| A 5V, 20MHz, 10-bits pipeline ADC converter is presented in this paper, following an analysis on various high speed ADC converters. This ADC in front stage of PAL video decoder is used for converting from analog video signal to digital video signal. The converter has a good tradeoff between conversion speed and conversion precision. It is a 1.5-bit per stage with 9 stage and digital correction technique. The sampling and holding circuit at the input and operation transconductance amplifier are used in same common input and output voltages so this converter can be conveniently reused as module in video process system. High speed, high gain and large swing are achieved by a single stage folded cascade OTA consuming very low power. The large output impedance ensures this architecture a very high DC gain. Simulation results show that our fully differential OTA is more excellence than the traditional one in size, power consumption and settling time. A dynamic comparator which has no DC power dissipation is used in sub-ADC of gain stage. The layout of the converter is designed in CSMC 0.6μm 2P2M CMOS technology. All the circuit is realized by full custom. The overall size is 1500x1500 μm~2. All modules of this design are simulated individually and the ADC is simulated at system level. The main performance parameters of the design are: 5V supply voltage, 10-bit resolution, 20MHz sample rate,-1V~+1V differential input voltage range. It consumes only 69.4mW working at 5V supply and 20MHz sample rate. The simulation results show that this design has met the requirement of spec. of the video signal converting. |
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