A Logarithmic Compression ADC Using Transient Response of a Comparator


IEICE TRANSACTIONS on Electronics   Vol.E100-C   No.4   pp.359-362
Publication Date: 2017/04/01
Online ISSN: 1745-1353
Type of Manuscript: BRIEF PAPER
logarithmic compression,  ADC,  subranging,  TDC,  latched comparator,  settling time,  

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This paper describes a logarithmic compression ADC using a subranging TDC and the transient response of a comparator. We utilized the settling time of the comparator for a logarithmic compression instead of a logarithmic amplifier. The settling time of the comparator is inversely proportional to the logarithm of an input voltage. In the proposed ADC, an input voltage is converted into a pulse whose width represents the settling time of the comparator. Subsequently, the TDC converts the pulse width into a binary code. The supply voltage of the proposed ADC can be reduced more than a conventional logarithmic ADC because an analog to digital conversion takes place in the time domain. We confirmed through a 0.18-µm CMOS circuit simulation that the proposed ADC achieves a resolution of 11 bits, a sampling rate of 20 MS/s, a dynamic range of 59 dB and a power consumption of 9.8 mW at 1.5 V operation.