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APW7071
White LED DC/DC Step-Up Converter
Features
* * * * * * * * * * * 2.4V to 6V Input Voltage Range 400mA, Internal Switch Current Up to 1MHz Switching Frequency 70A Typical No Load Quiescent Current 0.1A Typical Shutdown Current Internal Soft-start Available in a Tiny 6-Pin SOT-23 Package Up to 87% efficiency Operating Output Capacitor down to 0.1F Over Voltage Protection included Lead Free Available (RoHS Compliant)
General Description
The APW7071 is a high frequency step up DC/DC converter in a small 6 leads SOT-23 package specially designed to drive white LEDs with a constant current. The device can drive up to 4 LEDS in a series from one Li-Ion cell. The APW7071 is ideal for LCD panels requiring low current and high efficiency as well as white LED applications for cellular phone backlighting.
Package Pin Out
VIN OVP SHDN
Applications
* * * * * Cellar Phones White LED Back Light PDAs, Handheld Computers Digital Still Cameras MP3 Players GPS Receivers
6 1
5 2
4 3
SW GND FB
SOT-23-6 (Top View) APW7071
Ordering and Marking Information
APW7071
Lead Free Code Handling Code Temp. Range Package Code Package Code C : SOT-23-6 Operating Junction Temp. Range E : -40 to 85C Handling Code TU : Tube TR : Tape & Reel Lead Free Code L : Lead Free Device Blank : Original Device XXXXX - Date Code
APW7071 C :
W71X
Notes: ANPEC lead-free products contain molding compounds/die attach materials and 100% matte in plate termination finish; which are fully compliant with RoHS and compatible with both SnPb and lead-free soldiering operations. ANPEC lead-free products meet or exceed the lead-free requirements of IPC/JEDEC J STD-020C for MSL classification at lead-free peak reflow temperature.
ANPEC reserves the right to make changes to improve reliability or manufacturability without notice, and advise customers to obtain the latest version of relevant information to verify before placing orders. Copyright (c) ANPEC Electronics Corp. Rev. A.1 - Feb., 2006 1 www.anpec.com.tw
APW7071
Block Diagram
OVP(5)
VIN(6) 400ns Min. off-time Error Comparator FB(3) +
Under Voltage Lockout
Thermal Shutdown
OVP +
SW(1)
Vref=0.25V
Control Logic
Gate Driver
N-MOSFET
6us Max. on-time
Current Limit + RSENSE
SHDN(4)
Soft start GND(2)
Pin Description
No 1 2 3 4 5 6 Name SW GND FB SHDN OVP Vin Function Switch Pin. Connect to inductor/diode here. Minimize trace area at this pin to educe EMI. Ground Pin. Feedback Pin. Reference voltage is 0.25V. Connect cathode of lowest LED and resistor here. Calculate resistor value according to RFB = 0.25V/l LED Shutdown Pin. Tie to 1.3V or higher to enable device, 0.4V or less to disable. Over voltage protection sense pin. Connect this pin to VOUT for over voltage protection. Supply voltage Pin.
