REGISTER | LOGIN
Breaking News
Comments
Newest First | Oldest First | Threaded View
Chuck Sampson
User Rank
Author
Why no PDF?
Chuck Sampson   2/28/2015 11:59:28 AM
NO RATINGS
This is a very interesting and informative article. Why isn't there a PDF option so I can keep it for reference?

ABMorley
User Rank
Author
Re: IR losses in connectors and variable cable lengths still an issue
ABMorley   10/11/2013 4:18:46 AM
NO RATINGS
Whilst everything Teno says is true, quite a common scenario is a USB charger with captive cable - in which case the designer does control the cable resistance.  And if you don't have a captive cable then remote sensing isn't an option anyway.

Entirely true about not being able to rely on much more than 3.3v + LDO drop-out voltage.

Teno
User Rank
Author
IR losses in connectors and variable cable lengths still an issue
Teno   10/10/2013 9:47:18 PM
This isn't a derogatory comment about this tip but one shouldn't think they are getting accurate voltages to the load when remote sensing is not used, even with this tip.

This method only correctly compensates for static cable losses when the cable and contact resistance are known and constant. Unfortunately, especially in USB applications, the cable resistance is typically not constant because different length cables with varying quality can be interchanged. Furthermore, USB applications are often used in mobile applications where the cable is flexed and the contacts have varying strain and therefore varying resistance. 

This point doesn't critisize the tip or make it any less valid. It should serve as a warning to USB device designers to avoid pushing the designs to the limit because USB has very poor power regulation because it doesn't use remote sensing. I would design devices powered by USB to run from a 3.3V or less power supply regulated off the 5V USB voltage or if 5V is required use a buck/boost regulator to keep the voltage at 5V. Don't depend on having 5V at the end of a USB cable.



Most Recent Comments
Like Us on Facebook
EE Life
Frankenstein's Fix, Teardowns, Sideshows, Design Contests, Reader Content & More
Martin Rowe

Test Tool Finds Ethernet Wiring Errors
Martin Rowe
Post a comment
When my house was renovated several years ago, I had the electrician install network outlets in numerous places, then run the LAN cables to a wiring closet. But he didn't document the ends ...

Martin Rowe

Local Electronics Store Supplies Engineers and Hobbyists
Martin Rowe
5 comments
Rochester, N.Y. — Tucked away in this western New York city known for its optics is Goldcrest Electronics, a local store that's supplied businesses and individuals with electronic ...

Martin Rowe

How to Transform a Technology University (Book Review)
Martin Rowe
1 Comment
The Presiding Genius of the Place by Alison Chisolm. WPI, Worcester, Mass., 234 pp., 2016. Engineers love to discuss, and often criticize, engineering education. They often claim ...

Max Maxfield

Aloha from EEWeb
Max Maxfield
Post a comment
Just a few minutes ago as I pen these words, I posted this blog about this month's Cartoon Punchline Competition over on EEWeb.com.