No announcement yet.

gen4-ulcd-70d keep restarting on extenrnal Power

  • Filter
  • Time
  • Show
Clear All
new posts

  • gen4-ulcd-70d keep restarting on extenrnal Power


    I'm using a ulcd-70d UB coupled with a 4d-upa for the development part.

    Now in order to try all the function I was trying to run the solution in stand alone by feeding the 5v directly from a bench Digital Power Supply capable of 5amp and off course 5V using the same UPA (GND and 5V)

    When the UPA is connected to the PC USB no problem all works, as soon as I disconnect the usb and switch ON power to the PSU the display start rebooting every second

    I'm wondering if there is a requierement for some other signal to be connected.

    I'm using only digital pins connected to SPI and I2C to a SAMD21 , not using any Serial

    Is that something I'm missing?

  • #2

    Welcome to the forum.

    Since the display module works while connected to the PC's USB port with UPA, we can safely rule out the any of these being faulty. How much is the current coming from the Digital Power Supply? Kindly refer to gen4-uLCD-70D Datasheet, page 26, to see Supply Current(ICC).

    Thanks and best regards,


    • #3
      Hello Sherwin

      I read the datasheet before setting it up and the requirement for 960mA (SB full brightness)

      The bench power is set to constant voltage and is supplying the upa board at 5.0V with a limit of 2.0Amp. the weird thing is that when I connect the display current start to ramp up till 200 mA and then the display reset

      Do you think that supply using a different power regulator with a steeper ramp up will help?


      • #4
        Hi AndreaGini,

        We tried this on our end without encountering any hitch.

        You mentioned that the displayed current ramps up to 200mA, does it go higher than this? If not, perhaps you could try to adjust the current output limit to ~1A on the Digital Power Supply? It is possible that the maximum current output is set only to 200mA.

        Last edited by sherwin4D; 27 May 2020, 03:49 PM.


        • #5
          Hi Sherwin,

          The output limit is set to 2.5A , that's the weird part. I'm planning to run a test today from the same power source and add a CAP to see if it needs a bit more inrush .I'll keep you posted


          • #6
            Ok I tested it with a 7805CV (just for testing) and it works. The problem is that in full brightness (the display is a SB model) is peaking at 1.42A that is way outside the value indicated in the datasheet. Is not a big issue for me (I'll just plan for a bigger regulator in my circuit) but it makes me wonder if it's my screen that has a fault. Can you tell me what's your power supply current output reads at 5V

            Thank you


            • James_4DSystems
              James_4DSystems commented
              Editing a comment
              The value in the datasheet is 'Typical' - not Max. Its the typical current it will draw when its running.