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.

DRV10987: PCB layout review

Part Number: DRV10987
Other Parts Discussed in Thread: DRV10975

Hi Team,

Our customer is using DRV10987 together with Maxon motor. The motor starts to spin then suddenly stop and get too hot. Below is the specifications of the motor. 

Upon checking the PCB layout, I noticed that the thermal pad has no vias to dissipate the heat from the IC to the ground plane. The customer decided to switched to DRV10975 because the DRV10987 is out of stocks then revised the board and added vias based on the layout example from the datasheet. Please see the layout of the new board below.

Attached is the schematic diagram for reference.

Motor_Surucu_Son.pdf

Do you think the layout is good enough for this application? The customer would like to confirm also if there is any mistake in the configuration registers below for Maxon motor.

Config 1: 0x1349
config2 : 0x1C3B
CONFIG3 : 0x2366
CONFIG4: 1BA7
CONFIG4: 0x1BA7
CONFIG5: 0x389B
CONFIG 6: 0xB070
CONFIG 7 : 0x0B6B

Regards,

Danilo

  • Hi Danilo,

    I will review this tomorrow and get you a response by tomorrow EoD.

    Thanks,

    Michael

  • Hello Danilo,

    The team is on holiday due to Memorial Day in the US, and will get back to you tomorrow!

    Thanks,

    Matt

  • Hi Danilo,

    After reviewing your schematic and layout I have the following comments:

    The phase to center tap resistance in the EEPROM settings you sent us is 1.3968 ohms. This should be 1.3968/2 because the devices takes phase to center tap resistance as the input.

    Please review the layout recommendations on page 50 of DRV10975. You may want to have thicker traces for Vcc, GND, U/V/W since these traces have high current that passes through them.

    Are you using the same schematic for both devices? Both devices are pin to pin compatible, however the schematic is slightly different. Please note that the cap is a different value on CPP and CPN.

    When did this issue start happening? Was it before you switching to the DRV10975?

    Since this is a low inductance motor we recommend operating the device at 50KHz PWM switching frequency. 

    Please enable all three faults that are disabled (current limit, speed abnormal and abnormal kt). Then we can see if any of these are causing faults to happen as well.

    Thanks,

    Michael

  • Hi Michael,

    Thank you for your valuable feedback. I will forward your comment to the customer. He would like to know as well if the Maxon EC45 200189 is suitable for DRV10987 and DRV10975 or not. Please see the specifications of the motor above.

    Regards,

    Danilo

  • Hi Danilo,

    Yes that motor is fine as it falls within these parameters listen on the datasheet. 

    Thanks,

    Michael

  • Hi Michael,

    Thank you for your valuable feedback regarding the PCB layout. The overheating issue happened when the customer is using DRV10987. Now they have switched to DRV10975 and have revised the layout accordingly. The customer would like to confirm if the CONFIG registers below are correct.

    Config 1: 0x1349
    config2 : 0x1C3B
    CONFIG3 : 0x2366
    CONFIG4: 1BA7
    CONFIG4: 0x1BA7
    CONFIG5: 0x389B
    CONFIG 6: 0xB070
    CONFIG 7 : 0x0B6B

    Regards,

    Danilo 

  • Hi Danilo,

    Please ensure the phase to center tap resistance in the EEPROM settings you sent us is 0.6984 ohms. You will have to slightly modify config 1.

    See above for explanation on why this is required.

    All else is good.

    Thanks,

    Michael

  • Hi Danilo,

    My questions about DRV10987. As you know we use DRV10987 but we will change DRV.10975. I need Rm and Kt value for EC45-200189. From e-mail, I learned that the Rm value for this motor must be 0.7 Ohm (1.4 /2 Ohm). For Kt value my calculation is;

    374 rpm/60 = 6.23 Hz/V

    1/6.23 = 160mV/Hz

    For 8 poles => 160/8 = 20mV/Hz, so Kt = 20 mV/Hz (It is the same for DRV10975)

    Can you inform us whether our calculation is correct or not?

  • Hi Danilo,

    My questions about DRV10987. As you know we use DRV10987 but we will change DRV.10975. I need Rm and Kt value for EC45-200189. From e-mail, I learned that the Rm value for this motor must be 0.7 Ohm (1.4 /2 Ohm). For Kt value my calculation is;

    374 rpm/60 = 6.23 Hz/V

    1/6.23 = 160mV/Hz

    For 8 poles => 160/8 = 20mV/Hz, so Kt = 20 mV/Hz (It is the same for DRV10975)

    Can you inform us whether our calculation is correct or not?

  • Hi,

    Thanks for getting back. Your calculation is correct. Is there anything else I can assist you with?

    Regards,

    Michael

  • Thank you Michael,

    Is there any specific values for StAcce, StAccel2 and AlignTime for this driver?

    Regards 

  • Hi,

    By specific values what do you mean? There are min/max thresholds that are defined in the datasheet.

