Other Parts Discussed in Thread: UCD3138, ISO7831
Hi Team,
Customers are using the LMG3410-HB-EVM for testing at LLC on several of their products.
Currently, the two SN6505 on the EVM are removed, and the 3.3V on the secondary side provides power to pin1 of the ISO7831 and UCD3138; the GaN VDD on the primary side is provided by the 12V auxiliary power.
According to the user manual, U3, U4, and R2 have been removed and R1, R18, and D1 have been added.
It is found that once the Low side Gate is switched, the U2 fault pin signal will be pulled low, causing the high side gate to fail to work, and there is no 12V output.
However, if the SN6505 is used as an isolated power supply, the above problems will not occur.
Confirm that Vdd 12V and 3.3V are stable, and the first rule out the problem of UVLO. Could OCP cause it?
You can refer to the following waveforms
CH1: U2 pin5
CH3: U2 Pin4 Low side from UCD3138
CH4: Low side gate current
CH1: U2 pin5
CH3: U2 Pin4 Low side from UCD3138
You can see the fault pull low when the gate begins switching