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APW7071
Absolute Maximum Ratings
Symbol Vin FB SHDN SW TJ TSTG Parameter Supply voltage Feedback Voltage Shutdown Voltage Switch Voltage Junction Temperature Range Storage Temperature Range Rating 7 7 7 20 150 -40 to +150 Unit V V V V C C
Recommend Operating Conditions
Symbol Vin Vsw L Cin Cout Ta Tj Parameter Input supply voltage Switch voltage Inductor Input capacitor Output capacitor Operating ambient temperature Operating junction temperature Min. 2.4 Vin Value Typ. Max. 6.0 18 Unit V V H F F C C
4.7 4.7 0.1 -40 -40 85 125
Electrical Characteristics
VIN=2.4V, EN=VIN, TA=-40C to +85C, typical values are at TA=+25C (unless otherwise noted)
Symbol Parameter Test Condition Min. 2.4 Iout=0, not switching, VFB=0.3V SHDN=GND 2.1 100 1.3 SHDN=GND or VIN 0.1 0.4 1 20 500 7.5 1000 10 450 70 0.1 APW7071 Typ. Max. 6 90 1 2.3 Unit V A A V mV V V A V ns s m A mA
Supply Voltage and Current Vin Input Voltage Range Iq Isd UVLO Operating quiescent current Shutdown current Under-Voltage Lockout threshold Under-Voltage Lockout hysteresis
ENABLE VIH SHDN high level input voltage VIL SHDN low level input voltage Ii SHDN input leakage current Power Switch and Current limit Vsw Maximum switching voltage toff Minimum off-time ton Maximum on-time Rds,on ILIM MOSFET on-resistance MOSFET leakage current MOSFET current limit
350 4 Vin=2.4V, Isw=200mA Vsw=20V 350
400 6 600 1 400
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APW7071
Electrical Characteristics (Cont.)
Symbol OUTPUT Vout IFB VFB Parameter Test Condition Min. Vin 0.237 16 5 0.25 17 6 APW7071 Typ. Max. 18 1 0.263 18 7 Unit V A V V V
Adjustable output voltage range Feedback input bias current VFB=0.3V 2.4OVINO6.0V Feedback trip point voltage OVP threshold OVP hysteresis
Typical Application Circuit
Vin 2.7V~6V C1 4.7F 6 VIN
L1 4.7H 1
D1 MSCD052
Vout
Vin 2.4V~6V
L1 10H 6 1
D1 MSCD052
Vout
C2 0.1F
SW
C1 4.7F
C2 1F
VIN
SW
2
GND
OVP
5
2
GND
OVP
5
off on
4 SHDN
FB
3
off on
R1 13
4 SHDN
FB
3
R1 13
Fig.1 Typical 4LED application
Fig.2 4LED application with lower output voltage ripple
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APW7071
Typical Characteristics
(Circuit of Figure 1, VIN = 3.3V, ILED = 15mA, L1 = 4.7H, CIN = 4.7F, COUT = 0.1F,4 LEDs, TA = +25C, unless otherwise noted.)
Efficiency vs LED Current
90 88 86
Vin=3.6V
Efficiency vs Supply Voltage
90
Vin=4.2V
88
Efficiency(%)
86 84 82 80 78 76 74
ILED=15mA
Efficiency(%)
84 82 80 78 76 74 0.1 1 10 100
Vin=2.7V
72 70 2 3 4 5 6
LED Current(mA)
Supply Voltage(V)
Switch Rds,on vs Supply Voltage
0.7 0.6 0.5
0.6 0.5 0.4 0.3 0.2 0.1
Switch Rds,on vs Temperature
Rds,on()
0.4 0.3 0.2 0.1
Rds,on()
Ta=25C
0 2 3 4 5 6
0 -40 -20 0 20 40
Vin=3.3V
60 80 100
Supply Voltage(V)
Temperature(C)
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APW7071
Typical Characteristics (Cont.)
Non-Switch Quiescent Current vs. Supply Voltage
75
Non-Switch Quiescent Current vs. Temperature
80
Non-Switch Quiescent Current(A)
70 65 60 55 50 45 40 2 3 4 5 6
Non-Switch Quiescent Current(A)
75 70 65 60 55
Vin=3.3V
Ta=25C
50 -40
-20
0
20
40
60
80
100
Supply Voltage(V)
Temperature(C)
LED Current vs. Supply Voltage
25
Start-up Waveform
20
SHDN 2V/DIV VOUT 5V/DIV
LED Current(mA)
15
10
L=4.7H
5
Input Current 100mA/DIV
Cout=0.1F 4LED
0
1
2
3
4
5
6
Supply Voltage(V)
1 ms/DIV
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APW7071
Typical Characteristics (Cont.)
