Method and apparatus for controlling circuitry with particular application to smartcards

Abstract

A smartcard circuit for control of a near field RF communications chip () of a smartcard () is described. The circuit comprises a primary inductive coupler () for connection to a near field antenna () of a smart card for obtaining an RF electrical signal from the antenna, and a secondary inductive coupler () arranged for inductive coupling with the primary inductive coupler and connected to the chip for provision of the RF electrical signal from the primary inductive coupler to enable the chip to perform near field RF communications for the smartcard. The disclosure also provides switching circuitry () coupled to the secondary inductive coupler and comprising an RF conduction path selectively operable to disable said provision of the RF electrical signal thereby to inhibit the chip from performing near field RF communications. Advantageously the RF conduction path generally is controlled by a transistor () having a drain connected to one plate of at least one capacitor in the RF conduction path wherein a one-way conduction path is arranged so that transmission of RF signal along the RF conduction path causes accumulation of an electrical charge on the one plate of the at least one capacitor via the one-way conduction path.