Current booster for PC card

An integrated circuit card, such as PC Card, is provided in which a step-down converter in the form of a switching regulator provides a stable operating voltage at increased current beyond what is normally available from a single source. In particular, a quiet and stable power supply is obtained by modifying the standard configuration of a switching regulator such that the catch diode, or free-wheeling diode, instead of being connected to ground at the non-blocking terminal, is connected to a primary voltage source approximating the desired output voltage. If the desired output voltage is 5V, for example, the catch diode may be connected to Vcc supplied by a PC Card slot, which nominally supplies 5V. The block terminal of the catch diode is connected through the switch of the switching regulator to a higher, supplementary, voltage source, e.g. Vpp=12V in the case of a PC Card slot. During operation of the integrated circuit card at lower power levels, the primary voltage source is able to supply substantially all of the required power, such that the switch of the switching regulator may remain predominantly open, minimizing switching noise. During operation of the integrated circuit card at higher power levels, the switching regulator boosts the output voltage just enough to compensate for voltage droop. The integrated circuit card is therefore supplied with a stable, low-noise source of power.