side and low side switch? I think the highside switch have no common reference with low side
  2. SgtWookie


    Jul 17, 2007
    You should never allow the gate of a MOSFET to float; it can quickly be destroyed by static electricity or stray voltage.

    Connect the gate to the source terminal using a 10k resistor.

    Make your voltage measurements on the gate with respect to the source terminal.
    Set your 'scope to A-B.
    Put your B-channel probe on the source terminal, and your A-channel probe on the gate. You should then see a range of 0v to 10v for standard MOSFETs. If it is outside that range, you have a problem.
  3. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    If your scope doesn't have a Math menu, and you have more than one channel, you can use channel A, then invert B and add it, which will give you A-B.