From: Spehro Pefhany
Subject: Re: Complete newbie - about voltage regulator
X-Newsreader: Forte Agent 1.92/32.572
Date: Thu, 09 Jan 2003 21:31:52 GMT
NNTP-Posting-Date: Thu, 09 Jan 2003 16:31:52 EST
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.
>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.
"it's the network..." "The Journey is the reward"
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