FAN5341

FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface November 2009 FAN5341 Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface Features Asynchronous Boost Converter Internal Schottky Diode Up to 500mW Output Power Drives 3 to 5 LEDs in Series 2.7V to 5.5V Input Voltage Range Single-Wire Digital Control Interface to Set LED Brightness Levels − 32 Linear Steps 1.2MHz Fixed Switching Frequency Soft-Start Capability Input Under-Voltage Lockout (UVLO) Output Over-Voltage Protection (OVP) Short-Circuit Detection Thermal Shutdown (TSD) Protection Low Profile 6-lead 2.0 x 2.0 x 0.55mm UMLP Package Description The FAN5341 is an asynchronous constant-current LED driver capable of efficiently delivering up to 500mW to a string of up to five LEDs in series. Optimized for small formfactor applications, the 1.2MHz fixed switching frequency allows the use of small chip inductors and capacitors. The FAN5341 uses a simple single-wire digital control interface to program the brightness levels of the LEDs in 32 linear steps by applying digital pulses. For safety, the device features integrated over-voltage, overcurrent, short-circuit detection, and thermal-shutdown protection. In addition, input under-voltage lockout protection is triggered if the battery voltage is too low. The FAN5341 is available in a very low profile, small formfactor 2mm x 2mm x 0.55mm 6-lead UMLP package that is green and RoHS compliant. Applications Cellular Mobile Handsets Mobile Internet Devices Portable Media Players PDA, DSC, MP3 Players Ordering Information Part Number FAN5341UMPX Temperature Range -40 to 85°C Eco Status Green Package 6-lead, 2.0 x 2.0mm UMLP Packing Tape and Reel For Fairchild’s definition of Eco Status, please visit: http://www.fairchildsemi.com/company/green/rohs_green.html. © 2009 Fairchild Semiconductor Corporation FAN5341 • Rev. 1.0.0 www.fairchildsemi.com FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface Typical Application Diagram Figure 1. Typical Application Block Diagram Figure 2. Functional Block Diagram © 2009 Fairchild Semiconductor Corporation FAN5341 • Rev. 1.0.0 www.fairchildsemi.com 2 FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface Pin Configuration VOUT 1 6 GND VIN 2 3 P1 GND 5 4 SW FB EN Figure 3. UMLP6 Package, ^Top View Pin Definitions Pin # 1 2 3 4 5 6 Name VOUT VIN EN FB SW GND Description Boost Output Voltage. Output of the boost regulator. Connect the LEDs to this pin. Connect COUT (Output Capacitor) to GND. Input Voltage. Connect to power source and decouple with CIN to GND. Enable Brightness Control. Program dimming levels by driving pin with digital pulses. Voltage Feedback. The boost regulator regulates this pin to 0.253V to control the LED string current. Tie this pin to a current setting resistor (RSET) between GND and the cathode of the LED string. Switching node. Tie inductor L1 from VIN to SW pin. Ground. Tie directly to a GND plane. © 2009 Fairchild Semiconductor Corporation FAN5341 • Rev. 1.0.0 www.fairchildsemi.com 3 FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface Absolute Maximum Ratings Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. The absolute maximum ratings are stress ratings only. Symbol Parameter VIN VFB, VEN VSW VOUT ESD TJ TSTG TL VIN FB, EN Pins SW Pin VOUT Pin Electrostatic Discharge Protection Human Body Model per JESD22-A114 Level Charged Device Model per JESD22-C101 Junction Temperature Storage Temperature Lead Soldering Temperature, 10 Seconds Min. -0.3 -0.3 -0.3 –0.3 3.3 2.0 -40 -65 Max. 6.0 VIN + 0.3 22.0 22.0 Units V V V V kV +150 +150 +260 °C °C °C Recommended Operating Conditions The Recommended Operating Conditions table defines the conditions for actual device operation. Recommended operating conditions are specified to ensure optimal performance to the datasheet specifications. Fairchild does not recommend exceeding them or designing to absolute maximum ratings. Symbol VIN VOUT IOUT TA TJ Note: 1. Parameter VIN Supply Voltage VOUT Voltage (1) Comments Min. 2.7 6.2 Max. 5.5 17.5 25 +85 +125 Units V V mA °C °C VOUT Load Current Ambient Temperature Junction Temperature 500mW Maximum Output Power 5 -40 -40 Application should guarantee that minimum and maximum duty-cycle should fall between 20-85% to meet the specified range Thermal Properties Junction-to-ambient thermal resistance is a function of application and board layout. This data is measured with four-layer 2s2p boards in accordance to JEDEC standard JESD51. Special attention must