LT3081 Current Limit Not Adjustable via Ilim Resistor in Portable DC Bench Supply?

In the Portable DC Bench Power Supply circuit given, as per the data sheet of LT3081 output current can be controlled by varying the Ilim resistor, but the current cannot be changed by the resistor. What is the reason, give a solution?

Hi Anila,

How are you?

The Ilim resistor specifies the current limit of the output.

It does NOT function as a variable current source.

The output current is changed because of your load.


Hope this helps.

Warm Regards,

Justin




P.S. I see you're using Altium Designer. Why not use Eagle?

Hi Justin
The circuit is from " http://cds.linear.com/docs/en/lt-journal/LTJournal-V24N2-02-df-BenchSupply-Szolusha.pdf " according to the paper once the current limit is set, output voltage should not change, as the load vary from the 0A to the Ilim . But it doesn't work so. I couldn't set the output current by the Ilim resistor.

Did you build the circuit up slowly, checking that each sub section worked. If you didn't, you are probably going to end up with problems. Just try simulating one LT3081, and verify that it functions as it should, i.e. that the model supplied by LT actually works. The simulation times for the full circuit will be horrendous I would have thought, so the need to break it down becomes important. You can check the switcher separately, and supply a voltage to the feed back circuitry to verify that it tracks a few volts above the output voltage.
Cheers,
Richard

Hi.
When you say it doesn't work, do you mean the output voltage is changing when you vary the load? (maybe the set output current is exceeding the rated power the parallel regulators could deliver, it also does happen when you observe the load regulation of regulators)

Anyway, I'm not really sure I'm helping. I'm not an expert in this kind of thing.

I think Richard's suggestion is more sensible.
Good luck.

Warm Regards,
Justin