I'm looking for a way to switch the LEDs in a 8x8 LED matrix on the high side, so that the LEDs are between the IC and the ground connection. Almost all LED drivers that I found are intended to be used on the low-side with the IC between the LED and ground.
What I'm looking for: Vcc - switch - LED - ground
What's quite common: Vcc - LED - switch - ground
My requirements are:
- each pin should be able to source 20mA
- operating voltage is 3.3V
- LOW on output should bring the pin in high-impedance (not just short to ground)
- constant current circuitry onboard would be a plus, as I could save the resistors
- price is not a major issue
Ideally I'd like to use an 8 or 16 bit shift register with constant current delivery, but much to my surprise those are not very common.
As an alternative I could build a discrete solution with MOSFET arrays, but if there's a more specialized IC for that available I'd prefer a single device over many discrete components.
Any help is highly appreciated.