OVP Waveform
PFM Operation
VOUT(AC) 200mV/DIV VOUT 5V/DIV
Vsw 10V/DIV VFB 100mV/DIV
20 ms/DIV
1 s/DIV
Burst Mode Operation
VOUT(AC) 200mV/DIV
Vsw 10V/DIV VFB 100mV/DIV
2 s/DIV
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APW7071
Function Descriptions
OPERATION The APW7071 operates in a pulse frequency modulation (PFM) scheme with constant peak current control.The operation can be understood by referring to the block diagram of Figure 1. The converter monitors the output voltage, and if the feedback voltage falls below the reference voltage (typical 0.25V), the internal switch turns on and the inductor current ramps up. The switch turns off if the inductor current reaches the internally set peak current (typical 400mA) or maximum on-time detected. As the switch is turned off, the inductor current ramps down to zero and charge output capacitor through external Schottky diode. The switch remains off for a minimum of 400 ns (typical), or until the feedback voltage drops below the reference voltage again. The operation frequency is up to 1MHz and is determined by the output current, current limit, inductor value, input voltage and output voltage. This regulation scheme is inherently stable, allowing a wider selection range for the inductor and output capacitor. Enable Force SHDN pin greater than 1.3 V to enable the device works in normal operation. Pulling SHDN pin less than 0.4V to shut down reducing the shutdown current to 0.1 A (typical). The SHDN pin should not be left floating. Soft Start The APW7071 limits this inrush current by increasing the current limit at start-up. Under Voltage Lockout Transients during powering on or instantaneous glitches in the supply voltage can cause system damage or failure. The undervoltage lockout circuit turned the main switch off to prevent malfunction at low input voltage.
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Over Voltage Protection (OVP) OVP is integrated to prevent the output voltage increase over the maximum switching voltage rating. In some cases an LED may fail, this will result in the feedback voltage always being zero. The device will boost the output voltage higher and higher. When the output voltage exceeds the OVP threshold voltage (typical 17V), the switch turns off. The converter switch remains off until the output voltage falls below the OVP threshold voltage. Thermal Shutdown A thermal shutdown function is integrated to shutdown device when junction temperature exceed 160C. If thermal shutdown detected, converter switch turn off until junction temperature falls bellow 120C.
APW7071
Application Information
Setup the LED current The LED current is controlled by the reference voltage and resistor and R1 shows in Figure 1. The current through the LEDs is given by the 250mV/R1. Brigtness control a. By an adjustable DC voltage Uses a DC voltage to control the feedback voltage. As the DC voltage increases, current starts flowing down R3, R2 and R1. The loop will continue to regulate the feedback voltage at 250mV. Thus the current has to decrease through the LEDs by the same amount of current as is being injected from the DC voltage source. With a VDC from 0V to 3. 3V, the resistor values shown for R2 and R3 can control the LED current from 0mA to 20mA.
Vin 2.7V~6V C1 4.7F 6 VIN L1 4.7H SW 1 C2 0.1F 2 GND OVP 5
2 GND OVP 5
Vin 2.7V~6V C1 4.7F 6
L1 4.7H VIN SW 1
D1 MSCD052
Vout
C2 0.1F
2 100Hz~300Hz PWM brightness control
GND
OVP
5
4 SHDN
FB
3
Duty=100%, LED=20mA Duty=0%, LED off
R1 13
Fig. 4 Brightness Control by a PWM signal apply to SHDN
c. By a filtered PWM signal Brightness can be achieved by a filtered PWM signal. The PWM signal above 5KHz is recommended.
Vin 2.7V~6V C1 4.7F 6 VIN L1 4.7H 1 C2 0.1F D1 MSCD052 Vout
D1 MSCD052
Vout
SW
4 SHDN
FB
3 R3 120K
R2 10K R1 13
4 SHDN
FB
3 R3 120K
R2 10K R1 13 C3 0.1uF
Vadj=3.3V, LED off Vadj=0V, LED=20mA
3.3V PWM brightness 0V control Duty=100%, LED off Duty=0%, LED=20mA
R4 10K
Fig. 3 Brightness Control by an adjustable DC voltage
Fig. 5 Brightness Control by
a filtered PWM signal
b. By a PWM signal apply to SHDN The PWM signal is applied to the SHDN pin of the APW7071. The LEDs will switch between full load to completely shut off. The average current through the LEDs will increase proportionally to the duty cycle of the PWM signal. Due to the soft start function, the PWM signal should be 100Hz to 300Hz.
