I've got a simple single-digit 7-segment LED working properly (simply using 7 GPIO pins), but I'd like to scale it up to multiple digits and higher power. But I'd like to keep the number of GPIO pins to a minimum to leave some spare for other things.
I've seen a "BCD to 7-segment latch/decoder/driver" IC called a 4511, and this seems able to drive a single digit with a latch. So with 5 GPIO pins I can set a single digit. For four digits it looks like I'd need to either get four of these 4511 chips (total 8 GPIO pins), or I try to re-use the same IC for all four digits (total 9 GPIO pins plus a lot of work for the Pi and maybe flicker too).
I've also seen another "BCD to 7-segment latch/decoder/driver" IC called a 4543, and this seems to do the same thing except it says it's for "high voltage". And lastly I've seen a 16-channel TLC5940 which sounds like it could handle two digits at once, so I'd only need two of these chips (although more complex software to drive it).
There are two kinds of LED I want to drive with this, so it would be good if the solution could handle both. Firstly I want to just drive this tiny 4-digit display, so that's 3V and a few mA, no problem. But I also want to be able to drive some LED strips, and they're 12V with some tens of mA per segment. So whatever chip is driving this LEDs must be able to deal with higher voltages and higher currents, and I need to know how to limit the current properly (or get the driver chip to limit the current) too.
Additional info: The reason I suggested a TLC5940 "16-channel LED driver" for this is because the datasheet specifically says "Input voltage range Vcc = -0.3V to 6V; Output voltage range V(OUT0) to V(OUT15) = -0.3 to 18V", but on further searching there are examples where additional MOSFETs are needed to drive higher voltage LEDs.
I also looked at so-called power transistors instead of MOSFETs (as all the MOSFETs I could find were in single packages, hence lots required), but I read that these transistors were actually Darlington pairs and could generate a lot of heat, whereas MOSFETs are more isolating and hence more efficient.
Size isn't a big issue, but power, heat, cost and number of components are. So after reading about the TPIC6B595 "power logic 8-bit shift register" mentioned below, it seems well able to cope with this problem, and I only need 4 of these 20-pin chips, daisy-chained. And if I understand correctly, the chips will do the latching, so unlike the TLC5940s I don't need to continually provide a (very regular) clock signal to avoid flicker. And if I want to use a 7-segment display it has to be common anode for this to work.
I don't quite understand the output voltage clamp of 50V, can someone confirm that that's not going to be a problem when I plug 12V - resistor - LED - TPIC6B595?