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I've been looking for cheap and easy ways to drive a MOSFET with PWM and I came across a simple 555-based driver.

But that gave me an idea, since push-pull setup is used for driving MOSFETs, and an H bridge is basically a double push-pull, is it possible to use an H bridge motor driver IC, namely the l9110, to drive two MOSFETs?

The l9110 is intended to drive one motor, but I think I can connect each output to a MOSFET gate and drive 2 MOSFETs with it.

Here is the datasheet of l9110.

Another datasheet. It's in Chinese but has an internal diagram too.

Notes:

  • I couldn't find a maximum switching time for l9110 so I know that it probably can't handle more than a few kHz. But that's OK.
  • Please don't suggest using a dedicated driver. I'm specifically asking if this particular IC or other H bridge ICs can be used to drive 2 MOSFETs.
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  • \$\begingroup\$ If you're asking about a particular device, it's polite to put a link to the datasheet in your question. If the datsheet doesn't come up on the first page of google searches, then it's ESSENTIAL to link to it, I haven't got time to chase it down through the generic ad-driven datasheet providers. \$\endgroup\$
    – Neil_UK
    Oct 2, 2020 at 5:51
  • \$\begingroup\$ @Neil_UK Datasheet links added. \$\endgroup\$
    – Pouria P
    Oct 2, 2020 at 6:44

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Only if both external MOSFETs are low-side and only if the external MOSFETs have significantly more gate capacitance than the MOSFETs in the H-bridge IC. And since the MOSFETs in the H-bridge IC already have more gate capacitance than the typical input capacitance of a gate driver it will be slower to begin with.

And only if both MOSFETs don't have to be on at the same time since the L9110 doesn't allow that which you can see from looking at the truth table. This last one is probably a dealbreaker.

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    \$\begingroup\$ You'd probably be better off building your own gate drive circuit with discrete components. \$\endgroup\$
    – DKNguyen
    Oct 2, 2020 at 5:57
  • \$\begingroup\$ Can you explain why the MOSFETs will have to have significantly more gate capacitance? Thanks. \$\endgroup\$
    – Pouria P
    Oct 2, 2020 at 6:28
  • \$\begingroup\$ I managed to find this internal diagram of the l9110. It appears to be using NPNs instead of MOSFETs. So, good news? \$\endgroup\$
    – Pouria P
    Oct 2, 2020 at 6:40
  • \$\begingroup\$ @PouriaP Bigger MOSFETs = bigger gate capacitance. If it's using BJTs it could be better or could be worse. You do not normally use larger transistors for gate drive because they are slower and do not need to be so big. It's like using your finger to push a button to open an enormous dam, except instead of a small button it is a big 30kg button. As the button approaches the size of the dam it becomes more pointless to have the button. \$\endgroup\$
    – DKNguyen
    Oct 2, 2020 at 13:43
  • \$\begingroup\$ I'm confused. Regarding big transistors, the IC can only provide 800mA of current, I wouldn't call that a big transistor. Specially given the fact that MOSFET drivers can provide 1-2Amps. Also regarding the button terminology, I'm actually pushing a button (IC input) that pushes a button (H bridge) that opens the dam (MOSFET). With 800mA of current a MOSFET can switch at ~50kHz, I know that the IC's switching speed will be the limiting factor, but what's the big deal about it? Specially since the alternative is using 3 transistors for each MOSFET, while this tiny 8pin IC can drive 2. \$\endgroup\$
    – Pouria P
    Oct 2, 2020 at 15:34

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