Not sure how to use Half Bridge Gate Driver (LIN being in/out of phase and more in general)

Question

I am relatively new about semiconductors and I recently realized that driving MOSFETs requires a middle circuit for most microcontrollers. I followed schematics shared in this tutorial, except I couldn't find IRS2001, instead I bought IR2103. I carefully compared datasheets of both and they seem mostly identical or close enough for me. After trying to set a test circuit though, it didn't worked and I have noticed that IRS2001's LIN pin is labeled in phase, whereas my IR2103's is out of phase. ( I connected MOSFET's gate to LO, and triggered from LIN, while supplying 9V to VCC to driver.) I don't know what that means and couldn't find any helpful sources. I noticed that when I connect LIN to 3.3V or 5V nothing happens, but when I connect it to the ground MOSFET starts to conduct, maybe that's related.

If anyone can lead me to something I'd appreciate that. All the other Half Bridge Gate Driver example circuits consisted of two MOSFETs, why is that? Are those two MOSFETs work dependently to each other or independently? What is the actual use of HB Gate drivers? Can I use my IR2103 to drive as shown in the Instuctables link? Also, is it healthy to use common small BJTs as gate trigger circuit instead of a gate driver?

( I'm using IRFZ44N N-Channel MOSFET, which's load will pull around 10-20 Amps. It needs to respond relatively quickly, my guess is around 100 milliseconds at worst. )

Answer 1

The bar over LIN means that it is 'inverted'. Logical low on LIN will saturate the gate of your low side mosfet. This is likely to allow you to achieve complementary PWM output with only one pin. The full truth table is provided in the diagram below, from the datasheet.

It is fine to use BJT's to drive the gate of a low side n-channel MOSFET, or the gate of a high side p-channel MOSFET. However if you wish to drive a high side NMOS, you need more complicated drive circuitry.

The half bridge driver you linked uses a high side drive technique called 'bootstrapping', which uses the low side MOSFET to charge a capacitor which is then used to nudge the high side gate voltage high enough to properly saturate the gate. This means that they are not 'independent'. You need the low side in order to use the high side. It also means that you can't drive the high side continuously on (100% duty cycle) because eventually the bootstrapping capacitor will bleed out.

There is another common high side switching technique which uses a charge pump. These drivers do switch both MOSFETs independently, and allow for 100% duty cycle high side output. They're also more expensive and aren't made for high voltage applications (or at least, not as high voltage as bootstrapping drivers).

Answer 2

On the old part, the low side driver was noninverting. On the new part, the low side driver inverts, meaning that when it used to turn the FET on, it's now turning it off, and vice versa. You could go into the Arduino code and invert the output polarity.