Messages in this thread | | | Date | Wed, 07 Dec 2011 20:01:46 +0200 | From | Denis Kuzmenko <> | Subject | Re: [PATCH] leds: driver for ab5500 high voltage leds |
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On 12/07/2011 04:07 PM, Linus Walleij wrote: > On Sat, Dec 3, 2011 at 11:49 PM, Denis Kuzmenko <linux@solonet.org.ua> wrote: > >> (snip) >>> diff --git a/drivers/leds/leds-ab5500.c b/drivers/leds/leds-ab5500.c >> (snip) >>> +/* >>> + * Driver for HVLED in ST-Ericsson AB5500 analog baseband controller >>> + * >>> + * This chip can drive upto 3 leds, of upto 40mA of led sink current. >> >> Can't get these are High Voltage or High Current LEDs? >> If Voltage why haven't you wrote about supplied voltage but wrote about >> max. current? > > The three channels are indeed high-voltage LEDs, they supply > up to 20V from a supply voltage of some standard mobile handset > battery at say 3.8 V or so. But there is no register to control the > voltage or anything like that. > > My naive understanding is that you set the current limit and then > the HV transformer (I guess this is a buck converter of some kind) > will raise the voltage level until it either (A) cannot raise it any more > at c:a 20V or (b) the current limit is reached. > > I suspect this is because for LEDs of this type you get a > specified current but the voltage just has to be "high enough" > to break through some diode barrier threshold or so. After > that intensity is controlled by limiting the current. > > Does this suffice as explanation...? > > Yours, > Linus Walleij
Yeah, It does, thank you. Does it worth to make additional comment in code to avoid further questions?
-- Best regards, Denis Kuzmenko.
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