www.fairchildsemi.com FAN5607 LED Driver with Adaptive Charge Pump DC/DC Converter Features Description • • • • The FAN5607 generates regulated output current from a battery with input voltage varying between 2.7V to 5.5V. Switch reconfiguration and fractional switching techniques are utilized to achieve high efficiency over the entire input voltage range. A proprietary internal circuitry continuously monitors each LED current loop and automatically adjusts the generated output DC voltage to the lowest minimum value required by the LED having the highest forward voltage. This adaptive nature of the FAN5607 eliminates the need for LED pre-selection (matching) and ensures operation at high efficiency. When the input voltage is sufficiently high to sustain the programmed current level in the LEDs, the FAN5607 re-configures itself to operate as a linear regulator, and the DC-DC converter is turned off. Only two 0.1µF to 1µF bucket capacitors and two 4.7µF input/output capacitors are needed for proper operation. LED current can be programmed using an external resistor. The resistor sets the maximum LED current and a PWM signal applied to the enable pin can modulate that current level between 0mA (off) and the maximum level. • • • • • • • • • • • • • Parallel LED Driver Supports all Forward Voltages Adaptive VOUT Adjustment to the Highest Diode Voltage Internally Matched LED Current Sources Built-in Charge Pump has Three Modes of Operation: – 1X, 1.5X, and 2X Mode Up to 93% Efficiency Low EMI, Low Ripple Up to 120mA Output Current ( 4 × 30 mA ) External Resistor to Set Maximum (100%) LED Current Enable Input Can be Duty-Cycle-Modulated to Control LED Current Level Between 0 and 100% 2.4V to 5.5V Input Voltage Range ICC < 1µA in Shutdown Mode 1MHz Operating Frequency Shutdown Isolates Output from Input Soft-Start Limits Inrush Current Short Circuit Protection Minimal External Components Needed Available in a 4x4mm 16-lead MLP Package Applications • • • • • Soft-start circuitry prevents excessive current draw during power on. The device has built-in short circuit protection. Cell Phones Handheld Computers PDA, DSC, MP3 Players Keyboard Backlight LED Displays The device is available in 4x4mm 16-lead MLP package. Typical Application VOUT COUT VIN VOUT VIN LED- LED- EN LED- LEDCAP- CIN FAN5607 CAP2 CAP+ CAP+ RSET RSET CAP1 GND CAP- REV. 1.0.0 6/22/04 FAN5607 PRODUCT SPECIFICATION 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 Current Matching: refers to the absolute value of difference in current between the two LED branches. ( I LED branch 1 – I LED branch 2 ) × 100 Current Matching (%) = ---------------------------------------------------------------------------------------------------( I LED branch 1 + I LED branch 2 ) Efficiency: is expressed as a ratio between the electrical power into the LEDs and the total power consumed from the input power supply. 4 ∑ VLEDi × ILEDi i=1 Efficiency = -------------------------------------------V IN × I IN Note: 1. Some competitors calculate the power efficiency as a function of VOUT instead of VLED. This method neglects the power lost due to the cathode voltage ≠ 0 and provides an efficiency “improved” up to 5%. 