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DRV8706S-Q1EVM: Allowable current of VCP

oaku.hiroshi
Prodigy 150 points
Part Number: DRV8706S-Q1EVM

Hi

I would like to use it as a power source for an operational amplifier used in the reverse connection protection FET switching and motor output current detection circuits on the VCP line.

1.What is the allowable current of the circuit connected externally from the VCP line?
2.What is the allowable VCP current including GateDrive?

  • 0
    TI__Expert 5635 points

    Hi Oaku-san,

    In the datasheet it gives you the min, typical, and max values for the charge pump voltage based on the the PVDD voltage and the Ivcp. The allowable current if you want to get that voltage on the Vcp pin would be equal to or less than the test condition Ivcp. For example, if you needed at least 9.5 V then Ivcp would be 15 mA or less.  

    VCP load calculation from the datasheet to calculate the Ivcp for switching FETs.

    You would ensure that the total of the two currents would be less than the maximum lvcp current for a given Vcp. Let me know if you have any further questions.

    Best, 

    Keerthi 

  • 0 in reply to Keerthivasan Kumanan
    Prodigy 150 points

    Hi Keerthi-san

    The steady current appears to be Ihold written on the data sheet, but can't it flow up to 30mA?
    Is this only a requirement for the internal Gate current?
    Also, it seems that the peak current can flow up to 77.5mA depending on the SPI settings, but what is the maximum rating?

  • 0 in reply to oaku.hiroshi
    TI__Expert 5635 points

    Hi Oaku-san,

    That is the gate drive current and the gate hold current for the gate of the external MOSFETs. Can you clarify what you mean by the internal Gate current?

    The peak current is configurable (IDRVP and IDRVN) as you said and the maximum current for a given setting is given below:

    Let me know if this answers your question.

    Best regards,

    Keerthi 

  • 0 in reply to Keerthivasan Kumanan
    Prodigy 150 points

    Hi Keerthi-san

    I'm sorry. I made a typo.
     Error: Internal Gate current
     Correct: Motor driver Gate current (external FET)

    What I wanted to know is, is the following interpretation of the peak current values of Ihold, IDRVP, and IDRVN correct?

    ■Normal current
    Ihold > VCP external circuit (reverse connection protection FET and current detection circuit power supply) + motor driver gate current

    ■Peak current
    IDRVP or IDRVN > VCP external circuit (reverse connection protection FET and current detection circuit power supply) + motor driver gate current

    Or do they each have their own peak and norma current ratings?
    ・VCP external circuit (reverse connection protection FET and current detection circuit power supply)
    ・Motor driver gate current

  • 0 in reply to oaku.hiroshi
    TI__Expert 5635 points

    Hello Oaku,

    The motor drive current and the VCP external circuit have their own peak and normal settings. The current that the VCP external circuit can draw is shown in my first post. Let me know if I understood the question correctly.

    Best, 

    Keerthi 

  • 0 in reply to Keerthivasan Kumanan
    Prodigy 150 points

    Hi Keerthi-san

    The data sheet below states that it supports an average output current capability of 15 mA, so I would normally use it at 15 mA, but there are cases where peak current occurs. Please let me know if the maximum rating is also 15mA. (As long as you look at the wording, it does not seem to be the maximum rating)

  • 0 in reply to oaku.hiroshi
    TI__Expert 5635 points

    Hi Oaku, 

    For example, PVDD >= 13 V and IVCP <=15 mA is the current that we can guarantee that the VCP voltage will be within the margins (TYP and MAX) listed in the datasheet. Let me know if this answers your question.

    Best,

    Keerthi