FAN5608DHMPX

FAN5608 Serial / Parallel LED Driver with Current-Regulated, Step-Up DC/DC Converter August 2006 FAN5608 Serial / Parallel LED Driver with Current-Regulated, Step-Up DC/DC Converter Features Two independent channels drive up to six LEDs per channel Adaptive output voltage drive to maximize efficiency PFM mode of operation of the boost circuit Up to 85% efficiency Up to 2×20mA output Two built-in DACs for independent (digital) brightness control for both channels LED current can be duty-cycle-modulated, 0 to 20mA Digital, analog, and PWM brightness control 2.7V to 5.5V input voltage range 500KHz operating frequency Soft-start feature Low shutdown current: ICC< 1μA Open-load protection Minimal external components needed Space-saving 4x4mm 12-lead MLP packages Description The FAN5608 is an integrated Schottky diode LED driver, which generates regulated output currents from a battery input voltage of 2.7V to 5V. An internal MOS switch and the external inductor deliver the necessary voltage to the load. The proprietary internal compensation loop continuously monitors the lowest LED cathode voltage of both channels and adjusts the VOUT voltage to the minimum value. The minimum VOUT is determined by the highest LED forward voltage of the selected channel. This adaptive nature allows the FAN5608 architecture to deliver high efficiency. Up to twelve LEDs can be connected in series as long as the summed forward voltage does not exceed the maximum specification of 24V. It is not required to match an equal number of LEDs serially within each channel; FAN5608 delivers the highest efficiency and best current regulation in the balanced configuration. FAN5608 has two internal two-bit D/A converters that provide independent programmability to each output channel. In analog programming, "B" pins must be GND (logic “0”); a resistor must be connected between pin “A” and a fixed supply voltage. The output current can be programmed to any desired value within the specified range. The FAN5608DHMPX is available in a 4x4mm 12-lead MLP package. A single external resistor sets the current and turns the device ON and OFF. Applications Cell phones Handheld computers PDAs, DSCs, MP3 players Keyboard backlights LED displays Ordering Information Part Number FAN5608DHMPX Pb-Free Yes Schottky Diode Internal Package MLP-12 4x4mm Packing Method Tape and Reel © 2006 Fairchild Semiconductor Corporation FAN5608 Rev. 1.0.5 • 8/8/06 www.fairchildsemi.com FAN5608 Serial / Parallel LED Driver with Current-Regulated, Step-Up DC/DC Converter Block Diagram Figure 1. Block Diagram Pin Configuration TOP-VIEW NC 12 VOUT 11 10 INDB GND CH1 B1 1 2 3 9 8 7 INDA CH2 B2 4 5 6 A1 VIN A2 4x4mm 12-Lead MLP(QUAD) (Internal Schottky Diode) FAN5608DHMPX Figure 2. FAN5608M MLP package © 2006 Fairchild Semiconductor Corporation FAN5608 Rev. 1.0.5 • 8/8/06 www.fairchildsemi.com 2 FAN5608 Serial / Parallel LED Driver with Current-Regulated, Step-Up DC/DC Converter Pin Definitions Pin # 1 2 3 4 5 6 7 8 9 10 11 12 Name GND CH1 B1 A1 VIN A2 B2 CH2 INDA INDB VOUT NC Description Ground First LED Cathode DAC B1 DAC A1 Input Voltage DAC A2 DAC B2 Second LED Cathode SD Anode. INDA and INDB must be connected together externally on the PCB. Inductor. INDA and INDB must be connected together externally on the PCB. Output LEDs Anode No Connection Absolute Maximum Ratings The “Absolute Maximum Ratings” are those values beyond which the safety of the device cannot be guaranteed. The device should not be operated at these limits. The parametric values defined in the Electrical Characteristics tables are not guaranteed at the absolute maximum ratings. The “Recommended Operating Conditions” table defines the conditions for actual device operation. Parameter VIN to GND VOUT to GND CH1,CH2 Voltage to GND All Other Pins Junction Temperature (TJ) Storage Temperature Lead Soldering Temperature, 10 seconds Electrostatic Discharge Protection (1,2) HBM CDM Min. -0.3 -0.3 -0.3 -20 -65 1.5 2 Max. 6.5 35 25 VIN+0.3 150 150 300 Units V V V V °C °C °C kV Notes: 1. Using Mil Std. 883E, method 3015.7 (Human Body Model) and EIA/JESD22C101-A (Charge Device Model). 