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DRV8328: Using DRV8328 as three separate NMOS high side drivers

Michael Faure
Prodigy 10 points
Part Number: DRV8328
Other Parts Discussed in Thread: DRV8300

Hello,

I would like to know if it is possible to use the DRV8328B as three separate NMOS static high side drivers.

Specifically, I would like to use it to selectively shunt three high-power LEDs connected in series, according to the following schematic:

This would be for quasi-static operation, switching less than once per second, no fast PWM.

I am particularly concerned that the DRV8328 power supply (PVDD) is 5V and not the same as the MOSFET power supply, and that the later can be significantly higher (up to 50V).

Is this going to work?

Thanks.

Michael

  • 0
    TI__Genius 12231 points

    Hi Michael,  

    Thank you for using our forum!

    Can you explain further your concern regarding PVDD and the MOSFET supply difference?   

    The device supply,  PVDD,  can range from the recommended values of 4.5V < PVDD < 60V and is/can be the same as the MOSFET supply.  

    Let me look into this application further and provide any insight that I can. 

    Best Regards, 

    -Joshua

  • 0 in reply to Joshua Maize
    Prodigy 10 points

    Hi Joshua,

    Thank you for your answer.

    My concern is that in my application, PVDD is not the same as the MOSFET supply (VBUS on my schematic).

    PVDD is set at 5V, which should be fine according to the datasheet. On the other hand, VBUS is actually a constant current source. Depending on the load, the voltage can vary from ~0V to 50V. It will be close to 0V when all three LEDs are shunted (Q1, Q2 and Q3 conducting) and close to 50V when the three LEDs are on (Q1, Q2 and Q3 not conducting).

    My concern is wether or not the DRV8328 will be able to commute the high side MOSFETs when their source voltages (SHA, SHB and SHC) are much higher than PVDD. I guess it should be fine, since high side drivers are floating. But I am also not completely sure about this, because split power supply operation is not explicitly mentioned in the datasheet (or I missed it). In single power supply operation, source voltage of the MOSFETs is always less than PVDD.

    Best regards,

    Michael

  • 0 in reply to Michael Faure
    TI__Genius 12231 points

    Hi Michael, 

    Thank you for the clear explanation!

    Let me continue to look into this with my team and get back to you on the matter as soon as I can. 

    Best Regards,

    -Joshua

  • 0 in reply to Joshua Maize
    TI__Genius 12231 points

    Hi Michael, 

    I apologize for the delayed response. If this inquiry is still open, I have the following to say:

    it appears that the DRV8328 is not recommended for a split-supply operation. The DRV835x,  however, is designed with split supply architecture and has supply voltage range from 9 - 75V, and DRAIN voltage from 7-100V.   

    Still, I have a concern that operating VBUS as a current source down to 0V may trip the under voltage protection features we have implemented in our devices. Is this a possible case that the drain voltages would often reach below 4-5V? 

    I will follow up and confirm whether the DRV8328 truly can't operate in a dual-supply mode for this application and update you further by mid next week.

    Thank you for your patience and Best Regards,

    -Joshua

  • 0 in reply to Joshua Maize
    Prodigy 10 points

    Hi Joshua,

    Thank you for the follow-up.

    Yes, I saw the DRV835x devices, but I only have a 5V supply voltage available, and as you stated they need at least 9V.

    Regarding the undervoltage protection features, yes, it is entirely possible for the drain voltages to drop below 4-5V. I plan to disable some protection features by connecting the VDSLVL pin to GVDD through a 100k resistor, but I don't know if that will be enough.

    Basically, the ideal component for my application is the LTC7004 from Analog Devices. However, I would need several of them, which would increase the number of components and the area used on the PCB, not to mention that the DRV8328 is cheaper. So I thought I could use one DRV8328 instead of three LTC7004, but I understand that is a little bit far-fetched.

    If you have other components in mind that might be suitable, please let me know.

    Best regards,

    Michael

  • 0 in reply to Michael Faure
    TI__Genius 12231 points

    Hi Michael, 

    Thank you for the extra insight.

    Let me align with my team on this and update you on Wednesday if there are more suitable BLDC drivers for your application, or whether we can work around some potential issues.

    Best Regards,

    -Joshua  

  • +1 in reply to Joshua Maize
    TI__Genius 12231 points

    Hi Michael, just following up with an update.

    We are still looking into the possibilities for your application, and think that the DRV8300 may be able to just satisfy your requirements. (Min input voltage 5V, separate power architecture/drain up to 100V). 

    Can you please look into this device to see whether it meets your necessary application needs?

    Best Regards,

    -Joshua

  • 0 in reply to Joshua Maize
    Prodigy 10 points

    Hi Joshua,

    The DRV8300 might be suitable, although it does not support 100% PWM duty cycle.

    I will mark this question as resolved for now. Thank you for your time and your answers.

    Best regards,

    Michael