Method and apparatus for powder management in a multifunction controller with an embedded microprocessor

An apparatus for controlling a power source in an electronic system including a multifunction controller with an embedded microprocessor, the embedded microprocessor normally operating with a first clock signal supplied from a first clock source, the apparatus comprising:

• a second clock source having an output corresponding to a second clock signal, wherein said second clock source includes a ring oscillator and has a lower power consumption level than said first clock source, wherein said second clock source being separately and independently operable from said first clock source, and wherein said second clock source being powered by a standby power supply and said first clock source being powered by a main power supply, such that said standby power supply has a lower current output than said main power supply;
• a power control logic circuit having an input connected to receive an enter sleep mode indication from the microprocessor;
• and
• a clock multiplexer having a first signal input coupled to an output of the first clock source, a second signal input coupled to the output of the second clock source, a select signal input coupled to an output of the power control logic circuit, and an output corresponding to a selected one of the first and second clock signals,
• wherein the clock multiplexer is operative to switch a clock input of the microprocessor from the first clock signal to the second clock signal in response to the enter sleep mode indication, wherein the power control logic circuit is operative to turn off the first and second clock sources after expiration of respective first and second predetermined delays, such that the embedded microprocessor enters said sleep mode.