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mcp1703 voltage regulator

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devil6600

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hi
can any one tell me how to calculate capacitance for mcp1703 voltage regulator?
i have tried reading datasheet (page 13-14) but unable to understand how its calculated. i need output to be 3V from a 6v battery.
thanks
 

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kak111

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Data sheet says
• Stable with 1.0 μF to 22 μF output capacitance
If you use battery as source there is no ripple voltage.

Input C = 4.7µF
Output C = 4.7µF

if load current >100mA use output C 10µF
if load current < 20mA use 1...2.2µF

if load is higher frequency circuit f > 100kHz, connect 100nF capacitor ( f > 1MHz 10nF )
parallel to output capacitor.
 
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devil6600

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thanks kak111
can you please tell me how do you calculated 4.7uF
 

kak111

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Here is some calculation models
but they are for rectified power source.
In your case source is battery ie no ripple.

http://www.isce.org.uk/EnotesPDF/ENote%2016.2.pdf

Power Supply Design

Power Supply Integrity

Most important function in this circuit is that capacitors make the power source
circuit act like short circuit for all ac-currents supplied to load circuit.
( from f = 0.......needed fmax. )
If load circuit see power source as Z= 0 ohms, in all load situations
output voltage gonna be stable.
 
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