I'm designing a buck converter with an input voltage of 30V. For this I'm using a IRF9540 P-channel MOSFET which I need to drive from 0V to 30V relative to ground to fully turn it on and off respectively.

I always used a MC1407 to drive my N-channel MOSFET but now I can't use it because the maximum supply voltage is 18V, far from 30V. I tried the classic push-pull with BJT transistors and it works kind of well until I approximate to 20% duty cycle (I'm working at 150kHz).

My question is, can I put 15V in the GND pin of the MCP1407 and 30V on Vdd? On this way I wouldn't be exceeding the maximum operating voltage and I could drive the P Channel MOSFET perfectly.

I also thought about using gate driver transformers but my duty cycle can exceed 50% so they are not an option unfortunately.


1 Answer 1


My question is, can I put 15V in the GND pin of the MCP1407 and 30V on Vdd?

Yes you can but there is always a little demon in the detail - you have to drive the MCP1407 from a signal that is 15V lower and this takes a little care to ensure edges are maintained and you don't over-stress the input of the driver - this can sometimes happen at power up or power down so be aware.

Alternatively just use a high-side FET driver that uses boot strap techniques and an internal level shifter. Maybe the MCP14700: -

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  • \$\begingroup\$ Can I use a bootstrap driver where the high side can have duty cycles between 5% and 95% and the low side the opposite (synchronous buck topology)? \$\endgroup\$
    – Andres
    Commented Sep 22, 2016 at 18:20
  • \$\begingroup\$ That's close to full limit when bootstrapping but I've built one that ran at 28 volts that covered this range of pwm duties. Just needs a bit of care AMD maybe simulate it first to double check. \$\endgroup\$
    – Andy aka
    Commented Sep 22, 2016 at 18:47

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