Patent ID: 7262631

Claim:
A voltage level control device for controlling a voltage level supplied from a first voltage level source to circuitry, said voltage level supplied having one of at least four voltage levels, said circuitry being arranged between said first voltage level source and a second voltage level source, said first and second voltage level sources being operable to output different voltage levels; said voltage level control device comprising: a power transistor connected between said first voltage level source and said circuitry, said power transistor comprising a sleep signal input operable to receive a sleep signal; at least two switching devices connected in parallel with said power transistor and comprising at least two sleep signal inputs operable to receive at least two pseudo sleep signals; said voltage level control device is responsive to said sleep signal and said at least two pseudo sleep signals to output to said circuitry an output voltage said output voltage comprising one of said at least four voltage levels, said at least four voltage levels lying between voltage levels output by said first and second voltage sources; said at least four voltage levels comprise a first voltage level substantially equal to or approaching said voltage level of said first voltage source; a second voltage level substantially equal to or approaching said voltage level of said second voltage source; and at least two intermediate voltage levels, said at least two intermediate voltage levels lying between said first and second voltage levels; wherein said voltage level control device is responsive to said sleep signal having a first predetermined value to turn said power transistor on and to output said first voltage level, and said sleep signal having a second predetermined value to turn said power transistor off and in response to said first and second pseudo sleep signals having first predetermined values to turn said two corresponding switching devices off and to output said second voltage level; and in response to said first pseudo sleep signal having a further predetermined value and following a voltage across a corresponding first switching device reaching a threshold value of said first switching device to turn said first switching device on and to output said first intermediate voltage level; in response to said second pseudo sleep signal having a further predetermined value and following a voltage across a corresponding further switching device reaching a threshold value of said further switching device to turn said further switching device on and to output a second intermediate voltage level.