APW7071 Step-Up Converter for 4 Series White LEDs Driver Features General Description • 2.5 V to 6V Input Voltage Range The APW7071 is a high frequency step-up DC/DC con- • 400mA Internal Switch Current • verter in a small 6-lead SOT-23 package specially designed to drive white LEDs with a constant current. The device Up to 1MHz Switching Frequency • 70µA Typical No Load Quiescent Current • 0.1µA Typical Shutdown Current • Internal Soft-Start • Up to 87% Efficiency • Operating Output Capacitor Down to 0.1µF • Over Voltage Protection Included • Lead Free and Green Devices Available can drive up to 4 LEDs in 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 back-lighting. Pin Configuration V IN O V P S H D N (RoHS Compliant) Applications 6 5 1 2 4 3 SW GND FB • Cellar Phones White LED Back Light • PDAs, Handheld Computers • Digital Still Cameras • MP3 Players • GPS Receivers SOT-23-6 (Top View) Ordering and Marking Information APW7071 Package Code C : SOT-23-6 Operating Ambient Temperature Range I : -40 to 85oC Handling Code TR : Tape & Reel Assembly Material L : Lead Free Device G : Halogen and Lead Free Device Assembly Material Handling Code Temperature Range Package Code APW7071C : X - Date Code W71X Note: ANPEC lead-free products contain molding compounds/die attach materials and 100% matte tin plate termination finish; which are fully compliant with RoHS. 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 defines “Green” to mean lead-free (RoHS compliant) and halogen free (Br or Cl does not exceed 900ppm by weight in homogeneous material and total of Br and Cl does not exceed 1500ppm by weight). 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 ANPEC Electronics Corp. Rev. A.3 - Jul., 2008 1 www.anpec.com.tw APW7071 Absolute Maximum Ratings Symbol VIN (Note 2) Parameter Rating Unit -0.3 ~ 7 V -0.3 ~ VIN+0.3 V Input Supply Voltage Voltage on Pins FB, SHDN VOVP Voltage on Pin OVP -0.3 ~ 20 V VSW Switch Voltage on pin SW -0.3 ~ 21 V TJ Junction Temperature Range -40 ~ 150 °C TSTG Storage Temperature Range -65 ~150 °C TSDR Maximum Lead Soldering Temperature, 10 Seconds 260 °C Note 2: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Thermal Characteristics Symbol θJA Parameter Junction-to-Ambient Resistance in Free Air Typical Value Unit 250 °C/W (Note 3) Note 3: θJA is measured with the component mounted on a high effective thermal conductivity test board in free air. Recommended Operating Conditions (Note 4) Value Symbol Parameter Unit Min. Typ. Max. 2.5 - 6.0 V VIN Input Supply Voltage VSW Switch Voltage - - 20 V VOUT Output Voltage - - 19 V Inductor 2.2 - 10 µH Input Capacitor 4.7 - - µF Output Capacitor 0.1 - 1 µF TA Operating Ambient Temperature -40 - 85 °C TJ Operating Junction Temperature -40 - 125 °C L CIN COUT Note 4: Please refer to Typical Application Circuit Copyright ANPEC Electronics Corp. Rev. A.3 - Jul., 2008 2 www.anpec.com.tw APW7071 Electrical Characteristics VIN=3.3V, SHDN=VIN, TA= -40°C to +85°C, typical values are at TA=+25°C (unless otherwise noted). APW7071 Symbol Parameter Test Conditions Unit Min. Typ. Max. 2.5 - 6 V SUPPLY VOLTAGE AND CURRENT VIN Input Voltage Range IQ Operating Quiescent Current IOUT=0, not switching, VFB=0.3V - 70 90 µA IQ_SD Shutdown Current SHDN=GND - 0.1 1 µA UVLO Under-Voltage Lockout Threshold - 2.2 2.4 V Under-Voltage Lockout Hysteresis - 150 - mV ENABLE VIH SHDN High Level Input Voltage 1.3 - - V VIL SHDN Low Level Input Voltage - - 0.4 V - 0.1 1 µA - - 20 V Ii SHDN Input Leakage Current SHDN=GND or VIN POWER SWITCH AND CURRENT LIMIT VSW Maximum Switching Voltage toff Minimum Off-Time 300 400 550 ns ton Maximum On-Time 4 6 7.5 µs Rdson ILIM MOSFET On-Resistance VIN=2.5V, ISW =200mA - 600 1000 mΩ MOSFET Leakage