AN217 Datasheet, PDF (1/18 Pages) Silicon Laboratories – C8051F35X DELTA-SIGMA ADC USER’S GUIDE

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