If you only need higher voltage and less than 40ma it does not need to be complicated. You only need a driver on the high side (the segments). The digits can continue to connect back to the MAX7219 directly. I have tested using a pair of N-channel MOSFETS. You need two to invert the signal twice.
To make it easier I found a high side driver instead of using 16 MOSFETS. I am using a (TBD62783) with a resistor on each drive line output. I have not built it yet, but I did test using MOSFETS for one segment. If it works like that, then the driver should do the trick.
So far as the ISET resistor, the datasheet indicates to set it to 47K to reduce current draw when you are using an external driver.
