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PDF NCP5050 Data sheet ( Hoja de datos )
| Número de pieza | NCP5050 | |
| Descripción | 4.5 W Flash White LED Boost Driver | |
| Fabricantes | ON Semiconductor | |
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NCP5050
4.5 W Flash White LED
Boost Driver
The NCP5050 is a high powered fixed frequency PWM boost
converter optimized for constant current applications such as driving
high−powered white LEDs. This device has been designed with
high−efficiency for use in portable applications and is capable of
driving up to 5 high power LEDs in series for camera flash or
flashlight (torch) applications. To support the need of driving the
LEDs in a high current pulse mode for flash as well as a continuous
mode for focus or torch, a control pin and support circuitry is
incorporated which allows the user to program two LED currents. The
both output current are fully configurable via the use of 2 external
resistors and this average current can be reduced by applying a PWM
signal to the CTRL pin up to 50 kHz.
The PWM operates at 1.7 MHz which allows the use of small
inductors and ceramic capacitors. In addition the compensation is
internal to the device which simplifies the design and reduces the PCB
component count. To protect the device cycle−by−cycle current
limiting and a thermal shutdown circuit have been incorporated as
well as output over−voltage and time out protection. The maximum
peak current level of the power switch is adjustable to allow further
system optimization. The NCP5050 is housed in a low profile space
efficient 3x3 mm thermally enhanced WDFN.
Features
• High Efficiency Up to 88% for 2 LED (VF = 3.5 V by LED) at 200 mA
• High frequency Dimming PWM Control
• Maximum Vout of 20 V
• 1.7 MHz PWM DC/DC Converter
• Shut Down Control Facility with True−Cutoff
• Open LED (Output Overvoltage) Protection
• 1.2 s Timer out Function
• Soft Start to Limit Inrush Current
• Small 3x3x0.8 mm WDFN Package
• These are Pb−Free Devices
Typical Applications
• White LED Flash (Camera Phone, Digital Still Camera,
Personal Media Player)
• Portable Flash Lights
• Medium Size LCD Backlight (See Application Note AND8294/D for
Details)
2.7 to 5.5 V
C1
4.7 mF
9 PVIN
L1
2.2 mH
SW 10
D1
D2
C2
1 mF
R1
2.8 k
ENABLE
FLASH/
TORCH
5 PCA
3
4
CTRL
HCM
NCP5050
2.0 R2
RHCS
VS 2
FB 7
R3
RLCS 10.0
L1: TDK VLF5012T−2R2
D6
D1: ON MBR130LSF
C1: 4.7 mF 6.3 V 0603
TDK C1608X5R0J475M
C2: 1 mF 25V 0805
TDK C2012X5R1E105M
Figure 1. Typical Application Circuit
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MARKING
DIAGRAM
WDFN10, 3x3
CASE 522AA
ISSUE A
5050
ALYWG
G
A = Assembly Location
L = Wafer Lot
Y = Year
W = Work Week
G = Pb−Free Package
(Note: Microdot may be in either location)
PIN CONNECTIONS
PGND 1
VS 2
CTRL 3
CM 4
PCA 5
10 SW
9 PVIN
8 LCS
7 FB
6 HCS
(Top View)
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 13 of this data sheet.
© Semiconductor Components Industries, LLC, 2010
December, 2010 − Rev. 1
1
Publication Order Number:
NCP5050/D
1 page  
NCP5050
ELECTRICAL CHARACTERISTICS Minimum and Maximum Limits apply for TA between −10°C to +85°C and VIN between 2.7 V
to 5.5 V (Unless otherwise noted). Typical values are referenced to TA = +25°C and Vin = 3.6 V (Unless otherwise noted)
Characteristics
Symbol
Min Typ Max Unit
Operating Power Supply
Maximum Inductor Current (Notes 9 and 11) (see Figure 24)
Refer Switch Current Limit section @ 25°C
Vin 2.7 − 5.5 V
IPEAK_MAX
1.0
−
3.0
A
Power Switch ON Resistor
TA = 25°C (I = 100 mA)
SWRDSON
−
200
−
mW
High Current Sense Switch ON Resistor (I = 100 mA and 25°C)
HCSSRDSON
−
250
−
mW
Low Current Sense Switch ON Resistor (I = 100 mA and 25°C)
LCSSRDSON
−
750
−
mW
PWM Oscillator Frequency
FOSC
1.48 1.7 1.95 MHz
Maximum Duty Cycle
MDUTY
91.5 94
−
%
Efficiency (Notes 9 and 10)
EFF 85 90
%
Over−voltage Clamp Voltage
OVPON 20 − − V
Over−voltage Clamp Hysteresis
OVPH
− 1.0 −
V
Output power (Notes 9 and 12)
@ Vin = 3.3 V
@ Vin = 2.7 V
Pout
W
4.5 −
−
2.8 −
−
Feedback Voltage Ripple Rejection @ Iout = 20 mA
From DC to 300 Hz (0.2 VPP) (Note 9)
LREG
5.0 2.5
mV
Feedback Voltage in Steady State.@ TA = 25°C
FBV 215 250 285 mV
Input Feedback Current (CM = Low)
IFB − − 0.15 mA
Vin
Undervoltage Lockout
Vin Decreasing
UVLO
2.0
V
2.7
Undervoltage Lockout Hysteresis
UVLOH
− 100 − mV
Standby Current, Iout = 0 mA, CTRL = Low, Vin = 4.2 V @ TA = 25°C
ISTDB
− − 2.0 mA
Quiescent Current, Iout = 0 mA, Not Switching @ TA = 25°C
IQNOSW
−
− 2.0 mA
Startup Time (Note 9)
From CTRL =1.2 V to Start of Switching
STRT
− 50 200 ms
Inrush Peak Current Limit (Note 9)
Time Constant
IPCL
− 1 − ms
Upper Limit of PWM Dimming Frequency (Note 9)
DIM − − 50 kHz
Time out Protection (Note 9)
TOUT
−15% 1.2 +15%
s
Thermal Shutdown Protection (Note 9)
TSD
− 160 −
°C
Thermal Shutdown Protection Hysteresis (Note 9)
TSDH
− 20 − °C
Voltage Input Logic Low (Pin CM, CTRL)
VIL − − 0.4 V
Voltage Input Logic High (Pin CM, CTRL)
VIH 1.2 − − V
CTRL and CM Pin Pulldown Resistance
RPLD
175 250 375 kW
9. Guaranteed by design and characterized
10. Efficiency is defined by 100 * (Pout / Pin) at 25°C
Vin = 4.2 V, L = TDK VLF5014A−2R7M1R5
Load = 80 mA, 4 LED (VF = 3.5 V per LED, Cout = 1 mF X5R
11. The overall tolerance is dependent on the accuracy of the external resistor. A 1% tolerance metal film resistor is recommended to achieve
IPEAK_MAX $20 % accuracy.
12. With Schottky diode MBR130LSF and TDK VLF5014A−2R7M1R5 inductor.
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5
5 Page 
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
RPCA (kW)
Figure 24. IPEAK_MAX vs. RPCA
100
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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11
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| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet NCP5050.PDF ] | |
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