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UCC21750QDWEVM-025: Transformer drivers and UVLO test

Part Number: UCC21750QDWEVM-025
Other Parts Discussed in Thread: SN6505B, UCC21750-Q1

Hi E2E,

Good day.

Our customer is using the UCC21750QDWEVM-025 with a power supply of 0-30V DC with 6A rating. When the Vcc voltage is 4.65-.4.75 V, the pull up/down converter is supposed to drive 15 V/-5 V and the supply current is to be a few hundred mAs but they are reading 0.5 V at the secondary output is not 15 V and the supply current is 15mA, neither does the Ready LED turns on. What could be the possible issue, is it with the transformer drivers or the UVLO logic?

They’re able to read the filtered out Vcc(M4) and also the gate driver is not drawing more than 20 mA(M1) @ 4.7 V (M4). Can you suggest methods to test the UVLO or the transformer driver, if this works it will draw 300 mA?

The enable signal to U1 is 3.9 V, they’ve also checked the pin2 and pin 4 for U1 supply it's 5 V. It's supposed to drive the transformer right?,Vdd is still 0 & also the current drawn from supply is 13 mA.

Looking forward to your suggestions.