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DRV8301: Does Not Turn On when EN_BUCK Floating

Victor Salomon
Expert 3540 points
Part Number: DRV8301
Other Parts Discussed in Thread: TPS54160

Hello team,

I am supporting an application using the DRV8301 and when EN_BUCK is left floating the device does not power up unless there is an external pull-up, the datasheet recommends to "float to enable".

1. Is there any conditions under leaving EN_BUCK floating is contraindicated and a pull-up is required?
2. What is Absolute Max voltage on EN_BUCK/Pin 55? (Note: I see VLOGIC has a maximum of 7 V, but EN_BUCK is not listed under there).

  • 0
    TI__Guru** 114905 points
    Hi Victor,

    The buck regulator should power up if EN_BUCK is left floating and PVDD2 is above 3.5V.

    The EN_BUCK pin only enables the buck regulator when floating.

    What part of the device is not powered up; the buck, the driver, or both?
  • 0 in reply to Rick Duncan
    TI__Expert 3540 points

    Rick,

    More than one of the units that fails the buck has an output of 5.8 V (even though the resistor divider is set to 3.3 V). EN_BUCK is currently connected to one of the PVDD rails, which can see up to 32 V maximum during operating conditions.

    1. Are the Absolute Maximum Ratings for EN_BUCK characterized and available?
    2. Would EOS be a plausible reason for the buck's output being 5.8 V even though the voltage divider feedback is the to 3.3 V?

  • 0 in reply to Victor Salomon
    TI__Guru** 114905 points
    Hi Victor,

    The EN_BUCK pin should be left floating. Is pin 57 connected to GND? A common problem is the GND (pin 57) -- PowerPAD is not connected. The device will not work without this connection.

    The DRV8301 contains a TPS54160 buck converter. The TPS54160 datasheet for this device states the absolute maximum voltage on the EN_BUCK pin is 5V.

    This absolute rating are currently missing from the DRV8301 datasheet, although if the pin is left unconnected it is not violated.