# 74HC4094 vs 74HC595

I'm planning a large display board where I'll have to display 150 7 - segment digits. Which shift register is preferred here?

74HC4094 or 74HC595 or something else since I'm planning to chain these digits. The wire length maybe upto 2feet between each digit sometimes.

• Which shift register is preferred here? You need need to be a little more specific. Are you looking for a particular speed or something with less mechanical spacing or something that consumes less power, etc.? If it's anything I just listed in the previous sentence, then you'll need to refer to the datasheets.
– user103380
Jan 31 '20 at 20:19
• You can get larger shift registers, might be worth it if you're doing that many digits. 32 out, maybe more, often with higher current drivers built in. Like a TLC59581RTQR maybe, £5 in ones from digikey, cheaper in 10s or 100s, 48 outputs. Jan 31 '20 at 20:53
• If it is the distance between each digit is of most concern , then you need controlled impedance cables and termination to midpoint bias threshold. You don’t need to increase the LED lines but rather the serial high speed digit data. Jan 31 '20 at 21:00
• @KingDuken I just want to make sure if 74HC595 works in my case. Or if it doesn't work, are there any other shift registers that might work. Feb 2 '20 at 13:55
• You don’t tell anything about how you’re going to connect these digits, so it’s not easy to recommend one over the other. They function very similarly. I think your concern should be about how to let them work reliably over large distances. Feb 3 '20 at 8:25

As you provided no specs other than the shift register is used to drive 7-segment digits, the selection between these two chips is difficult.

If the 7-segment digits are LEDs, then maybe you would prefer higher current driving ability. So the choice between these two is clear, it would be 74HC595.

If the 7-segment digits are LCD, either will do.

If you want cheap, select cheaper of them. If you want a part that is more easily available, select it.

A shift register is a basic and essentially interchangeable part. You pick one to fit your functional requirements (number of outputs, price, etc.) and move on; deliberating over which functionally equivalent part to use is missing the forest for the trees. In such a situation, where I have two parts that both meet the design requirements for a project I'm working on, I usually just pick whichever is cheaper.

As mentioned in the comments, you may encounter problems chaining these together over long distances. It's unclear exactly how you're planning to set up this display, but if you encounter problems with signal integrity over such long distances you may want to consider using LVDS drivers and receivers between long runs of cable.

If you really are driving 7-segment displays, I suggest you look at MAX7219, which handles the entire drive system for 8 digits. (The data sheet is lengthy, but repays careful reading.) SPI protocol makes daisy-chaining easy, but you may have problems with the separation between digits.

I'd like to contribute mixing the @henros answer and @Tom 's piece of advice. I've assumed the major trouble you'll have will be the distances between digits and from the master controller. So, I'd like to suggest to you to split the 150 digits using several Maxim's MAX7219 IC's, one for each 8 digits. To connect all of them, I suggest to you to connect all SPI's interfaces of each MAX7219, applying strict control over the impedance of LOAD DATA and CLK lines, by the employing of shunt resistors between each 8 digits module.