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CD4504B: CD4504B Power Up Glitch

Varunesh Kumar
Intellectual 980 points

Part Number: CD4504B
Other Parts Discussed in Thread: UCC27524, OPA4197, VFC110

Hello 

I am trying to use this IC CD4504B for up-translating the 3.3 V Signals 

of my MCU to +15V., using the Vcc as 5V, Vdd as 15 V and the Mode Select pin

to Vcc.

I get a proper functioning except at power-up, when I see a glitch 

of sometimes 2V, sometimes over 10 V, lasting for a duration from a few mS to 

to sometimes tens of mS.

Is this behaviour normal?

To overcome the Power-up timing of 5 & 15V, I put a Diode 

With the anode to 5V and the cathode to the 15V pins, yet this glitch persists 

Is this behaviour to be expected.

Thanks in advance

 

IMG-20251216-WA0007.jpg

  • 0
    TI__Mastermind 34140 points

    Hello Varunesh,

    What's your power sequence?

    Before you power the part, what's the state of your inputs?

    Regards,

    Josh

  • 0 in reply to Joshua Salinas
    Intellectual 980 points

     Hello

    Thanks for your prompt reply.

    The 5 V is established first, followed by 15 V after 

    approx 5 mSec.

    The 3.3 V is almost simultaneous with the 5 V 

    The status of the Inputs I have not checked, but there is a Power On delay

    POR of approx 5 mSec.

    If you wish I can check the status of the Input pins.

    Going forward, what should the sequence be for an ideal situation?

    Thanks and have a great day ahead.

    Varun

  • 0 in reply to Varunesh Kumar
    TI__Mastermind 34140 points

    Hello Varun,

    Could we force the inputs to ground before we power up the device? I'm not aware this part has a particular power sequence but the glitch could be related to a floating input.

    Regards,

    Josh

  • 0 in reply to Joshua Salinas
    Intellectual 980 points

    Hi Josh

    There is a parallel reply from Albert, which I've replied to earlier.

    Trying to force the Inputs Low would require an additional IC.

    I can't use an RC at the Inputs, the PWM signals could be as high as 20 kHz..

    See if a simpler solution is workable, else 3 Nos of UCC27524 could be used,

    albeit a more expensive solution.

    Best regards, and have a wonderful Christmas.

    Varun

  • 0 in reply to Varunesh Kumar
    TI__Mastermind 34140 points

    Hello Varun,

    Have we tried using a blue wire to force the input low before powering up the device? 

    Would like to make sure driving your inputs low will resolve the issue before we start thinking about other workarounds.

    Regards,

    Josh

  • 0 in reply to Joshua Salinas
    Intellectual 980 points

    Hi Josh

    Good morning.

    I don't quite follow you regarding " blue wire." 

    to force the Inputs low.

    Please be good enough to elaborate.

    Best regards

    Varun

  • 0 in reply to Varunesh Kumar
    TI__Mastermind 34140 points

    Hello Varunesh,

    Blue wire means making a modification to a board via a neutral wire. Before you go and add another IC to force inputs low, it would be good to understand if doing this would fix the issue. 

    If you don't have a good way to force the inputs low, you can use a wire and solder one end to the input pin and the other to ground.

    Regards,

    Josh

  • +1 in reply to Joshua Salinas
    Intellectual 980 points

    Hi Josh

    1. Thank you for enlightening me reg the " Blue Wire."


    2. I am not sure if these CD4504 are genuine TI parts

    .It's not been available at TI Stores for some time.


    Earlier, I had some problems with OPA4197 reg it's Slew Rate,

    and VFC110 regarding the linearity at frequencies higher than 3.5 MHz

    The personnel from TI were very helpful, and after examining the OPA4197 declared 

    it is not an original TI part.

    Ditto for VFC110, which was sourced from Rochester via Digikey.

    My observation has been that when TI parts get stocked out, maybe similar duplicate 

    IC's flood the markets.

    3. My MCU has a Power Up delay of approx 200 mSec during which time it's O/Ps

        are kept low, so the Inputs to the CD4504 would certainly be low.

        The 5V is established first, followed approx 5 mS later, by the 15 V

        I've also tried a diode from 5V ( Anode ) to 15 V (Cathode) so that 

        5V and 15V are synchronous.

        

    4. I am closing this thread now, and changing my Design to 3 Nos of

        UCC27524 against one no of CD4504, though more expensive and 

        maybe a larger footprint.

    Thanks once again for a wonderful team at TI, and a very 

    Happy & Merry Christmas

    Varun