be paid not to exceed junction temperature TJ(max) at a given ambient temperature TA. Symbol Parameter θJA Junction-to-Ambient Thermal Resistance, UMLP6 Package Typical 70 Units °C/W © 2009 Fairchild Semiconductor Corporation FAN5341 • Rev. 1.0.0 www.fairchildsemi.com 4 FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface Electrical Specifications VIN = 2.7V to 5.5V and TA = -40°C to +85°C unless otherwise noted. Typical values are at TA = 25°C and VIN = 3.6V. Symbol ISD VUVLO VUVHYST Parameter Shutdown Supply Current Under-Voltage Lockout Threshold Under-Voltage Lockout Hysteresis HIGH-Level Input Voltage LOW-Level Input Voltage EN Pull-Down Resistance EN Low Time for Dimming Time Delay Between Steps EN Low, Shutdown Pulse Width Conditions EN = GND, VIN = 3.6V VIN Rising VIN Falling Min. Typ. 0.30 Max. 0.75 2.60 2.40 Units μA V mV Power Supplies 2.10 1.90 2.35 2.15 250 EN: Enable Pin VIH VIL REN TLO THI TSD 1.2 0.4 200 VIN = 3.6V; See Figure 14 VIN = 3.6V; See Figure 14 VIN = 3.6V; from Falling Edge of EN ILED = 20mA from -40°C to +85°C, 2.7V ≤ VIN ≤ 5.5V VFB = 253mV VIN = 3.6V, ISW = 100mA VIN = 2.7V, ISW = 100mA EN = 0, VIN = VSW = VOUT = 5.5V, VLED = 0 VIN = 3.6V 0.5 0.5 1 300 400 300 V V kΩ µs µs ms Feedback and Reference VFB IFB Feedback Voltage Feedback Input Current 240 253 0.1 600 650 0.1 750 2.0 266 1.0 mV μA Power Outputs RDS(ON)_Q1 ISW(OFF) ILIM-PK Boost Switch On-Resistance SW Node Leakage (1) mΩ μA mA Boost Switch Peak Current Limit Boost Regulator Switching Frequency Boost Output Over-Voltage Protection OVP Hysteresis VOUT Short Circuit Detection Threshold VOUT Short Circuit Detection Threshold Maximum Boost Duty Cycle Minimum Boost Duty Cycle (2,3) (2,3) Oscillator fSW 1.0 1.2 1.4 MHz Output and Protection VOVP VTLSC VTHSC DMAX DMIN TTSD THYS 18.0 18.9 0.8 VOUT Falling VOUT Rising 85 20 150 35 VIN – 1.4 VIN – 1.2 V V % °C °C 21.0 V Thermal Shutdown Thermal Shutdown Hysteresis Notes: 1. SW leakage current includes the leakage current of 2 internal switches; SW to GND and SW to VOUT. 2. Not tested in production and guaranteed by design. 3. Application should guarantee that minimum and maximum duty cycle should fall between 20-85% to meet the specified range. © 2009 Fairchild Semiconductor Corporation FAN5341 • Rev. 1.0.0 www.fairchildsemi.com 5 FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface Electrical Specifications 90 90 80 5 LEDs L = 10µH COUT = 1.0µF ILED = 25mA Efficiency (%) 80 5 LEDs L = 4.7µH COUT = 1.0µF ILED = 25mA Efficiency (%) 70 70 60 VIN=2.7V VIN=3.6V VIN=4.2V 60 VIN=2.8V VIN=3.6V VIN=4.2V 50 5 10 15 20 25 50 5 10 15 20 25 LED Current (mA) LED Current (mA) Figure 4. 5 LEDs: Efficiency vs. LED Current vs. Input Voltage 90 Figure 5. 5 LEDs: Efficiency vs. LED Current vs. Input Voltage 0.8 80 Delta Feedback Voltage (m V) 4 LEDs L = 10µH COUT = 1.0µF ILED = 25mA 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -40°C +25°C +85°C Efficiency (%) 70 60 VIN=2.7V VIN=3.6V VIN=4.2V 50 5 10 15 20 25 2.7 3 3.3 3.6 3.9 4.2 LED Current (mA) Input Voltage (V) Figure 6. 4 LEDs: Efficiency vs. LED Current vs. Input Voltage 90 Figure 7. Delta of VFB Over Input Voltage and Temperature for 4 LEDs with L=10µH and COUT=1.0µF at ILED=25mA 20.0 80 3 LEDs L = 10µH COUT = 1.0µF ILED = 25mA 19.5 4 LEDs L = 10µH COUT = 1.0µF ILED = 25mA Efficiency (%) 19.0 OVP (V) 70 18.5 18.0 60 VIN=2.8V VIN=3.6V VIN=4.2V 17.5 50 5 10 15 20 25 17.0 2.7 3 3.3 3.6 3.9 4.2 Input Voltage (V) LED Current (mA) Figure 8. 3 LEDs: Efficiency vs. LED Current vs. Input Voltage © 2009 Fairchild Semiconductor Corporation FAN5341 • Rev. 1.0.0 Figure 9. Over-Voltage Protection vs. Input Voltage www.fairchildsemi.com 6 FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface Electrical Specifications Figure 10. Line Transient Response for 4 LEDs at VIN=3.6V ± 0.6V with L=10µH, COUT=1.0µF and ILED=25mA Figure 11. FAN5341 Dimming Operation at VIN=3.6V for 4 LEDs with L=10µH, COUT=1.0µF and ILED=25mA Figure 12. Startup Waveform for Switch Voltage, Inductor Current, VFB and EN for 4 LEDs at VIN=3.6V± 0.6V with L=10µH, COUT=1.0µF and ILED=25mA Figure 13.Steady-State Waveform for VOUT, Switch Voltage and Inductor Current for 4 LEDs at VIN=3.6V ± 0.6V with L=10µH, COUT=1.0µF and ILED=25mA © 2009 Fairchild Semiconductor Corporation FAN5341 • Rev. 1.0.0 www.fairchildsemi.com 7 FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface Circuit Description Overview The FAN5341 is an inductive current-mode boost serial LED driver that achieves LED