how to use an LT1618

Hi,

hoopa said:

Yes but my input voltage variation isn't that big I don't think it will cause an issue.

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You think .. but you should know. We can't help you with this because we don't know the requirements.
The given input variation is more than 10% .. and I expect the output current variation in the same percentage. For the very most of my designs even 1% would be too high an error.

Klaus

KlausST said:

Hi,

You think .. but you should know. We can't help you with this because we don't know the requirements.
The given input variation is more than 10% .. and I expect the output current variation in the same percentage. For the very most of my designs even 1% would be too high an error.

Klaus

Click to expand...

Indeed i didn't test everything yet so i can't be sure.
My system isn't required to be extremely precise, my biggest issue is autonomy.
If I had to take everything into account I would also have calculated the changes when my LED heats up.


And about the mosfet before the IC controlled by the on/off controller, is it a good idea?

I will try to gather the max infos and and do all the calculations before Monday so i can be ready and test everything.

Hi,

hoopa said:

Indeed i didn't test everything yet so i can't be sure.

Click to expand...

No need to test or calculate.
What I call "requirements" is like the destination of a travel. You first need to know where to go. Then you can decide how you get there. A train may be good idea ... but not when you want to travel to an island.

The same is with the Mosfet. In most cases it is a good idea. So yes, try it.
... but in detail it depends on what exactly you want to achieve.
Example:
Switching On/Off LEDs may be used for dimming ... then I'd use the switch at the output
Switching On/Off LEDs may be used for power saving (night / day) ... then I'd use it at the input of the regulator

Klaus

And about the mosfet before the IC controlled by the on/off controller, is it a good idea?

Click to expand...

As Klaus implied, you can put an NFET in series with the LEDs...and just turn it ON/OFF

Also, attached is a LT1618 in buckboost mode, so you dont need a fet turn off

HV9910B is also a nice simple way of driving leds