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OPA4310: ESD

Yang Wu
Expert 3480 points

Part Number: OPA4310
Other Parts Discussed in Thread: OPA4348, OPA2348, OPA348

Tool/software:

Hi team,

we know that OPA4310's Input pins can swing beyond (V+) as long as they stay with in 6.0 V, there has No diode structure from input pins to (V+). The datasheet says OPAx310 features no current-steering diodes connected between the input and positive power supply pin. are they snapback ESD? Or it's just steering diode for TI's amplifier products (I see some comparator products say there has snapback ESD)? thanks.

In addition, OPA4348 doesn't have diode structure from input pins to (V+) neither, while the datasheet spec shows the max Common-mode voltage at input is (V+) + 0.5V. if there has no diode-clamp to V+, why the max common-mode voltage at input is not a fixed value (such as 6V in OPA4310)?

thanks a  lot.

Best regards,

Yang

  • 0
    TI__Mastermind 26620 points

    Yang

    Thanks for your post.  I agree with your statement about OPA4310.  It has fail safe inputs that are protected by a snapback ESD protection diodes as you have stated.  However, I am not following you when you say that the OPA4348 also has fail safe inputs.  I don't believe that is the case and thus, the abs max table that you shared is correct.  The inputs are limited to V+ and do not have an absolute voltage input range.

    Chuck

  • 0 in reply to Chuck Sins
    TI__Guru**** 169336 points

    Chuck, Yang

    The OPAx348 does have fail safe inputs, there is a task open to fix the data sheet. 

    The ESD cells on these may be Zener action or snap back. Always assume snap back so never connect low impedance sources to inputs directly. Use some series resistance in case an ESD/EOS event does snap back. 

  • 0 in reply to Ron Michallick
    TI__Expert 3480 points

    Hi Ron, Chuck,

    thanks. that's more clear. I was confused why datasheet says OPA4348 doesn't have diode structure from input pins to (V+), but the max Common-mode voltage at input is (V+) + 0.5V (I also verified by simulation). 

    By the way, do you have some application note/learning materials to know more about ESD cells behaviors, either Zener, snapback, or TVS? this is an interesting topic. I know there has an app note <[slvaex7a]Op Amp ESD Protection Structures>, but not discuss above things. thanks.

    Best regards,

    Yang

  • 0 in reply to Yang Wu
    TI__Expert 3480 points

    Hi Ron,

    I tested it in customer side and confirmed that OPA4348 has diode structure from input pins to (V+), but I am curious how OPA4348 achieve fail-safe with the diode to V+? For device like OPA4310, there has no diode to V+ to achieve fail-safe.

    thanks.

    Best regards,

    Yang

  • 0 in reply to Yang Wu
    TI__Mastermind 26620 points

    Thanks for your post.  We are on holiday break and will review when we return on Monday.

    Chuck

  • 0 in reply to Chuck Sins
    TI__Guru**** 169336 points

    Yang,

    Let me be more specific, I have seen or tested OPA348 and OPA2348 and these were fail safe, no diode.  OPA4348 was not tested; usually single, dual, and quad are identical in all ways. Usually is not always. Based on customer test, quad is different input ESD structure. I'll order quad to see for myself. 

  • 0 in reply to Ron Michallick
    TI__Expert 3480 points

    Hi Ron,

    thanks. will wait for your test results. 

    Best regards,

    Yang

  • 0 in reply to Yang Wu
    TI__Guru**** 169336 points

    Yang,

    Samples were ordered and I should receive them and test them by end of this week.

    In the mean time, is this for information purposes only or is a application design in process?

  • 0 in reply to Ron Michallick
    TI__Guru**** 169336 points

    Jang,

    How about that? There is no IN to VCC (positive supply) diode on my OPA4348 samples.

  • 0
    TI__Expert 3480 points

    Hi Ron,

    Thanks for your test. this is for application design purpose. we have both OPA4348 and TLV904 in customer and they have OPA4348 stock need to be consumed.

    How did you test the samples? we used multimeter to test in customer side. I also checked that there has no PCN recent years. It's very strange that we have different results.

    let me know your ideas.

    thanks.

    best regards,

    Yang

  • 0 in reply to Yang Wu
    TI__Guru**** 169336 points

    Yang,

    For single and dual , we tested in multiple ways. Including IIN vs VIN curves seeps charts with power on and off.

    For quad. we used our quick op amp diode checker. IN has diode to VEE, but not VCC. OUT has diode to both VEE and VCC

    IN to VCC test is VEE= VCC= 0V, IN+ 3.6V with LED and 120 ohms resistor in series. 

    Yang Wu said:
    we used multimeter to test in customer side.

    Used it how? In what mode, what pin connections, in or out of circuit?

  • 0 in reply to Ron Michallick
    TI__Expert 3480 points

    Hi Ron,

    thanks a lot for your help.

    we use diode mode of the multimeter from In to VCC to detect if there has a diode. do you see any issues with this method? thanks.

  • 0 in reply to Yang Wu
    TI__Guru**** 169336 points

    Yang,

    Diode mode works if used in correct polarity and device is out of circuit.