current regulation by maintaining 0.253V across the RSET resistor. The current through the LED string (ILED) is therefore given by: FAN5341 does not require the system processor to constantly supply a signal to it to drive the LEDs. Digital Dimming Control The FAN5341 starts driving the LEDs at the maximum brightness level. After startup, the control logic is ready to accept programming pulses to decrease the brightness level by the number of positive edges applied to the EN pin. Figure 14 shows the digital pulse dimming control. I LED = 0.253 RSET (1) The voltage VOUT is determined by the sum of the forward voltages across each LED, plus the voltage across RSET, which is always 253mV. Over-Current and Short-Circuit Detection The boost regulator employs a cycle-by-cycle peak inductor current limit of ~750mA. Driving Five LEDs in Series FAN5341 can drive five LEDs in series but, the forward voltage (VF) of the LED MUST be less than 3.5V such that it remains under the over-voltage specification of 18.9V. Over-Voltage / Open-Circuit Protection If the LED string is an open circuit, FB remains at 0V and the output voltag continues to increase in the absence of an over-voltage protection (OVP) circuit. The FAN5341’s OVP circuit disables the boost regulator when VOUT exceeds 18.9V and continues to keep the regulator off until VOUT drops below 18.1V. UVLO and Soft-Start If EN has been low for more than 1ms, the IC may initiate a “cold start” soft-start cycle when EN rises, provided VIN is above the UVLO threshold. Thermal Shutdown When the die temperature exceeds 150°C, a reset occurs and remains in effect until the die cools to 125°C, at which time, the circuit is allowed to begin the soft-start sequence. Digital Interface The FAN5341 implements a single-wire digital interface to program the LED brightness to one of thirty-two (32) levels spaced in linear steps. With this single-wire solution, the Figure 14. Digital Pulse-Dimming Control Diagram © 2009 Fairchild Semiconductor Corporation FAN5341 • Rev. 1.0.0 www.fairchildsemi.com 8 FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface Application Information Inductor & Output Capacitor Selection # of LEDs Inductor (L) 10.0µH 3, 4, 5 4.7µH Part Number LQH43MN100K03 NLCV32T-100K-PFR VLF3010AT-100MR49-1 LQH43MN4R7K03 NLCV32T-4R7M-PFR LPF2010T-4R7M Manufacturer Murata TDK TDK Murata TDK ABCO Min COUT 1.00µF Part Number CV105X5R105K25AT Manufacturer AVX/Kyocera 1.00µF CV105X5R105K25AT AVX/Kyocera Table 1. Recommended External Components Component Placement and PCB Recomendations Figure 1. Recommended Component Placement Input Capacitance In a typical application, the input and output capacitors should be placed as close to the IC as possible; no additional capacitance is needed to ensure proper functionality. However, in a testing environment, where the FAN5341 is typically powered by a power supply with relatively long cables, an additional input capacitor (10µF) may be needed to ensure stable functioning. This capacitor should be placed close to where the power supply cables attach to the FAN5341 evaluation board. PCB Recommendations The inductor can be connected to VIN with vias through another layer if needed. The feedback pin should be connected back to the IC on a sub-layer. © 2009 Fairchild Semiconductor Corporation FAN5341 • Rev. 1.0.0 www.fairchildsemi.com 9 FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface Physical Dimensions 0.10 C 2X 2.0 A B 2.0 6 1.60 1.50 4 0.50 0.10 C PIN1 IDENT 0.27 2X TOP VIEW 0.85 1 3 1.40 2.40 0.55 MAX 0.10 C (0.15) 0.65 0.30 0.08 C 0.05 0.00 RECOMMENDED LAND PATTERN C SEATING PLANE SIDE VIEW NOTES: PIN1 IDENT 1 1.35 1.45 3 6x 0.35 0.25 6 4 0.70 0.80 0.65 1.30 0.35 6x 0.25 0.10 C A B 0.05 C BOTTOM VIEW Figure 15. 6-Lead Molded Leadless Package (UMLP) Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner without notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representative to verify or obtain the most recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions, specifically the warranty therein, which covers Fairchild products. Always visit Fairchild Semiconductor’s online packaging area for the most recent package drawings: http://www.fairchildsemi.com/packaging/. © 2009 Fairchild Semiconductor Corporation FAN5341 • Rev. 1.0.0 www.fairchildsemi.com 10 FAN5341 — Series Boost LED Driver with Integrated Schottky Diode and Single-Wire Digital Interface www.fairchildsemi.com © 2009 Fairchild Semiconductor Corporation FAN5341 • Rev. 1.0.0 11