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DRV8305-Q1: DRV8305 PVDD question

Mike Jung
Intellectual 700 points
Part Number: DRV8305-Q1
Other Parts Discussed in Thread: DRV8305

Dear all.

We are working on a working sample with the same circuit as DRV8305-Q1EVM.
I have a question during testing.

The difference is that the power source A and the power source B are separated.

For power source A (12V), drop to 5V and 3.3V, and then 3.3V for MCU power

The 5V power supply is connected to the power supply of DRV8305 pull up resistor and Vref.

Power supply B (12V) is connected to PVDD of DRV8305 via power switch.

Questions)

The power source A is always on and the power source B is on / off so that the motor is driven according to the state of the power source B.

If power supply B is turned off through the power switch, PVDD becomes 5V-0.4V when pull-up and 5V is applied at Vref, and it is maintained at 3.3V-0.4V when 3.3V is applied.

I wonder if the voltage of Vref can affect PVDD.

Thanks.

  • 0
    TI__Intellectual 1345 points

    Hi Mike,

    Yes, there is an internal diode path from VREF to PVDD on the IC since there is an LDO in the IC on versions DRV83053xx and DRV83055xx. We are in the process of updating the applications section of the datasheet to reflect that.

    Section to be added for clarification :

    VREG reference voltage input (DRV8305N)

    For DRV8305N, the VREG pin is used for a reference voltage of current sense amplifier and SDO pull-up as described in "7.3.7 VREG: Voltage Regulator Output". The internal LDO is disabled but the LDO physically exists in the device, and there is a current path from VREG pin to PVDD pin through the internal LDO. The reference current specified in the datasheet flows to the device if PVDD voltage (VPVDD) is higher than VREG pin voltage (VVREG) . In case VVREG is higher than VPVDD during power up/down sequence, it is recommended to limit the current by adding a resistor to VREG pin so that the current does not exceed 50mA. The figure xx uses 330ohm and the resistor helps limit the current to approx. 15mA when VVREG = 5V and VPVDD = 0V.