NCP5050 Ver la hoja de datos (PDF) - ON Semiconductor
Número de pieza
componentes Descripción
Fabricante
NCP5050 Datasheet PDF : 15 Pages
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NCP5050
3000
2500
2000
1500
Switch Current Limit
Setup by RPCA
1000
500
Operating Inductor
Peak Current
0
50
150
250
350
450
Iout (mA)
Figure 21. Inductor Peak Currents Vs. IOUT (mA) for
3 LEDs, (10.5 V @ 350 mA)
3000
2500
2000
1500
1000
500
Switch Current Limit
Setup by RPCA
Operating Inductor
Peak Current
0
50
150
250
350
Iout (mA)
Figure 22. Inductor Peak Currents Vs. IOUT (mA) for
4 LEDs, (14 V @ 350 mA)
3000
2500
2000
1500
1000
500
Switch Current Limit
Setup by RPCA
Operating Inductor
Peak Current
0
25
75
125
175
225
Iout (mA)
Figure 23. Inductor Peak Currents Vs. IOUT (mA) for 5
LEDs, (17.5 V @ 350 mA)
Finally, an acceptable DCR must be selected regarding
losses in the coil and must be lower than 100 mW to limit
excessive voltage drop. In addition, as DCR is reduced,
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
This safety feature is clamping the maximum current
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
IPEAK maximum is 3.0 A, resulting in a minimum resistor
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 RPCA value versus IPEAK_MAX accordingly. By
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.
Table 1. IPEAK_MAX Versus RPCA
IPEAK_MAX (A)
3.0
2.5
2.0
1.5
1.0
RPCA (kW 1%)
2.8
3.4
4.12
5.76
9.09
3500
3000
2500
2000
1500
1000
500
0
1.0
10
100
RPCA (kW)
Figure 24. IPEAK_MAX vs. RPCA
Input and Output Capacitors Selection
COUT stores energy during the TOFF phase and sustains
the load during the TON phase. In order ensure the loop
stability and minimize the output ripple, at least 1.0 mF low
ESR multilayer ceramic capacitor type X5R is
recommended. Increasing the COUT capacitor improved the
output voltage ripple.
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