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
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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 ..
@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??
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