LM2596 with soft start

Srdjan Colic

Other Parts Discussed in Thread: LM2596, LM2597, LM22671

Dear TI,

I'm are trying to desing a switching circuit to regulate hight impedance r/c source. i tried with LM2596adj to achieve 6v with 130ma load but it failed because of heavy current startup load. I presume that I need to implement soft start circuit or to change the chip for some other with adjustable soft start. Can you advice additional soft start circuit for LM2596adj or if it's not possible to suggest replacement chip (40v input max load 300ma) with minimum of 0.5sec soft start?

over 11 years ago

0 Frank De Stasi over 11 years ago

TI__Guru 72625 points

The data sheet for the LM2596 shows a way to provice a delayed start funcion.

This may be of some help in your application.

If you need a true soft start then you can use the LM2597; this device has an external soft start feature.

You could also use the LM22671

0 Srdjan Colic over 11 years ago in reply to Frank De Stasi

Prodigy 120 points

Hey Frank, thanks for your prompt response. Unfortunately delayed start didn't worked for my app, so LM2597 looks like a candidate. I can't find info about max soft start time but I wonder is it possible to extend it to 05.-1sec? If yes than i can simply calculate the time by using info of known constant current of 5 μA for charging this capacitor.

0 Frank De Stasi over 11 years ago in reply to Srdjan Colic

TI__Guru 72625 points

Although I have never tried such a long soft start time, it should work.

0 Srdjan Colic over 11 years ago in reply to Frank De Stasi

Prodigy 120 points

Thanks Frank. Looks promising. Best, Srdjan

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LM2596 with soft start