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APW7071
Application Information (Cont.)
Inductor selection Since the PFM peak current control scheme is inherently stable, the inductor value does not affect the stability of the regulator. The selection of the inductor together with the nominal load current, internal set peak current, input and output voltage of the application determines the switching frequency of the converter. For the LED application, inductor values between 2.2 H up to 10 H are recommended. Recommended inductors
Part No. LQH32CN4R7M23L LQH32CN100K53L SH30184R7YSB SH3018100YSB Value(H) 4.7 10 4.7 10 Vendor Murata Murata ABC ABC
Part No. Value Vender GRM188R60J475KE19D 4.7F/X5R/ Murata 0603/6.3V GRM219R60J106KE19D 10F/X5R/ Murata 0805/6.3V
Recommended output capacitor
Part No. Value GRM185R61C105KE44D 1.0F/X5R/ 0603/16V Any 0.22F Any 0.1F Vender Murata Any Any
Input capacitor selection For good input voltage filtering, low ESR ceramic capacitors are recommended. A 4.7F ceramic input capacitor is sufficient for most applications. For better input voltage filtering the capacitor value can be increased. Recommended input capacitor
Output capacitor selection For better output voltage filtering, a low ESR output capacitor is recommended. Ceramic capacitors have a low ESR value, but depending on the application, tantalum capacitors can be used. The selection of the output capacitor value directly influences the output voltage ripple of the converter which also influences line regulation. The larger the output voltage ripple, the larger the line regulation, which means that the LED current changes if the input voltage changes. If a certain change in LED current gives a noticeable change in LED brightness, depends on the LED manufacturer and on the application. Applications requiring good line regulation 1%/V (typ) must use output capacitor values eqAl or large than 1 F. Diode selection To achieve high efficiency a Schottky diode must be used. The current rating of the diode must meet the peak current rating of the converter. Recommended diode
Part No. MSCD052 Reverse Voltage 20 Vender Zowie
Layout considerations Typical for all switching power supplies, the layout is an important step in the design; especially at high peak currents and switching frequencies. If the layout is not carefully done, the regulator might show noise problems and duty cycle jitter. The input capacitor should be placed as close as possible to the input pin for good input voltage filtering. The inductor and diode should be placed as close as possible to the switch
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APW7071
Application Information (Cont.)
Layout considerations (Conts.)() pin to minimize the noise coupling into other circuits. Since the feedback pin and network is a high impedance circuit, the feedback network should be routed away from the inductor. The feedback pin and feedback network should be shielded with a ground plane or trace to minimize noise coupling into this circuit.
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APW7071
Package Information
SOT-23-6
D
6
5
4 E H
1
2
3
S1 e
D
A A2
L1
A1
L2
L
Dim A A1 A2 b D E e H L L1 L2 S1
Millimeters Min. 1.00 0.00 0.70 0.35 2.70 1.40 1.90 BSC 2.60 0.30 0.08 0.60 REF 0 0.85 10 1.05 3.00 0.25 Max. 1.45 0.15 1.25 0.55 3.10 1.80
Inches Min. Max. 0.0394 0.0571 0.0000 0.0591 0.0276 0.0492 0.0138 0.0217 0.1063 0.1220 0.50551 0.0709 0.07480 BSC 0.1024 0.1181 000118 0.0031 0.0098 0.024 REF 0 10 0.0335 0.0413
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APW7071
Physical Specifications
Terminal Material Lead Solderability Solder-Plated Copper (Solder Material : 90/10 or 63/37 SnPb) Meets EIA Specification RSI86-91, ANSI/J-STD-002 Category 3.
