View NCP5050MTTXG_4127552.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

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
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)
* * * * * * * * * *
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
PIN CONNECTIONS
PGND 1 VS 2 CTRL 3 CM 4 PCA 5 10 SW 9 PVIN 8 LCS 7 FB 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 C1 4.7 mF L1 2.2 mH 2 to 5 LEDs 9 5 R1 2.8 k PVIN PCA PGND SW VS FB 6 8 HCS LCS 10 2 7 D1 D2 C2 1 mF
ORDERING INFORMATION
See detailed ordering and shipping information in the package dimensions section on page 13 of this data sheet.
L1: TDK VLF5012T-2R2 D6 D1: ON MBR130LSF C1: 4.7 mF 6.3 V 0603 TDK C1608X5R0J475M C2: 1 mF 25V 0805
3 CTRL 4 HCM NCP5050
ENABLE FLASH/ TORCH
1
2.0
R2 RHCS
R3 RLCS 10.0
TDK C2012X5R1E105M
Figure 1. Typical Application Circuit
(c) Semiconductor Components Industries, LLC, 2007
1
October, 2007 - Rev. 0
Publication Order Number: NCP5050/D
NCP5050
90 80 70 EFFICIENCY (%) 60 50 40 30 20 10 0 10 Vin = 3.7 V 100 Iout (mA) 1000 Vout = 2 LEDs (7.0 V @ 350 mA)
Figure 2. Typical Efficiency
2.7 to 5.5 V C1 4.7 mF 0603 6.3 V Cin PVIN 1 OSC 1.7MHz PCA 5 R1 2.8k CTRL 3 ENABLE 250k Band Gap PWM CONTROLLER Thermal Shut down
2.7 mH L1 SW
D1 1 mF 0805 25V
Up to 20 V / 4.5 W D2
C2 Cout 2 to 5 LEDs
10
OVP
2
VS
D6 FB 7
250k 4 CM FLASH/TORCH 6 HCS 2.0 R2 RHCS 8 LCS R3 10.0 RLCS 1
PGND
Figure 3. Simplified Block Diagram
http://onsemi.com
2
NCP5050
PIN FUNCTION DESCRIPTION
Pin 1 Pin Name PGND Type POWER Description 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. Voltage Sense: In order to sense Vout notably for over voltage protection, this input must be connected to the output bypass capacitor Cout. 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. 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 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. 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. 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. 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. 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.
2 3
VS CTRL
INPUT INPUT
4
CM
INPUT
5
PCA
INPUT
6 7
HCS FB
INPUT INPUT
8 9
LCS PVIN
INPUT POWER
10
SW
INPUT
http://onsemi.com
3
NCP5050
MAXIMUM RATINGS (Note 1)
Rating Power Supply Voltage (Note 2) Over Voltage Protection Human Body Model (HBM) ESD Rating (Note 3) HCS and FB Pins Machine Model (MM) ESD Rating (Note 3) HCS and FB Pins Digital Input Voltage Digital Input Current WDFN 3x3 Package Power Dissipation @ TA = +85C Thermal Resistance, Junction-to-Case Thermal Resistance, Junction-to-Air Operating Ambient Temperature Range Operating Junction Temperature Range Maximum Junction Temperature Storage Temperature Range Moisture Sensitivity Level (Note 7) Symbol PVin VS ESD HBM ESD MM CTRL, CM Value 7.0 25 2000 1000 200 150 -0.3 < Vin < Vbat + 0.3 1.0 (Note 5) 10 (Note 6) -10 to +85 -10 to +125 +150 -65 to +150 1 Unit V V V V V mA W C/W C C C C
PD RqJC RqJA TA TJ TJMAX Tstg MSL
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 = 25C. 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 160C (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 61C/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 -10C to +85C and VIN between 2.7 V