Current VSW =19V - 0.1 1 µA MOSFET Current Limit 350 400 500 mA Adjustable Output Voltage Range VIN - 19 V - - 100 nA 0.237 0.25 0.263 V OVP Threshold 16 17 18.5 V OVP Hysteresis 3 4 5 V OUTPUT VOUT IFB Feedback Input Bias Current VFB=1.3V VREF Feedback Trip Point Voltage 2.5≦VIN≦6.0V IOVP OVP Input Current VOVP=15V - 5 10 µA OVP Leakage Current SHDN=GND, VOVP=6V - 0.1 1 µA Copyright ANPEC Electronics Corp. Rev. A.3 - Jul., 2008 3 www.anpec.com.tw APW7071 Typical Operating Characteristics (Circuit of Figure 1, VIN = 3.3V, ILED = 20mA, L1 = 4.7µH, CIN = 4.7µF, COUT = 0.1µF,4 LEDs, TA = +25°C, unless otherwise noted.) Efficiency vs. LED Current Efficiency vs. Supply Voltage 90 90 88 86 86 VIN=3.6V 84 84 Efficiency(%) Efficiency(%) 88 VIN=4.2V VIN=2.7V 82 80 78 82 80 78 76 74 76 ILED=15mA 72 74 0.1 1 10 70 100 2 3 4 LED Current(mA) 6 Switch on Resistance vs. Junction Temperature Switch on Resistance vs. Supply Voltage 0.7 0.6 0.6 0.5 Switch on Resistance (Ω) Swiitch On Resistaance (Ω) 5 Supply Voltage (V) 0.5 0.4 0.3 0.2 0.1 0.4 0.3 0.2 0.1 VIN=3.3V 0 -40 0 2 3 4 5 6 -20 Supply Voltage (V) No-Switching Quiescent Current vs. Supply Voltage 20 40 60 80 100 LED Current vs. Supply Voltage 25 75 70 20 65 LED Current (mA) No-Switching Quiescent Current (µA) 0 Junction Temperature (°C) 60 55 50 15 10 L=4.7µH 5 45 40 COUT=0.1µF 4 LEDs 2 3 4 5 0 6 1 Supply Voltage (V) Copyright ANPEC Electronics Corp. Rev. A.3 - Jul., 2008 2 3 4 5 6 Supply Voltage (V) 4 www.anpec.com.tw APW7071 Operating Waveforms (Circuit of Figure 1, VIN = 3.3V, ILED = 20mA, L1 = 4.7µH, CIN = 4.7µF, COUT = 0.1µF,4 LEDs, TA = +25°C, unless otherwise noted.) OVP Waveform Start-up Waveform VSHDN 1 VOUT VOUT 1 2 IIN 3 CH1: VOUT, 5V/Div, DC Time: 20ms/Div CH1: VSHDN, 2V/Div, DC CH2: VOUT, 5V/Div, DC CH3: IIN, 100mA/Div, DC Time: 1ms/Div PFM Operation Pulse Burst Operation 1 1 2 2 3 3 CH1: VOUT, 200mV/Div, AC CH2: VSW, 10V/Div, DC CH3: VFB, 100mA/Div, DC Time: 2µs/Div CH1: VOUT, 200mV/Div, AC CH2: VSW, 10V/Div, DC CH3: VFB, 100mA/Div, DC Time: 1µs/Div Copyright ANPEC Electronics Corp. Rev. A.3 - Jul., 2008 5 www.anpec.com.tw APW7071 Pin Description NO NAME FUNCTION 1 SW 2 GND 3 FB Feedback Pin. Reference voltage is 0.25V. Connect this pin to cathode of lowest LED and resistor (RFB). Calculate resistor value according to RFB = 0.25V/lLED 4 SHDN Shutdown Pin. Pulling this pin to ground forces the device into shutdown mode reducing the supply current to less than 1µA. This pin should not be left floating. 5 OVP Over voltage protection sense pin. Connect this pin to output capacitor. Left it unconnected to disable OVP function. 6 VIN Supply voltage Pin. Switch Pin. Connect this pin to inductor/diode here. Ground Pin. Block Diagram OVP 5 Under Voltage Lockout VIN 6 1 SW OVP SHDN Comparator 400ns Min. off-time Error Comparator FB 3 Control Logic VREF=0.25V 6µs Max. on-time Gate Driver N-MOSFET Current Limit RSENSE Soft start SHDN 4 2 GND Copyright ANPEC Electronics Corp. Rev. A.3 - Jul., 2008 6 www.anpec.com.tw APW7071 Typical Application Circuits D1 MSCD052 L1 VIN VOUT 4.7µH 2.7V~6V C1 4.7µF 6 VIN SW 1 C2 0.1µF 2 GND OVP SHDN FB 3 4 off on 5 R1 13 Figure.1 Typical 4 LEDs application Using one or more output capacitors with larger capacitance like 1µF can reduce the LED ripple current as well as improve line regulation. Copyright ANPEC Electronics Corp. Rev. A.3 - Jul., 2008 7 www.anpec.com.tw APW7071 Function Description Operation Over Voltage Protection The APW7071 operates in a pulse frequency modulation In driving LED applications, the feedback voltage on FB pin falls down if one of the LEDs, in series, is failed. (PFM) scheme with constant peak current control. The operation can be understood by referring to the Block