www.fairchildsemi.com FAN5606 Serial LED Driver with Current-Regulated, Step-Up DC/DC Converter Features Description • • • • • • • • • • • • • • • The FAN5606 LED driver generates regulated output currents from a battery with input voltage varying between 2.7V to 5V. An internal NMOS switch drives an external inductor, and a Schottky diode delivers the inductor’s stored energy to the load. Soft start circuitry prevents excessive current drawn from the supply during power on. Any number of LEDs can be connected in series as long as the summed forward voltages do not lead to exceeding the specified operating output voltage range. Drives Up to Six LEDs in Series Pulse Skip PWM Mode of Operation of the Boost Circuit Up to 90% Peak Efficiency No External Schottky Diode Required Up to 25mA Output Built-in DAC for Digital Brightness Control LED’s Current Can be Duty-Cycle-Modulated Digital, Analog, and PWM Brightness Control 2.7V to 5.5V Input Voltage Range 0.5MHz Operating Frequency (8MHz internal clock) Soft Start Low Shutdown Current: ICC < 1µA LED Short Circuit Protection Minimal External Components Needed Available in an 8-lead MLP Package Applications • • • • • Cell Phones Handheld Computers PDAs, DSCs, MP3 Players Keyboard Backlights LED Display In the FAN5606 device, the internal two-bit D/A converters provide programmability of the output channel current. Analog programming of the output current is also possible in the FAN5606. To do this, ground the “B” pin and connect a resistor between the “A” pin and a fixed supply voltage. The output current can then be programmed to any desired value within its specified range. The analog version uses a single external resistor to set the current, and to turn the device ON and OFF. The device is available in an 8-lead MLP package. Typical Applications Digital Brightness Control Analog Brightness Control VOUT VOUT 2.7V to 5.5V L = 6.8µH VOUT GND IN VIN FAN5606 CIN VExternal R A 4.7µF 2.7V to 5.5V L = 6.8µH VIN CAT B GND IN IND CIN DAC Inputs A FAN5606 IND 4.7µF CAT B REV. 1.0.3 1/7/05 FAN5606 PRODUCT SPECIFICATION Pin Assignment A 1 8 VIN B 2 7 NC CAT 3 6 IND 4 5 GND VOUT FAN5606 8-Lead 3x3mm MLP Pin Descriptions Pin No. Pin Name Pin Function Description 1 A DAC A Input 2 B DAC B Input 3 CAT LED Cathode 4 IND Inductor 5 VOUT Output LED’s Anode 6 GND Ground 7 NC No Connection 8 VIN Input Voltage Definition of Terms Output Current Accuracy: reflects the difference between the measured value of the output current (LED) and programmed value of this current. ( I OUT measured – I OUT programmed ) × 100 Output Current Accuracy (%) = ------------------------------------------------------------------------------------------------------------I OUT programmed Efficiency: is expressed as a ratio between the electrical power into the LEDs and the total power consumed from the input power supply. ( V LED × I LED ) × 100 Efficiency (%) = --------------------------------------------------------V IN × I IN Although this definition leads to a lower value than the boost converter efficiency, it more accurately reflects better system performance, from the user’s point-of-view. 2 REV. 1.0.3 1/7/05 PRODUCT SPECIFICATION FAN5606 Absolute Maximum Ratings Parameter Min Max Unit VIN, A, B Voltage to GND -0.3 Typ 6.5 V VOUT, CAT Voltage to GND -0.3 24 V Any LED Short Circuit Duration (Anode to Cathode) Indefinite Lead Soldering Temperature (10 seconds) 300 Thermal Resistance θjc 8 Operating Junction Temperature Range Storage Temperature Range -55 Electrostatic Discharge (ESD) Protection (Note 1, 2) HBM 4 CDM 1 °C °C/W 150 °C 150 °C kV Electrical Characteristics VIN =2.7V to 5.5V, TA = 25°C, unless otherwise noted. Parameter Conditions Output Current Accuracy Efficiency (AVG) Min. mA VIN > 3.0V 80 % 0.5 850 Supply Current in OFF mode Units 0.9 × I NOM INOM = 20 1.1 × I NOM Multiplication Ratio (Note 3) VA = VB = 0V Digital Mode Digital Mode 1000 MHz 1150 µA 0.1 High VIN-0.7 VIN Low 0 0.6 Analog Mode Input B Threshold Max. A = HIGH, B = HIGH Switching Frequency Input A Threshold Typ. V 1.2 High 0.6 × V IN VIN Low 0 0.3 × V IN V Recommended Operating Conditions Parameter Min Input Voltage Range 2.7 Operating Ambient Temperature Range -40 Output Voltage Range VIN Typ 25 Max Unit 5.5 V 85 °C 18 V 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. 