Patent ID: 7839129

Claim:
An integrated circuit comprising: processing circuitry; a first power supply rail and a second power supply rail respectively coupled to said processing circuitry, electrical power at a power supply voltage difference being supplied to said processing circuitry via said first power supply rail and said second power supply rail; and voltage regulating circuitry, coupled to said first power supply rail and said second power supply rail, configured to regulate said power supply voltage difference, wherein said voltage regulating circuitry comprises: a supply regulating capacitor having a first terminal coupled to said first power supply rail and a second terminal; switching circuitry, coupled to said second terminal, said second power supply rail and a third power supply rail, configured to selectively couple said second terminal to one of said second power supply rail and said third power supply rail such that: (i) when said second terminal is coupled to said second power supply rail, charge accumulates within said capacitor; and, (ii) when said second terminal is coupled to said third power supply rail, said charge accumulated within said capacitor is supplied to said first power supply rail; and voltage difference sensing circuitry, coupled to said first power supply rail and said second power supply rail, configured to sense said power supply voltage difference, said voltage difference sensing circuitry, responsive to said power supply voltage difference falling below an undershoot threshold level, configured to control said switching circuitry to couple said second terminal to said third power supply rail so as to regulate said power supply voltage difference against undershoot.