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Original question:

LM5146-Q1: Query on LO,HO Current

DRV8353: Query on application

Sandeep Varma
Prodigy 170 points
Part Number: DRV8353

Hi,
 In DRV8353H, I have two queries:

Query 1:

 SPA,SPB,SPC pins are common for bottom phase gate current return path and Current sensing input to the driver for the respective phases of A,B,C. if i have to add filter after shunt sensing(i.e Filter at input of Gate driver current amplifiers), Could you please suggest a scheme for this ? I could see that, if i add filter, it will break the Current path bottom FET gate current.

Query2:
In data sheet, Charge pump current limit current reduces as VM voltage reduces as shown in yellow highlighted below. Does it mean that if i use at VM =10V, Only 15mA(Instead of Max 25mA) is the limit so that MOSFET selection to be there accordingly. Then, why did the absolute Max says 25mA is the limit ?



  • 0
    TI__Genius 12231 points

    Hi Sandeep, 

    Thank you for posting on our forum! 

    Please allow me to look into these queries and follow-up this week with a response. 

    Best Regards, 

    -Joshua 

  • 0 in reply to Joshua Maize
    Prodigy 170 points

    Hi,
    Could you please look into the queries  ? 

  • 0 in reply to Sandeep Varma
    TI__Genius 12231 points

    Hi Sandeep, thank you for your patience. 

    Sandeep Varma said:
     SPA,SPB,SPC pins are common for bottom phase gate current return path and Current sensing input to the driver for the respective phases of A,B,C. if i have to add filter after shunt sensing(i.e Filter at input of Gate driver current amplifiers), Could you please suggest a scheme for this ? I could see that, if i add filter, it will break the Current path bottom FET gate current.

    For filtering on the CSA input pins, we actually recommend a filtering capacitor from SPx to SNx, like the following diagram for the DRV835x: 

    This does not affect the current return path as current is still flowing through the shunt to GND, and the votlage differential across the shunt is what is being inputted. 

    Sandeep Varma said:
    In data sheet, Charge pump current limit current reduces as VM voltage reduces as shown in yellow highlighted below. Does it mean that if i use at VM =10V, Only 15mA(Instead of Max 25mA) is the limit so that MOSFET selection to be there accordingly. Then, why did the absolute Max says 25mA is the limit ?

    This understanding is correct, as the lower supply voltage will have corresponding lower charge pump current output - and the absolute maximum rating is stating that if the device is operating as intended then the VCP current should never be greater than 25mA regardless of VM voltage. 

    I hope this helps clear up any confusion. 

    Best Regards,

    -Joshua