to 5.5 V (Unless otherwise noted). Typical values are referenced to TA = +25C and Vin = 3.6 V (Unless otherwise noted) Characteristics Operating Power Supply Maximum Inductor Current (Notes 9 and 11) (see Figure 24) Refer Switch Current Limit section @ 25C Power Switch ON Resistor TA = 25C (I = 100 mA) High Current Sense Switch ON Resistor (I = 100 mA and 25C) Low Current Sense Switch ON Resistor (I = 100 mA and 25C) PWM Oscillator Frequency Maximum Duty Cycle Efficiency (Notes 9 and 10) Over-voltage Clamp Voltage Over-voltage Clamp Hysteresis Output power (Notes 9 and 12) @ Vin = 3.3 V @ Vin = 2.7 V Feedback Voltage Ripple Rejection @ Iout = 20 mA From DC to 300 Hz (0.2 VPP) (Note 9) Feedback Voltage in Steady State.@ TA = 25C Input Feedback Current (CM = Low) Vin Undervoltage Lockout Vin Decreasing Undervoltage Lockout Hysteresis Standby Current, Iout = 0 mA, CTRL = Low, Vin = 4.2 V @ TA = 25C Quiescent Current, Iout = 0 mA, Not Switching @ TA = 25C Startup Time (Note 9) From CTRL =1.2 V to Start of Switching Inrush Peak Current Limit (Note 9) Time Constant Upper Limit of PWM Dimming Frequency (Note 9) Time out Protection (Note 9) Thermal Shutdown Protection (Note 9) Thermal Shutdown Protection Hysteresis (Note 9) Voltage Input Logic Low (Pin CM, CTRL) Voltage Input Logic High (Pin CM, CTRL) CTRL and CM Pin Pulldown Resistance Symbol Vin IPEAK_MAX SWRDSON HCSSRDSON LCSSRDSON FOSC MDUTY EFF OVPON OVPH Pout 4.5 2.8 LREG FBV IFB UVLO 2.0 UVLOH ISTDB IQNOSW STRT IPCL DIM TOUT TSD TSDH VIL VIH RPLD -15% 1.2 175 100 50 1 1.2 160 20 250 2.7 2.0 2.0 200 50 +15% 0.4 375 mV mA mA ms ms kHz s C C V V kW 5.0 215 2.5 250 285 0.15 mV mV mA V Min 2.7 1.0 200 1.48 91.5 85 20 250 750 1.7 94 90 1.0 1.95 mW mW MHz % % V V W Typ Max 5.5 3.0 Unit V A mW
9. Guaranteed by design and characterized 10. Efficiency is defined by 100 * (Pout / Pin) at 25C 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
1000 1200 1000 Vin = 4.2 V Iout (mA) Vin = 3.8 V Vin = 3.3 V Iout (mA) 600 800 600 400 200 Operating Area 0 5 10 15 Vout (V) 20 25 0 2.5 3.0 3.5 4.0 Vin (V) 4.5 5.0 5.5 200 5 LEDs 2 LEDs 3 LEDs 4 LEDs
800
400
Figure 4. Maximum Output Current Available vs. Vout
90 90
Figure 5. Typical Maximum Output Current vs. Input Voltage, L = TDK VLF5014A-2R7M1R5 (Note 13)
80 EFFICIENCY (%) Vin = 5.0 V Vin = 4.2 V 70 Vin = 3.7 V 60 Vin = 3.3 V EFFICIENCY (%)
80 Vin = 5.0 V 70 Vin = 4.2 V
60
Vin = 3.7 V Vin = 3.3 V
50 10
100 Iout (mA)
1000
50 10
100 Iout (mA)
1000
Figure 6. Efficiency vs. Current @ 2 LEDs (7.0 V @ 350 mA), L = TDK VLF5014A-2R7M1R5, (Notes 13 and 14)
90 90
Figure 7. Efficiency vs. Current @ 3 LEDs (10.5 V @ 350 mA), L = TDK VLF5014A-2R7M1R5, (Notes 13 and 14)
80 EFFICIENCY (%) Vin = 5.0 V 70 Vin = 4.2 V Vin = 3.3 V 60 Vin = 3.7 V
80 Vin = 5.0 V 70 Vin = 4.2 V 60 Vin = 3.7 V Vin = 3.3 V
50 10 100 Iout (mA) 1000
50 10 100 1000
Figure 8. Efficiency vs. Current @ 4 LEDs (14 V @ 350 mA), L = TDK VLF5014A-2R7M1R5, (Notes 13 and 14)
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
NCP5050
TYPICAL OPERATING CHARACTERISTICS
Channel 1:VOUT DC Measurement, 5 V/Div
Channel 1:SW Pin DC Measurement, 5 V/Div
Channel 2:VOUT AC Measurement, 500 mV/Div
Channel 4:LED Current DC Measurement, 200 mA/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 3: Input current, 200 mA/Div
Channel 1:SW Pin DC Measurement, 5 V/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
TYPICAL OPERATING CHARACTERISTICS
50.0 45.0 40.0 35.0 Iout RMS (mA) 30.0 25.0 20.0 15.0 10.0 5.0 0.0 0 10 20 30 40 50 60 70 80 90 100 Iout RMS (mA) 50.0 45.0 40.0 35.0 30.0 25.0 20.0 15.0 10.0 5.0 0.0 0 10 20 30 40 50 Duty = 20% Duty = 50% Duty = 80%
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
NCP5050
DETAIL OPERATING DESCRIPTION
MBR130LSF 2.7 to 5.5 V 4.7uF X5R 6.3V C1 PVIN 1 L1 2.7 mH 10 1uF X5R 0805 25V
SW
D1
C2 Cout
UVLO REF
MAX DUTY CYCLE COMP M DUTY REF
THERMAL PROTECTION
OVP REF FB NMOS 750mW 7
VS
2 to 5 LEDs
+
UVLO COMP UVLO
OVP COMP OVP
+
2 D2
+ +
MAX D
FB
D5
FB FB REF
+
RAMP COMP
PWM COMP
RST Driver
CTRL
TIME OUT 250mW SET
CLOCK
ONE SHOT IPEAK MAX 250k IPEAK COMP
SENSE CURRENT OSC 1.7 MHz
CM 4 250k
HCS
CTRL ENABLE
PCA 2.8k RPCA
