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Fixed Voltage Regulator design for battery-powered device
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Alexandros81:
Hi!
I am designing a battery-powered device that consumes roughly at maximum load 300mA.
The battery I am thinking of using is this battery pack -> https://www.ebay.co.uk/itm/12V-3000mAh-Super-Rechargeable-Li-ion-Battery-Pack-Wall-Charger-UK-AU-US-EU-Plug/352353688806?hash=item5209ea9ce6:m:mpG0OmWIHYoYrvrJpgkLAHw:rk:16:pf:0

So I decided to go for this regulator -> https://export.farnell.com/microchip/mic5209-3-3ys/ic-reg-ldo-500ma-1-3-3v/dp/2510236

According to the datasheet my design should be like figure 5. (page 12 of the datasheet) A 0.1uF capacitor between IN and Ground and a 22uF capacitor
(tandalum electrolytic) between OUT pin and Ground.  Am I correct?
In page 10 of the datasheet it is mentioned that the input capacitor should be 1uF if a battery is used.

In my case the battery pack is 12V so according to equation:
 (VIN(MAX)-VOUT(MAX)) x IOUT + VIN(MAX) x IGND

I get a Power dissipation of [(12V-3.3V)x300mA] + (12Vx5mA) = 2.66W
Is it necessary a heat sink?

What if I use a 6V battery pack? then the power dissipation should be 0.87W. For this case no heat sink is required.

Also if I want to use my device for an hour what the minimum mAh value of the battery pack should be if my device consumes 300mA?

Thanks


 
Audioguru:
The battery and charger are extremely cheeeep, Chinese and purchased on ebay.
Beware. Then maybe they will not work properly. (Big explosion then a hot fire!)
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