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TLV1805: opamp keeps breaking

ramon commereuc
Prodigy 10 points
Part Number: TLV1805

In the following design this opamps keep on breaking.. Creating a (almost) shortage of around 100 ohm between V+ and GND.

Already connected some ESD protecfion to the input signal lines.

From 4x tested PCBA, 3 times this IC broke.

In the schematic:

Vbat = 28.7V

Delta Temp + and Tmin = 4.1V

The output only powers 7 Toshiba TLP3407S solid state relais.with a 3,9k ohm in series.

Does anyone has experienced this also? Or know a solution to prevent this?

8037.opamp.pdf

  • 0
    TI__Mastermind 24850 points

    Ramon

    Sorry to hear this.  At first glance, I don't see anything obvious but can you capture some waveforms of a device working properly.  If possible, please use a 4 channel scope and capture the two inputs, output and V+ waveforms.  I also did not understand the line about Detla Temp but it appears that you are sharing information about the inputs.  I still believe capturing the actual waveforms will be needed to help resolve.

    Thanks, Chuck

  • 0
    Guru 140200 points

    Hi Ramon,

    and the TLP3407S are installed in series with a current of (28.7V - 7 x 1.26V) / 3900 = 5.1mA flowing through them? Is the last TLP3407S connected to the signal ground of TLV1805?

    Connecting ESD protection devices to the input lines could make trouble beause of unwanted leakage currents ruining the high input resistance provided by the 8M2 resistors. So, you might have installed ESD protection with low leakage currents? But these can show high overvoltages during ESD no longer providing reliable protection? So, what ESD protection devices do you have installed?

    What is connected between the TEMP inputs? Can you show a complete schematic?

    Could ESD on the supply voltage line have destroyed the TLV1805? Or ESD arriving from the output?

    Kai

  • 0 in reply to kai klaas69
    TI__Genius 14560 points

    Hello Ramon,

    At your earliest convenience, please provide more details about your issue. We would like a scope capture with the input and output waveforms so that we can get a better idea about what the device is seeing.

    We look forward to the additional information that you will provide.

    Best Regards,

    Joe

    Applications Engineer

    Linear Amplifiers Business Unit | Comparators Product Line (CMPS)

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml)

  • 0 in reply to kai klaas69
    Prodigy 10 points

    Hello Kai,

    Thank you for the quick response.

    and the TLP3407S are installed in series with a current of (28.7V - 7 x 1.26V) / 3900 = 5.1mA flowing through them? correct Is the last TLP3407S connected to the signal ground of TLV1805? correct

    Connecting ESD protection devices to the input lines could make trouble beause of unwanted leakage currents ruining the high input resistance provided by the 8M2 resistors. So, you might have installed ESD protection with low leakage currents? But these can show high overvoltages during ESD no longer providing reliable protection? So, what ESD protection devices do you have installed? connected to the input signal a low leakage SM05T1G TVS diode array is used

    What is connected between the TEMP inputs? Can you show a complete schematic? Temp stands for thermistor here, nothing is attached to the input so far, with 2 of the boards however I put a little voltage of 1V with a current limiting power supply to acceptance test the design and see if the output goes high. This was OK. 1 week later after testing it again the TLV1805's where broken.

    Could ESD on the supply voltage line have destroyed the TLV1805? Or ESD arriving from the output

    I will make some scope measurements

  • 0 in reply to ramon commereuc
    Guru 140200 points

    Hi Ramon,

    hhm, I somehow think that the 8M2 resistors are too high ohmic to handle a thermistor. Wouldn't it be better to you connect one end of the thermistor to signal ground?

    Also, I'm not sure how the circuit shall work. With the thermistor being connected to the inputs, the comparator would always show the same output potential. Or is this exactly what you plan? To be able to detect whether the thermistor is connected to the circuit or not?

    Can you please give more details on the function of this circuit? And what thermistor are we talking about?

    Kai

  • 0 in reply to kai klaas69
    Prodigy 10 points

    The thermistor on the input is connected with an 10k resistor and VCC (2.5V) to make an voltage divider. So when room temperature the TLV1805 can switch.

    Don't you think the problem is more in the direction of the powerline since this is making a almost short circuit (100 ohm between V+ to GND on the TLV1805)? Maybe a low leakage TVS over the powerline will resolve.

    Do you think a small capacitor over Vbat line like this will be any help against ESD events?

    Attached also the output of the schematic and a scope image of the setup where:

    Vbat = 28.7V [not on scope]

    Delta Temp + and Tmin            [blue and yellow line]

    Math Temp + minus Tmin = 1V AVG  [purple line]

    Vout = 29.2V AVG [pink line]

    opamp2.pdf

  • 0 in reply to ramon commereuc
    TI__Genius 14560 points

    Hello Ramon,

    Is it fair to assume that while the output is high, there is no failure, and that switching on the output is causing inductive kick when the comparator output sinks?

    If this is the case, we would recommend placing a TVS on the non-comparator side of the output resistor. This way, the transients on the output from the inductive kickback of the relays will be reduced.

    Also placing a TVS between gnd and VCC may help with the issue.

    Do you have a scope capture where the output is switching at room? This will help us confirm the inductive kickback that we are assuming.

    Best Regards,

    Joe

    Applications Engineer

    Linear Amplifiers Business Unit | Comparators Product Line (CMPS)

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml)

  • 0 in reply to Joe Vanacore
    Prodigy 10 points

    Hello Joe,

    Some new insight since yesterday:

    During assembly this PCBA is placed on another PCBA (electrical connection with 2.54 pinheaders) where a battery [28.7V] is connected always ON. When connecting the assembler heart sparking...

    I am going to follow up on your advice and place TVS diodes on the non comperator side of the output resistor and between VCC and GND.

    Will do the output switching test with and without TVS.

    Thank you.

    Ramon

  • 0 in reply to ramon commereuc
    TI__Genius 14560 points

    Hello Ramon,

    I look forward to your results with the additional TVS placements.

    Best Regards,

    Joe

    Applications Engineer

    Linear Amplifiers Business Unit | Comparators Product Line (CMPS)

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml)

  • 0 in reply to ramon commereuc
    Guru 140200 points

    Hi Ramon,

    ramon commereuc said:

    Vbat = 28.7V [not on scope]

    Delta Temp + and Tmin            [blue and yellow line]

    Math Temp + minus Tmin = 1V AVG  [purple line]

    Vout = 29.2V AVG [pink line]

    Are you sure? Vout = 29.2V while the supply voltage of TLV1805 is only 28.7V?

    Kai

  • 0 in reply to kai klaas69
    TI__Genius 14560 points

    Thank you for posing that additional question, Kai.

    Ramon,

    Please provide your results with the new TVS placements and also did you mean to say the supply is actually 29.2V? I am glad that Kai pointed this out.

    Best Regards,

    Joe

    Applications Engineer

    Linear Amplifiers Business Unit | Comparators Product Line (CMPS)

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml)

  • 0
    Prodigy 10 points

    Yes, the problem seems to be solved. The sparking by connecting PCBA's together causes the TLV1805 to break. An TVS over the supply voltage and one over the output does the trick.

    Thank you very much for the support!

  • 0 in reply to ramon commereuc
    Guru 140200 points

    Bonjour Ramon,

    thank you for the feedback!

    Good luck Relaxed

    Kai

  • 0 in reply to kai klaas69
    TI__Genius 14560 points

    I am glad that Kai and I were able to help resolve your issue, Ramon.

    Best Regards,

    Joe

    Applications Engineer

    Linear Amplifiers Business Unit | Comparators Product Line (CMPS)

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml)