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SN74HC595: application of SN74HC595 for common anode digit LED

user021864
Intellectual 2145 points
Part Number: SN74HC595
Other Parts Discussed in Thread: SN74HC164

there are few question i want to confirm :

1. can SN74HC595 used to control the LED with common anode? from typical application, it's used for common cathode? 

Please let me know if there are any concern when using common anode.

2. can we connect SRCLK and RCLK together ? 

will this cause problem for the storage register to capture the output from shift register if they are sharing the same clock and trigger at positive edge of clock?

  • 0
    TI__Guru* 97046 points
    Hi,
    Yes, the device can be used with common anode LEDs -- just be sure that the SN74HC595 has the same supply voltage as the LEDs so that when the outputs switch 'high' the LEDs will be turned off.

    The SN74HC595 is ideal for LED applications since you can clock data through with SRCLK without the data showing up on the output until RCLK is activated. You definitely can use it with SRCLK and RCLK tied together - you just have to run an extra clock pulse (9 instead of 8 for getting all data to the outputs), however this kind of eliminates the benefit of using the SN74HC595 since the data will show up on the LEDs with each clock pulse, causing a flickering effect in the LEDs.

    If you need a shift register that doesn't have output latches, you might consider the SN74HC164
  • 0 in reply to Emrys Maier
    TI__Intellectual 2145 points

    Hi, 

    Thanks for your reply.

    Because now I am having issue about the display result of SN74HC595, using the same firmware and board but different SN74HC595. Some of them have the wrong display result. So I am wondering is there any possibility causing this result?

    Thank you.

  • 0 in reply to user021864
    TI__Guru* 97046 points
    Yes, there are many reasons why things can go wrong. Can you share a schematic and the type of error you are getting at the outputs?