2. Avoid positive polarity ESD stress at the cathode of the internal Schottky diode (Schottky diode cathode (VIN – 0.7V), as required for HIGH logic level. The logic level HIGH (VH) and logic level LOW (VL) of the PWM signal should be: (VIN – 0.7V) < VH < VIN and 0 < VL < 0.6V. EQ 4 EQ 3 Analog Static Control In Analog Mode, B1 and B2 inputs should be connected to GND or “0” logic. A1 and A2 control the LED current through an external resistor (R), as shown in Figure 4, or an external voltage (VEXT) input. The ILED value can be calculated using the formula or the graph below: The frequency of the PWM signal should be within the 50Hz to 1kHz range, by default, or 30kHz at any input if the other input is kept HIGH. PWM Control in Analog Dynamic Mode EQ 2 where 1.2V < VEXT ≤ R(kΩ) x 0.020(mA) + 1.2V and the current multiplication ratio is according to the Electrical Specifications table. The R value should be in the (10kΩ to 50kΩ) range. In Analog Dynamic Mode, the logic level HIGH (VH) and logic level LOW (VL) of the PWM signal should be: VH = VEXT and 0 < VL < 0.6V. EQ 5 25 R=10k 20 ILED (mA) 15 10 5 0 1.0 1.25 1.5 1.75 VEXT (V) 2 2.25 R=50k The frequency of the PWM signal should be in the range from 50Hz to 1kHz. The VEXT amplitude sets the maximum LED current, while the duty cycle of the PWM signal sets the average current between 0mA and ILED maximum. Open-Circuit Protection The FAN5608 has an internal over-voltage protection mechanism that prevents damage to the IC in a no-load condition. If CH1 and/or CH2 LEDs are enabled in an open-circuit condition, FAN5608 automatically sets the duty cycle to 25%. The output voltage can reach as high as 50V at maximum VIN (5.5V). Depending on the capacitor’s rating, the output capacitor may be at risk in this condition. Shutdown Mode Each channel can be independently disabled by applying LOW logic level voltage to the appropriate A and B inputs. When both channels are disabled, the FAN5608 enters shutdown mode and the supply current is reduced to less than 1μA. Figure 7. Analog Control © 2006 Fairchild Semiconductor Corporation FAN5608 Rev. 1.0.5 • 8/8/06 www.fairchildsemi.com 6 FAN5608 Serial / Parallel LED Driver with Current-Regulated, Step-Up DC/DC Converter PWM Control Figure 8. A is PWM controlled; B is LOW; ILED (average) – s x 5mA, where s is the duty cycle A Input (5) B Input (PWM) 30% Duty Cycle 1KHz 70% Duty Cycle 1KHz ILED 0mA OFF Figure 9. A is HIGH and B is PWM controlled; ILED (average) – s x 15mA +5mA, where s is the duty cycle A Input (PWM) 30% Duty Cycle 1KHz 70% Duty Cycle 1KHz (6) B Input (PWM) 30% Duty Cycle 1KHz 70% Duty Cycle 1KHz ILED 0mA OFF (7) Figure 10. A and B are PWM controlled; ILED (average) – s x 20mA, where s is the duty cycle Notes: 5. Proportionally select the duty cycle to achieve a typical LED current from 1mA to 4mA. 6. Maximum PWM frequency can be 30KHz. 7. Proportionally select the duty cycle to achieve a typical LED current from 1mA to 19mA. © 2006 Fairchild Semiconductor Corporation FAN5608 Rev. 1.0.5 • 8/8/06 www.fairchildsemi.com 7 FAN5608 Serial / Parallel LED Driver with Current-Regulated, Step-Up DC/DC Converter Typical Characteristics TA=25C, VBAT = 3.6V, unless otherwise specified. Figure 11. Peak power efficiency Startup Response LED Current 20mA/Div Figure 12. PWM Dimming Input Current 500mA/Div VIN =3.6V, L=6.8uH, COUT=4.7uF, 3-LEDs/CH Voltage at DAC Inputs Output Voltage 10V/Div Tim e 200µS/Div Figure 13. Startup Response Design and Component Selection Guidelines Inductor Selection The inductor is one of the main components required by the boost converter to store