Cirrus-logic AN263 Bedienungsanleitung PDF herunterladen

http://www.cirrus.com

AN263

Audio Conversion Systems Noise Calculations and

Requirements

Steve Green

Technical Marketing Manager

Mixed-Signal Products

1. Introduction

The skills required to predict the dynamic range of a combined Analog-to-Digital converter (ADC) and Dig-

ital-to-Analog converter (DAC) system, as well as determine the noise requirements for the analog input

and output stages, should be considered essential for an audio systems designer. The techniques re-

quired are relatively basic in that they are generally covered in the first analog circuit analysis class in

most engineering programs. However, applying these techniques to the conversion processes often gen-

erates some level of confusion. This discussion will detail the steps required to apply these techniques

and determine this critical system performance parameter.

Figure 1. Conversion System Block Diagram

The ADC and DAC system, Figure 1, contains four primary noise sources that must be considered. These

include the analog input buffer, ADC, DAC and the analog output buffer/ filter stage. Noise generated in

each of these stages adds as the “square root of the sum of the squares” as shown below. This funda-

mental relationship will be used throughout this discussion.

The analysis requires several initial assumptions and setting of limits.

1) The bandwidth is set to 20 kHz. This constraint is purely for convenience and allows the use of a com-

mon converter data sheet specification. The results can easily be scaled to other bandwidths as long

as assumption #2 remains valid.

2) The spectral content of the noise is “white”. This assumes that the contribution of 1/f noise is negligible

and the noise sources within the converters remain “white” to the upper limit of the analysis. A word

Buffer DACADC Filter

total

+++=

Oct ‘04

AN263REV1

1 2 3 4 5 6 7 8 9 10

Inhaltsverzeichnis

Seite 1 - Requirements

Seite 2 - ) or output (V

AN26310 AN263REV1Revision Date Changes1 18 Oct 2004 Initial ReleaseContacting Cirrus Logic SupportFor all product questions and inquiries contact a Ci

Seite 3 - AN263REV1 3

AN2632 AN263REV1of warning, the spectral noise content of digital-to-analog converters often do not retain this charac-teristic at bandwidths well bey

Seite 4 - 4 AN263REV1

AN263AN263REV1 3 Figure 2. Effective Conversion System Gain2.3 Equivalent System Noise CalculationThe output referred system noise voltage (Vnsys) c

Seite 5 - AN263REV1 5

AN2634 AN263REV12.4 System Dynamic Range CalculationThe un-weighted system dynamic range (in dB) can be calculated using the equation for the equival

Seite 6 - 6 AN263REV1

AN263AN263REV1 53.1 Generalized Noise ErrorIt is very informative to create a generalized noise relationship and a “rule-of-thumb” design goal such t

Seite 7

AN2636 AN263REV1 Figure 4. Normalized Noise Error - Wide View Figure 5. Normalized Noise Error - Zoomed View0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

Seite 8 - 8 AN263REV1

AN263AN263REV1 73.1.1 Illustrative Noise Budget CalculationLet's calculate the required buffer noise for the CS5381 to meet the assumption of n

Seite 9 - 4. Conclusion

AN2638 AN263REV1 Figure 6. System vs. DAC Dynamic Range - 10K Filter Figure 7. System vs. DAC Dynamic Range - 1K Filter100 105 110 115 120 125 1301001

Seite 10 - 1 18 Oct 2004 Initial Release

AN263AN263REV1 9Figure 7 displays a similar series of plots where the filter/ buffer circuit has been redesigned to scale theresistors to 10% of the p

Kommentare zu diesen Handbüchern

Keine Kommentare

Cirrus-logic AN263 Bedienungsanleitung

Stöbern Sie online oder laden Sie Bedienungsanleitung nach Hardware Cirrus-logic AN263 herunter. Cirrus Logic AN263 User Manual Benutzerhandbuch

Inhaltsverzeichnis

Kommentare zu diesen Handbüchern

Verwandte Produkte und Handbücher für Hardware Cirrus-logic AN263