3. Multiplication Ratio is ILED /I INPUT A . REV. 1.0.3 1/7/05 3 FAN5606 PRODUCT SPECIFICATION Block Diagram V V OUT IN OSC DBB IND COIL DRIVER CAT LINEAR REGULA TOR START-UP AMPLIFIER B A DAC BG REF POWER GOOD GND Circuit Description When the input voltage is connected to VIN pin, the system is turned on, the bandgap reference acquires its nominal voltage and the soft-start cycle begins. Once "power good" is achieved (0.5mA in the diodes), the soft-start cycle stops and the boost voltage increases to generate the desired current selected by the input control pins. The FAN5606 DC/DC converter automatically adjusts its internal duty cycle to achieve high efficiency. If the output external capacitor is shorted, the Schottky diode can be damaged, therefore such a condition should be avoided. LED Brightness Control The inputs A and B can be digitally controlled LOW (GND) and HIGH (VCC) signals. In analog mode, A input is connected to an external stable voltage source via an external resistor and B input is connected to ground. The current flowing through the resistor is scaled by a factor of approximately 1000. 4 Digital Control The FAN5606’s digital decoder allows selection of the following modes of operation: OFF, 5mA, 10mA, 20mA per branch. A 0 1 0 1 B 0 0 1 1 ILED OFF 5mA 10mA 20mA Analog Control with PWM In analog control mode, the LED current can go up to 25mA. Input A is used to control the LED currents. Input B should be connected to GND (logic level "0"). An external resistor (R) is connected from A to a stable voltage source (VEXTERNAL) to control the LED current, ILED. The ILED is given by the formula or the graph below: V External – V Ref I LED = ----------------------------------------- × Multiplication Ratio R REV. 1.0.3 1/7/05 PRODUCT SPECIFICATION FAN5606 Pulse-Width-Modulation (PWM) Control A variable duty cycle (δ) can modulate any DAC input. Care should be taken not to use a too low frequency, otherwise a flickering effect may occur. The minimum range is 100Hz to 1KHz. For a maximum range of LED current, both A and B inputs can be modulated at the same time. Where V Ref = 1.22V 25 R=10Kohm I LED (mA) 20 15 10 Open Circuit Protection R=100kohm 5 0 1.25 1.5 1.75 2 2.25 2.5 2.75 3 3.25 3.5 VExternal (V) If the analog input A is driven in digital mode by an open drain output, it is important to choose the appropriate value of the pull-up resistor. Its resistance should be low enough to ensure less than 0.7V dropout, hence VA > (VIN–0.7V), as required for HIGH logic level: 700mV Rpull-up < ------------------ = 11kΩ 60µA A built-in over voltage protection circuit prevents the device from being damaged when it is powered up with no load. This circuit reduces the boost converter duty cycle, to a minimum thus limiting the output voltage to a safe value when no load condition is detected. However, the FAN5606 can be damaged when a full load (Six LEDs driven by 20mA) is suddenly disconnected from VOUT. To protect the FAN5606 against this unlikely event, an external 24 V Zener diode can be connected between VOUT and GND. Shutdown Mode The device can be disabled by applying LOW logic level voltage to the A and B inputs. In Shutdown mode the supply current is reduced to less than 1µA. PWM Control 1. A is PWM Controlled, B is Low. ILED (Average) = δ x 5mA, where δ is Duty Cycle. (Note 4) A Input (PWM) ss ss ss 30% Duty Cycle 70% Duty Cycle 1KHz B Input (0) 1KHz ILED (Average) = 0.7 x 5mA = 3.5mA ILED (Average) = 0.3 x 5mA = 1.5mA ILED 0mA ss OFF 2. A is High and B is PWM. ILED (Average) = 5mA + δ x 15mA, where δ is Duty Cycle.