C8051F35X DELTA-SIGMA ADC USERS GUIDE
Description
AN217
C8051F35 X D E L TA -S I G M A ADC U S E R ’ S G U I D E
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.
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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
AIN+ AINΣ
Voltage Reference SINC 3 Filter Fast Filter
PGA
Σ
Modulator
8-Bit Offset DAC
Figure 1.
ADC0 Block Diagram
MDCLK
÷
SYSCLK
Rev.
0.
2 2/05
Copyright © 2005 by Silicon Laboratories
AN217
AN217
2.
Using the C8051F35x Delta-Sigma ADC
Using delta-sigma ADCs require an understanding of how to properly configure the modulator, use of the digital filter/decimator, and the nature of high-precision measurements of small signal voltages.
Additionally, the C8051F35x family of devices’ ADC provides functions such as calibration and offset adjustment that should be...
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