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DRV8343-Q1: DRV8343-Q1 current sense resistor calculation

Uday Pastagia
Prodigy 40 points
Part Number: DRV8343-Q1

Hello Ti Team,

I am developing a driver board for the BLDC Motor and Brushed DC Motor.

My Motor working voltage =+24V and Max Current rating is 1.2 A.

For these i selected DRV8343H IC as i want to work in Hardware configuration.

The external MOSFET , I am using is SIZ240DT-T1-GE3.

In datasheet, I am not able to find, how to calculate the Current Sense Resistor as you mention the low side driver.

As mention below image where i have to connect the VRef? (Should I connect to VM?)

Thanks and Regards,

Uday.

  • 0
    TI__Mastermind 18916 points

    Hi Uday,

    Thanks for posting your question to the e2e forum - please see the below answers to your questions:

    1. Vref connection to Vcc
      1. This pin should not be connected to VM (since VM would end up being ~24V for your system) 
      2. the VREF pin is only meant to withstand between 3V to 5.5V
      3. Vcc should be ~5V provided by another power supply to handle logic-level circuits (like the current shunt amplifiers).
    2. Rsense calculation
      1. Datasheet table 36 'External Components' suggests 2.5mOhm value for the shunt resistor (this is Rsense) 
      2. For each phase, the motor phase current will flow through the low side MOSFET and then across the Rsense resistor and produce a voltage drop (V=I*R).
      3. This voltage drop is then amplified based on your current shunt amplifier Gain setting (G_csa), and then compared with 0.5*VREF input to produce SOx.
      4. Your motor control unit (MCU) can monitor SOx to determine motor phase current using the equation below
        1. this is useful for detecting current across each motor phase, as well as overcurrent detection.

    Let me know if that answers your questions, or if there is further clarification needed. 

    Thanks and Best Regards,
    Andrew