Meanwhile, the converter unceasingly boosts the output voltage like a open-loop operation. Therefore, an over- Diagram. The converter keeps monitoring the output voltage through the resistor-divider connected with FB, GND, and VOUT. When the feedback voltage on FB falls below voltage protection (OVP), monitoring the output voltage via OVP pin, is integrated into the chip to prevent the SW the reference voltage (typical 0.25V), the internal switch turns on and the inductor current ramps up. The switch and the output voltages from exceeding their maximum voltage ratings. When the voltage on the OVP pin rises turns off if the inductor current reaches the internal peak current limit (400mA typical). The second criterion that above the OVP threshold (17V typical), the converter stops switching and prevents the output voltage from rising. turns off the switch is the maximum on-time control. As the switch is off, the external Schottky diode forwards bias, The converter can work again when the OVP voltage falls below the OVP voltage threshold. so that the current is delivered to the output. The switch remains off for a minimum of 400ns (typical), and it wouldn’t be turned on again until the feedback voltage drops below the reference voltage. This regulation scheme allows a wider selection range for the inductor and output capacitor. Shutdown Driving SHDN to ground places the A P W 7 0 7 1 in shutdown. When in shutdown, the internal power MOSFET turns off, all internal circuitry shuts down and the quiescent supply current of VIN reduces to <0.1µA (typical). Soft-Start The APW7071 limits this inrush current by increasing the current limit at start-up. Under Voltage Lockout Transients cause system damage or failure when powering on or undergoing instantaneous glitches in the supply voltage. Then, the undervoltage lockout circuit turns the main switch off to prevent malfunction at low input voltage. Copyright ANPEC Electronics Corp. Rev. A.3 - Jul., 2008 8 www.anpec.com.tw APW7071 Application Information Setting the LEDs Current b. Using a PWM signal to apply to SHDN In figure 1, the converter regulates the voltage on FB pin, An external PWM signal applied to SHDN pin cyclically connected with the cathod of the lowest LED and the current-sense resistor R1, at 0.25V(typical). Therefore, turns on or off the converter. The average current through the LEDs will increase proportionally to the duty cycle the current (ILED), flowing via the LEDs and the R1, is calculated by the following equation: of the PWM signal. Due to the soft-start duration, the PWM signal with frequency from 100Hz to 300Hz is ILED = recommended. 0.25V R1 VIN Brightness Control C1 4.7µF 6 2 a. Using an adjustable DC voltage applied to the R3 is PWM 100Hz~300Hz brightness control shown in figure. 2. and R1. An adjustable DC voltage (VADJ), connected with R3, injects a constant current (I1, I1=(VADJ-0.25V)/R3) into R2 × ( VADJ − 0.25 ) R3 R1 D1 MSCD052 C1 4.7µF VIN 2 VOUT GND SHDN C2 1 0.1µF OVP SHDN FB 4 6 4 GND VOUT 4.7µH 2.7V~6V 4.7µH SW D1 MSCD052 L1 SW C2 1 0.1µF L1 2 R1 13 VIN controlled from 0mA to 20mA. VIN 3 FB SHDN PWM signal with frequency above 5kHz is recommended. With the VADJ from 0V to 3.3V, the LED current can be 6 4 applying a PWM signal to an RC filter (R4 and C3) to generate a filtered PWM signal instead of the VADJ. The The LED current is calculated by the following equation: C1 4.7µF 5 OVP c. Using a filtered PWM signal In figure. 4, the brightness control can be achieved by Therefore, the voltage across R1 is reduced by the offset voltage (I1xR2), reducing the LED current and brightness. 2.7V~6V GND Figure. 