FEDEVEL
Platform forum

Abrar , 09-11-2025, 01:47 PM

I am currently working on a motor driver circuit. using H-bridge topology. and I am using a gate driver ic(ir2103) for controlling the mosfet. but the thing is am applying 5v supply to the logic input but not getting any output. there is a typical schematic mentioned at the datasheet of the IC. but no clear value or any BOM is given there. I follow @Phil youtube channel. this IC is used in there for an ESC circuit. so I used that schematic as a reference for this IC.

Is there anybody who used this IC or have any experienced with it, I would really appreciate if anybody can help.

FuzzyOtter , 09-11-2025, 02:21 PM

Show us the exact schematic, don't just show us some random snippet. Explain, exactly, what troubleshooting you've done.

Abrar , 09-11-2025, 02:25 PM

this is the schematics.

Abrar , 09-11-2025, 02:29 PM

I supplies 5v to H-1(net) and L-2(net) to get 24v output from the mosfets

QDrives , 09-11-2025, 07:58 PM

Did you check this comment:
But check figure 1 on page 8 of this datasheet https://www.infineon.com/assets/row/public/documents/60/49/infineon-ir2103-datasheet-en.pdf to see where your thinking goes wrong (hint).

Abrar , 09-11-2025, 08:29 PM

I did. but the problem was. Q3 and Q4 mosfet were turning on. I mean the low side mosfets are working but only the high side were not

QDrives , 09-11-2025, 08:35 PM

Q1 should turn on when both H_1 and L_1 are high.

Abrar , 09-12-2025, 05:00 AM

are you refering to this?

Abrar , 09-12-2025, 05:01 AM

does that mean when both H_1 and L_1 are low, Q3 should turn on?

QDrives , 09-12-2025, 01:51 PM

Yes. A table would have been better.
So, both inputs high -> high side output on.
Both inputs low -> low side output on.
The other two cases -> both outputs off.

Abrar , 09-12-2025, 02:38 PM

In this case, if i don't give any supply to both inputs, then the low side output will always be on.

Correct me if I'm wrong

FuzzyOtter , 09-12-2025, 02:44 PM

It sounds like you don't understand what that silly little line over "L IN" means

FuzzyOtter , 09-12-2025, 02:44 PM

It means that input is active low

QDrives , 09-12-2025, 11:05 PM

HIN has an internal pull-down and /LIN has an internal pull-up.
If you do not connect anything, both outputs will be off.

Abrar , 09-22-2025, 06:28 AM

Is it possible to just use 5v logic to control, or PWM signal is mandatory?
because 100% duty cycle = 5v

QDrives , 09-22-2025, 12:27 PM

The shown gate drivers use simple a bootstrap circuit, so no, you cannot do 100% high side on.
For the low side you can.

Tushar_642 , 10-20-2025, 07:34 PM

Hi,
I am Erfan Mahmud Tushar and I was also working with the @Abrar in the same project. For Both of us working with bootstrap circuit is totally a new experience. So consider me a total noob at this.

you said that can not put it to 100% at the high side at Low side I can do 100%. May I know why is that?

If you may suggest me any write up that I can read about the whole bootstrapy thing. I will be very much thankful.

QDrives , 10-21-2025, 01:28 AM

I could not find anything quickly.
But it is quite simple: your bootstrap capacitor drains. When the high side is on, it is not replenished. That only happens when the low side is on.

kyfion , 10-21-2025, 06:08 AM

You need charge pump circuit for 100% driving at high side due to the boostrap capacitors loose charge if you hold them in on state. Boostrap capacitors needs the toggling of a switching circuit in order to replenish their charge.
I don't know though what switching speeds you can achieve with a charge pump circuit VS the boostrap topology.