ncp5050 ON Semiconductor, ncp5050 Datasheet - Page 11

• Manufacturer Part Number: ncp5050
• Description: 4.5 W Inductive Boost Led Driver For Flash And Lcd Backlight
• Manufacturer: ON Semiconductor

losses in the coil and must be lower than 100 mW to limit
excessive voltage drop. In addition, as DCR is reduced,
Figure 23. Inductor Peak Currents Vs. I
Figure 22. Inductor Peak Currents Vs. I
Figure 21. Inductor Peak Currents Vs. I
3000
2500
2000
1500
1000
3000
2500
2000
1500
1000
Finally, an acceptable DCR must be selected regarding
3000
2500
2000
1500
1000
500
500
500
0
0
0
50
50
25
Switch Current Limit
Switch Current Limit
4 LEDs, (14 V @ 350 mA)
3 LEDs, (10.5 V @ 350 mA)
Setup by R
Setup by R
Switch Current Limit
LEDs, (17.5 V @ 350 mA)
75
150
Setup by R
150
PCA
PCA
PCA
I
I
125
I
out
out
out
250
Operating Inductor
(mA)
(mA)
(mA)
Peak Current
Operating Inductor
Operating Inductor
Peak Current
Peak Current
250
175
OUT
350
OUT
OUT
(mA) for 5
(mA)
(mA) for
225
http://onsemi.com
for
350
450
NCP5050
11
overall efficiency will improve. Some recommended
inductors include but are not limited to:
TDK VLF5012A-2R2M1R5
TDK VLF5014A-2R7M1R5
TDK RLF7030T-3R3M4R1
Switch Current Limit
allowed in the inductor according to external RPCA resistor,
which is connected between PCA input and the ground. This
allows the user to reduce the peak current being drawn
according to the application's specific requirements. The
I
value of 2.8 kW. After selecting the switch current limit in
section above, please refer to Table 1 or Figure 24 below to
choose R
limiting the peak current to the needs of the application, the
inductor sizing can be scaled appropriately to the specific
requirements. This allows the PCB footprint to be
minimized.
Input and Output Capacitors Selection
the load during the T
stability and minimize the output ripple, at least 1.0 mF low
ESR
recommended. Increasing the C
output voltage ripple.
PEAK
Table 1. I
This safety feature is clamping the maximum current
3500
3000
2500
2000
1500
1000
C
500
OUT
0
1.0
maximum is 3.0 A, resulting in a minimum resistor
multilayer
I
stores energy during the T
PEAK_MAX
PCA
PEAK_MAX
Figure 24. I
3.0
2.5
2.0
1.5
1.0
value versus I
(A)
ceramic
Versus R
ON
PEAK_MAX
phase. In order ensure the loop
R
PCA
PEAK_MAX
10
capacitor
OUT
PCA
(kW)
OFF
vs. R
capacitor improved the
R
PCA
phase and sustains
PCA
accordingly. By
4.12
5.76
9.09
type
2.8
3.4
(kW 1%)
X5R
100
is