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RE: DRV8842: DRV8842 about the OCP issues

March 20, 2017, 11:43 pm
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Hi Rick,

I would like to explain my words. I said the motor stalled. That is the motor is locked rotor.

The customer uses a brush motor. The rated current is 1.5A for the motor. The rated voltage is 12V for the motor.

He would like to detect the motor stall phenomenon and then the IC can output a FAULT signal to indicate that the motor stall phenomenon

has been occurred.

Can DRV8842 meet the customer's requirement? If it can, would you explain more about detecting the motor stall ?

If it cannot, would you recommend a suitable IC?

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RE: DRV8711: Overcurrent shutdown while running: current regulation doesn't work anymore after a while

March 21, 2017, 3:02 am
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Hello,

now I have a direct junction between the bridge supply and the driver supply. The overcurrent errors nearly disappeared and I also can use a lot more current. In the image I attached you can see current and voltage of one winding of the motor with roughly 9.5A current (max. motor current).

When accelerating with a ramp first a sine current is seen but after some steps the current decreases and at the ruler X2 the motor stops.

I currently use microstepping with 32 steps. The behavior of the motor doesn't change with a small mechanical load. I already changed the starting speed and the ramp but only the time until the current breaks changes.

Do you have any advice what problem I am facing here?

Cheers,

Christoph

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DRV8711: Overcurrent shutdown while running: current regulation doesn't work anymore after a while

March 9, 2017, 4:47 am
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Part Number: DRV8711

Hello,

we are using the DRV8711 driver IC in an application with this stepper motor: Nanotec ST8918M6708 (https://de.nanotec.com/produkte/566-st8918-schrittmotor-nema-34/).

The schematic is nearly the same than on the eval board, only other FETs were used. We use CSD19532QB5 (http://www.ti.com/lit/ds/symlink/csd19532q5b.pdf). The supply is 48V

The motor is specified to run until 2100/min, but when we reach about 1200/min the current regulation cannot hold the current on the desired value and then the overcurrent protection stops the driver. Here you can see when this happens:

In detail: The desired current is 2.6A (the orange line) but neither slow nor fast decay can decrease the current.

To config the driver I do the following:

    Stepper.Driver.Ctrl |= STEPPER_CTRL_ENBL;
    Stepper.Driver.Ctrl |= STEPPER_CTRL_EXSTALL;
    Stepper.Driver.Ctrl |= STEPPER_CTRL_MODE_HALF_STEP;
    Stepper.Driver.Ctrl |= STEPPER_CTRL_ISGAIN_20;
    Stepper.Driver.Ctrl |= STEPPER_CTRL_DTIME_450;

    Stepper.Driver.Torque |= TORQUE;
    Stepper.Driver.Torque |= STEPPER_TORQUE_SMPLTH_50;

    Stepper.Driver.Off |= 20;

    Stepper.Driver.Blank |= 50;

    Stepper.Driver.Decay |= 100;
    Stepper.Driver.Decay |= STEPPER_DECAY_DECMOD_ALL_AUTO;

    Stepper.Driver.Stall |= 60;
    Stepper.Driver.Stall |= STEPPER_STALL_SDCNT_4;
    Stepper.Driver.Stall |= STEPPER_STALL_VDIF_8;

    Stepper.Driver.Drive |= STEPPER_DRIVE_OCPTH_500;
    Stepper.Driver.Drive |= STEPPER_DRIVE_OCPDEG_2;
    Stepper.Driver.Drive |= STEPPER_DRIVE_TDRIVEN_250;
    Stepper.Driver.Drive |= STEPPER_DRIVE_TDRIVEP_250;
    Stepper.Driver.Drive |= STEPPER_DRIVE_IDRIVEN_300;
    Stepper.Driver.Drive |= STEPPER_DRIVE_IDRIVEP_200;

I tested all decay modes and modified all other settings, but it always is the same result. When reaching a specific rpm value (maximum around 1200/min) this behavior happens.

