The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
Date: Sat, 18 Jan 2003 09:44:25 -0700
From: Jim Drew
User-Agent: Mozilla/5.0 (Windows; U; Win98; en-US; rv:1.0.2) Gecko/20021120 Netscape/7.01
X-Accept-Language: en-us, en
Subject: Re: PIC controlled variable power supply
References: <3E27B2A3.email@example.com> <firstname.lastname@example.org> <3E2830B5.email@example.com> <firstname.lastname@example.org>
X-Comments: This message was posted through Newsfeeds.com
X-Comments2: IMPORTANT: Newsfeeds.com does not condone, nor support, spam or any illegal or copyrighted postings.
X-Comments3: IMPORTANT: Under NO circumstances will postings containing illegal or copyrighted material through this service be tolerated!!
X-Report: Please report illegal or inappropriate use to You may also use our online abuse reporting from: http://www.newsfeeds.com/abuseform.htm
X-Abuse-Info: Please be sure to forward a copy of ALL headers, INCLUDING the body (DO NOT SEND ATTACHMENTS)
Organization: Newsfeeds.com http://www.newsfeeds.com 100,000+ UNCENSORED Newsgroups.
Spehro Pefhany wrote:
>>I was under the impression from the data sheets on the LM317 that the
>>adjust pin can sink up to the output level in current. Normally just
>>resistors are used for the adjustment, and these are required to be
>>values that can handle the power. Is this not correct?
> No. You must sink a minimum current through the load or the output
> voltage may not regulate, see the data sheet, it's a few mA. The 240R
> resistor takes care of that by drawing about 5mA from the regulator
> regardless of output voltage. The adjust pin itself doesn't sink or
> source much current (microamps). So, in this case, the op-amp must
> sink 5ma. In this case we want to cover 5-8 V output. Suppose the
> op-amp covers 1-4V. Then we might make R2 such that the output voltage
> is nominally 5V with 1.5V out, -> R2 is about 430R.
Ok, but 5ma is way to much current draw for idle times. Is there a
specification for the minimum requirement?
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup