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DRV2700EVM: Driver damaged while testing

user5766479
Prodigy 30 points
Part Number: DRV2700EVM
Other Parts Discussed in Thread: DRV2700

Hi

 

We have bought 4 pieces of DRV2700EVM recently, and tested them right after their arrival, finding that three of them worked well with correct amplification while the rest one only doubled the input voltage as output. After our first test, we went back to check whether the wrong amplification was induced from human error. Just after we connected and turned on the power supply of DRV2700EVM, a lot of smoke came out from the circuit board, and we turned off the power supply immediately. We then checked circuit and found one circuit line burning out.

        We want to make an exchange to our local supplier and they asked us to provide a complete test report to your engineers in order to check if any of the test step was wrong, leading to the failure of the circuit.

        Here are our test steps:

  1. We set our jumpers as follows:

JP 2, 3, 4, 12, 13: Connected

JP 5, 6: Opened

JP7, 8, 9: PU

JP10, 11: VIN

  1. Connect TP8 to ground and connect DC_IN to a voltage supply supporting continuous square wave signals ( the power of voltage supply is off). The square wave signals have peak to peak voltage of 2V along with a DC offset of 1V.
  2. Connect J2’s + port to a 5V DC voltage power supply and – port to ground. ( The power supply is off.)
  3. Connect the high voltage output to the Oscilloscope: Vin+ to Channel 1, Vin- to Channel 2, and GND to both channels’ ground. To assure Input and Output have a common ground, connect GND to TP8.
  4. Turn on the voltage supply of J2 and turn on the power supply of DC_IN.
  5. Check the result on the oscilloscope.

 

Since we didn’t record the output result of the wrong amplification signals before the circuit burned out, we can only provide the output signals of the rest well-functioning drivers and of the damaged drivers:

 

The yellow curve represents the signals of Ch1, while the blue curve represents the signals of Ch2.Both the signals show square wave with peak to peak voltage of 50V. The purple curve is the difference of signals in Ch1 and Ch2, revealing a square wave with peak to peak voltage of 100V (50X amplification rate).

 

        However, the damaged driver shows no amplification, even no output signal when measuring.

 

        Please leave any comment if find any incorrect setup or step in the test step description above. Thank you.

  • 0
    TI__Guru** 111175 points
    Hi,

    We will review your test procedure and provide comments shortly.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • 0
    TI__Guru** 111175 points
    After review of the above test procedure, there are a couple things I would like to highlight:
    - Square wave signals (PWM) should be used on the J5 connector, in order to use the LPF to take the PWM into an analog-like signal.
    - DC_IN (TP4) should be used only when DC voltage is input to the device to drive the output in a steady state.

    Perhaps the first three devices were able to withstand the direct PWM input but the last one did not.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • 0 in reply to Ivan Salazar
    TI__Guru** 111175 points
    It has been a while since last communication. I'll mark this thread as resolved.
    If you have further questions please reply or start a new post in case this one is closed due to time-out.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • 0 in reply to Ivan Salazar
    Prodigy 30 points

    Hi,

    Thank you for your reply, and we would like to ask a few questions:

    1. According to the driver user guide, sections in Chapter 5 describe how to amplify an AC coupled or DC coupled signal; it seems that DRV2700EVM isn’t able to amplify an AC signal with a DC offset. Base on your second point of reply, if I want to amplify an AC signal with a DC offset, I need to separate the DC and AC part and send the former part to DC_IN and the later one to J5. Is it how this driver amplifies the signal?
    2. Though DC_in only accepts DC signals, there should be a threshold (lowest) frequency of signal that the driver could tolerate and amplify. With an input over this threshold frequency, the drivers should all burn out or show no output signals. But 3 of our drivers could withstand square wave input with over frequency 100Hz and 1 cannot, we don’t think a low frequency AC signal would be the cause of the damage. Furthermore, if the driver cannot tolerate such a low frequency signal, the device cannot either tolerate a DC input, since an instant voltage jump from 0V to a target voltage was sent into the device. Is there a standard for such threshold frequency?

  • 0 in reply to user5766479
    TI__Guru** 111175 points
    I'll comment about the questions below:
    1. The way the document is redacted might have confused you: Section 5.3 makes reference of an analog signal, and section 5.4 makes reference to a DC signal (like bias voltage). The device is able to work with an analog input signal, however it needs at least the AC coupling capacitors at the input, this is needed so that the input analog signal is centered at the bias of the DRV2700 itself. The explanation of these AC coupling capacitors can be found on section 8.2.3 of the user's guide. You do not need to separate DC offset and AC signal, just use AC coupling caps at the input of the device.
    2. The device is able to work with AC signal (analog signal) and DC signal (stable DC voltage). Although it cannot support PWM signal as input signal, that's why a filter must be used in case PWM signal is required.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • 0 in reply to Ivan Salazar
    Prodigy 30 points

            Thank you for your reply, we have still some questions to ask:

    1. We now use a NI-DAQ card( USB-6212) as an input source which gives a sine wave of 4V Vpp along with an offset voltage of 2V and the source is connected to J5 (Ain). The jumpers were set as in the initial question except the JP13 was removed. The result of amplification showed on the oscillator is a 54.8V Vpp sine wave with 0V offset voltage. Since the gain jumpers were all in logic high state, the driver should supply 40.7 dB amplification but the result is only 11.4dB. Is this amplification rate correct under our jumper settings?
    2. Furthermore, the offset voltage has gone nowhere. According to your reply, we should add an AC capacitor by following the steps in section 8.2.3 of the user guide to see the amplification of the DC offset, is this correct?

  • 0 in reply to user5766479
    TI__Guru** 111175 points

    I'll provide my comments below:
    1. Do you have captures of the input and output signals? If possible, captures of the signals on TP7 and TP8 would be helpful. If input signal is a sine-wave (not PWM) the input filter should be modified (removed) according to section 8.2.3:

    1. Replace resistors R6, R7, R13, and R14 with 0-Ω resistors
    2. Remove resistors R17 and R18
    3. Remove capacitors C8, C9, C13, and C14. Do not remove ac coupling capacitors C4 and C5.

    In addition to that, JP5, JP6 and JP13 should be open, although I think you already did this.

    2. Also as stated in section 8.2.3, the ac coupling capacitors are present in the EVM board, that is correct. There would be no DC offset, since the device operates in a differential mode.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators