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Interfacing 12 seven segment display to SN74LS47

Anand Kumar Rai
Intellectual 720 points
Other Parts Discussed in Thread: SN74LS47

Hi all!!

I am using SN74LS47 to connect 12 seven segment displays to LM4F232H5QD MCU, I am planning to use BCD to SEVEN SEGMENT DIVIDER SN74LS47. As per the datasheet 46A, 47A and LS47 will be used for common anode seven segment displays. But same series has got 3 blanking  and LT pins, Can I short all these three pins of all SN74LS47 all together for all 12 drivers? My intention is to display DD.MM.YY and HH.MM.SS

Thanks and Regards

-Anand

  • 0
    Guru 25210 points

    LT is an active-low lamp-test pin, so this pin should be set high for normal use. If you don't want to suppress leading zeros, then RBI should also be high.

    BI/RBO is a wire-and input/output, so I would tie this high through a pull-up resistor.

    You can certainly tie all 12 in parallel if you want (I assume you have 12*4 I/O lines driving each driver individually and not time slicing the digits).

  • 0 in reply to Brian Boorman
    Intellectual 720 points

    Hi Brian,

    Thank you very much for you reply!!!

    Actually now I am using 74HC4511D from NXP as my LED's are Common Anode LED's and this particular seven segment driver can operate on 3.3V also which is the only supply I have on board.

    As far as GPIO's are concerned I am using

    4 GPIO lines to control DD.MM.YY

    and 4 GPIO lines to control HH.MM

    and other 4 GPIO lines to control SS

    based on their update rates maximum update is required on second and for date its required only to change once in a day. 

    All the BCD to 7-segment drivers have a latch input which I am connecting individually to GPIO of controller, to latch their outputs once the update is done.

    LAMP TEST(LT) and BLANKING INPUT(BI) I am planning to short all of LT to transistor "emitter" and control though single GPIO, similarly planning to short all BI. Please let me know whether my approach is correct or need to change something in the circuitry.

    Thanks in advance!!!!

    Thanks and Regards

    -Anand Kr. Rai 

  • 0 in reply to Anand Kumar Rai
    Guru 25210 points

    In all fairness, I'm here to help answer questions, not provide detailed design review services :-)

    It sounds like you are on the right track though. Just make sure you double check all your DC & AC specs, look for connection errors, etc.

    Good Luck!

  • 0 in reply to Brian Boorman
    Intellectual 720 points

    Hi Brian,

    Sorry if I have hurted your sentiments in any way.

    Thank you very much for your feedback. Will look into all aspects of AC and DC specs.

    Thanks and Regards

    -Anand 

  • 0 in reply to Anand Kumar Rai
    Prodigy 10 points

    Hello, I'm looking for ECCN - Classification of following

    Please refer attached Excel File

    Thanks and Regards,

    Premachandra

    TEXAS INSTRUMENTS.xlsx
  • 0 in reply to prema chandra
    Guru 25210 points

    Prema,

    1st, this is posted in the wrong place. You shouldn't expect an answer by replying to an unrelated post with an unrelated question. At the very least you should start a new post.

    2nd, this is something probably best handled with your local TI Sales/FAE support staff.

    3rd, the forum has a search feature. Use it.

    Reference this post related to your question: http://e2e.ti.com/support/amplifiers/high_speed_amplifiers/f/10/t/215775.aspx