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DRV8244S-Q1LEVM: Thermal Shutdown (TSD) triggering at low temperatures

Jacob Vartanian
Prodigy 10 points
Part Number: DRV8244S-Q1LEVM
Other Parts Discussed in Thread: DRV8145-Q1, DRV8706-Q1, DRV8144-Q1

I am using the evaluation module for the DRV8244S motor driver to drive a load with the following test setup:

  • 15V (max 40A) Power supply into J14 (Battery Input Terminal)
  • Brushed DC (max 28A) motor connected to OUT1 and OUT2
  • 0R1 power resistor in series with motor for current measurements (have also tested without this resistor)
  • Ramp rate of 10
  • PWM 50%, 20kHz
  • PH/EN Drive mode

The motor with driver is able to operate without issues under small loads, however, under higher loads, the "thermal shutdown" (TSD) fault appears on the GUI, stopping the motor.

From measuring over a 0R1 power resistor in series with the motor, with an oscilloscope, this shows a 1V drop i.e. about 10A of current at the time of fault.

A thermocouple placed on top of the motor driver IC has only shown a maximum of 50°C during testing, the fault even appeared when this was only around 30-40°C. Datasheet indicates around 150°C is the thermal cut-off.

Connecting the motor direct to my DC supply shows the motor is able to handle loads much greater with ease.

Setting the TSD to self-reset does not help, and will oscillate between fault/no fault every 20ms.

My question is, is there anything else besides excessive temperatures that could cause this fault to be set, such as current-spikes, voltage drops etc.? Or could this indicate a faulty component.

  • 0
    TI__Mastermind 32365 points

    Hi Jacob,

    I think you may be using the default Slew Rate SR setting which is slow for this high current. You may want to try one of the last three highest values. I noticed the GUI values had typo mismatch with the datasheet but functionally they match the datasheet.  

    You mentioned "A thermocouple placed on top of the motor driver IC has only shown a maximum of 50°C during testing, the fault even appeared when this was only around 30-40°C.". This may be true. For such fast thermal transients the die temperature would not have enough time to heat up the plastic package and/or the PCB because of their thermal masses. The die temperature temperature definitely hit the threshold specification. This is expected behavior. A fast thermal camera might provide better insight to the die temperature transient peak. 

    You can check out the anticipated thermal performance using the Full Bridge Driver Junction Temperature Estimator https://www.ti.com/tool/download/SLVRBI3 in the DRV8244 product webpage, https://www.ti.com/product/DRV8244-Q1. The thermal modeling was done with the EVM PCB with choice 1, FYI.

    I plugged in the values using the test conditions you mentioned in your post with default SR setting. When the DC motor is driven from stop condition there will be an inrush current perhaps 20+ A for your motor. With the default SR even it starts hitting the TSD threshold at a much lower current. When I plugin that value for the inrush current and 0 A after a thermal shutdown you can see the die temperature exceeds TSD threshold quickly. After shutdown the device cools rapidly because of the PCB thermal dissipation. 

    I increased the SR and got the below estimation. Significantly improved but could trigger a TSD if the duty cycle does not ramp up slowly (Ramp Rate = 0).

    The DRV8245S-Q1 would give you more head room. But the estimator suggests 18 A may be the peak current it can support with some head room before hitting a TSD. You could also use the Itrip current regulation to keep the inrush current to below the TSD. This would reduce the starting torque output though.

    If your BDC motor's inrush is in excess of 20 A, I'd recommend considering 2x DRV8145S-Q1, two half-bridge devices to form a full-bridge. See below image from the DRV8145-Q1 datasheet.


    A smart gate driver such as the DRV8706-Q1, www.ti.com/.../drv8706-q1.pdf with external power MOSFETs could be an option as well. I hope this helps you understand the TSD behavior of the DRV8144-Q1 for your BDC operating conditions and potential solutions to choose the right driver.

    Regards, Murugavel

  • 0 in reply to Murugavel4637
    Prodigy 10 points

    Hi Murugavel,

    Thank you for the insights. Increasing the SR did seem to help, as well as running at full 100% PWM, however, it still struggled and tripped the TSD.

    If running at slower speeds with PWM (say 50%), should the slew rate and frequency be selected such that the motor has enough time to switch between zero and 12V each PWM period (that is, have a PWM period longer than what the rise/fall time would be?)

    I think I will be taking your advice and aim to use two half bridge drivers for this application. Even though the datasheet for this part specifies max current of 21A, I suppose that is more relevant for pulses such as solenoid applications, rather than running continuously.

    Thanks again, Jacob

  • 0 in reply to Jacob Vartanian
    TI__Mastermind 32365 points

    Hi Jacob,

    The slew rate directly impacts switching losses in the power FETs. The longer the SR higher the switching loss. Higher currents will allow the FET to conduct in the linear region longer dissipating a lot of power and result with TSD. So regardless of the duty cycle the SR should be as fast as the system allows. However faster SR will result with EMI issues. This is where you'll have to trade off. 

    This device's maximum current can be supported as long as it does not hit TSD which is a function of the duration of the max. current. You're correct 21 A will not be continuous current that can be supported. The thermal estimator Excel gives you a pretty good idea of what continuous current can be supported. In my experience for such higher currents two half bridge drivers would be the way to go for this application. Thank you.

    Regards, Murugavel