STGAP3SXS not working

[Jay Dhimmar]

Hi everyone,

I am using the STGAP3SXS isolated gate driver on my custom PCB, but I am unable to get it to operate correctly.

I have attached my schematic for reference.

I tested the driver in two different configurations:

1. With all protection circuits enabled (DESAT, Miller clamp, etc.)
2. With the protection circuitry removed/disabled (minimal configuration)

In both cases, the behavior is exactly the same.

Observations

• Pin 13 (DIAG) remains HIGH.
• Pin 14 (RST) also remains HIGH.
• No gate output is generated.

According to the datasheet, DIAG is the diagnostic output and RST is the active-low reset/shutdown input. I expected the device to operate normally when RST is kept HIGH, but the driver never starts.

I have verified:

• Logic supply (VDD)
• Isolated gate supply (VH/VL)
• Input signals (IN+ and IN−)
• PCB connections and soldering

However, the behaviour remains unchanged in both hardware versions.

Could someone please review the attached schematic and let me know if there is anything obviously incorrect or if there are any common mistakes when using the STGAP3SXS?

Any suggestions or troubleshooting steps would be greatly appreciated.

Thank you.