(Note 5, 6) A Input B Input (PWM) ss ss ss ss 30% Duty Cycle 70% Duty Cycle 1KHz 1KHz ILED (Average) = 0.7 x 20mA + 0.3 x 5mA = 15.5mA ILED (Average) = 0.3 x 20mA + 0.7 x 5mA = 9.5mA ss ILED REV. 1.0.3 1/7/05 0mA OFF 5 FAN5606 PRODUCT SPECIFICATION PWM Control (Continued) 3. A and B are PWM. ILED (Average) = δ x 20mA, where δ is Duty Cycle. A Input (PWM) ss 70% Duty Cycle 1KHz B Input (PWM) ss ss 30% Duty Cycle 1KHz ss ss ss 30% Duty Cycle 70% Duty Cycle 1KHz 1KHz ILED (Average) = 0.7 x 20mA = 14mA ILED (Average) = 0.3 x 20mA = 6mA LED CURRENT 0mA ss OFF Notes: 4. Proportionally select the duty cycle to achieve a typical LED current between 1mA to 4mA. 5. Maximum PWM frequency can be up to 30KHz. 6. Proportionally select the duty cycle to achieve a typical LED current between 1mA and 19mA. Applications Information 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 PWM and pulse skipping techniques. In most cases, the FAN5606 operates the inductor in discontinuous conduction mode. To ensure proper operation of the current regulator over the entire range of conditions, the inductor should be selected based on the maximum required power (POUT) and the minimum input voltage (VIN). 2 ( V IN ) × F L < --------------------------P OUT where units of L, VIN, and POUT are in µH, Volt, and Watt, respectively and F = 0.4 is a factor depending upon the FAN5606 architecture. 6 The above relation is applicable up to POUT = 0.6W and L = 4.3µΗ , or greater. The peak current in the inductor is: T ON_Max × V IN_Max I = -------------------------------------------------L where TON_Max = 1.25µS. The recommended inductor for driving upto 6 LEDs, type QTLP670CiW is L = 6.8µH rated at minimum 0.5A. Low ESR capacitors should be used to minimize the input and output ripple voltage. Use of CIN = 4.7µF/6.3V and COUT = 4.7µF/25V type X5R/X7R multi layer ceramic capacitor are recommended. A larger value input capacitor placed as close as possible to FAN5606 may be needed to reduce the input voltage ripple in noise sensitive applications. An additional LC filter between the battery and the FAN5606 input can help to further reduces the battery ripple to the level required by a particular application. REV. 1.0.3 1/7/05 PRODUCT SPECIFICATION FAN5606 Typical Performance Characteristics TA = 25 °C, CIN = 47µF, COUT = 4.7µF, L = 6.8µH, unless otherwise noted. Regulated LED Current vs Input Voltage Efficiency vs Input Voltage 0.95 10.5 4.8 A=1, B=0 Scale1 A=0, B=1 Scale2 A=1, B=1 Scale3 4.6 2.5 3.0 3.5 4.0 4.5 9.0 8.5 5.5 5.0 19 18 17 16 15 Efficiency (%) 9.5 5.0 0.90 LED Current (mA) Scale3 10.0 5.2 LED Current (mA) Scale2 LED Current (mA) Scale1 2 x 20mA Load, L = 22µH 20 5.4 0.85 0.80 0.75 0.70 4 x 20mA Load, L = 6.8µH 0.65 0.60 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Input Voltage (V) Input Voltage (V) Shutdown Current vs Input Voltage Shutdown Current (µA) 0.065 0.060 0.055 0.050 0.045 0.040 0.035 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Input Voltage (V) REV. 1.0.3 1/7/05 7 FAN5606 PRODUCT SPECIFICATION Mechanical Dimensions 3x3mm 8-Lead MLP (Internal Schottky Diode) 2.54 1.37 1.27 GND A 3.0 0.15 C 8 2X VOUT 0.76 5 B 1.99 1.18 3.30 1.40 3.0 (0.65) 1 0.15 C 2X 0.65 TYP 4 0.42 MAX TOP VIEW RECOMMENDED LAND PATTERN 0.8 MAX 0.10 C (0.20) 0.08 C 0.05 0.00 SEATING PLANE C SIDE VIEW 2.54 MAX 1.37 1.26 4 1 PIN #1 IDENT 0.76 0.45 0.43 1.40 MAX 1.18 8 5 0.65 1.95 0.25~0.35 0.10 M C A B 0.05 M BOTTOM VIEW NOTES: A. CONFORMS TO JEDEC REGISTRATION MO-229, VARIATION VEEC, DATED 11/2001 B. DIMENSIONS ARE IN MILLIMETERS. C. DIMENSIONS AND TOLERANCES PER ASME Y14.5M, 1994 8 REV. 1.0.3 1/7/05 PRODUCT SPECIFICATION FAN5606 Ordering Information Product Number Package Type Order Code FAN5606 8-Lead 3x3mm MLP FAN5606DMPX DISCLAIMER FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. 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. 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 THE PRESIDENT 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. www.fairchildsemi.com REV. 1.0.3 5/12/04 2005 Fairchild Semiconductor Corporation