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  • Powering the uOLED-160-G2

    I'm replacing my existing LCD with the uOLED-160-G2 (same basic size) in my existing design. I'm having issue with how to power the new display though. My circuit up to this point has been running off of 3.3V for battery longevity. All of my ICs are running off of the same. My input voltage is 9V.

    I'm in the process of updating my board to be more power efficient by adding in sleep modes and a switching regulator as well as mosfets to turn off components on the board when not in use.

    My question: What is your recommendation for powering the display at the required 4-5V? Do I need to run another switching regulator (as linear from 9V to 5V is not very efficient)? Or do you have another approach? I'd rather not have another regulator just for the display.

    From the schematic in the datasheet, it looks like the only thing that utilizes the 5V other than the 3.3 regulator on your board is the LCD 30V boost converter (which from it's datasheet can run at 3.3V as well). Knowing this, I must ask if there is a 3.3V only version available for your displays or possibly a future of 3.3V only? I'm planning on using the uOLED-96, 128, and 160 in my foreseeable designs.

    Thanks,
    Jeremy

  • #2


    Hello Jeremy

    No we do not have 3.3V versions of our displays sorry, however keep reading....

    Generally when running our display products, you use a 5V supply of some description, but since you are using a battery then you will most likely need to use a battery (or 2 in series) which provides > 5V and regulate it down, or add some series diodes to ensure it is around 6V.
    If you look at the TPS datasheet, you will see it has a max of 6V input, but absolute max of 7V, so if you are under that by a safe margin you may be OK. The LP2985 has a higher input level, so can be ignored.

    You are welcome to try, however if you are operating outside the recommended specifications from our datasheets then you will void the warranty.

    You mention a 9V battery. If you are talking about the rectangular ones you use in smoke detectors etc, unless you have one that is high capacity with high output current capability, you may run into problems as these generally are not suited to be used as they cannot output enough current. Just FYI

    As I am typing, I just grabbed a uOLED-160-G2 I had and connected 3.3V to pin 2 of the header, which is the 5V pin, and then GND to pin 7. Display powered up seemingly fine. So inputting 3.3V will be going into the 3.3V regulator input and it will be failing to regulate (obviously), so appears to be just passing the 3.3V to the 3.3V rail. The TPS boost regulator is then using 3.3V to generate the 30V for the LCD correctly also. You are welcome to try this. It obviously is not ideal, but looks like it could work for what you need. I have not tired using a microSD card however. You will need to ensure that your input is a nice clean 3.3V however as this will be fed directly to everything on the board, so your margin for error will be less. Note, this is NOT recommended practice, but you are welcome to try and see if it works for you.

    Regards
    James

    Comment


    • #3


      First off, thanks for your quick reply. As stated in my previous post, my battery input voltage is 9V (lithium 9V replacement) which is well beyond your absolute maximums. So some sort of regulation/step down is required.

      As my company sells hundreds of these devices a year, I do not want to be guessing or hoping that running the display at 3.3V will not cause the display to undervolt (brown-out) on a customer just because you got one display to power up at 3.3V. I wish it were that simple, really. If this has not been tested thoroughly and you say that running the display outside of the operating limits will void warranty/support then that is obviously a bad course of action. I'm a little surprised that you would even recommend it.

      Comment


      • #4


        Jeremy

        To start with, I mentioned this without any knowledge of your application or intended use. For all I knew you were a hobbyist trying to make a 1 off project and simply wanted a solution to run off 3.3V.

        As I mentioned, this is not recommended practice and I was merely trying to suggest a solution for you so you have something to start with.

        If you require a custom module which is designed appropriately to run off a 3.3V supply, then please contact our sales department and we can go through the process of designing a custom module for your requirements. This is obviously subject to volume and may involve NRE charges.

        Regards
        James

        Comment


        • #5


          To continue with this, if you refer to the datasheet for the 3.3V regulator
          http://www.ti.com/lit/ds/symlink/lp2985-n.pdf
          Page 13

          If you apply 3.3V to the output of the regulator, ie pin 10 of the uOLED-160-G2 header, and have no 5V present, then the 3.3V will flow on to the 5V rail via the internal diode.
          Since there is no 5V input, this is a valid and 'in spec' situation with respect to the regulator itself.

          So if you were to apply 3.3V to the 3.3V pin, and disregard the 5V pin I mentioned above, then this could be seen as a valid situation for the regulator. This also powers the display correctly.
          However if this is still not a valid solution for you, as mentioned, please contact our sales department.

          Regards
          James

          Comment


          • #6


            Thank you, James. This is more the caliber reply and suggestion I was wanting. Sorry for not being more forthcoming with my intentions. I never want to be pushy and say that my design deserves more attention because it isn't a 1 off. After re-reading my first post I can easily see how you would get that impression.

            I will do some further testing with this by back-feeding the 3.3V pin as you mentioned to see if my display acts the same (it should though from the datasheet).

            I am also contacting your sales department as verification of this and also to discuss large quantity purchasing.

            Thanks again,
            Jeremy

            Comment

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