output current in lm 723 ckt

[arin23]

lm723

i need 3-12v variable dc supply with 100ma as the maximum current , how can i control it using the resistance between CL and CS terminals??? also do i need to give foldback limiting for short ckt protection with so small current?? i have put 3.9 ohm. please

 

[IanP]

lm 723

Open:
**broken link removed**
On Pages 5/6 you will find how to configure and calculate fold-back-current limit ..
And one more thing, as I[knee] depends on the output voltage you have to be aware of the consequences of varying the output voltage on the fold-back current ..

As far as the voltage adjustment is concerned, you have to use fixed voltage divider between the output and In(-) and a potentiometer between Vref, In(+) and GND ..

Rgds,
IanP

 

[arin23]

rsc lm723

@ian
i agree wid u but the problem is that i dont need foldback current limiting in my circuit as its max current is just 100ma and max voltage across external pass transistor is 20v. so max dissipation of just 2watt . why shd then i put foldback current limiting?? if i just put a resistor across CL and CS how can i control the current using that resistor??

 

[IanP]

lm723 current limited

To understad how the LM723 limits the output current using external (Rsc) resitor refer to the internal schematic diagram of the LM723 ..
You will find there a current sense transistor hooked-up between pins CL and CS ..
All what is required is to add an external resistor and it's value can be calculated using a simple formula:
Rsc = 0.6V / Imax
what for 0.1A gives you the value of 6Ω ..
Also, see fig.3 @:
http://www.aimtec.com/site/Aimtec/f...onNotes/external current limiting circuit.pdf

Rgds,
IanP