• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 31 subscribers
  • Views 569 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV8350: DRV835x Ivcp/vgls dependence on Vm

Rajeev Singh
Prodigy 20 points
Part Number: DRV8350

The datasheet for the DRV835x 100-V Three-Phase Smart Gate Driver mentions (on Page 68) that "IVCP/VGLS is the charge pump or low-side regulator capacity, dependent on the VM pin voltage."  However, I cannot find additional information regarding the dependence of IVCP/VGLS on VM.  Please provide the dependence.

  • +1
    TI__Mastermind 26046 points

    Hi Rajeev,

    Please refer to figures 6 through 13 in Section 7.7 of the datasheet and specifications for VVCP and VVGLS in section 7.5 of the datasheet. 

    Thanks,
    Aaron

  • 0 in reply to Aaron Barrera
    Prodigy 20 points

    Thank you!  Do those figures imply, for example in Figures 12 & 13, that load current is limited to 10mA for the case of Vvm = 9V?  What happens when 10mA load current is exceeded?

  • +1 in reply to Rajeev Singh
    TI__Mastermind 18981 points

    Hi Rajeev,

    Thanks for the follow-up. 

    The info above should be correct - VM voltage is the main DRV IC power supply, and it's used by the VCP (Charge Pump) and VGLS (Linear) regulators to generate +10V VGS over-drive voltage. This is why having lower VM reduces the capability of these regulators to output voltage and current as needed. 

    For your example of VM=9V, 10mA will be typical current loading capability. 

    • If your total MOSFET gate-drive current is more than 10mA, then this will gradually deplete the charge on the VGLS and VCP regulator capacitors. 
    • And eventually, the voltage on these capacitors will reduce below undervoltage threshold and trigger a GDUV-type fault. 
      • this will indicate that the overdrive voltage supplies are not reliably high enough to switch your MOSFET gates ON reliably. 

    A typical estimate of gate-drive current loading is: Iavg = #MOSFETs x MOSFET Qg spec x freq_PWM

    • You'll also have to account for some system-level inefficiencies caused by things such as PCB parasitics (in capacitor layout and gate-drive signal traces) 

    Best Regards, 
    Andrew