PGND
2.0 RHCS
10.0 RLCS
Figure 18. Functional Block Diagram Operation
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 IL Ivalley Ton Toff Ipeak
Iout
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
Figure 19. Basic DC-DC Operation
http://onsemi.com
9
LCS
3
+
5
REF
FLASH/TORCH
1
6
8
NCP5050
internally and provide a phase margin greater than 45 whatever the current supplied or the battery voltage.
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 + 250 mV 20 mA + 12.5 W
(eq. 1)
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:
I PEAK + I out h(1 * D) ) V inD 2LF
(eq. 3)
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:
D+ 1* V in V out
(eq. 4)
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 + LED Dimming FBV IoutH + 250 mV 500 mA + 0.5 W
(eq. 2)
IPEAK (mA)
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.
Inductor Selection
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.
3000 2500 2000 1500 1000 500 0 100 Switch Current Limit Setup by RPCA Operating Inductor Peak Current
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
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
3000 2500 2000 1500 1000 500 0 50 Switch Current Limit Setup by RPCA
IPEAK (mA)
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
Operating Inductor Peak Current
150
250 Iout (mA)
350
450
Figure 21. Inductor Peak Currents Vs. IOUT (mA) for 3 LEDs, (10.5 V @ 350 mA)
3000 2500
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 (mA)
2000 1500 1000 500 0 50
Switch Current Limit Setup by RPCA Operating Inductor Peak Current
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
150 Iout (mA)
250
350
3500 3000 IPEAK MAX (mA) 2500 2000 1500 1000 500
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
IPEAK (mA)
0 1.0
10 RPCA (kW)
100
Figure 24. IPEAK_MAX vs. RPCA Input and Output Capacitors Selection
0 25
75
125 Iout (mA)
175
225
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,
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.
http://onsemi.com
11
NCP5050
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
Schottky Diode Selection Overvoltage Protection (OVP)
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)
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
Timeout Protection
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.
Thermal Considerations
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.
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 160C. When the junction temperature drops below 140C, normal operation will resume.
CTRL
CM
Timeout
Flash Current Torch
1.2s
Figure 25. Timeout Operation http://onsemi.com
12
NCP5050
ORDERING INFORMATION1
Device NCP5050MTTXG Package WDFN-10 3x3 mm (Pb-Free) Shipping 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 A B
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. DIM A A1 A3 b D D2 E E2 e K L MIN 0.70 0.00 0.18 2.45 1.75 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
E
PIN ONE REFERENCE
2X 2X
0.15 C
0.15 C
0.10 C
10X
0.08 C SIDE VIEW D2
10X
L
1 5
10X
K
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: orderlit@onsemi.com 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 ON Semiconductor Website: www.onsemi.com Order Literature: http://www.onsemi.com/orderlit For additional information, please contact your local Sales Representative
III III III
10
TOP VIEW A3 A A1 C
SEATING PLANE
0.35
SOLDERING FOOTPRINT*
2.6016
e
E2
2.1746
1.8508 3.3048
6
b
10X
10X
0.10 C A BOTTOM VIEW 0.05 C
B
0.5651
10X
NOTE 3
0.3008
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.
http://onsemi.com
14
NCP5050/D

▲Up To Search▲

Price & Availability of NCP5050MTTXG

	To Download NCP5050MTTXG Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .