A 9-bit 100-MS/s flash-SAR ADC without track-and-hold circuits

A 9-bit 100 MS/s flash-successive approximation register (SAR) analog-to-digital converter (ADC), which is suitable for wireless communication systems, is presented. To reduce the active area and power consumption, front-end track-and-hold circuits in the flash ADCs are substituted by dynamic ones. A variable delay loop for enhancing dynamic performances is also included in the ADC. The prototype was fabricated using a 45 nm complementary metal-oxide-semiconductor technology with an active area of 0.068 mm2. The differential and integral nonlinearities of the ADC are less than 0.94 and 0.66 LSB, respectively. At a 1.0 V supply and 100 MS/s, the ADC achieves a peak signal-to-noise-distortion ratio and spurious-free dynamic range of 51.94 and 65.87 dB, respectively and consumes 6.1 mW with the internal reference buffer.