HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
AnandY
User Rank
Gold
Silicon area
AnandY   6/12/2013 5:22:50 AM
NO RATINGS
In a SCF, capacitors and switches take the place of resistors...

High-value resistors can be implemented in very little silicon area. For example, a 1-Mohm resistor can be realized with a 1-pF capacitor switched at a clock rate of 1-MHz.

AnandY
User Rank
Gold
Capacitor ratios
AnandY   6/12/2013 5:16:08 AM
NO RATINGS
So, for an SCF, the frequency response depends solely on the ratio of two capacitors, C and C1, and the switching-clock frequency, fclk.

@Jon, thanks for the very informative post. Capacitor ratios can take advantage of the superior matching of capacitances fabricated on silicon. Especially in monolithic form capacitor ratios are very robust against changes in temperature.

Jon Titus
User Rank
Blogger
Switched-Cap Filter Applications?
Jon Titus   6/11/2013 5:41:48 PM
NO RATINGS
You will find switched-capacitor filters (SCFs) in audio circuits, in anti-aliasing filters, and in tracking filters. The latter type of filter can track a signal by adjusting the filter's clock frequency to "tune" filter characteristics as a sampled signal changes frequency. You also can use SCFs in tone-detection circuits. Unlike a PLL circuit that requires external passive components (and trimming) to detect a tone, an SCF requires only a clock signal. SCFs also serve as notch filters.

Because the filtering occurs based on a "master" clock signal's frequency, you might consider an SCF is you want to scan a given bandwidth to obtain information within it at certain frequencies.  The SCFs would act like the front end of a spectrum analyzer.

Cabe Atwell
User Rank
Blogger
app
Cabe Atwell   6/11/2013 5:20:43 PM
NO RATINGS
Jon,

Can you suggest some applications for the filter you describe?

C



Partner Zone
Latest Analysis
National Instruments sees 5G WiFi and software-enhanced test equipment as advances that will change technology and business.
The new $120,000 Model S P85D boasts a 221-horsepower front motor and a 470-horsepower rear motor that packs a punch. The car is able to go from 0-60 MPH in just 3.1 seconds … quietly.
The new composites manufacturing innovation center is intended to be a source of grand challenges for industry, like the kind that got us to the moon under JFK. These aren't the words its new CEO Craig Blue used, but that's the idea and the vision behind the Institute for Advanced Composites Manufacturing Innovation (IACMI).
The ideal gas law, first stated in 1834, has suddenly become big news.
Bill Gates took to Reddit for an AMA (Ask Me Anything) and fielded fielded questions on everything from his outlook on the future of technology to who he's rooting for in the Super Bowl.
More:Blogs|News
Design News Webinar Series
12/11/2014 8:00 a.m. California / 11:00 a.m. New York
12/10/2014 8:00 a.m. California / 11:00 a.m. New York
11/19/2014 11:00 a.m. California / 2:00 p.m. New York
2/25/2015 11:00 a.m. California / 2:00 p.m. New York
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Feb 9 - 13, Embedded Development Using Microchip Microcontrollers and the CCS C Compiler
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  67


Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Last Archived Class
Sponsored by Stratasys
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2015 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service