2 REV. 1.0.0 6/22/04 PRODUCT SPECIFICATION FAN5607 Pin Assignments LED- LED- LED- LED- Top-View 16 15 14 13 CAP2+ NC 3 10 CAP2- NC 4 9 CAP1- 6 OUT 5 7 8 CAP1+ GND 11 VIN 12 2 RSET 1 V EN NC FAN5607 4x4mm 16-Lead MLP Pin Descriptions Pin No. Pin Name Pin Function Description 1 EN Enable Pin 2 NC No Connection 3 NC No Connection 4 NC No Connection 5 RSET External resistor to set LED current 6 VOUT Output to LEDs Anode 7 VIN 8 CAP1+ Bucket capacitor positive connection 9 CAP1- Bucket capacitor negative terminal 10 CAP2- Bucket capacitor negative connection 11 CAP2+ Bucket capacitor positive terminal 12 GND Ground 13 LED- 4th LED Cathode 14 LED- 3rd LED Cathode 15 LED- 2nd LED Cathode 16 LED- 1st LED Cathode Input Test Circuit To VOUT Pin 16 EN 1 NC 13 12 CAP2 FAN5607 1µF NC NC 4 5 8 9 1µF RSET 4.7µF 4 White LEDs Fairchild QTLP670C-IW Super Bright LED VOUT VIN = 2.7V to 5.5V CIN CAP1 4.7µF COUT All capacitors are Ceramic chip capacitors Figure 1. Test Circuit REV. 1.0.0 6/22/04 3 FAN5607 PRODUCT SPECIFICATION Absolute Maximum Ratings (Note 2) Parameter Min Max Unit VIN, VOUT Voltage to GND -0.3 6.0 V Any other Pin Voltage to GND -0.3 VIN + 0.3 V Power Dissipation Internally Limited Lead Soldering Temperature (10 seconds) 300 °C Operating Junction Temperature Range 150 °C 150 °C Storage Temperature Electrostatic Discharge Protection Level (Note 3) -55 HBM 4 CDM 2 Typ kV Recommended Operating Conditions Parameter Min Input Voltage Range, VIN 2.4 Operating Ambient Temperature Range -40 25 LED Forward Voltage Current through each LED 2 Max Unit 5.5 V 85 °C 4 V 30 mA Note: 2. Operation beyond the absolute maximum ratings may cause damage to device. 3. Using Mil Std. 883E, method 3015.7(Human Body Model) and EIA/JESD22C101-A (Charge Device Model) 4 REV. 1.0.0 6/22/04 PRODUCT SPECIFICATION FAN5607 Electrical Characteristics VIN = 2.7V to 5.5V, TA = -40ºC to +85ºC, Test Circuit Figure 1, Unless otherwise noted. Typical values are at TA = 25˚C Parameter Conditions Input Undervoltage Lockout Min. Typ. Max. 1.7 1.8 2.3 Units V ILED Accuracy I LED ≤ 20mA 5 % Current Matching I LED ≤ 20mA 3 % LED Vf = 3.5V 3.62 VIN = 5.5V, IOUT = 0mA 130 Output Voltage (VOUT = Vf + VCathode) Quiescent Current, IQ Shutdown Supply Current Output Short Circuit Current VEN = 0V VIN = 5.5V, VOUT = 0V VOUT Over Voltage Protection V 400 µA 1 µA 65 mA 5.1 V VIN At Mode Transition From 1X to 1.5X LED Vf = 3.5V, IOUT = 4 x 20mA 3.76 V VIN At Mode Transition From 1.5X to 2X LED Vf = 3.5V, IOUT = 4 x 20mA 2.85 V VIN = 3.75V, LED Vf = 3.5V, ILED= 20mA 93 % Peak Efficiency Oscillator Frequency 0.8 1 1.2 MHz Thermal Shutdown Threshold 145 ºC Thermal Shutdown Hysteresis 15 ºC EN Logic Input High Voltage 1.6 EN Logic Input Low Voltage EN Input Bias Current REV. 1.0.0 6/22/04 EN to VIN or GND -1 V 0.4 V 1 µA 5 FAN5607 PRODUCT SPECIFICATION Typical Performance Characteristics TA = 25°C, CIN= COUT =4.7µF, CAP1 = CAP1 = 0.1µF, FAN5607 driving four LEDs with Vf = 3.5V at 20mA, unless otherwise noted. Upper Mode Change Voltage vs LED Forward Voltage Efficiency vs Battery Voltage 1.0 Efficiency 0.9 Battery Voltage (V) 4.5 ILED = 20mA 0.8 0.7 0.6 t I LED 4V a VF = 4.0 mA = 20 D at I LE 3.5V VF = 3.5 VF 3.0 mA = 20 D at I LE = 3V mA = 20 ILED = 2mA 0.5 2.5 3.0 3.5 4.0 4.5 5.0 5.5 0 5 Battery Voltage (V) LED CathodeVoltage vs Battery Voltage 15 20 25 LED Current vs BatteryVoltage 22 0.14 ILED = 20mA High LED Current (mA) LED Cathode Voltage (V) 10 LED Current (mA) 0.13 0.12 0.11 0.10 0.09 2.2 ILED = 2mA 21 2.1 20 2.0 19 1.9 ILED = 20mA Low LED Current (mA) 2.5 ILED = 2mA 18 0.08 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Battery Voltage (V) 1.8 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Battery Voltage (V) Supply Current vs Battery Voltage Supply Current (mA) 180 160 140 120 100 80 60 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Battery Voltage (V) 6 REV. 1.0.0 6/22/04 PRODUCT SPECIFICATION FAN5607 Typical Performance Characteristics (cont.) TA = 25°C, CIN = COUT = 4.7µF, CAP1 = CAP1 = 0.1µF, FAN5607 driving four LEDs with Vf = 3.5V at 20mA, unless otherwise noted. Startup at VIN = 5V Startup at VIN = 3.6V