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LMG1210: Controlling dead time with DAC

Mike Twieg
Intellectual 960 points
Part Number: LMG1210

I'm using several LMG1210 in an interleaved converter, and wanted to adjust the dead time in PWM mode on the fly. Is there any problem with driving the DLH/DHL pins with a DAC to set the dead time? Can I connect the DLH/DHL pins directly together if I want equal dead time on both edges? What about directly connecting the DLH/DHL pins of multiple LMG1210?

  • 0
    TI__Genius 13445 points

    Hello Mike,

    Thanks for your interest in our drivers.

    From the datasheet block diagram, there is an internal pull-up resistor at DHL/DLH pin, which would form a voltage divider with an external resistor to set the voltage Vdt on DHL and DLH. This Vdt decides the final dead time according to Equation 5 in datasheet: tdt = (1.8-Vdt ) x20.

    Setting Vdt through DAC might be OK assuming DAC output stage interaction with internal RC filter (10kHz corner frequency) is OK.

    Regards,

    -Mamadou

  • 0 in reply to Mamadou Diallo
    Intellectual 960 points

    I attached a schematic showing how I plan on driving the DLH/DHL pins. VDT_DAC is connected to a DAC with a 0-3V range. By my math, this will adjust VDT between 0.9-1.8V.

    My main concern is that there might be some switching or otherwise time-varying behavior of the DLH/DHL pins. But if they just look like passive RC filters then it should be fine.

    Thanks!

  • 0 in reply to Mike Twieg
    TI__Genius 13445 points

    With adequate layout, DLH and DHL should maintain the same voltage assuming no noise coupling from board parasitic to the pins.

    Also, optional but for flexibility, I would recommend having a placeholder shorting resistor from DLH and DHL which you may short or remove and 2 external pulldown resistors to GND on each DLH and DHL that you may remove when shorting dead-time pins

    Regards,

    -Mamadou.