    -STAccel has a min value of 0.019 Hz/s

    -STAccel2 has a min value of 0.0026 Hz/s^2

    -Align time as a min value of 40ms

    I don't know if this answers your question.

    Thanks,

    Michael

  • Hi Michael,

    We use DRV10987 as a motor controller at MAXON EC45 200189 motor.  The IC overheats in our circuit and breaks down. Our software engineer set the following data to the driver. ;I think that there should bee mistake,. Here is the setting:

    -FG output

    -8 pole

    -Rm 1.3968

    -Kt 25.76

    -Tsetting 220us

    -OpenLoopCurrent Ramp 6.3 Hz

    -StAccel2 0.66Hz/sn2

    --StAccel 4.5Hz/snAlignTime 5.3sn

    -Driver Dead Time 440ns

    -IPD Clock 95 Hz

    -IPD Thr 0.4A

    -SlewRate 120V/us

    -ClosedLoopAccel 0.37Vcc/s_I2C Protocol

    One of these (or more) can be caused overheating

  • Hi All,

    I would start with evm board, then if it works well with the motor I would proceed with my own board. I would just add capacitor around 470-1000uF between Vcc and GND or TVS diode to limit any possible overvoltages at Vcc during trials.

    Coming back to pcb layout I agree with what Michael said, additionally for me ground layers on both sides look nonoptimal and might be source of problems.

    I would try to determine if IC gets hot and then stops to work or stops to work and then gets hot. The first case would indicate overheating problems, the second one electric failure.

    Regards,

    Grzegorz

  • Hi,

    This does not appear to be a device config issue.

    Have you made any modifications to the PCB? If not, please try to implement the suggestions I made in my previous post. After you implement those we can review your new layout and go from there.

    Thanks,

    Michael

  • Hi Michael,

    You can see the modification about the PCB on the top 2 picture. In new design,, we use DRV10975 instead of DRV10987. When the IC come us we will use with new Config.  and you say that this CONFIG does not effect the overheating., right? So the problem seems only old layout.

    Regards

  • Hi User,

    Yes the config is fine, no issues. It won't effect overheating.

    Please let me know if you have any more questions, best of luck.

    Thanks,

    Michael

  • Thank you Michael,

    The new PCB as soon as come, i will try the circuit. If i see any problem, i will write again.

    Regards

  • Hi,

    I want to ask an extra poroblem about DRV10975. My motor, MAXONEC45 200189, has got Rph-ph resistance is 1.4 Ohm so its Rph-ct value will be half of this value. 0.7 Ohm In Table 2 sheet 19 , for value for 0.7 Ohm it must be 3C. But the calculation for formula Rmdig =0.7/0.00735 is equal to 95. which is 5F. Which one is correct?

  • Hi!

    Rmdig is not same as Rm. Below are the steps to convert actual phase to CT resistance to the hex code. 

    Rm’ = (bin) (RPH_CT/0.00735);

    If the length of Rm’ is within 4 bits.
    Rm<3:0> = Rm’;
    Rm<6:4> = “000”;


    If the length of Rm’ is 5 bits.
    Rm<3:0> = Rm’<4:1>;
    Rm<6:4> = “001”;


    If the length of Rm’ is 6 bits.
    Rm<3:0> = Rm’<5:2>;
    Rm<6:4> = “010”;


    If the length of Rm’ is 7 bits.
    Rm<3:0> = Rm’<6:3>;
    Rm<6:4> = “011”;

    And so on....

    In this example, let's consider RPH_CT = 0.7 ohms

    Rm' = RPH_CT/0.00735 = 0.7/0.00735 = 96.

    Rm' = (bin) 1100000

    Rm' is 7 bit.

    Rm<3:0> = Rm’<6:3> = "1100";
    Rm<6:4> = “011”;

    Rm = (bin) 0111100 = 3C

    3C is the correct hex code for 0.7 ohms.

    Regards,

    Vishnu

  • Thank you.

    Regards

  • I'm hoping all the questions are answered in this thread so I'm closing this thread. Please click the "Ask a related question" at the top right of this page if you need further assistance. 

    Regards,

    Vishnu

  • Hi,

    We checked the system today. Motor does not turn. It starts to turn but stop within a 2 second. System gives Lock0 fault. Motor locks suddenly. I could not understand why.

    Regards

  • Hi user641139,

    It seems you are asking an additional questions outside of the original scope of this thread. We ask E2E users to use the "Ask a related question" button if the original question has been answered. We do this to improve search ability and create a repository of questions that other engineers can find using the TI thinks resolved or resolved fields.

    In the case of this thread, there are now several replies containing multiple questions that can not be utilized by the community, as they are unverified and unrelated in some cases. As such, please copy and paste your most recent question about the motor startup failure in a new thread by using the ask new question functionality. The question about PCB layout will be finished in this thread. Failure to do so will cause this thread to be locked.

    Regards,

    Vishnu