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DRV8302: Buck converter output voltage issue

Vijay pawar
Prodigy 120 points
Part Number: DRV8302

1) I am using DRV8302 IC for buck as well motor driver. Designed output voltage is 5VDC. As the buck converter is independent from motor driver section, hence provided supply voltage to only 53&54 pin. (input voltgae 24VDC). 

2) The Output was as per design and the voltage at VSENSE pin was 0.8V.

3) Now as i provided the same supply voltage to pin no. 29 ( 24VDC ), the output of buck converter changes from 5V to 8.5V. and voltage at VSENSE pin becomes 1.34 V. ???

4) again to get the desired output voltage the lower resistor of divider circuit need to increase ,by adjusting we achieve required voltage , but the resistor value and the Voltage at VSENSE pin are not as per provided in datasheet 

Please help in above problem..

  • 0
    TI__Guru** 114905 points
    Hi Vijay,

    Please double check your connection to the GND pad on the bottom of the device. We have seen several issues with the buck when the device does not have a solid ground.

    One way to check the connection is to measure the internal pulldowns resistors of the inputs.
  • 0 in reply to Rick Duncan
    Prodigy 120 points
    Hello Rick,
    Thanks for your great suggestion,
    I have resolved the previous issue but facing the new one,

    When i provide the supply to the IC , The Buck section is working OK but the voltages at DVDD and AVDD is 0V ??

    Kindly suggest on above.

    Thanks
    Vijay.
  • 0 in reply to Vijay pawar
    TI__Guru** 114905 points
    Hi Vijay,

    Did you set the EN_GATE input to a logic high?
    What are the voltages at the other inputs?
    What are the voltages at the GVDD output, and the BST_x pins?
  • 0 in reply to Rick Duncan
    Prodigy 120 points
    Hello Rick,

    As u suggested i have set EN_GATE pin to Logic high. and it is working OK
    And the voltages at DVDD 3.3V , AVDD 6.6V, BST_x pin 11V ,

    Do i have to keep EN_GATE pin always logic High ?
    Can I use DVDD pin Voltage as a input to REF pin ? Because a divider from DVDD is also using to OC_ADJ pin ...
    If i am not using SP2 and SN2 , can i connect those pins to ground ? and also SO2 pin ?

    Regards,
    Vijay
  • 0 in reply to Vijay pawar
    Prodigy 120 points
    Also, One more question,
    What if, i am not using the SN_x SP_x pins, and connecting them to ground. What to do with OC_ADJ, & REF pins. ? They too connect to ground or keep open.


    Regards,
    Vijay
  • 0 in reply to Vijay pawar
    TI__Guru** 114905 points

    Hi Vijay,

    If you are not using the SN_x and SP_x pins, it is recommended to connect the inputs to GND.

    The REF pin can be left floating or connected to GND.

    The SO_x amplifier outputs can be left floating.

    OC_ADJ should be used per section 7.3.4.2 of the datasheet to protect the FETs.

  • 0 in reply to Rick Duncan
    TI__Guru** 114905 points
    Hi Vijay,

    Sorry, forgot your first two questions:

    Do i have to keep EN_GATE pin always logic High ?
    >>> No, you only need EN_GATE high when you are controlling the motor. If there are times that motor is idle, you can set the EN_GATE to low to conserve power.

    Can I use DVDD pin Voltage as a input to REF pin ? Because a divider from DVDD is also using to OC_ADJ pin ...
    >>> Yes, you can connect DVDD to the REF pin.
  • 0 in reply to Rick Duncan
    Prodigy 120 points
    Hello Rick,

    Above information was very helpful. Thanks a lot for your great support.


    Regards,
    Vijay.