Dears
Please help check my SCH thanks,Input voltage VDD=12V,LED:5ch, 10 led in series; will use Hybrid Dimming
How to set Vmaxboost and Vminboost for my application:10 led in series within 26V-35V ; Vmaxboost setting main function is as LED-OPEN protection?20% higher than max led voltage is suitable? but what's meaning of Vminboost ? and how to set it?(Vminboost is comfirmed after Vmaxboost setting)
Hi,
Since you use three-resistor method to set the output voltage, you can use equation 6 in the datasheet to set the maximum boost voltage. Then you can get the resistor value of RFB1(R39). Vmaxboost is based on the maximum LED string voltage. 20% higher is suitable. This is also the voltage for LED open string detection.
With the resistor value of RFB1, the minimum boost voltage can be determined with equation 7. Just to ensure that the Vminboost from equation 7 is higher than the minimum LED forward voltage which is 26V.
Regarding the schematic, one problem I can see is there is no sufficient input capacitor in the design. And please check the power rating of the R35. I'm afraid 0603 package is not large enough for the power.
Hi Shirley
Thanks,
Due to Ti's other P/N or other Brand LED/Backlight Driver doesn't mention the "Vminboost", just to set the Vmaxboost as the Open-Protection,
Could you explain the meaning and function of Vminboost value's existence ?thanks
Below is my understanding of "Vminboost value" : "when I(LED current ) decreased lead to total LEDs voltage decreased,then result in trigger LED_DRV_HEADROOM+500mV (not trigger SHORTED _LED_THRESHOLD yet), So Adaptive control step voltage down, actually, it just need to step down to ( Minimum LEDs voltage+HEADROOM), in order to get margin, recommend Vminboost could be less than Minimum LED Voltage"
is my understanding right?
