ONSEMI NCP5050MTTXG

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
http://onsemi.com
MARKING
DIAGRAM
5050
ALYWG
G
WDFN10, 3x3, 0.5P
CASE 522AA-01
ISSUE A
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
10 SW
VS 2
9 PVIN
CTRL 3
8 LCS
CM 4
7 FB
PCA 5
6 HCS
(Top View)
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
D1
L1
2.2 mH
ENABLE
SW
PCA
VS
3
CTRL
4
HCM
PGND
R1
2.8 k
PVIN
NCP5050
FLASH/
TORCH
2.0
FB
2
7
R2
RHCS
2 to 5 LEDs
5
D2
10
6
8 HCS
LCS
9
1
C1
4.7 mF
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 13 of this data sheet.
C2
1 mF
L1: TDK VLF5012T-2R2
D6
D1: ON MBR130LSF
C1: 4.7 mF 6.3 V 0603
TDK C1608X5R0J475M
C2: 1 mF 25V 0805
R3
RLCS 10.0
TDK C2012X5R1E105M
Figure 1. Typical Application Circuit
© Semiconductor Components Industries, LLC, 2007
October, 2007 - Rev. 0
1
Publication Order Number:
NCP5050/D
NCP5050
90
80
EFFICIENCY (%)
70
Vout = 2 LEDs
(7.0 V @ 350 mA)
60
50
40
30
20
10
Vin = 3.7 V
0
10
100
1000
Iout (mA)
Figure 2. Typical Efficiency
L1
Cin
PVIN
C2
Cout
SW
1
OSC
1.7MHz
10
Thermal
Shut down
2
OVP
VS
PCA
D2
D6
5
R1
2.8k
FB
PWM CONTROLLER
7
CTRL
3
Band Gap
250k
ENABLE
Up to 20 V / 4.5 W
2 to 5 LEDs
C1
4.7 mF 0603
6.3 V
D1
1 mF 0805 25V
2.7 mH
2.7 to 5.5 V
250k
4
CM
FLASH/TORCH
6
HCS
2.0
R2
8
1
RHCS
R3 10.0
RLCS
Figure 3. Simplified Block Diagram
http://onsemi.com
2
PGND
LCS
NCP5050
PIN FUNCTION DESCRIPTION
Pin
Pin
Name
Type
Description
1
PGND
POWER
Power Ground: This pin is the power ground and carries the high switching current. A high quality
ground must be provided to avoid any noise spikes/uncontrolled operation. Cares must be observed to
avoid high-density current flow in a limited PCB copper track.
2
VS
INPUT
Voltage Sense: In order to sense Vout notably for over voltage protection, this input must be
connected to the output bypass capacitor Cout.
3
CTRL
INPUT
Control and Enable: An active high logic level on this pin enables the device. A built-in pulldown
resistor disables the device if the pin is left open. Also in disable condition the device provide a true
cut-off thank to the high impedance on FB input. This pin can also be used to control the average
current into the load by applying a low frequency PWM signal. If a PWM signal is applied, the
frequency should be high enough to avoid optical flicker but be no greater than 50 kHz.
4
CM
INPUT
Current Mode: An active high logic on this input enables the High Current Sense used for flash and
disables the LCS resistor. This pin has a low voltage threshold so it can be driven directly from 1.8 V
logic signals. If this function is not needed, this pin should be grounded. Only when CM pin is high, a
safety function switch off the output if CTRL pin is high longer than 1.2 s
5
PCA
INPUT
Peak Current Adjust: A resistor between this input and ground controls the maximum peak current
allowed in the inductor. The minimum value for this resistor is 2.8 kW and increasing this value
decreases the peak current. This allows the user to adjust the current based on the application needs
and scale the size of the inductor accordingly. See “Switch Current Limit” guidelines in application
section.
6
HCS
INPUT
High Current Sense: This pin is used for Flash Mode. If the user desires two levels of LED current
then a resistor should be connected from this pin to ground. This function is controlled by the CM input.
7
FB
INPUT
Feedback: The reference is 250 mV. This pin provides the feedback voltage by means of the sense
resistors fixed by LCS or HCS pin. When the device is enables and CM low, the LCS resistor is
connected to this pin, thereby the LCS setup the LED current. The tolerance of the LED current is
dependant upon the accuracy of this sense resistor and a $1% metal film resistor, or better, is
recommended for best output accuracy.
