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DRV8350: Application problems

Zoey Wu
Expert 3970 points
Part Number: DRV8350

hi team,

my customer is using DRV8350H and below are some problems that need your help:

1. the OCP current limit: do we have a specific formula how to calculate the current limit between VDS? 

2. Can DRV8350 work with AMC1306? 

3. the datasheet shows that DRV8350 supports 100% PWM. Could u kindly help to explain the principle? because when the PWM is up to 100%, when will the charge pump of high side be charged? 

4. Is there any error in figure 20 about the VCC? One VCC is the output pin of the chip, one is the pull up voltage of nfault.thanks!

  • 0
    TI__Expert 7401 points

    Hi Zoey,

    Thank you for your questions. 

    Please allow me to look into these and the appropriate documentation and follow-up soon by the end of this week. 

    Best Regards,

    -Joshua

  • 0 in reply to Joshua Maize
    TI__Expert 3970 points

    Hi Joshua,

    Any update? my customer is very urgent to finish the design.thanks!

  • 0 in reply to Zoey Wu
    TI__Expert 3970 points

    Hi team,

    Any update? thanks!

  • 0 in reply to Zoey Wu
    TI__Expert 7401 points

    Hi Zoey, 

    Please allow me to follow-up by tomorrow with the update to your inquiry. 

    Best Regards,

    -Joshua

  • 0 in reply to Joshua Maize
    TI__Expert 7401 points

    Hi Zoey, 

    Zoey Wu said:
    1. the OCP current limit: do we have a specific formula how to calculate the current limit between VDS? 

    The formula for selecting the OCP current limit can be found in section 9.2.1.2.3.1. of the DRV8350 datasheet, along with an example calculation: 

       

    Zoey Wu said:
    2. Can DRV8350 work with AMC1306? 

    Can you please clarify how the AMC1306 would be used with our device? I do not believe there should be an issue with implementing protection.

    Zoey Wu said:
    3. the datasheet shows that DRV8350 supports 100% PWM. Could u kindly help to explain the principle? because when the PWM is up to 100%, when will the charge pump of high side be charged? 

    The DRV835x charge pump architecture includes a doubler charge pump for lower supply voltage situations that allows the device to function at 100% PWM. The doubler regulates VCP to be ~ VDRAIN + 10.5V. 

    At 100% duty cycle, one phase will still has the lowside MOSFET on and is able to charge the VCP capacitor while the other two phases will have their highside MOSFETs on.  Hope this helps clear up any confusion. 

    Zoey Wu said:
    4. Is there any error in figure 20 about the VCC? One VCC is the output pin of the chip, one is the pull up voltage of nfault.thanks!

    These figures appear to be correct, as VCC is the regulator output from the internal buck which is capable of being used as the supply that nFAULT can be pulled up to! It is not uncommon to use our driver voltage regulators/LDOs for other driver supply voltages within the range of 3.3V - 5V.

    Hope this information has been helpful!

    Best Regards,

    -Joshua

  • 0 in reply to Joshua Maize
    TI__Expert 3970 points

    Hi Joshua,

    This really helps a lot. Thanks!

  • 0 in reply to Zoey Wu
    TI__Expert 7401 points

    Happy to hear so, Zoey!

    Best Regards,

    -Joshua