From: Zalek Bloom
Subject: Re: Complete newbie - about voltage regulator
X-Newsreader: Forte Agent 1.92/32.572
Date: Fri, 10 Jan 2003 00:36:57 GMT
NNTP-Posting-Date: Thu, 09 Jan 2003 19:36:57 EST
Organization: Road Runner - NYC
On Thu, 09 Jan 2003 21:31:52 GMT, Spehro Pefhany
>On 9 Jan 2003 13:04:44 -0800, the renowned firstname.lastname@example.org
>(Zalek Bloom) wrote:
>>I built an external battery pack for my PDA. My PDA has built-in 1000
>>mAh battery, and I built an external battery pack composed from 4 AA
>>1.2V, 1800mAh batteries - so I have exactly 5V. I am thinking about
>>using sometimes 4 regular AA alkaline batteries, but a regular
>>alkaline battery has 1.5V, so my pack will have 6V.
>>Can you give me a name/type of a simple voltage regulator that has an
>>input of 5 -12 Volt and an output of exactly 5V?
>Do you know how much current it draws? Or to put it another way,
>with the backlight (if any) on etc. what is the shortest time
>it will run from the internal 1000mAh battery? Something like the
>LP3961/4 might do it. The output capacitor size and type is critical
>on this kind of part, and you also need the input cap.
Using it as MP3 player with screen setup to the highest brightness I
can get over 2 hours of use. What kind of capasitors I need?
>>Another question: if I'll build a pack composed from 8 AA 1.2V,
>>1800mAh batteries (togather 14,400 mAh) and I will use a voltage
>>regulator for 5V - what will be the capacity of my battery pack?
>>14,400 mAh, or some of the capacity will be wasted to keep output of
>If you connect them in series and use a linear voltage regulator,
>you'll get 1800mAh and waste half the energy in the regulator. With
>a switching regulator, it will be closer to double.
That means that using LP3961/4 a I am going to waste energy too?
I didn't understand if a linear or switching regulator is more