Hi, I am currently implementing a buck converter using UCC27212A-Q1 gate driver. My PCB was working fine on Saturday but when I tested it again yesterday, it was shorting. After debugging, I realized that the high output of the gate driver is not displaying a digital pulse. I have replaced the gate driver and the bootstrap capacitor five times but that does not solve the problem. I even tried starting from scratch on a new PCB. I have removed the MOSFETS for debugging purposes such that the only remaining components in my circuit are shown in the image below:
Here is some additional information:
- Vin comes from a 12V regulator
- The PWM has a maximum of 5V and minimum of 0V. Switching frequency is 200kHz.
- There is a 0 ohm resistor connecting the signal and power grounds.
- When I probe the LO pin, I see a PWM with 0 to ~12V, matching the LI input.
- The HO pin displays a constant voltage of ~8.3V, which is identical to the HS output. I have measured the two pins with an ohmmeter and made sure they are not shorted.
- The HB pin displays a voltage of ~11.3V, so that the difference in HB and HS pins is 3V, not the VDD supply (12V) I would expect.
- The thermal pad sits on a PCB pad that is grounded, but I'm uncertain if it is physically connected/soldered (it is hard for me to manually solder underneath the IC).
The gate driver did work before, so it is not an issue with my circuit. I have no idea why it suddenly stopped working. Any suggestions or help is greatly appreciated!