8
LCS
INPUT
Low Current Sense: This pin is used for Torch Mode. In order to fix the current when CM logic pin is
low, a resistor should be connected from this pin to ground.
9
PVIN
POWER
10
SW
INPUT
Power Supply: The external voltage supply is connected to this pin. A 4.7 mF / 6.3 V high quality
capacitor must be connected across this pin and the power ground to achieve the specified output
power parameters. The X5R low DC/C versus DC bias ceramic types are highly recommended.
Switch: Power switch connection for inductor. Typical application will use a coil from 2.2 mH - 4.7 mH
and must be capable of handling the peak current.
http://onsemi.com
3
NCP5050
MAXIMUM RATINGS (Note 1)
Rating
Symbol
Value
Unit
PVin
7.0
V
VS
25
V
Human Body Model (HBM) ESD Rating (Note 3)
HCS and FB Pins
ESD HBM
2000
1000
V
Machine Model (MM) ESD Rating (Note 3)
HCS and FB Pins
ESD MM
200
150
V
CTRL, CM
-0.3 < Vin < Vbat + 0.3
1.0
V
mA
WDFN 3x3 Package
Power Dissipation @ TA = +85°C
Thermal Resistance, Junction-to-Case
Thermal Resistance, Junction-to-Air
PD
RqJC
RqJA
(Note 5)
10
(Note 6)
W
°C/W
Operating Ambient Temperature Range
TA
-10 to +85
°C
Operating Junction Temperature Range
TJ
-10 to +125
°C
TJMAX
+150
°C
Storage Temperature Range
Tstg
-65 to +150
°C
Moisture Sensitivity Level (Note 7)
MSL
1
Power Supply Voltage (Note 2)
Over Voltage Protection
Digital Input Voltage
Digital Input Current
Maximum Junction Temperature
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
1. Maximum electrical ratings are defined as those values beyond which damage to the device may occur at TA = 25°C.
2. According to JEDEC standard JESD22-A108B.
3. This device series contains ESD protection and passes the following tests:
Human Body Model (HBM) per JEDEC standard: JESD22-A114 for all pins.
Machine Model (MM) per JEDEC standard: JESD22-A115 for all pins.
4. Latch up Current Maximum Rating: $100 mA per JEDEC standard: JESD78.
5. The thermal shutdown set to 160°C (typical) avoids irreversible damage on the device due to power dissipation.
6. For the 10-Pin 3x3 WDFN Package, the RqJA is highly dependent on the PCB heat-sink area. For example, RqJA can be 61°C/W for 2 layers
board having 51 mm2 dissipation area on circuit side and board size ground plane on other side.
7. Per IPC/JEDEC standard: J-STD-020A.
8. The maximum package power dissipation limit must not be exceeded.
Pd +
125 * T A
R qJA
http://onsemi.com
4
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
Vin
2.7
-
5.5
V
Maximum Inductor Current (Notes 9 and 11) (see Figure 24)
Refer Switch Current Limit section @ 25°C
IPEAK_MAX
1.0
-
3.0
A
Power Switch ON Resistor
TA = 25°C (I = 100 mA)
SWRDSON
200
-
Operating Power Supply
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
FOSC
1.48
1.7
1.95
MHz
MDUTY
91.5
94
-
%
PWM Oscillator Frequency
Maximum Duty Cycle
Efficiency (Notes 9 and 10)
EFF
85
90
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
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
FBV
215
250
285
mV
IFB
-
-
0.15
mA
Over-voltage Clamp Voltage
Feedback Voltage in Steady State.@ TA = 25°C
Input Feedback Current (CM = Low)
%
W
mV
Vin Undervoltage Lockout
Vin Decreasing
UVLO
V
Undervoltage Lockout Hysteresis
UVLOH
-
100
-
2.0
2.7
mV
ISTDB
-
-
2.0
mA
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
Standby Current, Iout = 0 mA, CTRL = Low, Vin = 4.2 V @ TA = 25°C
Quiescent Current, Iout = 0 mA, Not Switching @ TA = 25°C
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.
