MAX7221 + Voltage Level Shifter?


I’ve been working (or not as as the case may be) away at a 8x8 matrix powered by a MAX7221. I’ve kind of come unstuck because I think I’ve been a bit ambitious with my power requirements (typical guy - buy the fattest LED’s you can find with out thinking it through!)

I’ve got LED’s with quite a high (fV 3.4-3.8) and I’m having doubts that the 5V supply can drive them all (though it seems to work ok with just a couple of rows wired up).

I’m totally open to the idea that I misunderstood something, but Maxim appear to have an app-note dealing with higher power draw that the 7221 can support ( Their description of the solution assumes rather more knowledge than I have so a translation would be very much appreciated.

Did I mess up entirely with my thinking or are some of these difficulties negated by the use of the 7221?

Thanks in advance