energy. The amount of energy stored in the inductor and transferred to the load is controlled by the regulator, using pulse-frequency modulation (PFM) and pulse-skipping techniques. In most cases, the FAN5608 operates in discontinuous conduction mode, resulting in higher inductor current ripple. To ensure proper operation of the current regulator over the entire range of conditions, select the inductor based © 2006 Fairchild Semiconductor Corporation FAN5608 Rev. 1.0.5 • 8/8/06 8 on the maximum output power (POUT) and the minimum input voltage (VIN): L≤ (VIN )2 × T POUT EQ 6 where units of L, VIN, and POUT are in μH, Volt, and Watt, respectively and T = 0.4μs is a factor depending upon the FAN5608 internal architecture. The above relationship is applicable up to POUT = 0.8W and L ≥ 2.2μH . At lower inductor values, the efficiency www.fairchildsemi.com FAN5608 Serial / Parallel LED Driver with Current-Regulated, Step-Up DC/DC Converter decreases due to the resistive loss in the switching power FET. Using L = 3.3μΗ and increasing the load to 12 LED x 20mA (POUT = 800mW) requires VIN > 3.5V to maintain a constant 20mA current through LEDs. An inductance L = 4.7μH ensures proper operation for 2 x 4 white LEDs with regulated 20mA current if VIN > 2.7V. For any lighter load or higher VIN, the inductance may be increased to improve the system efficiency. Application examples are given in Figures 16 - 25. The peak current in the inductor depends on the maximum battery voltage and the inductance, according to the equation: I pk = 1.4 μS × VIN max L The current feeding the string of LEDs is the sum of the currents programmed for each channel in digital or analog mode. Using all four inputs in digital mode, the LED current can be programmed within the 0 to 40mA range, according to the following table: EQ 7 which gives the maximum rated current for the inductor. For L =4.7μH and VIN = 4.2V, the inductor saturation current should be at least 1A. Capacitors Selection Low ESR capacitors should be used to minimize the input and output ripple voltage. Use of a CIN > 4.7μF/6.3V and COUT = 4.7μF/25V type X5R/X7R multilayer ceramic capacitor is recommended. A larger value input capacitor placed as close as possible to FAN5608 may be needed to reduce the input voltage ripple in noise-sensitive applications. An additional LC filter between the battery and the FAN5608 input can help reduce the battery ripple to the level required by a particular application. Driving Two Independent Strings of LEDs For best efficiency, the two strings of LEDs driven by the FAN5608 should have close forward voltages. This recommendation is met when the same number and type of LEDs are serially connected in each channel. If the application requires the two channels be significantly unbalanced, an external resistor may be added in series with the shorter string of LEDs to reduce the voltage difference between the two channels and enhance performance. The maximum differential LEDs connected in series to CH1 and CH2 is not recommended to exceed three LEDs. Driving Higher Current LEDs To increase the LED current range to 50mA, the CH1 and CH2 outputs may be connected, as shown below: CIN 2.7V to 5.5V L = 4.7µH INDB INDA GND 4.7µF DAC Inputs A1 B1 A2 B2 CH1 CH2 Specific Layout Recommendations The FAN5608 is available in a dual Die Attach Pad (DAP) package. One DAP is connected to GND and another to VOUT, making it unnecessary to provide any external connection to the DAPs. Since the internal power dissipation is low, the 4x4mm MLP package is capable of dissipating maximum power without requiring an extra copper field on the printed circuit board. When viewing the bottom of the dual-DAP device package, two electrically isolated exposed metal islands are visible. The two IND pins should be connected externally. Depending on the application noise sensitivity, an external