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This paper proposes a 10-bit mixed current mode low power SAR ADC for sensor node application. The different entities of a successive approximation register (SAR) analog-to-digital converter (ADC) circuit has a hybrid or mixed mode approach i.e.,voltage mode regenerative comparator; mixed SAR logic; and current mode digital-to-analog converter (DAC). The performance limitation of speed and the kick-back noise of a dynamic comparator is resolved using duty cycle controlled regenerative comparator. A mixed mode logic of a SAR is partitioning the design into synchronous ring counter and asynchronous output register. The data shifting of a ring counter is with the common clock tick while the output register exchanged it asynchronously using handshake signals, resulting in a low power SAR. The current mode switching function in a DAC to reduce asynchronous switching effect resulting in a low energy conversion per step. In overall, the proposed mixed SAR ADC consumes a 41.6 W  power and achieves an SFDR 69.3 dB at 10 MS/sec and 1 V supply voltage. It is designed and simulated in the 0.18  m TSMC CMOS process. Index Terms-Successive approximation register (SAR), mixed-mode, current-mode, regenerative-comparator, analog-to-digital-converter (ADC), digital-to-analog converter (DAC).

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A low power regenerative comparator is very useful in Successive Approximation Register (SAR) type Analog to Digital Converter (ADC) for a Wireless Sensor Node (WSN). A regenerative type comparator generates output pulses by comparing input with a reference input. This paper deals with control of a power with an adjustable duty cycle. The regenerative comparator with an adjustable duty cycle and a positive feedback of a latch will help in improving accuracy, speed and also in achieving the less power consumption. The optimum value of a duty cycle is determined with metastability timing constraints. The proposed low power regenerative comparator circuit is designed and simulated by using TSMC 180 nm CMOS technology. The comparator consumes power as low as 298.54 nW with a regenerative time 264 ps at 1 V power supply.