SLAA494B May 2011 – September 2023 MSP430AFE221 , MSP430AFE222 , MSP430AFE223 , MSP430AFE231 , MSP430AFE232 , MSP430AFE233 , MSP430AFE251 , MSP430AFE252 , MSP430AFE253
Figure 4-1 shows a simple capacitor power supply for a single output voltage of 3.3 V directly from the mains voltage of 110/220 VRMS alternating current (ac).
Appropriate values of resistor R22 and capacitor C49 are chosen based on the required output current drive of the power supply. Voltage from the mains is fed directly to an RC-based circuit followed by rectification circuitry to provide a direct current (dc) voltage for the operation of the MSP430. This dc voltage is regulated to 3.3 V for full-speed operation of the MSP430. For the circuit in Figure 4-1, the approximate drive provided approximately 12 mA. If additional drive is required, either an NPN output buffer or a transformer-/switching-based power supply may be used.