3 Brightness Control by applying a PWM signal to SHDN the FB node when the FB voltage is regulated at 0.25V. VIN C2 1 SW Duty=100%, LED=20mA Duty=0%, LED off In figure 2, an additional network (R2 and R3) is connected between the FB, the junction of the LED cathode ILED = VIN 0.1µF methods to adjust the brightness of the LEDs : 0.25V - VOUT 4.7µH 2.7V~6V The brightness of the LEDs is controlled by adjusting the LED current. There are three following recommended D1 MSCD052 L1 FB 3.3V PWM brightness 0V control Duty=100%, LED off Duty=0%, LED=20mA 5 3 OVP 5 3 R2 R3 120K R4 10K 10K R1 13 C3 0.1uF R2 Figure. 4 Brightness Control by a filtered PWM signal R3 120K 10K R1 13 Inductor Selection VADJ=3.3V, LED off VADJ=0V, LED=20mA The inductor together with the load current (IOUT), internal peak current (IPK), input (VIN) and output voltage (VOUT) of the application determines the switching frequency of the Figure. 2 Brightness Control by an adjustable DC voltage Copyright ANPEC Electronics Corp. Rev. A.3 - Jul., 2008 9 www.anpec.com.tw APW7071 Application Information (Cont.) Recommended inductors Inductor Selection (Cont.) converter. The switching frequency is calculated as: FSW = 2 ⋅ IOUT ⋅ (VOUT − VIN + VF ) L 2 ⋅ IPK where Part No. LQH31CN2R2M03L Value (µH) 2.2 Vendor Murata LQH32CN4R7M23L SH30184R7YSB 4.7 4.7 Murata ABC LQH32CN100K53L SH3018100YSB 10 10 Murata ABC VF is the foward voltage of the Schottky diode. Output capacitor selection A smaller inductor gets higher switching frequency but For better output voltage filtering, a low ESR output capacitor like ceramic capacitors is recommended. The se- lower efficiency. To operate under discontinuous conduction mode, the inductor can be selected as below: lection of the output capacitance directly influences the output voltage ripple of the converter. The output voltage TOFF,MIN ⋅ (VOUT + VF − VIN ) L≤ ripple is calculated as: IPK ∆VOUT = For the white LED applications, the inductor values between 2.2 µH and 10 µH are recommended. The inductor also affects the maximum output power. In white LED applications, the output ripple is propor- The maximum output current is calculated as: IOUT ,MAX = L ⋅ IPK 1 1 ⋅ ⋅ IPK − IOUT C VOUT − VIN + VF 2 tional to the LED current. A proper output capacitor from 0.1µF to 1µF is recommended to limit the maximum cur- T + TOFF VIN V 1 ⋅ IIN,AVG ⋅ η = IN ⋅ ⋅ IPK ⋅ ON ⋅η VOUT VOUT 2 TS rent ripple of the LED current. where Recommended output capacitor TON TOFF L ⋅ IPK = VIN L ⋅ IPK = VOUT − VIN + VF T =T S ON +T OFF, MIN =T ON + 0.4µs (typical) Part No. Value Vender GRM188R61E105KA12 1.0µF/X5R/0603/25V Murata Any 0.22µF Any Any 0.1µF Any Input capacitor selection It can be understood by the following figure. For good input voltage filtering, low ESR ceramic capacitors are recommended. A 4.7µF ceramic input capacitor ILX IPK is sufficient for most applications. For better-input voltage filtering the capacitor value can be increased. Ton Toff Recommended input capacitor t Toff,min Ts Part No. Value GRM188R60J475KE19D 4.7µF/X5R/0603/6.3V Vender Murata GRM219R60J106KE19D 10µF/X5R/0805/6.3V Murata Figure.5 Discontinuous Conduction Mode Operation Waveform Diode selection The efficiency can be estimated by the section of “Typical The current rating of the diode must meet the peak current rating of the converter. To achieve high efficiency, a Schottky diode must be used. Operating Characteristics”. Copyright ANPEC Electronics Corp. Rev. A.3 - Jul., 2008 10 www.anpec.com.tw APW7071 Application Information (Cont.) Diode selection (Cont.) Recommended diode Part No. Reverse Voltage Vender MSCD052 20 Zowie Layout consideration For all switching power supplies especially with high peak currents and switching frequency, the layout is an important step in the design. If the layout is not carefully done, the regulator may show noise problems and duty cycle jitter. 