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DRV8662: DRV8662

user5875975
Prodigy 210 points
Part Number: DRV8662

Dear Sir,

We use your motor driver IC DRV8662.

It fails so often. We estimate some causes for the failures.

Would you pleae tell me your advices?

1) We ues that IC in 200V output mode. We apply 200 to 300 Hz rectagle waveform.

 During our operation, the Enable input is set to High.  We measured the current. The magnitude of current was 0.18 A.

According to the datasheet, at 300Hz in 200V mode, the consumption current is 400 mA. We regard 0.18 A is within the tolerance,

and think our operation is allowable.

My idea is corrent?

2)The ouput teminals are connected to a tiny connector. The receptacles which connet each IC output are ajacent. Due to position tolerance of the plug and receptacle,

we suspect ajacent terminals may be short circuited. If that happen, does that IC fail?  Or over current can be detected by the thermal sensor and the sensor will switch off

the ciruit?

I think if that IC have some protection circuit at the output terminal, the IC will not fail so easily. Does that IC have that kind of protection circuit?

Regards,

Shozo Ohtera

  • 0
    TI__Guru* 84915 points

    Hi, Shozo,

    Could you provide your circuit schematic in order to have a better approach to this issue?

    Thank you.

    Best regards,
    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    Prodigy 210 points

    Hello　Luis、

     

    I uploaded the circuit diagram here. It was sucessful or not, I am not sure.

    If you canot find it, would you please let me know by e-mail?

    My e-mail address is   sootera@murata.com ".

     

    We have adapted the typical circuit according to the data sheet.

    We usually set the enable terminal to High level and apply the burst type of waveform.

     

    Our waveform is rectangular type. High level is 3.3V and Low level is 0.0V.

    The middle level is 1.65V.

                     ____       ____

                     |     |       |     |             High level

                     |     |     |     |

                           |       |      |             Middle level

                           |       |     |

                           -------       ------       Low level

    Thanks,

    Shozo Ohteraアンプ回路_20200923.pdf

     

  • 0 in reply to user5875975
    TI__Guru* 84915 points

    Hi, Shozo,

    I have some questions. 

    1) Do you refer that the current consumptions is limited to 0.18A? As you mentioned, the datasheet specifies that the average current can be ~400mA. Could you increase the current limitation to around 0.5A?

    2) This device actually doesn't have output short-circuit protection. I think it is protected due to the thermal protection generated by a high current consumption during the short-circuit event.

    3) Do you have this kind of failure when there's no load connected? Do you have some captures of the output before and after the device fails?

    Thank you.

    Best regards,
    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    Prodigy 210 points

    Hi, Luis,

    As for 1), I might get you confused. What I want to say that according to the datasheet, approximate 400mA is allowed under the condition of 300Hz operation.

    As I said, we set the Enable terminal High. In that case, the mangitude of current flow is 180mA. So we think setting the Enable terminal High might not cause the failure. I want to confirm my idea with you.

    As for 2), from your answer, I understand that the IC has no output short-circuit protection. Yesterday we check how the short circuit happen. We found that the output terminals are short circuited at the ratio of one to ten or twenty when we do some operation about our connector, which is used in our module.

    As I said before, the connector is very tiny and the pads of IC outputs are very close.

    According to your explanaion, in that case, high current consumption will be caused and, when the temperature excees the threshhold, the thermal protecion circuit will protect the IC. My qeusiton is even if this short-circuit repeat to happen, the IC can resisit it? Or the times of short circuit exceeds certain times, the IC may corrupt soon?

    Thanks,

    Shozo Ohtera

     

  • 0 in reply to user5875975
    TI__Guru* 84915 points

    Hi, Shozo,

    Thank you for your clarification.

    1) Understood. Yes, based on the current values you mentioned, the enable terminal shouldn't be causing an issue.

    2) Actually this is a normal protection in our devices. Even if they don't have a short-circuit protection to disable the outputs when there's a low load or when the output pins are shorted, the thermal protection can work to disable the device. The current is actually taken from the boost (and VDD consequently). So your power supply must be capable to handle the high amount of current during this short-circuit event. Otherwise, there's risk of the supply damage.

    Please let me know if you have additional questions or comments.

    Best regards,
    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    Prodigy 210 points

    Hi Luis,

    Thank you for your seggestion.

    I understand that the most possible failure portion may be the power suppy or the boost.

    DRV8662 is incorporated with the boost circuit, isn't it?

    Is there any possibility that the boost circtuit fails?

    Regards,

    Shozo

  • 0 in reply to user5875975
    TI__Guru* 84915 points

    Hi, Shozo,

    There could be a possibility of the boost damage if the resistors array are selected to reach a current value too high for the inductor. A way to see if the boost is damaged is by measuring the VBST pin voltage level. You should see how the VBST is powered up once the EN pin is activated.

    Best regards,
    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    Prodigy 210 points

    Hi, Luis,

    I checked the VBST pin and measured the voltage.

    The normal board showed 100V, but the not-normal one, which is broken, showed around 20V.

    We determined the boost logic was damaged.

    My understanding is that the reverse voltage induced by the inductor might damage the switching transistor, which is one of elements of the boost.

    Is this possible?

    Regards,

    Shozo Ohtera

  • 0 in reply to user5875975
    TI__Guru* 84915 points

    Hi, Shozo,

    It could be a possible cause. However, have you reviewed all the external components connected to the DRV8662 and ensure that they are not damaged? 

    Especially, the switching inductor, was it also damaged? Do you see the same impedance level at the feedback circuit? I mean, are the feedback resistors correctly connected to the FB pin? Or are they damaged?

    Best regards,
    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    TI__Guru* 84915 points

    Hi, Shozo,

    Excuse me, do you have a feedback on this?

    Thank you.

    Best regards,
    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    Prodigy 210 points

    Hi Luis,

    Sorry to be late for replying.

    We experienced that replacing the IC recovered the funtion of our module.

    I understand that some devices, such as inductor or resistors, might have failed, but in this case, those are not the cause, I think.

    We will avoid short-circuit state during our operation.

    Thanks,

    Shozo

  • 0 in reply to user5875975
    TI__Guru* 84915 points

    Hi, Shozo,

    Thank you for your update. Please avoid short-circuit or add an external circuit protection in order to avoid this kind of failures.

    In case of additional questions or comments, I recommend to start a new E2E thread. We will be glad to help you.

    Best regards,
    Luis Fernando Rodríguez S.