UCC27531: How can I improve this setup to resolve the issue?

Hi Emad,

The reference point of the gate driver (-3) is not the same as the source of the FET (GND_Iso), so you are most likely shorting the -3V reference voltage to ground when you connect the source of the FET to the gate driver.

Generally, you should keep the reference point of VDD, IN, and GND the same as the reference point of the FET's source. If you would like to use isolation for using a low-side driver as a high-side driver, then please read this FAQ: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1082920/faq-ucc27624-can-i-use-a-low-side-driver-as-a-high-side-driver

Thanks,
Rubas

Hi Emad,

Can you clarify what you meant about this sentence in your original post: "when I connect the gate and source to the gate driver, the signal remains constant, causing a short circuit in the power supply. When I disconnect the source, the gate driver produces a proper square waveform."

What are you connecting the source of the FET to, and what are you disconnecting the source from?

I also see that the optocoupler that supplies your IN pin is referenced to a different ground (GND_3.3) than the gate driver (-3). If GND_3.3 = 0V, then the input of the gate driver will see 3V more than expected. This is because the reference for the gate driver is 3V below the reference of the input signal.

For example, if you intend to output 0 to 3.3V from the optocoupler into the input of the gate driver, then the gate driver will actually see 3 to 6.3V. This will result in the gate driver being stuck on, which is possibly your original case.

If you would like to configure for a bipolar drive with the UCC27531, please view this FAQ: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1083720/faq-ucc27614-how-to-drive-a-sic-fet-or-igbt-with-a-negative-bias-using-a-low-side-gate-driver-bipolar-drive

We also have the UCC57108, which is our newest low-side gate driver that allows for bipolar drive without external circuitry. It also features desaturation protection.

Thanks,
Rubas