LM3410XSD/NOPB National Semiconductor, LM3410XSD/NOPB Datasheet - Page 18

• Manufacturer Part Number: LM3410XSD/NOPB
• Description: IC LED DRVR WT/OLED BCKLGT 6-LLP
• Manufacturer: National Semiconductor
• Series: PowerWise®r
• Type: Backlight, OLED, White LEDr

Specifications of LM3410XSD/NOPB

• Constant Current: Yes
• Topology: PWM, SEPIC, Step-Up (Boost)
• Number Of Outputs: 1
• Internal Driver: Yes
• Type - Primary: Automotive, Backlight, Flash/Torch
• Type - Secondary: High Brightness LED (HBLED), OLED, White LED
• Frequency: 1.2MHz ~ 2MHz
• Voltage - Supply: 2.7 V ~ 5.5 V
• Voltage - Output: 3 V ~ 24 V
• Mounting Type: Surface Mount
• Package / Case: 6-LLP
• Operating Temperature: -40°C ~ 125°C
• Current - Output / Channel: 2.8A
• Internal Switch(s): Yes
• Efficiency: 88%
• For Use With: LM3410XSDLEDEV - BOARD EVAL LM3410 BOOST LLP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LM3410XSDTR

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Steady State Analysis with Loss
Elements
Using inductor volt-second balance & capacitor charge bal-
ance, the following equations are derived:
Therefore:
One can see that all variables are known except for the duty
cycle (D). A quadratic equation is needed to solve for D. A
less accurate method of determining the duty cycle is to as-
sume efficiency, and calculate the duty cycle.
I
L1
= (I
I
L2
LED
= (I
and
) x (D/D')
LED
)
FIGURE 15. SEPIC Simplified Schematic
18
SEPIC Converter PCB Layout
The layout guidelines described for the LM3410 Boost-Con-
verter are applicable to the SEPIC OLED Converter. Figure
16 is a proper PCB layout for a SEPIC Converter.
TABLE 3. Efficiencies for Typical SEPIC Applications
V
I
V
LED
I
OUT
IN
η
IN
FIGURE 16. HB/OLED SEPIC PCB Layout
770mA
500mA
2.7V
3.1V
75%
V
I
V
LED
I
OUT
η
IN
IN
600mA
500mA
3.3V
3.1V
80%
V
I
30038559
V
LED
I
OUT
η
30038565
IN
IN
375mA
500mA
3.1V
83%
5V