1.The input capacitor must be placed close to the device, which can reduce copper trace resistance and effect input ripple of the IC . 2.The inductor and diode should be placed as close as possible to the switch pin to minimize the switching noise. 3.The feedback pin and feedback network should be far away from the inductor and shielded by a ground plane or trace to minimize the noise. Copyright ANPEC Electronics Corp. Rev. A.3 - Jul., 2008 11 www.anpec.com.tw APW7071 Package Information SOT-23-6 D e E E1 SEE VIEW A b c 0.25 A L 0 GAUGE PLANE SEATING PLANE A1 A2 e1 VIEW A S Y M B O L SOT-23-6 MILLIMETERS MIN. INCHES MAX. A MAX. MIN. 0.057 1.45 0.006 A1 0.00 0.15 0.000 A2 0.90 1.30 0.035 0.051 b 0.30 0.50 0.012 0.020 c 0.08 0.22 0.003 0.009 D 2.70 3.10 0.106 0.122 E 2.60 3.00 0.102 0.118 E1 1.40 1.80 0.055 0.071 e 0.95 BSC e1 1.90 BSC 0.037 BSC 0.075 BSC L 0.30 0.60 0 0° 8° 0.012 0° 0.024 8° Note : 1. Follow JEDEC TO-178 AB. 2. Dimension D and E1 do not include mold flash, protrusions or gate burrs. Mold flash, protrusion or gate burrs shall not exceed 10 mil per side. Copyright ANPEC Electronics Corp. Rev. A.3 - Jul., 2008 12 www.anpec.com.tw APW7071 Carrier Tape & Reel Dimensions P0 P2 P1 A B0 W F E1 OD0 K0 A0 A OD1 B B T SECTION A-A SECTION B-B H A d T1 Application A H 178.0±2.00 50 MIN. SOT-23-6 P0 P1 4.0±0.10 4.0±0.10 T1 C d 8.4+2.00 13.0+0.50 1.5 MIN. -0.00 -0.20 P2 D0 D1 1.5+0.10 2.0±0.05 1.0 MIN. -0.00 D 20.2 MIN. W E1 8.0±0.30 1.75±0.10 F 3.5±0.05 T A0 B0 K0 0.6+0.00 3.20±0.20 3.10±0.20 1.50±0.20 -0.40 (mm) Cover Tape Dimensions Package Type Unit Quantity SOT-23-6 Tape & Reel 3000 Copyright ANPEC Electronics Corp. Rev. A.3 - Jul., 2008 13 www.anpec.com.tw APW7071 Reflow Condition (IR/Convection or VPR Reflow) tp TP Critical Zone TL to TP Ramp-up Temperature TL tL Tsmax Tsmin Ramp-down ts Preheat 25 t 25°C to Peak Time 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 245°C, 5 sec 1000 Hrs Bias @125°C 168 Hrs, 100%RH, 121°C -65°C~150°C, 200 Cycles VHBM > 2KV, VMM > 200V 10ms, 1tr > 100mA Classification 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 (TL) - Time (tL) Peak/Classification Temperature (Tp) Time within 5°C of actual Peak Temperature (tp) Ramp-down Rate Time 25°C to Peak Temperature Sn-Pb Eutectic Assembly Pb-Free Assembly 3°C/second max. 3°C/second max. 100°C 150°C 60-120 seconds 150°C 200°C 60-180 seconds 183°C 60-150 seconds 217°C 60-150 seconds See table 1 See table 2 10-30 seconds 20-40 seconds 6°C/second max. 6°C/second max. 6 minutes max. 8 minutes max. Notes: All temperatures refer to topside of the package. Measured on the body surface. Copyright ANPEC Electronics Corp. Rev. A.3 - Jul., 2008 14 www.anpec.com.tw APW7071 Classification Reflow Profiles (Cont.) Table 1. SnPb Eutectic Process – Package Peak Reflow Temperatures 3 3 Package Thickness <2.5 mm ≥2.5 mm Volume mm ≥350 225 +0/-5°C 225 +0/-5°C Volume mm <350 240 +0/-5°C 225 +0/-5°C Table 2. Pb-free Process – Package Classification Reflow Temperatures 3 3 3 Volume mm Volume mm Volume mm <350 350-2000 >2000 <1.6 mm 260 +0°C* 260 +0°C* 260 +0°C* 1.6 mm – 2.5 mm 260 +0°C* 250 +0°C* 245 +0°C* ≥2.5 mm 250 +0°C* 245 +0°C* 245 +0°C* * Tolerance: The device manufacturer/supplier shall assure process compatibility up to and including the stated classification temperature (this means Peak reflow temperature +0°C. For example 260°C+0°C) at the rated MSL level. Package Thickness 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 : 2F, No. 11, Lane 218, Sec 2 Jhongsing Rd., Sindian City, Taipei County 23146, Taiwan Tel : 886-2-2910-3838 Fax : 886-2-2917-3838 Copyright ANPEC Electronics Corp. Rev. A.3 - Jul., 2008 15 www.anpec.com.tw