Regulator circuits to generate both 3.3V and 5V outputs from 3.3V or 5V to run computers and RS232 are described.
Many portable microprocessor-based systems use a mix of 3.3V and 5V circuits. Some are still using only 5V and inevitably some systems will end up being solely 3.3V based. If accessories are to be plugged into, or connected to, any of these systems, a voltage conversion/power generation problem presents itself. The circuit shown in Figure 22.1 addresses the situation where either 5V or 3.3V power is available ...