Current Limiting / Negative Voltage Regulator LM723

[RenE3]

Hi folks,

I'm trying to build a 0 to -15 V power supply with the LM723 but i get stuck trying to use the current limiter that the chip offers, i want a 1A Output,  am i wrong in trying to use the current limiter in that mod. I will prefer not to use a external sensing transistor.

Note: This is my first post and the first time that i use the LM723, is a very good ic but is somehow difficult.

Thanks in Advance,

[danadak]

That regulator will not handle 1A with internal pass transistor, you need
to use external power transistor. The datasheet has a number of externally
boosted circuits for consideration.


http://www.ti.com/lit/ds/symlink/lm723.pdf


Regards, Dana.

[RenE3]

Hi Dana,

Thanks for your post, but i forget to put the picture of my circuit to give a better idea of what i'm doing.


regards,

[RenE3]

I will expand my problem i think it is too ambiguous.

 I'm trying to design a split power supply with a LM723, i already builded the positive one,
my problem is in the negative part, i want a negative supply with a variable voltage of 0 to -15 volts with a current limiter of aproximately 1A, i don't need 1A exactly. I already saw the datasheet but it only gives a figure (figure 18 and figure 23 of the datasheet above) with a pnp external pass transistor, i am not sure but i think that this configuration only gives more current and it will not limit the current.

my circuit is in my first post, i already did physically and it gave me a voltage of  -0.85 to -15 volts but when i turned the potentiometer to it's 0% (as in my circuit) the voltage at the output stays at 0.85v until i turned off and then on the circuit.

another thing , i thought that putting the C.L and C.S pins (figure 19 and 22 of the datasheet) as show in the positives configurations  would limit the current in the negative ones. that's why i was asking for and external sensing transistor.

in resume my questions are:
1) How i get variable negative voltage with the lm723?   (I think that fixed one is easier because the datasheet says the values of R1,R2,R3 and       R4.)
2) It could get current limiter with a negative voltage configuration with the lm723 ?

I will  apreciate if someone know about it.

Regards,