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PMP8740: No PWM from IC for Synchronous Rectification at No-Load and Load Up-to 5A with 32V

Chethan S
Prodigy 60 points
Part Number: PMP8740

we are working Reference Design for the Same Output Voltage and Current. But, we are not getting the PWM for Synchronous Rectification from IC itself.

Then we applied Load up-to 5A with 32V(around 150W), still there is no PWM.

Please tell us, till what Power the PWM are disabled and please tell us how to remove light load condition.

Thanks

Chethan S

  • 0
    TI__Expert 5875 points

    Chethan,

    If I remember correctly in PMP8740 the sync-FET were disabled for Pout < 200 W, but I am not sure about that.

    I increased this power threshold on purpose because in a battery charger it's important to avoid energy flowing back from the battery to the source of power.

    Nevertheless you can decrease this threshold by reducing the voltage on DCM pin (pin 12), which translates into a reduced resistor value of R18 on PMP8740 schematic.

    If you short the DCM pin to ground, then both sync-FET outputs will always be active (not suggested for battery chargers, but suitable for standard power supply).

    Regards,

    Roberto