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Part Name

Description

Manufacturer

AN217

C8051F35X DELTA-SIGMA ADC USER’SGUIDE

Silicon Laboratories 

AN217

C8051F35X DELTA-SIGMA ADC USER’S GUIDE

Relevant Devices

This application note applies to the following devices:

C8051F350, C8051F351, C8051F352, C8051F353

1. Introduction

Delta-sigma analog-to-digital converters (ADCs) are oversampling ADCs: to reduce noise and analog front-end

circuit cost and complexity, they sample signals at very high rates and produce a low-noise, high-resolution output.

Oversampling at a “high” rate means sampling a signal at a frequency that is well above the bandwidth of interest’s

Nyquist rate and is done to lower in-band noise. The output word rate of the ADC will be close to the bandwidth of

interest.

Delta-sigma ADCs also add benefit by shaping noise and digitally filtering the information to enhance performance.

The oversampling, noise shaping, and digital filtering allow highly linear, high-resolution signal measurements, and

reduce the cost and complexity of circuits that must filter the signal at the input of the ADC.

Delta-sigma ADCs oversample a signal and produce relatively low output data rates and are best used in

applications requiring high precision measurements (16 to 24 bits) of low-bandwidth signals (i.e., typically 20 kHz

or less). Example applications include digital phones, temperature measurements, pressure measurements, and

weigh-scales. The maximum C8051F35x ADC output word rate is 1 kHz.

AV+

Input

Buffers

Voltage

Reference

AIN+

AIN-

Σ

Σ

PGA

Modulator

SINC3

Filter

Fast

Filter

8-Bit

Offset

DAC

Figure 1. ADC0 Block Diagram

÷ SYSCLK

Rev. 0.2 2/05

Copyright © 2005 by Silicon Laboratories

AN217

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