Bus / Line driving

[banedon]

I'm creating a digital circuit to program a parallel 64Kb EEPROM using dip switches (I know: slow. But it's a "can I do it" project ) for inputs and 7 segmented displays for ouputs.

I'm sort of getting there with the circuit (will post it here for comments ), but have run into an issue and have hopefully resolved it myself - but I need to be sure I have.

The issue is that I'm trying to drive a Kingbright 4x 7 segmented display using four 74HC4511 7 segment display driver ICs (please - if anyone has a better way of doing this please say ).
The way I see it, the output from the 74HC4511 is a max of 10mA. Where-as the display can pull up to 25mA.
I could limit the current that the display draws to 10mA using resistors, but that might result in a display which is too dim.
So... can I use a Buffer/Line driver?  I have a74ABT244 in mind as it says it'll sink up to 25mA. Do Buffer/Line drivers work in this fashion? Everything I've read seems to say they do.

Data sheets:
Kingbright 4x7 Segment display (CC56-11CGKWA) - http://www.kingbrightusa.com/images/catalog/SPEC/CC56-11CGKWA.pdf
74HC4511 Driver - http://www.farnell.com/datasheets/308800.pdf
Octal Buffer/Line driver - http://www.nxp.com/documents/data_sheet/74HC_HCT244.pdf

Many thanks

Mike

[SeanB]

The displays will be quite bright at 10mA, and still readable in normal room light at 5mA. No need to have them run ar 25mA, that is a maximum current, not a current to be aimed for. At 25ma you probably will be blinded looking at them, and will have a lot of light bleed through to off segments. If you look at the data sheet the leds are meant to be driven at 10mA, that is where they are specified at DC. The other ratings are for pulsed operation, where you might only have a single display on for 1% of the time yet need it to appear bright.

[banedon]

Thanks Sean.  I'm getting a little confused reading the data sheets regarding DC maximums and limits - atleats for some of them! Although I wasn't going to try 25mA - probably 15mA and then adjust from there.
One thing: the datasheet for the 74HC4511 (page 11) seems to indicate that a current limiting resistor should still be used with a common cathode 7 seg unit.  Do you stil think this is necessary? It seems not form where I sit.

[c4757p]

Yes, it is. Why would you not need it?

[banedon]

I see. The max isn't 10mA for the display and as it's LED it'll try and draw as much as possible. So I need the resistor to limit it to 10mA, yes?