http://onsemi.com
5
NCP5050
TYPICAL OPERATING CHARACTERISTICS
1200
1000
1000
800
800
Iout (mA)
Iout (mA)
Vin = 4.2 V
600
Vin = 3.8 V
Vin = 3.3 V
400
2 LEDs
600
3 LEDs
4 LEDs
400
200
5 LEDs
200
Operating Area
0
2.5
0
5
10
15
20
25
3.5
4.0
4.5
5.0
5.5
Vin (V)
Figure 4. Maximum Output Current Available
vs. Vout
Figure 5. Typical Maximum Output Current vs.
Input Voltage, L = TDK VLF5014A-2R7M1R5
(Note 13)
90
90
80
EFFICIENCY (%)
80
EFFICIENCY (%)
3.0
Vout (V)
Vin = 5.0 V
Vin = 4.2 V
70
Vin = 3.7 V
Vin = 3.3 V
60
Vin = 5.0 V
Vin = 4.2 V
70
Vin = 3.7 V
60
Vin = 3.3 V
50
10
100
Iout (mA)
1000
50
10
Figure 6. Efficiency vs. Current @ 2 LEDs
(7.0 V @ 350 mA),
L = TDK VLF5014A-2R7M1R5, (Notes 13 and 14)
90
1000
Figure 7. Efficiency vs. Current @ 3 LEDs
(10.5 V @ 350 mA),
L = TDK VLF5014A-2R7M1R5, (Notes 13 and 14)
90
80
EFFICIENCY (%)
100
Iout (mA)
80
Vin = 5.0 V
70
Vin = 5.0 V
Vin = 4.2 V
70
Vin = 4.2 V
Vin = 3.3 V
Vin = 3.7 V
60
Vin = 3.7 V
60
50
Vin = 3.3 V
50
10
100
Iout (mA)
1000
Figure 8. Efficiency vs. Current @ 4 LEDs
(14 V @ 350 mA),
L = TDK VLF5014A-2R7M1R5, (Notes 13 and 14)
10
1000
Figure 9. Efficiency vs. Current @ 5 LEDs
(17.5 V @ 350 mA),
L = TDK VLF5014A-2R7M1R5 (Notes 13 and 14)
13. Pulse of 500 ms every 3 s in Flash Mode (Current following through HCS pin).
14. Efficiency = 100 x (Number of LED stacked x VLED x ILED)/Pin.
http://onsemi.com
6
100
NCP5050
TYPICAL OPERATING CHARACTERISTICS
Channel 1:VOUT
DC Measurement, 5 V/Div
Channel 1:SW Pin
DC Measurement, 5 V/Div
Channel 4:LED Current
DC Measurement, 200 mA/Div
Channel 2:VOUT
AC Measurement, 500 mV/Div
Figure 10. Typical VOUT Ripple in OVP
Condition, No Load
Figure 11. Continue Current Mode (CCM),
IOUT = 100 mA
Channel 1:CRTL Pin
DC Measurement, 5 V/Div
Channel 2: FB Pin, 200 mV/Div
Channel 1:SW Pin
DC Measurement, 5 V/Div
Channel 3: Input current,
200 mA/Div
Channel 4:LED Current
DC Measurement, 100 mA/Div
Channel 4: LED Current,
500 mV/Div, t = 50 ms/Div
Figure 12. Discontinuous Current Mode
(DCM), IOUT = 20 mA
Figure 13. . Startup for 3 LEDs Operating,
ILEDs: 100 mA, Rsense = 2.5 W
Channel 1: CTRL Pin, 5 V/Div, DC Measurement
Channel 1: CTRL Pin, 5 V/Div, DC Measurement
Channel 2: FB Pin, DC, 200 mV/Div
Channel 2: FB Pin, 200 mV/Div, DC Measurement
Channel 3: Input Current, 200 mA/Div
Channel 3: Input Current, 500 mA/Div
Channel 4: ILED, 50 mA/Div, t = 1.0 ms/Div
Channel 4: ILED, 50 mA/Div, t = 10 ms/Div
Figure 14. Low Frequency Dimming Control,
F = 250 Hz
Figure 15. High Frequency Dimming Control,
F = 20 kHz
http://onsemi.com
7
NCP5050
50.0
50.0
45.0
45.0
40.0
40.0
35.0
35.0
Iout RMS (mA)
Iout RMS (mA)
TYPICAL OPERATING CHARACTERISTICS
30.0
25.0
20.0
15.0
30.0
20.0
15.0
10.0
5.0
5.0
10
20
30
40
50
60
70
80
90
100
Duty = 50%
25.0
10.0
0.0
0
Duty = 80%
0.0
0
Duty = 20%
10
20
30
40
DUTY CYCLE (%)
FREQUENCY (kHz)
Figure 16. Dimming on CTRL: IOUT RMS vs.
