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DRV8353RH-EVM: Understanding Queries on DRV8353R – 100-V

Part Number: DRV8353RH-EVM
Other Parts Discussed in Thread: DRV8353R, DRV8353

Hello Team,

I am using “DRV8353R – 100-V Three-Phase Smart Gate Driver” there are below queries I have could you help me for the same

  1. Setting Current Threshold: By using VDS overcurrent protection (OCP): VDS overcurrent trip voltage "DRV835x: VDS_LVL" by using OCP Control Register (address = 0x05h) OR VSEN_OCP: VSENSE overcurrent trip voltage "SEN_LVL" CSA Control Register (DRV8353 and DRV8353R Only)
  2. Other than Fault(29) pin is there any INTP present? If yes what are the Interrupts OR if No : How can I disabled Fault pin ? -> in GDU enable mode)
  3. Charge Pump (VCP) how to make enabled & Disabled : CPH(4) & CPL(3)
  4. Setting up Driver output high : is the process followed is correct? INHA(34) > high, INLA(35) > Low accordingly GHA(8)>high GLA(9)>Low & what about SHA(9) pin status?
  5. Does SHA(9) pin is used as feedback for Driver output status
  6. Reading of “Charge Pump Voltage”: "How can we get the voltage is there any specific resistor"
  7. How can we read GDU state, (Sleep/Enable/Fault)?
  8. How can we get/read present current value? (that is used for checking with actual over current setting)
  9. How can we get/read present voltage value? (that is used for checking with actual over voltage or under voltage setting)
  • Hello Kiran,

    Our team will get back to you tomorrow.

    Thanks,

    Matt

  • Hello Kiran,

    1. To set the overcurrent protection feature for VDS monitoring, you want to determine what is the max allowable current you expect in your motor. Then based on the Rds(on) resistance of the FETs you can calculate the voltage drop across the FET at this current (Imax)x(Rds(on)). Once this is determined you can select a setting by using the VDS_LVL bits to cause the overcurrent limit to trip at that particular voltage. Keep in mind that as your MOSFETs heat up during operation this will cause an increase in the Rds (on) resistance. In order to configure the SEN_OCP feature, you need to determine what is the max allowable current you expect through a motor phase. Based on the sense resistor value you are using, this will create a voltage drop across the sense resistor. The SEN_LVL bits can be configured through SPI to select a voltage that is equal to the current at which you want it to trip multiplied by the sense resistor resistance. Once the voltage drop across the sense resistor reaches the voltage set by the SEN_LVL bits, it will trigger an overcurrent fault. 

    2. The fault pin is simply an output pin that is used to indicate when a fault has occurred in the device. For the SPI device there are certain faults that can be disabled (such as VDS overcurrent protection). You can refer to section 8.3.6 for more information on what faults are reported and which ones can be configured to not be reported on the nFault pin. 

    3. The charge pump cannot be disabled. The charge pump is used to fully enhance the high side MOSFET to about 10V above the supply voltage to properly bias the VGS of the high side FET. 

    4. You are correct, when INHA is high and INLA is low then GHA will be high and GLA will be low, so the high side FET for phase A will be on and the Low side FET for phase A will be off. SHA is an input pin that is used to monitor the voltage at the source of the high side MOSFET. So when the high side FET is turned on, then it is expected for the source of that FET to be about the same voltage as the supply voltage (Since the drain of the high side FET is connected to the supply voltage)

    5. The SHA pin is used to monitor the VDS voltage. It is also used to sink current from the high side gate to the source of the FET when turning off the FET. The SHA node is connected to the source of the high side FET as well as to the motor phase.

    6. In order to monitor the charge pump voltage, you can use a resistor divider to step down the VCP voltage to a voltage that can be safely inputted to an ADC of your MCU. Just make sure to use high enough resistor values to ensure that only minimal current (A couple hundred microAmps should be fine) is drawn from the VCP pin through the voltage divider. 

    7. To determine the state of the driver, a few tests can be performed:

          a. To check if the driver is in a Fault state, the fault pin can be monitored. It will be pulled low when a fault is present.

          b. To determine if the driver is enabled or in sleep mode, you can check the DVDD, VGLS, and VCP pins to ensure that they are outputting the expected                    voltages. If enable is low and DVDD, VGLS, and VCP are low, then the driver is in sleep mode. if enable is high and DVDD, VGLS, and VCP are outputting            the correct voltages, then the driver is enabled. 

    8. You can use the outputs of the current sense amplifiers to monitor the current through the phases. The actual current can be calculated using the equation below, where Vvref = reference voltage of the current sense amplifier, Vsox = the output voltage of the sense amplifier, Gcsa = gain of the current sense amplifier, and Rsense = the resistance of the sense resistor.

    9. One solution to monitor the voltage is to use a resistor divider between the voltage that you want to monitor and ground, and use it to step down the voltage to a voltage that your MCU can handle. This can go into an ADC in the MCU to monitor the voltage. An example of this done on our EVM is shown below:

  • Thank you for your valuable input

  • Glad I can help! If you have any further questions please let me know.