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I'm testing this circuit and I found some issues in driving ZXMC4559DN8TC n-p channel MOSFET.

schematic

simulate this circuit – Schematic created using CircuitLab

I have some problem in driving ZXMC4559DN8TC. PWM signal is correct at the gate of the ZXMC4559DN8TC. On the output load there is always 15V (even if a keep low PWM duty cycle). Am I missing something?

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  • \$\begingroup\$ Show pin numbers of the FET devices. \$\endgroup\$
    – Andy aka
    Commented Jun 27, 2017 at 12:31
  • \$\begingroup\$ Schematic updated \$\endgroup\$
    – Daniele
    Commented Jun 27, 2017 at 12:37

1 Answer 1

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Your pin out is correct on all devices and I think this points to the push-pull MOSFETs being damaged due to shoot-through. You get shoot-through because of the common source configuration you have - imagine the common gate voltage was at 7.5 volts and ask yourself what happens next.

Both P channel and N channel are going to be pretty much hard-on and conducting many amps from your 15 volt power supply. Even if you are switching really fast from 0 volts to 15 volts there will be a few tens of nano seconds where the common gate voltage will turn on both devices. That common voltage will be somewhere between 4.5 volts and 10.5 volts. If you read the data sheet, at 4.5 volts on the common gate terminal the N channel MOSFET could be conducting more than 10 amps from the P channel MOSFET.

Continuous drain current is between 2 amps and 3 amps.

This is why many people using this configuration use a driver with anti-shoot-through protection. With a 10 kohm pull-up, the rise time will be slow making this even worse.

Your dual MOSFET package is likely dead now.

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  • \$\begingroup\$ "... because of the common source configuration you have" isn't it common drain in OP's question? Sources are tied to the positive and negative terminals of the supply. Am I seeing something wrong? \$\endgroup\$ Commented Jun 27, 2017 at 13:22
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    \$\begingroup\$ @RohatKılıç common source means source is tied to a power rail and I suppose the confusion is the the drains are connected together implying they share a "common" pin maybe? \$\endgroup\$
    – Andy aka
    Commented Jun 27, 2017 at 13:38

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