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DRV10970EVM: no 5V VINT on the board

Part Number: DRV10970EVM
Other Parts Discussed in Thread: DRV10970

Good Morning,

I have the same problem that was reported in the related question.

Problem can be solved only if I provide an initial voltage <9V (when I turn on switch S1 VINT correctly goes up to 5V) and then if I ramp up the VM voltage up to 12V (which is the voltage required for my application) VINT stays to 5V. However, if I directly provide the required voltage of 12V, when I turn on the switch VINT goes up to only 100mV!

This is really a big problem, since I cannot make the VM voltage slowly ramp up in my final application, and I also don't know which the correct slew rate needs to be.

I need to know if such problem is related to the Evaluation Module (for example, due to the presence of the timer, which is powered from VINT) or if it is related to the component itself DRV10970 (maybe there is a recommended powering sequence when applying certain VM voltages).

If the behaviour was unpredictable, I cannot rely on such component for my application, since the VINT voltage would be required in order to power the Hall ICs of the motor.

Please let me know.

Thank you so much! Kind regards.

  • Update: sometimes it occurs that even if I directly provide the 12V VM voltage, when I turn on the switch the system correctly powers up (VINT goes to 5V); sometimes it simply does not happen; such random behaviour is however unwanted.

  • Hello Alessandro,

    Thanks for posting to the MD forum. Have you been able to confirm if the device is in sleep mode? This disables the internal regulator and this occurs when the PWM input is driven low for at least 1.2ms. If you try to enable the PWM signal this should wake up the device and check if this enables VINT back to 5V.

    Are you currently powering up the hall sensors from the EVM directly? If the 20mA max load current is being hit on VINT this could be another reason why it is having odd behavior. VINT is used to power a couple of items on the EVM and if it is also powering the hall sensors then this could be the issue. If you could check the current draw of the hall sensors on your motor this might paint a better picture if this could be part of the problem.

    Best,

    Isaac

  • Good Morning,

    thanks for your reply.

    I guess that the reason might be the device being put in sleep mode, as you suggested. I thought that this cannot occur, since I'm using the embedded timer to generate the PWM signal and the minimum DC is 5% and never 0, therefore the device should never be put in sleep mode.

    I think it's a matter of timings and voltages (charging/discharging of capacitors): if the 5V VINT regulator is not enabled, then it won't power the timer which will not generate the PWM, thus maintaining the device in sleep mode; I can recover from this situation by applying an external 5V signal to the PWM input pin, therefore making the device exit from sleep mode; I guess that sometimes it may occur that the 5V VINT regulator is enabled faster than the time required for the device to enter sleep mode, and in that situation the system correctly starts. I do not see this as a big problem, since in the final application I would use an external signal as PWM input, therefore not dependent from the fact that the 5V VINT regulator is yet enabled or not.

    Concerning the current consumptions, I'm indeed powering the Hall ICs from the EVM using the 5V VINT. The current consumption of the Hall ICs is MAX 10mA (there are also embedded pull-ups on the motor PCB). Since the VINT is powering other elements on the EVM, I do not know if there may occur some current transients which overcome the max limit of 20mA and cause the odd behaviour. Again, I do not see this as a big problem since in the final application I will be using the VINT to power Hall ICs only.

    Thank you! Regards.

  • Hello Alessandro,

    Correct, it could all be due to a small timing irregularity as you described above since this is not a problem we have encountered consistently. You should be able to test your use case on the EVM by removing the R15 resistor and applying the external voltage to TP3 to make sure the device is awake and by checking if VINT is pulled up to the 5V as expected. This can help confirm that there are not any other issues going on with the device.

    Okay thanks for confirming the max current draw of your hall sensors, thought this would be good to check since we have encountered some motors current draw sometimes exceed the 20mA current limit of the device, typically they are larger motors but thought it would be useful to check. This should not be a problem on your actual system then, since you wont be powering other items off of VINT like on the EVM. I hope this helps!

    Best,

    Isaac

  • Good Morning,

    Thanks for all the clarifications.

    Just one last quick question: I see that the PWM input has an internal pull-up of 100k to 5V VINT, therefore if I do not provide a fixed GND signal as PWM input (for example if when an external microcontroller disables its PWM output this is put to High-Z state and not forced to GND), the motor will start spinning at maximum speed. This also occured when I disconnected the R15 resistor and left the PWM input floating without applying any external signal.

    Could you please confirm such behaviour?

    Thank you again. Regards.

  • Hello Alessandro,

    I will get back to you tomorrow with a response, thank you for your patience!

    Best,

    Isaac

  • Hello Alessandro,

    Yes this is expected behavior due to the internal pullup resistor on the PWM input. Without anything to pull it down the system is getting a PWM with a 100% duty cycle which is why you are seeing max speed on the motor.

    Best,

    Isaac

  • Ok, thank you again for all the support.

    Kind regards!

  • Ok, thank you again for all the support.

    Kind regards!

  • Thanks Alessandro!