The ARM7 core requires 1.8 V to operate and the I/O and peripherals requires 3.3 V. The LPC2300 and 2400 series has an on-chip DC-DC converter so only the 3.3 V supply is required as the core power will be supplied by the on-chip DC-DC converter. If the RTC is operated in power down mode, then power needs to be supplied to the RTC as well. To minimize power consumption, the core can be configured with modified clock sources, reconfigured PL values, altered CPU clock divider values, and divided or shut off clocks to individual in-chip peripherals.