Hi there,
I recently got a LM3410Y in a SOT23-5 package to power an LED back-light of a TFT LCD screen. The screen requires 19.2V @ 40mA for 12 LEDs. There no mention of forward voltage for each LED in the datasheet.
Here is a link to the LM3410Y datasheet:
http://www.ti.com/product/lm3410
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Here is a link to the LED TFT LCD screen:
http://www.newhavendisplay.com/nhd43480272efatxlt-p-5571.html
My Vin is going to be 3.3V @ 100mA and my Vout can be between 19.2 to 22V, so I am going with 20V @ 40mA.
Vin = 3.3V @ 100mA
Vout= 20V @ 40mA
Looking at the datasheet I calculated that the series resistance required is Rset= VFBmax/ ILED => 202mV / 40mA => 5.05 ohms.
To get the inductor value it is D= (Vout-Vin)/Vout => (20V-3.3V) / 20V =>.835
Ts => 1 / fsw => 1 / 525KHz => 1.9048 x 10^-6 seconds or 1.09048us
(525KHz used since this is the LM3410Y and not X)
L = (Vin/ (2*dela IL)) x DTs
delta IL = ??? it is unclear how to obtain this from the graphs and equations shown.
In sum, I am not sure how to calculate the inductor and capacitance values required as this part is a bit confusing to me. If anyone can assist me with trying to figure out how to properly calculate the required inductance and capacitance values it would be much appreciated. Thank you.