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This paper presents a prototype analog-to-digital converter (ADC) that uses a calibration algorithm to adaptively overcome constant closed-loop gain errors, closed-loop gain variation, and slew-rate limiting. The prototype consists of an input sample-and-hold amplifier (SHA) that can serve as a calibration queue, a 12-bit 80-MSample/s pipelined ADC, a digital-to-analog converter (DAC) for calibration, and an embedded custom microprocessor, which carries out the calibration algorithm. The calibration is bootstrapped in the sense that the DAC is used to calibrate the ADC, and the ADC is used to calibrate the DAC. With foreground calibration, test results show that the peak differential nonlinearity (DNL) is -0.09 least significant bits (LSB), and the peak integral nonlinearity (INL) is -0.24LSB. Also, the maximum signal-to-noise-and-distortion ratio (SNDR) and spurious-free dynamic range (SFDR) are 71.0 and 79.6dB with a 40-MHz sinusoidal input, respectively. The prototype occupies 22.6 mm2 in a 0.25-μm CMOS technology and dissipates 755 mW from a 2.5-V supply.
Date of Publication: May 2005