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A 10-bit, 20–30 MSPS CMOS Subranging ADC with 9.5 Effective Bits at Nyquist

  • Brian Brandt
  • Joseph Lutsky

Abstract

A CMOS subranging ADC incorporates several features to enhance performance and reduce power dissipation. The combination of an extended settling period for the fine references, absolute-value signal processing, and interpolation in the comparator banks alleviates the principal speed-limiting operation. A front-end sample-and-hold amplifier (SHA) provides sustained dynamic performance at high input frequencies and performs single-ended to differential conversion with a signal gain of two and with low distortion. The SHA holds its differential output for a full clock cycle while it simultaneously samples the next single-ended input, thereby allowing it to drive two comparator banks on consecutive clock phases. The remaining analog circuits are implemented in a fully differential manner. The use of pipelining allows every input sample to be processed by the same channel, thereby avoiding the use of ping-pong techniques, while providing a conversion latency of only two clock cycles. The dynamic performance with a single-ended input approaches that of an ideal 10-bit ADC, typically providing 9.7 effective bits for low input frequencies and 9.5 bits at Nyquist. This performance level is comparable to the best reported for 10-bit CMOS ADCs with differential inputs and significantly better than those with single-ended inputs. The typical maximum DNL is ±0.4 LSB and the maximum INL is ±0.55 LSB without trimming or calibration. At 20 MSPS, the ADC power is 55mW and the SHA power is 20mW from a 5V supply. The active area is 1.6 sq. mm in a 0.5-μm double-poly, double metal CMOS technology.

Keywords

Clock Cycle Input Frequency Differential Output Differential Input Fine Reference 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer Science+Business Media New York 2000

Authors and Affiliations

  • Brian Brandt
    • 1
  • Joseph Lutsky
    • 1
  1. 1.National Semiconductor SalemNew HampshireUSA

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