Hi,
I am planning to use BQ25756 to design a Li-ion battery charger (55V 10A). I am conducting my tests on the BQ25756EVM to verify if the chip is compatible. During these tests, I encountered an issue. I noticed that the Q4 MOSFET on the board heats up more compared to the other MOSFETs during boost mode operation. While Q1, Q2, and Q3 operate between 60-70 °C at room temperature, Q4 reaches up to 94°C (in Boost mode). I have tried to drive the MOSFETs both internally and externally using the J6 connector with 5V 500mA or 12V 1A supply, but the results remained unchanged. Operating parameters of the EVM and the ID of the MOSFET are listed below;
- Vsupply: 45V 20A
- CV mode Load: adjusted 40V for Buck, 50V for Boost operation
- Vout:55V
- Iout:10A
- Iin(max):20A
- fsw:200kHz
- All MOSFETs are the same: Alpha&Omega AONS66614
- Gate resistance of MOSFETs: 0R
Considering the polygon size on the Q4 and all these parameters, is it expected for the Q4 to heat up so much? If not, do you have any recommendations to solve this issue and reduce the operating temperature of Q4? Thank you in advance for your valuable support.
Best regards,
