This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV8243-Q1: DRV8243-Q1: SPI (P) variant voltage change issue with PWM

Part Number: DRV8243-Q1
Other Parts Discussed in Thread: DRV8245-Q1, DRV8244-Q1

Tool/software:

DRV8243-Q1: SPI (P) variant we are using.
The motor driver functions normally when operated at 12 volts, but it does not function in reverse when operated at 24 volts.
"Not function"(PWM and EN ON but OUT 1 and OUT 2 No voltage)
FW direction :-75% to 100%
RW direction :-100% to 75%
 
There is no problem with the power source.

Do the necessary action on this.
  • Hello Ankit,

    Thank you for posting in this forum. Could you please provide more information about the H-Bridge control logic used? Were you using PH/EN mode or PWM mode bridge control. Which input(s) were PWM input(s). The H-Bridge works in both directions as per the corresponding control tables in the datasheet - please see below.

    FW direction :-75% to 100%
    RW direction :-100% to 75%

    Please provide details of what this meant. Thank you.

    Regards, Murugavel

  • Hello Murugavel,

    We are using H-bridge in PH/EN mode.

    • EN/IN1: PWM output we are using to regulate the speed of the motor.
    • PH/IN2: GPIO pin to control the direction of the motor.

     As we are using SPI(P) variant, via register settings we have disabled

    • ITRIP regulation
    • VM disabled for over voltage detection

    Another observation is from 12V to 17V motor works fine.

    As we increase input voltage till 24V, issue starts. 

    For 100% PWM duty cycle, even at 24V motor works fine, but this fails our application need in the field.

  • Hello Ankit,

    Thanks for the additional info.

    We are using H-bridge in PH/EN mode.

    • EN/IN1: PWM output we are using to regulate the speed of the motor.
    • PH/IN2: GPIO pin to control the direction of the motor.

     As we are using SPI(P) variant, via register settings we have disabled

    • ITRIP regulation
    • VM disabled for over voltage detection

    The above settings align with supported use case for this product. 

    Another observation is from 12V to 17V motor works fine.

    As we increase input voltage till 24V, issue starts. 

    For 100% PWM duty cycle, even at 24V motor works fine, but this fails our application need in the field.

    What is the behavior observed in reverse direction? Does "Not function" mean motor stops with a nFAULT pin pulled LOW? Is it possible to get motor current waveforms? Do you have a device EVM with you to reproduce this issue? Thank you.

    Regards, Murugavel

  • Hello Murugavel,

    What is the behavior observed in reverse direction?

    Functionality ,Turn on the motor forward 75% PWM reaches 100% PWM and stop, waits 45 seconds, backward from 100% PWM to 75% PWM and stop.

    behavior observed facing issue at backward direction start 2 sec and stop.

    Does "Not function" mean motor stops with a nFAULT pin pulled LOW? :- Yes

    Is it possible to get motor current waveforms?:- Not Possible

    Do you have a device EVM with you to reproduce this issue?:- yes

  • Hello Ankit,

    Functionality ,Turn on the motor forward 75% PWM reaches 100% PWM and stop, waits 45 seconds, backward from 100% PWM to 75% PWM and stop.

    After waiting 45 s the backward 100% PWM, was the PWM 100% instantly? This would result in a very high inrush current depending on the motor parameters and its load and could potentially cause an OCP trip. To mitigate this you can enable the on-chip peak current regulation feature based on ITRIP. See datasheet page 37, section 8.3.3.3 ITRIP Regulation.

    behavior observed facing issue at backward direction start 2 sec and stop.

    Please confirm this was start backward direction 100% PWM the motor ran for 2 s and stopped. It appears to be an OCP fault happening. 

    nFAULT pulled LOW means some fault has happened. While the nFAULT = LOW could you please read the contents of the FAULT_SUMMARY register and share the read out contents with us? 

    Do you have a device EVM with you to reproduce this issue?:- yes

    With my motor and EVM setup I was unable to reproduce this issue. I suspect an OCP happening with your system. The reason why I requested the current waveform was to see how much peak current was achieved while the fail condition happened. 

    Regards, Murugavel

  • Hello Murugavel,

    We have check our side and are encountering a TSD Fault.
    why ?

  • Hello Ankit,

    This means the current through the driver is exceeding the power dissipation capability that can be supported. This also depends on the ambient temperature and the PCB design. See below table from the datasheet. This is based on the EVM PCB design. Because you were driving the motor with 100% PWM duty you can see the currents that can be supported for a specific duration "without PWM". DC value column is the continuous current that can be supported indefinitely. Your PCB design may give different results. 

    For higher currents you'll have to consider the variants from this family of devices either the DRV8244-Q1 or DRV8245-Q1. You can use the SLVRBI3 — Full Bridge Driver Junction Temperature Estimator Excel in the product webpage https://www.ti.com/product/DRV8243-Q1 to estimate junction temperature vs. time for these devices.

    Alternatively you can use the ITRIP current regulation feature of this device to mitigate the peak inrush current. However this will reduce the maximum torque output from the motor. This may or may not be a solution based on your end application requirement. If the continuous current (DC) requirement which would be steady state motor current with full load exceeds the current that can be supported by the device you'll have to consider higher current variants of this device. Thank you.   

    Regards, Murugavel