UCC28700EVM-068: About UCC28700EVM Question

Hello Kuo,

You can test the OVP function as follows.
1. Connect a bias supply through a diode to the output.
a. Anode to the supply cathode to the positive side the EVM output.
2. Monitor the gate drive and VDD with oscilloscope.
3. Lightly load the supply, 5 k ohm resistor should work.
4. Apply power
5. Set the bias supply to the regulated output and slowly increase.
6. When the over voltage fault occurs switching will stop and the VDD capacitor will be discharged with 2.1 mA (IFAULT is the specified discharge current for a fault)
a. Section 7.5 electrical characteristics in the data sheet.
b. VDD will cycle between UVLO turn off and turn on before switching will begin again.
7. The output voltage is detected through the primary to auxiliary turns ratio.
a. Vs will trip OVP when VS pin during sampling is = VOP 4.6V
i. This tolerance varies roughly 3.5%
ii. With leakage inductance and resistor variation OVP could vary roughly +/- 5%.

Regards,

Mike