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LTC7004 with PWM as buck converter

I've designed a PCB around the LTC7004 gate driver for stepping down 6-21V to a 3-4.2V LiIon cell.

The INP pin is connected to a microcontroller which is deciding the duty cycle on a 6kHz PWM. Due to the input voltage possibly being over the absolute maximum rating for VCC, there is a 5V LDO specifically for the LTC7004. I've used the dual MOSFET circuit recommended in the datasheet to prevent current flowing back into the input.

Unfortunately the LTC7004 sometimes does not work when the PWM is applied. If I bridge the LDO, it is working all the time, but only with limited input voltages.

What can I do to have the gate driver work at all times and how can I debug the IC?

I've attached a screenshot of the schematics in question and can supply oscilloscope traces if needed.

  • To answer my own question and for the people going down the same path I did:

    The LTC7004 is NOT suited as buck converter gate driver. The second the PWM frequency goes above 50Hz it gets really unstable, doesn't start at times and needs a Vcc of >8V to do anything. It really is only suited for quasi DC applications.