Power Shift Register: high current SOURCING (?)

Seems all of the Power Shift Registers I find are designed for current sinking.

I'm in need of powering many Bi-Color (3-lead) LED's that all must be wired in parallel. And unfortunately, it seems the huge majority of Bi-Color (3-lead) LED's are COMMON CATHODE.

(so I can't simply SINK current to turn the individual colors on)

So...

Does anyone know of a Power Shift Register that is designed for high-current (ideally 250 mA per pin) and SOURCES current?

actually, I could live with the ability to source up to 100 mA per pin.

Nope. Think the best you can do is roll your own with 74HC595 and current source parts, MIC2981 would be good. http://www.digikey.com/product-detail/en/MIC2981%2F82YN/576-1158-ND/771627

A small logic P-Channel fet could reverses the logic of a low power shift register, and increase LED drive to several amps.

It migh be better to dump the LEDs you have.

Did you look at Adafruit’s NeoPixels.
They also come in the shape of a 5mm LED.
Maybe not a cheapest option @$1.00 each.
Leo…

Wawa: A small logic P-Channel fet could reverses the logic of a low power shift register, and increase LED drive to several amps.

It migh be better to dump the LEDs you have.

Did you look at Adafruit's NeoPixels. They also come in the shape of a 5mm LED. Maybe not a cheapest option @$1.00 each. Leo..

Thanks for the tip, but a little more research on it and according to this tutorial:

I wouldn't actually need logic-level Fets, because my driving voltage would actually be the same level as my logic (3.3V). That's because all of my Bi-Color LED's need to be wired in parallel (wiring them in series is not possible because they share a common cathode).

It seems a Bi-Color LED that share a common ANODE would allow me to use a conventional High Power Shift Register to turn 'em ON/OFF. But unfortunately, Bi-Color common-ANODE LED's are sure rare, and I'd rather not have such a rare item as part of my BOM.

CrossRoads: Nope. Think the best you can do is roll your own with 74HC595 and current source parts, MIC2981 would be good. http://www.digikey.com/product-detail/en/MIC2981%2F82YN/576-1158-ND/771627

I am not familiar with Gate Drivers... a quick google search tells me they are used to drive the gates of Mosfets, which isn't really a problem for me considering if I were to use mosfets, they would only be switching the same voltage as the micro logic (3.3V).

Are you saying I could use Gate Drivers to drive the LED's directly? in other words: Are you saying that combo-ing a conventional low-power Shift-Register with a Gate Driver is basically a High-Power Shift Register (that can actually source current, as opposed to other High Power Shift Registers that can only sink current) ??

Look at the circuit used for high power LEDs you drive the LEd via a transistor which is conneted to the shift reg's output pin.

Mark

holmes4: Look at the circuit used for high power LEDs you drive the LEd via a transistor which is conneted to the shift reg's output pin.

Mark

Thanks Mark. I'm hoping to avoid using transistors since I would need 2 per LED in my circuit. (my 3-lead Bi-Color LED's require parallel wiring, so I can't simply string together a bunch in series and power each string w/ a single Fet)

joshpit2003: I wouldn't actually need logic-level Fets, because my driving voltage would actually be the same level as my logic (3.3V).

That's exactly why you need a logic get. Normal fets need 10volt gate drive.

joshpit2003: I'm hoping to avoid using transistors since I would need 2 per LED in my circuit. (my 3-lead Bi-Color LED's require parallel wiring, so I can't simply string together a bunch in series and power each string w/ a single Fet)

All LEDs (six ?) of one whole segment of the display can be put in parallel, and driven by one mosfet. That is, all the red halfs of a segment need a mosfet, and all the green halfs need another mosfet. Ideally, every LED needs two current limiting resistors. One for red, and one for green. :( Leo..

Have you considered max7219? Each chip could drive 32 of your bi-colour leds. You can string multiple chips off the same 3 Arduino pins.

Paul