Does anyone has an idea what I am doing wrong?

Cheers,

Christoph

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RE: DRV8801: VPROPI Output current

March 21, 2017, 5:52 am
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Hi Sheldon,

We will investigate and reply soon.

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DRV8801: VPROPI Output current

March 20, 2017, 5:27 pm
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Part Number: DRV8801

I am using the DRV8801 with a total of 50K load resistance on the VPROPI output pin, with the resistance the voltage is reading 1.31V ( this is not 5X the current) if i remove the resistance I am getting 2.0V ( this is the 5X coil current). It seems that the pin has an output impedance I am exceeding but I can not find anything in the datasheet. What is the max load that this pin can drive accurately?

Thank you,

Sheldon

(8801_VPROPI_OUT is connected to an ADC) 

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RE: drv110

March 21, 2017, 8:09 am
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David,

I apologize for the inconvenience this caused you. I submitted the request to update the datasheet today to better describe the operation of the STATUS pin. The changes should be live on the web in the next two weeks.

Thank you for your feedback here. Somehow this information didn't get applied in our last update, so I appreciate you bringing it to my attention.
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drv110

November 20, 2015, 1:28 pm
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Would like a live Engineer to contact me directly at 781-565-1370 to discuss the following observation:

STATUS pin goes high even though I do not see a thermal issue or under-voltage condition on the VIN pin. According to datasheet, those are the only 2 conditions that would cause the STATUS line to go high.

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RE: DRV8871: The maximum rise time and fall time of IN1/2(logic input)

March 21, 2017, 9:00 am
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Hi Tao2199,

We expect the inputs to be controlled by an mcu, which has outputs in the 20ns/V range.

What type of anomalous oscillation is observed? This could be due to noise causing the inputs to switch between a logic low and logic high when the input is between 0.5V and 1.5V.
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DRV8871: The maximum rise time and fall time of IN1/2(logic input)

March 21, 2017, 2:56 am
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Part Number: DRV8871

Hello,

 

Regarding to IN1/2(logic input) on DRV8871, my customer is asking a question.

(Question)

･How is rise time and fall time in IN1/2?

I am understanding that generally, the maximum rise time and fall time of CMOS logic(Vcc5V) are approximately 20ns/V.

Is it same as above value?

They use very slow rise time and fall time(20us~) signal as IN1/2 and they are facing the anomalous oscillation on this device output.

 

Regards,

Tao2199

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RE: DRV8842: DRV8842 about the OCP issues

March 21, 2017, 9:04 am
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Hi Mickey,

The DRV8842 does not have the ability to output a FAULT signal on motor stall.

There are two devices in the portfolio that can detect stall, the DRV8830 and DRV8832. The operating voltage is too low. The stall detection method is similar to the reference design www.ti.com/.../slva858.pdf
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DRV8842: DRV8842 about the OCP issues

March 17, 2017, 12:53 am
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Part Number: DRV8842

Hi Team,

The customer is using DRV8842. When OCP occurs, the nFAULT outputs a low level. The customer would like to use this low level signal as a detection

signal in his design when the motor stalls. But he sets the ICHOP value. He made the mistake of ICHOP as the overcurrent value.

When he set ICHOP is 3.3A, then the motor stall current is test 2A.  When he set ICHOP is 0.66A, then the motor stall current is test 0.5A.

I would like to confirm the following information:

Q1: The OCP value is 6A. This value cannot be changed. Is my understanding correct?

Q2: What is ICHOP? Is ICHOP the output current for DRV8842?

Q3: Is the customer's idea correct? I don't think the customer use this low level signal as a detection signal.

Q4: Why is the motor stall current less than the ICHOP set value?

Best Wishes,
Mickey Zhang
Asia Customer Support Center
Texas Instruments

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RE: DRV8830: VIH for I2C line

March 22, 2017, 3:32 am
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Hello Rick-san,

I have one more question about VIH. What is the acceptable maximum voltage when VCC=6V supply ?