filter may be required between the battery and the IC input. Figure 14. Digital Brightness Control CIN 2.7V to 5.5V L = 4.7µH INDB VIN INDA GND 4.7µF VEXT A1 A2 CH1 CH2 Figure 15. Analog Brightness Control © 2006 Fairchild Semiconductor Corporation FAN5608 Rev. 1.0.5 • 8/8/06 www.fairchildsemi.com 9 FAN5608 Serial / Parallel LED Driver with Current-Regulated, Step-Up DC/DC Converter FAN5608 Efficiency Curves 2.7V to 5.5V L = 6.9µH INDB VIN A1 A2 B1 B2 INDA VOUT FAN5608DHMPX GND CH2 CH1 NC 4.7µF VOUT DAC Input for CH1 DAC Input for CH2 Figure 16. FAN5608 with four LEDs Figure 17. FAN5608 efficiency with four LEDs 2.7V to 5.5V L = 6.8µH INDB VIN A1 A2 B1 B2 INDA VOUT FAN5608DHMPX GND CH2 CH1 NC 4.7µF VOUT DAC Input for CH1 DAC Input for CH2 Figure 18. FAN5608 with six LEDs Figure 19. FAN5608 efficiency with six LEDs 2.7V to 5.5V L = 4.7µH INDB VIN A1 A2 B1 B2 INDA VOUT FAN5608DHMPX GND CH2 CH1 NC 4.7µF VOUT DAC Input for CH1 DAC Input for CH2 Figure 20. FAN5608 with eight LEDs Figure 21. FAN5608 efficiency with eight LEDs © 2006 Fairchild Semiconductor Corporation FAN5608 Rev. 1.0.5 • 8/8/06 www.fairchildsemi.com 10 FAN5608 Serial / Parallel LED Driver with Current-Regulated, Step-Up DC/DC Converter 2.7V to 5.5V L = 3.3µH INDB VIN A1 A2 B1 B2 INDA VOUT FAN5608DHMPX GND CH2 CH1 NC 4.7µF VOUT DAC Input for CH1 DAC Input for CH2 Figure 22. FAN5608 with ten LEDs Figure 23. FAN5608 efficiency with ten LEDs 2.7V to 5.5V L = 2.7µH INDB VIN A1 A2 B1 B2 INDA VOUT FAN5608DHMPX GND CH2 CH1 NC 4.7µF VOUT DAC Input for CH1 DAC Input for CH2 Figure 24. FAN5608 with twelve LEDs Figure 25. FAN5608 efficiency with twelve LEDs © 2006 Fairchild Semiconductor Corporation FAN5608 Rev. 1.0.5 • 8/8/06 www.fairchildsemi.com 11 FAN5608 Serial / Parallel LED Driver with Current-Regulated, Step-Up DC/DC Converter Dimensional Outline Drawings Dimensions are in millimeters unless otherwise noted. Figure 26. 4x4mm 12-Lead MLP © 2006 Fairchild Semiconductor Corporation FAN5608 Rev. 1.0.5 • 8/8/06 www.fairchildsemi.com 12 FAN5608 Serial / Parallel LED Driver with Current-Regulated, Step-Up DC/DC Converter TRADEMARKS The following are registered and unregistered trademarks Fairchild Semiconductor owns or is authorized to use and is not intended to be an exhaustive list of all such trademarks. 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FAIRCHILD DOES NOT ASSUME ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS. THESE SPECIFICATIONS DO NOT EXPAND THE TERMS OF FAIRCHILD’S WORLDWIDE TERMS AND CONDITIONS, SPECIFICALLY THE WARRANTY THEREIN, WHICH COVERS THESE PRODUCTS. LIFE SUPPORT POLICY FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body or (b) support or sustain life, and (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury of the user. 2. A critical component in any component of a life support, device, or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. PRODUCT STATUS DEFINITIONS Definition of Terms Datasheet Identification Advance Information Product Status Formative or In Design First Production Definition This datasheet contains the design specifications for product development. Specifications may change in any manner without notice. This datasheet contains preliminary data; supplementary data will be published at a later date. Fairchild Semiconductor reserves the right to make changes at any time without notice to improve design. This datasheet contains final specifications. Fairchild Semiconductor reserves the right to make changes at any time without notice to improve design. This datasheet contains specifications on a product that has been discontinued by Fairchild Semiconductor. The datasheet is printed for reference information only. Rev. I20 Preliminary No Identification Needed Full Production Obsolete Not In Production © 2006 Fairchild Semiconductor Corporation FAN5608 Rev. 1.0.5 • 8/8/06 www.fairchildsemi.com 13