Patent ID: 7468624
Filing Date: 2008-12-23
Classification: G05F

Abstract:
1. A step-down power supply for lowering an external power supply voltage with respect to a ground voltage to generate an internal power supply voltage equal to a reference voltage and providing the internal power supply voltage to a load in a semiconductor chip, the step-down power supply receiving a chip activation signal indicating activation of the semiconductor chip preparatory to activation of the load, the step-down power supply comprising: an internal power supply node through which the internal power supply voltage is provided to the load; a control node; a differential amplifier having an output terminal connected to the control node, for comparing the internal power supply voltage with the reference voltage and adjusting a voltage of the control node when the internal power supply voltage differs from the reference voltage; a driver having an input terminal receiving the external power supply voltage, a control terminal connected to the control node, and an output terminal connected to the internal power supply node, for supplying power to the internal power supply node at a voltage lower than the external power supply voltage by an amount responsive to the voltage of the control node; and a leak circuit for supplying the ground voltage to the internal power supply node for a predetermined time in response to the chip activation signal, thereby causing current to leak from the internal power supply node to ground for a first interval before the load is activated, thereby causing the differential amplifier to alter the voltage of the control node in a direction that enables the driver to supply additional current to the internal power supply node, then ceasing to supply the ground voltage to the internal power supply node for a second interval in which the load is activated and draws the additional current.