mcp1703 voltage regulator

[devil6600]

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

 

[kak111]

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.

 

[devil6600]

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

 

[kak111]

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

**broken link removed**

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.