Duty Cycle RBF = 5 W, F = 20 kHz
Figure 17. Dimming on CTRL: IOUT RMS vs.
Frequency RBF = 5 W
http://onsemi.com
8
50
NCP5050
DETAIL OPERATING DESCRIPTION
MBR130LSF
2.7 to 5.5 V
1uF X5R 0805 25V
L1
2.7 mH
PVIN
UVLO
COMP
UVLO
OVP
COMP
M DUTY REF
FB
+
-
+
RAMP
COMP
2
VS
OVP REF
THERMAL
PROTECTION
MAX D
PWM
COMP
FB
FB
750mW
D2
D5
7
RST
Driver
CTRL
FB REF
+
+
OVP
MAX DUTY
CYCLE COMP
C2
Cout
10
NMOS
UVLO REF
+
D1
SW
1
2 to 5 LEDs
4.7uF X5R 6.3V
C1
TIME
OUT
250mW
ONE
SHOT
SENSE
CURRENT
IPEAK
COMP
REF
3
5
CTRL
1
PCA
ENABLE
250k
250k
PGND
2.8k
RPCA
2.0
RHCS
6
8
FLASH/TORCH
LCS
OSC
1.7 MHz
CM
4
HCS
IPEAK MAX
+
CLOCK
SET
10.0
RLCS
Figure 18. Functional Block Diagram
Operation
The internal oscillator provides a 1.7 MHz clock signal to
trigger the PWM controller on each rising edge (SET signal)
which starts a cycle. During this phase the low side NMOS
switch is turned on thus increasing the current through the
inductor. The switch current is measured by the SENSE
CURRENT and added to the RAMP COMP signal. Then
PWM COMP compares the output of the adder and the
signal from ERROR AMP. When the comparator threshold
is exceeded, the NMOS switch is turned off until the rising
edge of the next clock cycle. In addition there are five
functions which can reset the flip-flop logic to switch off the
NMOS. The MAX DUTY CYCLE COMP monitors the
pulse width and if it exceeds 94% (nom) of the cycle time the
switch will be turned off. This limits the switch from being
on for more than one cycle. Thank to IPEAK COMP, the
current through the inductor is monitored and compared
with the IPEAK_MAX threshold setup by RPCA (See Inductor
Selection). If the current exceeds this threshold the
controller is will turn off the NMOS switch for the remainder
of the cycle. This is a safety function to prevent any
excessive current that could overload the inductor and the
power stage. The three other safety circuits are, OVP,
UVLO, and THERMAL PROTECTION. Please refer to the
details in following sections.
The loop stability is compensated by the ERROR AMP
built in integrator. The gain and the loop bandwidth are fixed
The NCP5050 DC-DC converter is based on a Current
Mode PWM architecture which regulates the feedback
voltage at 250 mV under normal operating conditions. The
boost converter operates in two separate phases (See
Figure 19). The first one is TON when the inductor is charged
by current from the battery to store up energy, followed by
TOFF step where the power is transmitted through the
external rectifier to the load. The capacitor COUT is used to
store energy during the TOFF time and to supply current to
the load during the TON stage thus constantly powering the load.
Start
Cycle
SW
588 ns
Ipeak
IL
Ivalley
Ton
Toff
Iout
Figure 19. Basic DC-DC Operation
http://onsemi.com
9
NCP5050
internally and provide a phase margin greater than 45°
whatever the current supplied or the battery voltage.
efficiency is. But in other hand for a given inductor package
size and magnetic material, higher the inductor value is
worst the saturation current and DCR are. So a good
compromise is to use a 2.7 mH with better DCR possible.
