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TLV342: TLV432 input current maximum rating.

Qi Wang
Prodigy 10 points

Part Number: TLV342
Other Parts Discussed in Thread: TLV341

We will use TLV432 as amplifier for optocoupler secondary side.

In case the TLV432 doesn’t suppled, the primary side of optocoupler will still given energy that at the secondary side a current like 100µA is generated.

I need to know whether this 100µA is dangerous for TLV432 or not. In datasheet the maximum rating for input current is not given, only input voltage level is given.

Regards

  • 0
    TI__Mastermind 18960 points

    Hi Qi, 

    Welcome to E2E!

    Just to confirm, are you using the TLV342 in your application? You mention a "TLV432" multiple times so want to make sure which part you are using. 

    Also, do you have a schematic you can share so we can see how the amplifier is connected to the optocoupler? 

    Thank you!

    Best Regards,
    Ashley

  • 0 in reply to Ashley Kang
    Prodigy 10 points

    Yes, it is the OPAMP TLV342, the two channel version of TLV341. The schematic is attached. The question is about, whether the current of 100µA from optocoupler OC69 could damage the OPAMP IC1 in TLV342, if TLV342 doesn't have supply voltage. 

    Thanks. Best Regards

  • 0 in reply to Qi Wang
    TI__Mastermind 18960 points

    Hi Qi, 

    Could you please re-upload your schematic? I do not see it in the thread. Is there anything connected between the optocoupler and the opamp? 

    Thanks!
    Regards,
    Ashley

  • 0 in reply to Qi Wang
    TI__Mastermind 18960 points

    Hi Qi, 

    Thank you for the schematic. 100uA on the inputs should be fine in this scenario if the op amp does not have a supply voltage. 

    Regards,
    Ashley

  • 0 in reply to Ashley Kang
    Prodigy 10 points

    Hallo, Ashley:

    Thanks a lot for your answer. I could need a little more clarification. 

    1. Could you please introduce yourself.
    2. Could I count on your answer because I need to proceed the design. Otherwise I have to ask Texas Instruments for an official statement.
    3. What is the mechanism to protect the part. Does the part has clamp diode or the transistor can take the 100µA, even the input voltage is more than 0.3V over supply.

    Best regards.

  • 0 in reply to Qi Wang
    TI__Mastermind 18960 points

    Hi Qi,

    I am an engineer from Texas Instruments as indicated by the "TI_" level on the top right side of my posts. Only TI employees can have "TI" in their level type.

    Our forums are here to help answer questions with our parts however as stated in our terms of sale and datasheet, design and validation responsibility falls on the customer. We cannot give an official statement on customer designs. 

    I will need to validate in our lab what the input structures are. Please give me until end of day Wednesday (May 1) for my update. 

    Regards,
    Ashley

  • 0 in reply to Ashley Kang
    Prodigy 10 points

    Hallo,

    Thanks for your answer.

    1. The datasheet gives 0.3V input voltage over supply. No external clamp diode can guarantee this voltage. For me the reasonable explanation is that the part has internal clamp diode which can deal with small input current, but not input voltage with low impedance which generate high input current. Could you please confirm whether the part has internal clamp diode.
    2. It the part has internal clamp diode, which input current shall not be exceeded. Usually it is 1mA – 3mA. I think 100µA is fine. Could you please confirm it.

    Best Regard

  • 0 in reply to Qi Wang
    TI__Mastermind 18960 points

    Hi Qi, 

    I tested the TLV342 in lab and confirmed that there are internal diodes from inputs to negative supply rail (VEE), but not the positive supply rail (VCC). These diodes are generally what determine how much input current limit could damage the internal input structure. 

    For CMOS input devices, the current limit is 10mA, which is why I stated earlier that 100uA should be fine.

    Regards,
    Ashley

  • 0 in reply to Ashley Kang
    Prodigy 10 points

    Hallo, Ashley:

    Thanks a lot for your clarification. Let me summarize the facts.

    1. In TLV342, the clamp diode from input to negative supply is existing.
    2. An input current from input to negative supply up to 10mA is actable.
    3. In my application the input current up to 10µA is applied to negative input. Therefore, it is acceptable.

    Are the points correct.

    Then an additional current beside my application, maybe for the future. What would be the acceptable input current from input to positive input, if for example the part used for comparator with positive feedback?

    Regards

  • 0 in reply to Qi Wang
    TI__Genius 17776 points

    Hi Qi,

    Qi Wang said:
    In TLV342, the clamp diode from input to negative supply is existing.

    Correct, internal ESD diodes exists between the inputs and VEE

    Qi Wang said:
    An input current from input to negative supply up to 10mA is actable.

    Currents beyond 10mA will be capable of damaging the device. I would recommend staying below 1mA if possible.

    Qi Wang said:
    In my application the input current up to 10µA is applied to negative input. Therefore, it is acceptable.

    Correct, this will be acceptable for the device. 

    This device does not have diodes from input to input, therefore the comparator example is not a concern.

    Thanks,

    Jacob