help on voltage booster

[bent]

Hello,

i,m trying the voltage booster from +24vdc to +48vdc with lm2586
schematic on page 23 : http://www.ti.com/lit/ds/symlink/lm2586.pdf

it's not working normal.... on first start, the output goes to 10vdc and keeps dropping down...
if i keep turning off and on, voltage goes up by +/- 3vdc each time i switch power on/off, so 10vdc, 13vdc, 17vdc , 20vdc, etc... but if i keep on, then voltage drop...

i verify every connection, and seems ok...

idea?

[brett]

Hi
what sort of inductor are you using?
Maybe it's going into thermal or current-limited shutdown? How good is your heatsink?
Do you have a load on it? Resistive or capacitive?
Can you measure the supply current?

[R.G.]

(1) Do you have the disable pin (pin 1) pulled to ground? If not, you can have everything else correct, and it will obediently do nothing.
(2) The voltage on the output should go to your input voltage minus one Schottky diode drop, even if you cut the switching chip out of there. If it does not do this, something is wrong with the wiring from input voltage to the inductor, to the diode, to the output cap.

[bent]

I finally end up buying a complete board on ebay at 6$ ( very less cheaper than me doing one)....

thank's

bent