Hey guys, I could use some assistance. I am trying to get 40mA @ 20V using the LM3410 from USB.
However, by default, USB 2.0 can only deliver 5V @ 100mA, which is 500mW. And, 40mA @ 20V is 800mW. I know by using string descriptors I can get 800mW from USB 2.0. However, I need to understand a bit more about the LM3410 and I could use some help.
The reason I need 20V @ 40mA is to the backlight of an LED display. Here is a link to the LED TFT LCD screen:
https://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.
However, by default, USB 2.0 can only deliver 5V @ 100mA, which is 500mW. And, 40mA @ 20V is 800mW. I know by using string descriptors I can get 800mW from USB 2.0. However, I need to understand a bit more about the LM3410 and I could use some help.
The reason I need 20V @ 40mA is to the backlight of an LED display. Here is a link to the LED TFT LCD screen:
https://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.