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TPS40303: Gate drivers voltage waveform

ArTzy
Genius 15009 points
Part Number: TPS40303

Hi Experts,

We are looking for the information at the TPS40303's HDRV and LDRV pin drivers.

If the device is designed to convert from 3.3V to 1.0Vout, can you share us the average DC level of these pins, and waveform? We are requesting this information for derating calculation.

Thank you.

Regards,
Archie A.

  • +1
    TI__Guru 51555 points

     

    HDRV is a floating high-side driver powered internally from a diode-switch from BP to BOOT and referenced to the SW pin.  The exact voltages will depend on external connections of BP and BOOT pin but will approximate a square-wave with low voltage equal to GND and high voltage equal to 2x VIN, 300kHz frequency and duty-cycle equal to VOUT/VIN (actual will be slightly higher due to efficiency losses)

    The average "DC" voltage of this pulse-train will be approximately 2x VOUT (Again, slightly higher due to efficiency)

    LDRV is a GND referenced driver power internally from BP.  Again, the exact voltages will depend on the external connections of BP, but it will be approximately a square-wave with low voltage equal to GND and a high voltage equal to VIN.  300kHz frequency and duty-cycle equal to 1- VOUT/VIN (actual will be slightly lower due to efficiency losses)

    The Average "DC" voltage of this pulse-train will be approximately VIN - VOUT (Again, slightly lower due to efficiency)

    Note:  For a 3.3V input, there are some recommended external connections to maximize gate-drive voltage and improve performance

    1) Connect BP directly to the 3.3V input to avoid the internal LDO drop-out and maximize the available LDRV and HDRV gate drive voltages.

    2) Provide an external low-forward drop Schottky diode from 3.3V to BOOT to minimize the drop from BP to BOOT and recharging the BOOT to SW capacitor to maximize the available HDRV voltage.

    Without these external connections, BP will be less than VIN and BOOT will recharge to a voltage lower than BP, reducing the above listed HDRV and LDRV voltages somewhat, decreasing the Vgs applied to the external MOSFETs and and thus their Rdson, which will decrease converter efficiency.