SC4505 High Efficiency Boost Converter for Backlight/Flash LED Driver POWER MANAGEMENT Features Description The SC4505 is a high-frequency PWM current-mode step- Two independent current sources for dual LED strands up switching regulator with an integrated 2A power tran- with optimal current/light matching. Backlight up to 75mA, Flash up to 125mA sistor. Its high switching frequency (1MHz) allows the use of tiny surface-mount external passive components. The Wide input range from 2.6V to 12V internal switch is rated at 36V which makes the con- Adaptive output voltage up to 28V with OVP protec- verter ideal for multiple LED series operation with opti- tion against open circuit conditions mal current matching. Two programmable independent Low shutdown current (<1 A ) Internal Flash/Torch mode with flash timeout to pro- current source structure allows dual panel LED backlight and flash operation. tect LEDs 1MHz Fixed Frequency Current-Mode Control The operating frequency of the SC4505 is set at 1MHz. Internal 2A current limit for driving large numbers of The selected operating frequency gives the SC4505 de- LEDs Supports PWM Dimming from 50Hz to 50kHz sign flexibility for size, cost and efficiency optimization. The SC4505 is available in thermally enhanced 16-pin Internal undervoltage lockout MLPQ package (3x3x0.9mm) with embedded over tem- Small, low profile, thermally enhanced 16-MLPQ pack- perature protection. age is fully WEEE and RoHS compliant Applications White LED power supplies Flat screen LCD bias supplies TFT bias supplies Dual panel Handset/Liquid Crystal Display Monitor Portable media players Digital video cameras Digital still cameras Typical Application Circuit Boost Converter Efficiency vs Input Voltage LED: SML-LX0603UWD (2 String of 3 LEDs 30mA) L1 VIN: 2.6V ~ 6.0V D1 2 1 IHLP-2525CZ-01-1R5-M-01 10BQ015 D3 87 D2 C2 LED LED C1 2.2u PGND 2.2uF 85 SC4505 D5 D4 0 0 16 1 VIN PGND LED LED C3 15 2 0 FTO PGND 83 0.33uF FL TRB 14 3 FL TRB SW EN FL 13 4 EN FL SW D6 D7 LED LED EN BL 12 5 81 EN BL VO AGND 11 6 IO1SET IO2 RO1SET 10 7 IO2SET IO1 79 6.98k C5 R1 C4 9 8 AGND COMP 12n C6 3.01k 12n RO2SET (Optional) (Optional) 12n 1.54k 77 0 0 0 2.5 3 3.5 4 4.5 5 Power Analog Ground Ground Input Voltage (V) All Capacitors are Ceramic. Figure 1. SC4505 Application Circuit for Backlight and Flashlight LED Driver Revision: December 12, 2007 1 www.semtech.com Efficiency (%)SC4505 POWER MANAGEMENT Absolute Maximum Rating Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters specified in the Electrical Characteristics section is not implied. Exposure to Absolute Maximum rated conditions for extended periods of time may affect device reliability. Plarameter Spymbo Tsy Unit SVupply Voltage -V0.3 to 20 IN SVW Voltage, Output Voltage, Current Source Voltage , V , V , V -V0.3 to 36 SW O IO1 IO2 IVVoltage V -V0.3 to 2 0SET IO1SET, IO2SET FVTO Voltage -0.3 to V+V0.3 FTO IN V , V EN BL EN FL EN BL, EN FL, FL TRB Voltage -0.3 to V+V0.3 IN V FL TRB Thermal Resistance Junction to Ambient 3W7 C/ JA MTaximum Junction Temperature 1C50 J STtorage Temperature Range -C65 to +150 STG ITR Reflow (Soldering) 10s to 30s 2C60 PKG EDSD Rating (Human Body Model) E1S kV Electrical Characteristics Unless specified: V = 3.6V, -40C < T = T < 85C, R =6.98K , R =1.54K IN A J O1SET O2SET Psarameter Tnest Condition Mpi Txy Mta Uni Supply Input Voltage V 22.6 1V IN UVVLO Threshold r5ising 29.4 2V.5 IN UVLO Hysteresis 5V0 m VSgupply Current N7ot switchin 1A. m IN VS0upply Current in ShutdownE0N FL = FL TRB = EN BL = 1A. IN STwitching Frequency =825C 01. 1z.2 MH J Maximum Duty Cycle 805 9 % Minimum Duty Cycle 0% Switch Current Limit 15.752A.2 V=128V 01.0 A Switch Leakage Current SW I=01A 3V0 m Switch Saturation Voltage SW EN FL, FL TRB, EN BL V=22.6V to 4.7V V IN High Voltage EN FL, FL TRB, EN BL V=42.6V to 4.7V 0V. IN Low Voltage 2007 Semtech Corp. www.semtech.com 2