I'm looking to buy a few LED Driver IC's for an 11*11 LED Bi-color display. Here is what I need:
Have you considered the Microchip MCP23017 (I2C) or MCP23S17 (SPI) IO extenders ? Each chip has two independent 8-bit I/O ports.
Don
Common cathode LEDs are not very common and so not many chips are designed to drive them.
what is the minimum mA's "THIS LED" can use?
There is no minimum, the smaller the current the dimmer it is but you will always get some photons out of it for some current through it.
Grumpy_Mike:
Common cathode LEDs are not very common and so not many chips are designed to drive them.
Really? That is all i seem to find when I look at bi-color & RGB LEDs...
[quote author=TECH GEEK link=topic=62178.msg450397#msg450397 date=1306359864]
Grumpy_Mike:
Common cathode LEDs are not very common and so not many chips are designed to drive them.
Really? That is all i seem to find when I look at bi-color & RGB LEDs...[/quote]
What do you expect - he drives on the wrong side of the road, his light switches are upside down, his electrical outlets have too much voltage and low frequency, and he spells some words wrong. Actually I think Mike is referring to 7-segment LED displays not bi-color LEDs.
Don
and he spells some words wrong
Who invented the language? 
Actually I think Mike is referring to 7-segment LED displays not bi-color LEDs.
No, why do you think there are very few common cathode LED drivers? The reason is that traditionally you always had a greater current sink capacity from logic gates than current source. So it made sense to drive them with current sinking. This is no good for driving common cathode LEDs.
his light switches are upside down
I didn't know that.
No matter how hard the U.S try we will always be at least 5 hours ahead of you. 
I don't know we are talking about common anode when the led the subject is about is common cathode...
Still want a good led driver IC
I think I will revise what I need from the driver:
I'm not sure it meets all your requirements but the MAX7219 / MAX7221 will allow you to drive 64 LEDs (32 Bi Colour C/C LEDS). You can chain them but depending on your update rate that may not be suitable.
sixeyes:
I'm not sure it meets all your requirements but the MAX7219 / MAX7221 will allow you to drive 64 LEDs (32 Bi Colour C/C LEDS). You can chain them but depending on your update rate that may not be suitable.
what do u mean by the update rate?
It needs to be controlling a 111111 Bi-color LED cube... with only one layer on at a time. (121 Bi-color LEDs max on at any time)
so it would need to cycle between 11 to 22, (22 layers if i have only one color per layer on at a time,)
layers at a rate that the human eye will see no flickering... 40Hz???? I don't know for sure...
The MAX7219/MAX7221 is controlled by sending a 16 bit command to the chip. If you want individual control of each LED you're going to have to send one command per LED. If you have 242 LEDs and 40Hz that means ~ 10,000 updates a second, so you've got lots of time. There is a library to drive the chip although I've not used it (yet).
although I've not used it (yet).
That is quite clearbfrom this rubbish
If you want individual control of each LED you're going to have to send one command per LED.
no you don't.
This chip is totally unsuitable for the op
This chip is totally unsuitable for the op
Totally unsuitable seems harsh. It will drive common cathode LEDs. What makes it so totally unsuitable?
What makes it so totally unsuitable?
OK maybe it is harsh but I think it is true, the OP said:-
I'm looking to buy a few LED Driver IC's for an 11*11 LED Bi-color display.
That chip handles an 8 X 8 matrix for a single colour. So how are you going to extend it to handle an extra 3 columns and rows and an extra colour? It's internal memory is only 8 X 8.
So how do you propose using that chip for this situation?
and be @ a reasonable price
This is an expensive chip, are you suggesting that he uses three of them?
That chip handles an 8 X 8 matrix for a single colour. So how are you going to extend it to handle an extra 3 columns and rows and an extra colour? It's internal memory is only 8 X 8.
So how do you propose using that chip for this situation?
I was planning to use the chip myself for use with bi colour common cathode LEDs. That's why I posted when no one else had suggested anything. If you have 4 LEDs per bank and 8 banks per chip. I was imagining that he would need 4 chips.
This is an expensive chip, are you suggesting that he uses three of them?
Depends where you source them. I bought 5 on ebay from Hong Kong for < £10. But I agree if you're buying from Farnell / RS it's way too expensive.
I was imagining that he would need 4 chips.
yeah except every single cathode is connected to ground, so no columns or rows, just 121 or 242 pins to control...
yeah except every single cathode is connected to ground, so no columns or rows, just 121 or 242 pins to control...
Well as Mike pointed out there aren't many chips to drive common cathode LEDs and they can be pricey.
If you want to drive the LEDs using the MAX7219 you'd need to connect 32 LEDs to each chip. You will get individual control over each LED, it's just that the chip does not have 64 pins.
The chip is designed to drive seven segment displays but you can use it to control 64 LEDs or 32 BiColour LEDs.
OK but I only saw 2 sets of 8 output pins... 2*8=16 right? not 32... how am i to wire a 32 LEDs if i can't use ground as a controllable pin?
It's a matrix chip, 8 * 8 = 64.
You don't connect the common cathodes to ground. You connect them to the anodes to SEG A-G/DP pins and the cathodes to DIGIT 0-7 pins.
If you imagine a chess board, the SEG pins connect to the rows and the DIGIT pins connect to the columns. You place you LED in each square connected between the two lines.
yeah but it's one of 11 layers... so all the cathodes per layer need to be connected to make it a layer, and in addition I already have soldered the cube up..
In that case Mike was right "totally unsuitable".