A low-power reconfigurable analog-to-digital converter

A low-power CMOS reconfigurable analog-to-digital converter that can digitize signals over a wide range of bandwidth and resolution with adaptive power consumption is described. The converter achieves the wide operating range by (1) reconfiguring its architecture between pipeline and delta-sigma modes; (2) varying its circuit parameters, such as size of capacitors, length of pipeline, and oversampling ratio, among others; and (3) varying the bias currents of the opamps in proportion to the converter sampling frequency, accomplished through the use of a phase-locked loop (PLL). This converter also incorporates several power-reducing features such as thermal noise limited design, global converter chopping in the pipeline mode, opamp scaling, opamp sharing between consecutive stages in the pipeline mode, an opamp chopping technique in the delta-sigma mode, and other design techniques. The opamp chopping technique achieves faster closed-loop settling time and lower thermal noise than conventional design. At a converter power supply of 3.3 V, the converter achieves a bandwidth range of 0-10 MHz over a resolution range of 6-16 bits, and parameter reconfiguration time of twelve clock cycles. Its PLL lock range is measured at 20 kHz to 40 MHz. In the delta-sigma mode, it achieves a maximum signal-to-noise ratio of 94 dB and second and third harmonic distortions of 102 and 95 dB, respectively, at 10 MHz clock frequency, 9.4 kHz bandwidth, and 17.6 mW power. In the pipeline mode, it achieves a maximum DNL and INL of ±0.55 LSBs and ±0.82 LSBs, respectively, at 11 bits, at a clock frequency of 2.6 MHz and 1 MHz tone with 24.6 mW of power