JX5094PHT LCD and TC7106CPL Driver

Discussion in 'General Electronics Chat' started by paw, Feb 8, 2012.

  1. paw

    Thread Starter New Member

    Jan 11, 2012
    18
    0
    Hi All,

    I am having a bit of bother with the following two components:

    TC7106CPL 3.5 digit display driver:
    http://uk.rs-online.com/web/p/adc/2070253/

    JX5094PHT 3.5 digit LCD display:
    http://uk.rs-online.com/web/p/produ...67573743D4A58353039345048542677633D424F544826

    Now, I have connected up both components with the configuration as shown in Figure 10-8 as found here:
    http://ww1.microchip.com/downloads/en/DeviceDoc/21455d.pdf

    The problem I am having is that the LCD constantly displays all of the LCD segments, as if the test pin was active. From the datasheet, it says that pulling this test pin to +Vsupply will do this, but I have not got this connected to anything. Using a multimeter, I found that the voltage on this pin was around 9Volts (n.b Vsupply is 15V)

    I am struggling to understand what has gone wrong and I thank all in advance for assistance.

    Cheers,
    Paw
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,395
    1,607
    Having never used either device... Seems the TEST pin is internally pulled to ground. but you may try a hard wire there.

    Do you have a 'scope to check if the segments & common are getting square waves and not a DC level? Note: to be on, a segment & common are out of phase, in phase to be off.
     
  3. paw

    Thread Starter New Member

    Jan 11, 2012
    18
    0
    Hi,

    Yes I have a scope that I can use to help me test.

    What parts would you recommend I check?

    Thanks,
    Paw.
     
  4. paw

    Thread Starter New Member

    Jan 11, 2012
    18
    0
    Hi,

    So I tried to pull TEST to down via a hard wire, but this resulted in the driver IC getting very hot, so I am assuming that this was not correct.

    Now, I tested the segments and I am getting a square wave out of here.
    I know you said to test the common, did you mean analogue common? Because this pin is grounded as per the circuit schematic.

    I am not sure what the BP(backplane) pin does, as this is also outputting a square wave in phase with the segments.

    Also, I am not sure what the COM pin as shown on the datasheet for the LCD is for?

    Thanks,
    Kind Regards,

    Paw.

     
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