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RE: DRV8701: 36V 300A motor controller design

January 11, 2018, 5:36 am
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Hi Daniel,

The device can be operated at 36V. Care must be taken to avoid voltages that could damage the device.

When stopping the motor, the voltage spikes could exceed the maximum ratings.
Circuitry like large bulk capacitors and TVS diodes are typically used to limit the voltages.
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RE: DRV8412: The output is absent

January 11, 2018, 5:46 am
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Hi Serafino,

You should have seen the waveform if you zoomed in to a 10us/div. The 100nF bootstrap capacitor is intended to be used at frequencies higher than 10kHz. If you planning to run a lower PWM frequency, the bootstrap capacitor should be increased and a 5 Ohm series resistors should be added between the GVDD supply and the GVDD_x pins as described in section 7.3.2.1 of the datasheet.

The development board is intended to demonstrate several applications such as brushed motor, stepper motor, and thermo electric cooling (TEC).

Are you planning to control a TEC? If not, the capacitors are not required.
The series inductors are recommended to protect against a short. Please refer to the 6th paragraph in section 7.3.2.2 of the datasheet for more details.
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RE: DRV8833: Regenerative braking

January 11, 2018, 6:06 am
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Hi Ben,

The device does this automatically when limiting the current in fast decay. Please refer to Figure 6 of the datasheet.

Coast mode (sometimes referred to as asynchronous fast decay) can also recirculate the current through the body diodes, but care must be taken to avoid exceeding device operating temperatures. The device is considered disabled in this mode and offers no protection.
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RE: DRV8711: Predriver Fault(XPDF) condtion

January 11, 2018, 6:47 am
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Hi Matsumoto-san,

The predriver fault (xPDF) indicates a failure on the gate of the FET. The predriver fault may not catch a short between xOUT1/xOUT2 and GND.
The OCP fault (xOCP) indicates a failure between the drain and source of the FET. The OCP fault should catch a short between xOUT1/xOUT2 and GND.

These faults are detected in both PWM and indexer mode.
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RE: DRV8841: Possible to control speed of DC through current regulation feature?

January 11, 2018, 8:20 am
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Hi Kevin,

I don't think the DRV8841 will work very well for a speed control application. The current regulation feature will control your torque rather than your speed. Depending on the torque requirements of your load, it may be possible for your system to find four different operating points on the torque-speed curve of your motor. However, for no-load/free spinning conditions, the speed will always be maximum.

The DRV8832 and DRV8830 are our only devices that have a speed control feature, however the voltages are lower than the DRV8841.

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RE: DRV8302: Wrong voltage output at GH_B pin

January 11, 2018, 8:42 am
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Hi Rishav,

Are you operating in 6-PWM or 3-PWM mode? What are voltages at the other inputs when you measured 24 and 10.8V?
Do you have FETs connected? Have you checked that the FETs are operating properly?
What voltage are you measuring on SH_B?
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RE: DRV8302: Wrong voltage output at GH_B pin

January 11, 2018, 9:22 am
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I am operating in 6-PWM mode.
I am putting 5v at INH_B when it gives 24V at GH_B. When I give 5V at INH_A and INH_C (separately), I get 31V at GH_A and GH_C resectively.
I don't have FETs connected.
I am getting 24V at SH_B.
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DRV8302: Wrong voltage output at GH_B pin

January 11, 2018, 8:12 am
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Part Number: DRV8302

I am working wiht the following simple schematic:

I am using PVDD at 24V. When I apply 5V to channels A and C, the voltage output at GH_A and GH_C give the correct voltage output (31.0 V). However, when I apply 5V to INH_B, the voltage output comes to be around 24V at GH_B as well as SH_B. Also when I put INH_B to ground, GH_B gives an output of around 10.8V. There is also no over-current or fault indication. What might be causing this?

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RE: DRV8832: Need to detect stall condition

January 11, 2018, 9:31 am
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Hi James,

Can you suggest a current-sense circuit for stall detect to be used with DRV8837C ? Will Op-amp ckt in page 26 (Figure 16) of the DRV8312 datasheet work for me?

Also if i have to add a series sense resistor I think it cant place it in series with motor as the direction of current & voltage will change depending on which direction the motor spins. Can i add it in series sense resistor in high side (VM) or low side (GND) of DRV8837C pins ?

