An identification (ID) tag includes a substrate having an input capable of receiving a
high frequency signal. For instance, the
high frequency signal can be a
radio frequency (RF)
signal that is generated as part of a
radio frequency (RF) ID
system. A first
charge pump is coupled to the input and is configured to convert the
high frequency signal to a substantially
direct current (DC)
voltage. A
data recovery circuit is coupled to the input and is capable of recovering data from the high frequency signal. A back scatter switch is coupled to the input and is capable of modifying an impedance of the input, responsive to a
control signal. A state
machine is disposed on the substrate and is responsive to the data recovered by the second
charge pump, where the state
machine is capable of generating the
control signal for the back scatter switch in response to the data. The
DC voltage from the first
charge pump is capable of providing a
voltage supply for at least one of the
data recovery circuit, the back scatter switch, and the state
machine. The
data recovery circuit includes a second charge pump that is capable of operating on the high frequency signal simultaneously with the first charge pump. In other words, the first charge pump can generate the supply
voltage for the ID tag from the high frequency signal, while the second charge pump simultaneously retrieves the data from the high frequency signal. The first charge pump also includes a means for limiting the amplitude of the
DC voltage by reducing the charge pump efficiency, once a
threshold voltage is reached.