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DRV8412: Current sensing, HS, LS or IN line?

Benyuan Liu
Prodigy 93 points
Part Number: DRV8412
Other Parts Discussed in Thread: INA240, INA253, INA254, INA241A, DRV8962

Hi,

We are designing current sensing schematic for DRV8432,

1, In the datasheet, it states that HS sensing is preferred, and if using LS sensing, 10mΩ or less then 100mV drop is required. For DRV8432, the current rating is much higher than DRV8412, it is hard to select a LS shunt resistor. Is there any recommended current sensing strategies (HS or LS or IN line, resistor value or BOM of the shunt resistor) for DRV8432?

2, we would like to copy the current sensing reference designs from DRV8412-C2-kit, which is using LS current sensing with a 10mΩ resistor, in the schematic, it states that ROUTED GROUNDS (SHIIELDED FROM GND PLANE), what does this mean and how could I route the PCB traces?

3, We plan to use DRV8432 as two H-bridge (BTL) mode and operate at 500 KHz, and if we are using IN line current sensing, which current sensing amplifier should we use? Should the bandwidth of the difference amplifier larger than 500 KHz or 1 MHz? I think the feature "enhanced PWM rejection" is preferred, right? We are considering INA240, but its bandwidth is 400KHz, and those current sensing amplifiers with "integrated shunt resistors" (INA253, INA254) only have a maximum bandwidth of 350 KHz.

Thanks!

benyuan

  • 0
    TI__Guru 55605 points

    Benyuan,

    1)  Really depends on what you are trying to sense and the reason for it.  The limitation on the low-side sense is there as you can't have that much separation between the GND pins of the device and the board ground.  You might find the following article interesting.

    https://www.ti.com/lit/an/slla528/slla528.pdf

    2)  This is referring to the GND pins of the DRV8412 itself.  Since you inserted a sense resistor in the GND path, one end is connected to the GND of the DRV8412 itself and the other end is connected to the GND plane of the board.  

    3)  The INA241A looks like it would do the job.  

    Regards,

    Ryan

  • 0 in reply to Ryan Kehr
    Prodigy 93 points

    Thank you. The document is very intuitive. I found that DRV8412 do not have a blanking feature (tBLK), DRV8962 do. DRV8962 also has IPROP. May be DRV8962 is really worth upgrading.

    1) In DRV84x2 data sheet, "a high bias voltage on the low side sensing could affect device operation." which operation/features will be affected? Regardless of DRV8412 or DRV8432, so long as I kept the LS sense voltage below 100 mV, DRV8432 will for sure operation normally? 

    3) In the INA241 datasheet, it has a 1.1MHz bandwidth for all gains and can reject PWM up to 125KHz. Is INA241 capable of inline current sensing when operate DRV84x2 at a PWM frequency of 500KHz?

  • 0 in reply to Benyuan Liu
    TI__Guru 55605 points

    1) Device will be damaged.

    2)  Yes, INA is made for inline.

    Regards,

    Ryan