Secondly we have to consider the maximum peak current
through the inductor (IPEAK). Obviously, the peak current
inductor is higher when this device supplies the maximum
required current so in heavy load conditions. In this case this
device is intended to operate in Continuous Conduction
Mode (CCM) so the following equation below can be used
to calculate the peak current:
LED Current Selection
Two different currents can be setup by external resistor.
The first one is setup by Low Current Sense Resistor (RLCS)
connected between LCS pin and GND. Usually LCS pin is
used to determine the lower current for Torch Mode or
indicator mode. The second current is setup by High Current
Sense Resistor (RHCS) connected between the HCS pin and
GND. HCS pin is dedicated setup the current for Flash Mode
(see Timeout Section). An active high logic level is applies
to CM input, RHCS resistors is selected when a low level on
this pin select the RLCS resistor. The control loop regulates
the current such that the average voltage to HCS or LCS pin
is 250 mV (nominal). For example, should one need a
20 mA low output current (IOUTL) in the LED branch, RLCS
should be selected according to the following equation:
R LCS +
FBV
IoutL
+
250mV
20mA
+ 12.5W
I PEAK +
FBV
IoutH
+
250mV
500mA
+ 0.5W
h(1 * D)
)
V inD
(eq. 3)
2LF
In the equation above, VIN is the battery voltage, IOUT is
the load current, L the inductor value, F the switching
frequency, and the duty cycle D is given by:
ǒ
D+ 1*
(eq. 1)
V in
V out
Ǔ
(eq. 4)
h is the global converter efficiency which vary with load
current (see Figure 6 though Figure 9). If we select an
excessive load current, the global efficiency will be too poor
and Power Dissipation (PD) excessive (see Maximum
Ratings). A good compromise is to use in worst case h =
0.75. The dotted curve in Figure 20 through Figure 23 gives
the inductor peak current as a function of IOUT, at VIN =
3.3 V, and the number of LEDs in series (VF = 3.5 typical).
It is important to analysis this at worst case conditions to
ensure that the inductor current rated is high enough such
that it not saturate. So for that refer to the continuous line
named “Switch Current Limit Setup by RPCA” in Figure 20
through Figure 23 that gives peak current which the inductor
has to withstand.
In high current mode (IOUTH), when an active high logics
level is applies to CM input, RHCS should be selected
according to the following equation:
R HCS +
I out
(eq. 2)
LED Dimming
In white LED applications it should be desirable to
operate the LEDs at a specific operating current because as
the biasing current is changed as the color is shifting. As a
result of this effect, it should be recommended to fix the
maximum current wishes accordingly Equations 1 and 2
and to dim the LED brightness by a pulse width modulation
techniques. The PWM signal is applied to CTRL input and
thereby the RMS current through LED is proportional to the
duly cycle (see Figure 16). In other word by reducing the
duty cycle the brightness of the LED is dimmed. The
NCP5050 as been design to sustain high PWM dimming
frequency up to 50 kHz. Finally to avoid any optical flicker
the frequency must be at least higher than 100 Hz.
3000
2500
IPEAK (mA)
2000
1500
Inductor Selection
Switch Current Limit
Setup by RPCA
1000
Three main electrical parameters need to be considered
when choosing an inductor: the value of the inductor, the
saturation current and the DCR (parasitic serial resistance in
DC). Firstly, thank to the high switching frequency at
1.7 MHz (nominal), the NCP5050 allows choosing a low
inductor value. This is a key feature mainly in portable
application because as inductor value in lower as inductor
size in smaller. The recommended inductor value should
range from 2.2 mH to 4.7 mH. In one hand higher the inductor
value is lower the ripple of current is and in theory better the
Operating Inductor
Peak Current
500
0
100
200
300
400
Iout (mA)
500
600
Figure 20. Inductor Peak Currents Vs. IOUT (mA) for
2 LEDs, (7.0 V @ 350 mA)
http://onsemi.com
10
NCP5050
overall efficiency will improve. Some recommended
inductors include but are not limited to:
TDK VLF5012A-2R2M1R5
TDK VLF5014A-2R7M1R5
TDK RLF7030T-3R3M4R1
3000
IPEAK (mA)
2500
2000
Switch Current Limit
Setup by RPCA
1500
Switch Current Limit
1000
Operating Inductor
Peak Current
500
0
50
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.