Rgds

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RE: DRV8840: PWM input to output timing

January 11, 2018, 10:14 am
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Rick,

Looks like my text got removed from the previous post. The top plot is pin 7 of a passing board the bottom plot show the same pin once the DRV8840 was replaced with a different lot code. The motor is not attached during this measurement. The pulse width is definitely different between lot code with the same system (PCB, motor and load). I'd like to know what to expect from part to part so I can adjust the software to account for the full range of tolerances. The datasheet only lists rise and fall times but there appears to be more at play here. Can you help?

Thanks,

Mike

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RE: Stepper Motor Driver DRV8835 Voltage Problem

January 11, 2018, 10:15 am
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Hi Rick

If you know of any application note to use this DRV8835 as stepper motor driver please let me know

John

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RE: Stepper Motor Driver DRV8835 Voltage Problem

January 11, 2018, 10:30 am
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Hi John,

I am not aware of an application note. There is a DRV8835EVM available through the TI store to allow experimentation.
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RE: DRV11873: Cut-out at certain duty cycles - why?

January 11, 2018, 10:36 am
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Brian-

   I've confirmed that I am receiving false rotor lock occurrences, but unfortunately dithering by 1% around this duty cycle (at a 1s interval) does not solve the problem, nor does 2%, and at 2%, the motor pitch change is too irritating to be a solution anyway. I'm measuring frequency with the host MCU, and at this duty cycle, with dithering, I'm measuring an RPM of 7065-7290. Or 471 - 486Hz. Does this information shed any light on what the problem may be?

-Chris

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RE: DRV8832: Need to detect stall condition

January 11, 2018, 11:10 am
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Sundar,

I think the circuit in the DRV8312 datasheet will not be the best solution for the reason you mentioned. Check out TI's integrated current sense amplifier portfolio or post to our Amplifiers forum for a good recommendation. Some of our current sense amplifiers may be able to handle the change in polarity, but I'm not sure.

Is there a reason you don't want to use the DRV88850? That's our only device in your voltage range that is designed for this kind of current sense application.

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RE: Stepper Motor Driver DRV8835 Voltage Problem

January 11, 2018, 12:44 pm
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Hi Rick

Thanks for the EVM link. We are waiting for another board. If that did not work, we will get the eval board.

John
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RE: Stepper Motor Driver DRV8835 Voltage Problem

January 11, 2018, 3:03 pm
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Hi Rick,

Thanks for the details for the stepper motor. This is helpful.
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RE: DRV10983: USB2ANY purchasing

January 11, 2018, 3:30 pm
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David,

TI doesn't sell USB2ANY standalone. It's probably easiest to just order a DRV10983 EVM which comes with a USB2ANY. The EVMs can be ordered here: http://www.ti.com/tool/drv10983evm

Is your customer looking for a larger number of USB2ANY devices?

Thanks,

Brian

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RE: DRV8840: PWM input to output timing

January 11, 2018, 3:59 pm
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Hi Mike,

Let me look into this. I hope to have a response by Wednesday of next week.
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RE: DRV8711: Predriver Fault(XPDF) condtion

January 11, 2018, 7:39 pm
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Rick san

Thank you for your reply.
The predriver fault (xPDF) indicates a failure on the gate of the FET. The predriver fault may not catch a short between xOUT1/xOUT2 and GND.
The OCP fault (xOCP) indicates a failure between the drain and source of the FET. The OCP fault should catch a short between xOUT1/xOUT2 and GND.
->OK, we got your saying.
   Otherwise, could you let us know the method to occurs predriver fault (xPDF) concretely?

Kind regards,

Hirotaka Matsumoto

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RE: DRV8302: Brushless Sensorless Motor speed oscillates, which causes it to lose sync and shut off once it goes too fast.

January 11, 2018, 11:26 pm
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100% sure its not the interrupts. The problem is with the way I use the zero cross time to predict when to commutate.

  1. Reset timer T on commutation
  2. Look for zero cross time Tcross
  3. Predict next commutation time and set the compare value for T: Tcommutate = Tcurrent + B* (2 * Tcross - Tcurrent)

Tcurrent is the previous/current Timer T compare value, Tcommutate is the new Timer T compare value, Tcross is the measured zero cross time in counts. B is a scale factor, .25 seems to work.

I'm sure there is a better way to predict the correct commutation time but I have no idea what that is. The app notes are really good about finding the zero cross and explaining the commutation cycle, but they are not so good on the exact algorithm. Most of them just say Tcommutate = 2*Tcross.

This is the motor running. The green and blue are the hall signals. Go figure the hall signals are not aligned with where the motor needs to commutate, guess that explains why it won't run in sensored mode. Guess that's a cheap motor for ya. But every motor should run sensorless :( I would appreciate any hints about how to predict the correct commutation time.

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