The schematic for the DC DC converter is the reference design shown in 40V_Power_Stage_Board_PMP5306_RevD5.pdf. I am using the DC DC as a battery charger. I am trouble-shooting the PWMIC to determine why there is no PWM pulse from the LDRV pin 10 or the HDRV pin 13.
I have some questions about what I should be seeing at the IC pins.
The voltage at pin 2, RT, is 2.4V DC -should this be a continuous DC or a ramp?
The voltage at pin1, KFF, is 3.49Vs, which according to the data sheet appears normal. This particular implementation does not use UVLO and simply connects the KFF pin to BP5, pin3, via a 17.5k ohm resistor. This gives an IFF of approximately 80uA. Since the resistor at RT, pin 2, is 180k, and the frequency of operation is approximately 300kHz, is this proper value IFF?
The voltage at pin 6, SS/SD, is approximately 3.5V -is this correct for operation?
What can I do to determine what is preventing the PWMIC to pulse? I have checked all pins for noise or oscillation and have found none.
Will this chip run with the gate drive outputs tied to ground via a large resistor - say 10K? That way I could determine if the Mosfet gate inputs were the problem.
Thanks for your time.