Is it only up to 3.3V or can it accept VCC voltage which is 6V ?
Test condition shows VIN=3.3V, however, absolute maximum rating is 7V. What is your recommendation ?

Best Regards,
Kawai
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RE: DRV8830: VIH for I2C line

March 22, 2017, 5:42 am
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Hi Kawai-san,

At VCC=6V, the recommended maximum voltage is 6.5V. Above that, diodes may begin to forward bias.

The IIH 3.3V test condition provides pulldown information for a 3.3V mcu.
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DRV8830: VIH for I2C line

March 14, 2017, 2:54 am
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Part Number: DRV8830

Hi Team,

Please allow me to ask you about VIH level for I2C line used in DRV8830. Below is the specification in the datasheet.

[Question]
Does this mean that when VCC = 6.0V, the device SDA/SCL CANNOT accept 3.3V ? Not 3.3V tolerant and requires a level shifter ?
If you look at the Absolute Maximum Ratings spec, input pin voltage is up to 7V.

Thanks in advance.

Best Regards,

Kawai

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RE: DRV8812: OCP time

March 22, 2017, 5:53 am
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Hi Shimizu-san,

The OCP deglitch time is typically 3us.
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DRV8812: OCP time

March 22, 2017, 5:10 am
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Part Number: DRV8812

Hi,

Could you let me know the value of OCP time, please?

OCP time means the description of 7.4.6.1 Overcurrent Protection (OCP) in datasheet.

"If this analog current limit persists for longer than the OCP time, all FETs in the H-bridge will be disabled and the nFAULT pin will be driven low."


Best regards,
Shimizu

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RE: DRV8308EVM: Use Back EMF instead of Hall Sensors?

March 22, 2017, 6:08 am
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Hi Bryan,

It may be possible, but is not recommended due to the complexity.

Prior to starting the motor, there is no Back EMF. To start the motor, the hall inputs would have to be sequenced in the proper direction.

Once running, the back emf does not transition at the same point as a hall sensor. In addition to the back emf detection, a delay would be required to mimic the hall sensor operation.

After starting and running the motor, there may be other unexpected issues that appear requiring additional circuitry.

In short, a mcu is probably required to monitor the back emf and create the hall inputs. Instead of using the mcu to make the DRV8308 operate, it is recommended to use the mcu to control a device like the DRV8305.
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DRV8308EVM: Use Back EMF instead of Hall Sensors?

March 21, 2017, 8:23 pm
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Part Number: DRV8308EVM

Is it possible to use Back EMF instead of Hall sensors on the DRV8308? Perhaps a biasing circuit and comparator on each phase?

The DRV8308 seems perfect for our design, but most low-cost BLDC motors do not have Hall sensors built-in. Retrofitting Hall sensors (DRV5813) is a possibility, but not ideal.

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RE: finding a motor driver to 0308 FAULHABER's motor

March 22, 2017, 6:14 am
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Hi Sam,

Our experts have been notified and should reply soon.
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finding a motor driver to 0308 FAULHABER's motor

March 22, 2017, 12:42 am
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hello,

I am trying to find a motor driver to the FAULHABER 0308 sensor-less BLDC motor that i am using.

[View:/cfs-file/__key/communityserver-discussions-components-files/38/0308_5F00_B_5F00_DFF.pdf:1230:0]

i want to be able to spin the motor in 40000 rpm with a motor voltage of 5.5V

i have already purchased your DRV10963 motor driver , but it didn't spin the motor well.

i tried all the parameters there but it didn't reached even close to my desired RPM. i think that the problem was that the driver was not able to pass from open loop to closed loop because the BEMF in low RPM was hard to read.

do you have any recommendations for another motor driver that will be to handle that motor ?

thanks - SAM

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