8x8 Matrix and TLC5940 current confusion

Other Hardware LEDs and Multiplexing
1

So I'm looking in to building an 8x8 monochrome led matrix, in preparation for a large RGB wall. I plan to use a TLC5940 to drive the rows and columns.

The data sheet says the 5940 can handle either 60ma or 120ma of current. From what I see around the net that is 60/120ma per channel? The way the data sheet is worded would lead me to belive that the 60/120ma is how much current the entire chip can source. I was hoping someone could clear this up for me.

If the 60/120ma figure is shared between all channels, how would one wire a uln2803 to boost current? Usually I would stick the 5940 on the led anodes and the Darlington array on the cathodes, but in a matrix with a row/column multiplex scheme I'm not sure that works...

2

TI list 120 for this chip under "Per Channel Drive (mA)": http://www.ti.com/product/tlc5940

Were you planning to use twelve chips per board so that each LED has a separate PWM output? It's not generally practical to share a PWM output across a scanned matrix.

3

TLC5940 does not source current (to anodes), it only sinks current (from cathodes).
See Fig 22.
So you could perhaps try wiring the outputs to pull gates of p-channel mosfets low, or the bases of pnp transistors.