Electronics > Projects, Designs, and Technical Stuff
Using an AD584 for a 10.0 Volt 1.0 Amp DC Supply
eevjohn:
Hi all,
I built a DC Supply to give 2.5, 5.0, 10.0 Volts.
I used an AD584JH with a Darlington current boost as per the classic AD Application Notes.
The AD suggested bypass device 2N6040 is a little harder to get, so I used a BDX54 and TIP2955, as a triple Darlington to safely generate over 1.0 amps with ease, and no loading on the 10mA output of the AD584.
For a DC 15V supply I used a 7815 and TIP2955 bypass device to generate 15 V at 1.5 amp without any voltage sag.
I run the whole unit off an external 20V DC 5 amp DC supply.
I came to grief because, although I had 0.1 MFD ceramic bypass caps everywhere, the AD584 was still oscillating at about 250 KHz.
The AD584 was ok at low current outputs of 10mA or less, but operated in a funny mode for higher currents.
Solution was to put a 220MFD to ground on the DC supply to the AD584 on pin 8, which is actually the base of the Darlington chain.
As per the AD Notes, this may not help in all cases; it depends on layout and the loop gain of AD584 and boost Darlington.
Experiment, but have a CRO on the AD584 output.
Now it all works like a charm.
SiliconWizard:
OK, thanks for sharing your experience. A small attached schematic would have been nice to illustrate your project.
:-+
eevjohn:
Here you go.
Roughie cct.
Ysjoelfir:
Nice project, looks quite simmilar to the thing I built with the AD584 some time ago. :) I like the 584, pretty versatile thing and not to expensive.
Would you mind showing an inside photograph? I would be interested how you built it.
Dave:
How exactly is this supposed to provide an accurate current? A reference is not supposed to change its value with respect to load resistance (within reasonable limits).
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