Reflow Condition
TP
(IR/Convection or VPR Reflow)
tp Critical Zone T L to T P
Ramp-up
Temperature
TL Tsmax
tL
Tsmin Ramp-down ts Preheat
25
t 25 C to Peak
Time
Classificatin Reflow Profiles
Profile Feature Average ramp-up rate (TL to TP) Preheat - Temperature Min (Tsmin) - Temperature Max (Tsmax) - Time (min to max) (ts) Time maintained above: - Temperature (T L) - Time (tL) Peak/Classificatioon Temperature (Tp) Time within 5C of actual Peak Temperature (tp) Ramp-down Rate Sn-Pb Eutectic Assembly 3C/second max. 100C 150C 60-120 seconds 183C 60-150 seconds See table 1 10-30 seconds Pb-Free Assembly 3C/second max. 150C 200C 60-180 seconds 217C 60-150 seconds See table 2 20-40 seconds
6C/second max. 6C/second max. 6 minutes max. 8 minutes max. Time 25C to Peak Temperature Notes: All temperatures refer to topside of the package .Measured on the body surface.
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APW7071
Classificatin Reflow Profiles(Cont.)
Table 1. SnPb Entectic Process - Package Peak Reflow Temperature s Package Thickness Volume mm 3 Volume mm 3 <350 350 <2.5 mm 240 +0/-5C 225 +0/-5C 2.5 mm 225 +0/-5C 225 +0/-5C
Table 2. Pb-free Process - Package Classification Reflow Temperatures Package Thickness Volume mm 3 Volume mm 3 Volume mm 3 <350 350-2000 >2000 <1.6 mm 260 +0C* 260 +0C* 260 +0C* 1.6 mm - 2.5 mm 260 +0C* 250 +0C* 245 +0C* 2.5 mm 250 +0C* 245 +0C* 245 +0C* *Tolerance: The device manufacturer/supplier shall assure process compatibility up to and including the stated classification temperature (this means Peak reflow temperature +0C. For example 260C+0C) at the rated MSL level.
Reliability test program
Test item SOLDERABILITY HOLT PCT TST ESD Latch-Up Method MIL-STD-883D-2003 MIL-STD-883D-1005.7 JESD-22-B, A102 MIL-STD-883D-1011.9 MIL-STD-883D-3015.7 JESD 78 Description 245C , 5 SEC 1000 Hrs Bias @ 125 C 168 Hrs, 100 % RH , 121C -65C ~ 150C, 200 Cycles VHBM > 2KV, VMM > 200V 10ms , Itr > 100mA
Carrier Tape
t P P1 D
Po E
F W
Bo
Ao
Ko D1
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APW7071
Carrier Tape(Cont.)
T2
J C A B
T1
Application
A 178 1
B 72 1.0 D 1.5 0.1
C
J
T1 8.4 2 P1
T2 1.5 0.3 Ao
W 8.0 0.3 Bo 3.2 0.1
P 4 0.1 Ko 1.4 0.1
E 1.75 0.1 t 0.20.033 (mm)
13.0 + 0.2 2.5 0.15 D1 1.5 0.1 Po 4.0 0.1
SOT-23-5/6
F 3.5 0.05
2.0 0.1 3.15 0.1
Cover Tape Dimensions
Application SOT- 23-5/6 Carrier Width 8 Cover Tape Width 5.3 Devices Per Reel 3000
Customer Service
Anpec Electronics Corp. Head Office : No.6, Dusing 1st Road, SBIP, Hsin-Chu, Taiwan, R.O.C. Tel : 886-3-5642000 Fax : 886-3-5642050 Taipei Branch : 7F, No. 137, Lane 235, Pac Chiao Rd., Hsin Tien City, Taipei Hsien, Taiwan, R. O. C. Tel : 886-2-89191368 Fax : 886-2-89191369
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