150
250
350
450
Iout (mA)
Figure 21. Inductor Peak Currents Vs. IOUT (mA) for
3 LEDs, (10.5 V @ 350 mA)
3000
2500
Table 1. IPEAK_MAX Versus RPCA
IPEAK (mA)
2000
Switch Current Limit
Setup by RPCA
IPEAK_MAX (A)
RPCA (kW 1%)
3.0
2.8
2.5
3.4
2.0
4.12
1.5
5.76
1.0
9.09
1500
Operating Inductor
Peak Current
1000
500
0
50
150
250
350
3500
Iout (mA)
Figure 22. Inductor Peak Currents Vs. IOUT (mA) for
3000
4 LEDs, (14 V @ 350 mA)
IPEAK MAX (mA)
2500
2000
3000
1500
2500
IPEAK (mA)
1000
2000
500
1500
Switch Current Limit
Setup by RPCA
1000
0
1.0
Operating Inductor
Peak Current
10
RPCA (kW)
100
Figure 24. IPEAK_MAX vs. RPCA
500
Input and Output Capacitors Selection
0
25
75
125
175
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.
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,
http://onsemi.com
11
NCP5050
Overvoltage Protection (OVP)
The PVIN input pin need to be bypassed by a X5R or an
equivalent low ESR ceramic capacitor. Near the PVIN pin at
least 4.7 mF 6.3 V or higher capacitor is needed.
Also a particular care must be observed for DC-bias
effects in ceramic capacitor. Actually smaller the case-size
and higher the DC bias voltage, the bigger drop in
capacitance. For a stability viewpoint the percentage drop in
capacitance for the chosen input or output operating voltage
must be limit to 20%. Some recommended capacitors
include but are not limited to:
1.0 mF 25 V 0805
TDK: C2012X5R1E105M
4.7 mF 6.3 V 0805
TDK: C1608X5R0J475M
The NCP5050 regulates the load current. If there is an
open load condition such as a loose connection to the White
LED, the converter keeps supplying current to the Cout
capacitor causing the voltage to rise rapidly. To prevent the
device from being damage and to eliminate external
protections such as zener diode, the NCP5050 incorporates
an OVP circuit, which monitors the output voltage with a
resistive divider network and a comparator and voltage
reference. If the output reaches 22.5 V (nominal), the OVP
circuit will detect a fault and inhibit PWM operation. This
comparator has 1.0 V of hysteresis so allow the PWM
operation to resume automatically. when the load is
reconnected and the voltage drops below 21.5 V (nominal).
Undervoltage Lock Out (UVLO)
Schottky Diode Selection
To ensure proper operation under all conditions, the
device has a built-in undervoltage lock out (UVLO) circuit.
During power-up, the device will remain disabled until the
input voltage exceeds 2.4 V (nominal). This circuit has
100 mV of hysteresis to provide noise immunity to transient
conditions.
An external diode is required for the boost rectification.
The reverse voltage rating of the selected diode must be
equal to or greater than the maximum output voltage. The
average current rating of the diode must be greater than the
maximum output load current. The peak current rating must
be larger than the maximum peak inductor current. It is
recommended to use a Schottky diode with lower forward
voltage to minimize the power dissipation and therefore to
maximize the efficiency of the converter.
Also a particular care must be observed for parasitic
capacitance versus reverse voltage and leakage current
versus junction diode temperature. Both parameters are
impacting the efficiency in low load condition and switching
quiescent current.
Some recommended Schottky diodes include but are not
limited to:
ON SEMICONDUCTOR: MBR130LSFT1G
ON SEMICONDUCTOR: MBR120LSFT3G
Thermal Considerations
Careful attention must be paid to the internal power
dissipation of the NCP5050. The power dissipation is a
function of efficiency, input voltage and output power.
Hence, increasing the output power requires better
components selection. For example, should one change
inductors: larger inductor value (in micro Henri) and/or
lower DCR may improve efficiency.
The exposed thermal pad that is designed to be soldered
to the ground plane to used the PCB as a heat-sink. This
ground should then be connected to an internal copper
ground plane with thermal via placed directly under the
package to spread out the heat dissipated by the device.
Finally the NCP5050 is switched off to protect the device
if junction temperature exceeds 160°C. When the junction
temperature drops below 140°C, normal operation will
resume.
Timeout Protection
To avoid a failure in LEDs caused by a timing violation in
Flash Mode (CM high), a timeout function turn off the
output after 1.2 second. Any rising edge of CTRL reset this
function. In torch mode (CM low) this circuit is disabled. For
the logic diagram please refer to Figure 25 below.
CTRL
CM
Timeout
Flash
Current
1.2s
Torch
Figure 25. Timeout Operation
http://onsemi.com
12
NCP5050
ORDERING INFORMATION1
Device
NCP5050MTTXG
Package
Shipping†
WDFN-10 3x3 mm
(Pb-Free)
3000/Tape & Reel
†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging
Specification Brochure, BRD8011/D.
Demo Board Available:
• The NCP5050EVB/D evaluation board that configures the device to drive high current through white LED in serial.
Application Note Available:
• AND8294: Drive Up to 120 LEDs (6 to 10 in Series Configuration)
http://onsemi.com
13
NCP5050
PACKAGE DIMENSIONS
WDFN10, 3x3, 0.5P
CASE 522AA-01
ISSUE A
D
PIN ONE
REFERENCE
0.15 C
2X
ÍÍÍ
ÍÍÍ
ÍÍÍ
0.15 C
2X
NOTES:
1. DIMENSIONING AND TOLERANCING PER
ASME Y14.5M, 1994.
2. CONTROLLING DIMENSION: MILLIMETERS.
3. DIMENSION b APPLIES TO PLATED
TERMINAL AND IS MEASURED BETWEEN
0.15 AND 0.30mm FROM TERMINAL.
4. COPLANARITY APPLIES TO THE EXPOSED
PAD AS WELL AS THE TERMINALS.
B
A
E
DIM
A
A1
A3
b
D
D2
E
E2
e
K
L
TOP VIEW
A3
0.10 C
10X
A
0.08 C
C
1.75
0.35
2.6016
L
e
1
5
2.1746
E2
K
2.45
SOLDERING FOOTPRINT*
SEATING
PLANE
D2
10X
0.18
MILLIMETERS
NOM
MAX
0.75
0.80
0.03
0.05
0.20 REF
0.24
0.30
3.00 BSC
2.50
2.55
3.00 BSC
1.80
1.85
0.50 BSC
0.19 TYP
0.40
0.45
A1
SIDE VIEW
10X
MIN
0.70
0.00
10
6
b
10X
10X
0.10 C A
BOTTOM VIEW
1.8508 3.3048
0.05 C
B
0.5651
10X
0.3008
NOTE 3
0.5000 PITCH
DIMENSIONS: MILLIMETERS
*For additional information on our Pb-Free strategy and soldering
details, please download the ON Semiconductor Soldering and
Mounting Techniques Reference Manual, SOLDERRM/D.
ON Semiconductor and
are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice
to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability
arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages.
“Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All
operating parameters, including “Typicals” must be validated for each customer application by customer's technical experts. SCILLC does not convey any license under its patent rights
nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications
intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur. Should
Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates,
and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death
associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an Equal
Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.
PUBLICATION ORDERING INFORMATION
LITERATURE FULFILLMENT:
Literature Distribution Center for ON Semiconductor
P.O. Box 5163, Denver, Colorado 80217 USA
Phone: 303-675-2175 or 800-344-3860 Toll Free USA/Canada
Fax: 303-675-2176 or 800-344-3867 Toll Free USA/Canada
Email: [email protected]
N. American Technical Support: 800-282-9855 Toll Free
USA/Canada
Europe, Middle East and Africa Technical Support:
Phone: 421 33 790 2910
Japan Customer Focus Center
Phone: 81-3-5773-3850
http://onsemi.com
14
ON Semiconductor Website: www.onsemi.com
Order Literature: http://www.onsemi.com/orderlit
For additional information, please contact your local
Sales Representative
NCP5050/D