There was a period of time, thanks to RS232 transceivers with on-chip charge pumps, where we could build many projects with a single 5V supply. Those were the good-old-days.

We are now working on a DSL MODEM design. It has three main components:

1) DSL Framer/DSP chip
2) DSL AFE (Analog Front End) chip
3) FPGA

To power these three parts we need 1.2V, 1.8V, 2.5V, 3.3V and 12V. The input supply voltage is 5V. We needed a six-input voltage supervisor.

I think we are stuck with this mess of voltages for the foreseeable future.