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ISO7710-Q1: iso7710d

robin gangopadhya18
Mastermind 6050 points
Part Number: ISO7710-Q1
Other Parts Discussed in Thread: UCC28780, ISO7710

We are having no luck with ISO7710D ( by a misunderstanding - did not get ISO7710F)

Since all devices are being blown just in DC bias conditions with low frequency (100kHZ) 50% pulse, there must be something I have not understood how to use it.

See attached schematic & screenshot of placement/routing.

It is tiny PCB with GaN & controlled by UCC28780( we are far from having power yet..)

Now we measure with nothing else connected &  pin 2 is lifted off the pad on the PCB. & it measures 2V.

Connecting to the driver TTL, of course, input switches 2v to 5V with the TTL getting smoking hot.

Q#1 is: since there is a 1.5Meg at the input, ok we see 2V but why would the driver at pin2 be getting hot ..is it because there is another low impedance path to pin 2?

Then what is the proper way to drive pin 2?

We are running bother at 5V & there is no visible

And also running low in parts count in the bag!

Will appreciate if you can help us shipping ISO7710FD samples by overnight shipping like good old days...5 will suffice.

-robin

ISO7710FAILURES.pptxringing at either Vcc.

Any help will be appreicated.

-robin\

  • 0
    TI__Genius 17100 points

    Hi Robin,

    Thank you for posting to E2E! We appreciate you evaluating ISO7710D and ISO7710F.

    There is not a state where pin 2 (digital input) is expected to have 2V present without being driven, so there may be a misconnection or unexpected overvoltage condition. Please confirm the voltage level of Vcc1 (pin 1) is greater than 2.25V and no greater than 5.5V during operation.

    To ensure there is no damage to the isolator, please do remove the IC from the PCB and measure impedances between pins 1 - 3, 1 - 4, and 2 - 4, and let us know the results. I will reach out shortly to you via PM regarding samples.


    Thank you,
    Manuel Chavez

  • 0 in reply to Manuel Chavez
    Mastermind 6050 points

    Manuel

    So much appreciate your prompt reply. And appreciate samples...

    As you can imagine we are sitting on the bench & looking up on the screen for a solution.

    The output  of TPS7A24500 is pretty stable at 5.0V

    Vcc1 is thus decoupled well by 1uF close by at 5.0v

    This 2V at the input is being sourced internally to ISO7710 somehow,  by a low impedance for it to fry the TTL. The output of the TTL is a typical TTL classic output.

    In one experiment, we had pin2 off the pcb. Even then it was 2v

    Is it possible EN connection to pin 1 is problematic? Should it be with a resistor to VCC1?

    In real circuit, UCC28780 output is connected directly to pin 2 of ISO7710 isolator. The PCB is designed with EN connected to pin 1(VCC1)

    But we can cut & add a 0402 chip between pin 1 and 3

    Any reviews highly appreciated.

    robin

  • 0 in reply to robin gangopadhya18
    TI__Genius 17100 points

    Hi Robin,

    You're welcome. May I reach out to the email address associated with you myTI profile regarding samples?

    Thank you for this analysis. Does the 2V on pin 2 also exist immediately when the ISO7710 is replaced with a new ISO7710 and powered on with pin 2 lifted off of the PCB?  If possible, please do measure the resistance of pins 1 to 2, pins 2 to 4, and pins 1 to 4 on the suspect ISO7710 unit when it's removed from the PCB.

    Pin 3 of the device should be tied to Vcc (pin 1) directly since it is a second power supply pin instead of an EN pin.


    Thank you,
    Manuel Chavez

  • 0 in reply to Manuel Chavez
    TI__Genius 17100 points

    Hi Robin,

    May I follow up over email and regarding samples of ISO7710?


    Respectfully,
    Manuel Chavez

  • 0 in reply to Manuel Chavez
    Mastermind 6050 points

    Thanks Manuel: no news about samples. We will get them from Mouser asap.

    robin