A reconfigurable very low-power sensor interface for microwave RFID transponders

DDLA versatile very low-power four-channel sensor interface for active RFID transponders based on an incremental ??-ADC is presented. Each channel has its own switchedcapacitor second-order single-bit ??-modulator. The power consumption can be regulated through variation of the sampling frequency (up to 1MHz), signal bandwidth (8Hz - 16kHz), output resolution (up to 16 bits) and/or output rate. Furthermore, the bias current of all transconductance amplifiers (OTAs) is programmable, thus dynamically exchanging DC-gain, gainbandwidth- product and slew-rate against power consumption. In addition, two channels may be cascaded (2-2 MASH configuration), further incrementing the resolution and/or reducing the number of clock cycles to obtain a particular resolution. The converter is of incremental nature, so that all integrating capacitors are reset and a new conversion is obtained after a minimal number of clock cycles. In order to fit a power budget of maximal 100?W, the power consumption per channel ranges from 10 to 25?W, having a stand-by power drain of some pW.