ADC Oversampling

Abstract

C2000™ real-time microcontrollers offer analog-to-digital converters (ADCs) that are widely used across numerous applications from controlling motor to reading sensors. There are times when a customer design demands a resolution higher than the ADC of the selected device. This application note describes how an oversampling method can be incorporated to increase ADC resolution past the currently available number of bits. This can help reduce the cost in building a system by utilizing lower resolution ADCs to oversample a signal and obtain a higher resolution result. Detailed instructions are provided and were tested on the TMDSCNCD28P65X device for Software oversampling and Hardware oversampling for the device initialization.

Trademarks

C2000™ is a trademark of Texas Instruments.

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1 Introduction

Analog-to-Digital Converter (ADC) modules have a discrete number of bits available to digitize an analog signal, or resolution. An ideal ADC faithfully reproduces the digitized signal to within the specified resolution. However, in the real world, various electrical imperfections and noise factors contribute to reduce the realized signal resolution below the specified value. The realized signal resolution when these imperfections are considered is referred to as the effective number of bits, or ENOB.

ADC signal oversampling is a technique that can overcome these inherent imperfections, and achieve a higher ENOB than is nominally possible at the baseline for the device. This application report discusses the purpose behind oversampling, and provides the following details of an oversampling example: the theory, the hardware and software setup, and the measured results. The example provided in this application note uses a TMDSCNCD28P65X device for Software oversampling and Hardware oversampling, with a 12-bit ADC.