ILED = 20mA LED Current (10mA/div) LED Current (10mA/div) ILED = 20mA Input Current (200mA/div) Input Current (200mA/div) Input current when driving 4 LEDs x 20mA Input current when driving 4 LEDs x 20mA Time (100µs/div) Time (100µs/div) VIN = 4.2V VIN = 3.2V LED Current (10mA/div) Input Voltage (1V/div) Line Transient Response Time (100µs/div) REV. 1.0.0 6/22/04 7 FAN5607 PRODUCT SPECIFICATION Block Diagram 1µF VOUT Linear Regulator Voltage Selector EN Oscillator 5µF Reference Analog Detector Range Selection Low Battery Ref. Ref2 Ref1 Regulator I. LIM. Bandgap Reference I. LIM. On Off And Current Range Power Good P U M P I. LIM. R SET D R I V E R S I. LIM. V IN Ref3 Mode Change VIN Ref4 (BG) GND 1µF Figure 2. Block Diagram Circuit Description The FAN5607’s switched capacitor DC/DC converter automatically configures its internal switches to achieve high efficiency and to provide tightly regulated output currents for the LEDs. An analog detector determines which diode requires the highest voltage in order to sustain the pre-set current levels, and adjusts the pump regulator accordingly. Every diode has its own linear current regulator. In addition, a voltage regulator controls the output voltage when the battery voltage is within a range where linear regulation can provide maximum possible efficiency. If the battery voltage is too low to sustain the diode current in the linear mode, a fractional 3:2 charge pump is enabled. When the battery voltage drops further and this mode is no longer sufficient to sustain proper operation, the pump is automatically reconfigured to operate in 2:1 mode. As the battery discharges and 8 the voltage decays, the FAN5607 switches between modes to maintain a constant current through LED throughout the battery life. The transition has hysteresis to prevent toggling. Supply Voltage The internal supply voltage for the device is automatically selected from VIN or VOUT pins, whichever is higher. Soft Start The soft-start circuit limits inrush current when the device is initially powered up and enabled. The reference voltage controls the rate of the output voltage ramp-up to its final value. Typical start-up time is 0.4ms. The rate of the output voltage ramp-up is controlled by an internally generated slow ramp, and an internal variable resistor limits the input current. REV. 1.0.0 6/22/04 PRODUCT SPECIFICATION FAN5607 Switch Configurations VIN VIN VOUT + CAP1 VOUT = 2 X VIN + CAP2 GND C - OUT Figure 3. Step-up, 2:1 Configuration Switch positions shown in charge phase Reverse all switches for pump phase GND Figure 4. Step-up, 3:2 Configuration Switch positions shown in charge phase Reverse all switches for pump phase Shutdown and Short Circuit Current Limit Set both DAC inputs low to shut down the device. Built-in short circuit protection limits the supply current to a maximum of 65mA. The resistor value establishes the reference current needed for a constant LED current. Value of RSET for a fixed LED current are given in the table above and also in the graph below, using the function: RSET = 250/ILED. LED Brightness Control Methods LED Current vs RSET RSET Only-Analog The basic method is to use external resistor to set the LED current. Connect the resistor with the appropriate value between RSET and GND to set the LED current. RSET (KΩ) 8.25 12.5 25 50 62.5 ILED (mA) 20 10 5 4 30 LED Current (mA) 35 30 25 20 15 10 5 0 0 10 20 30 40 50 60 70 RSET (KΩ) REV. 1.0.0 6/22/04 9 FAN5607 PRODUCT SPECIFICATION PWM Control Unless otherwise noted, RSET = 12.5KΩ, ILED_MAX = 20mA Enable is Controlled by PWM Signal ENABLE Input (PWM) ss 30% Duty Cycle 70% Duty Cycle 1KHz 1KHz ILED (Average) = 0.7 x ILED-MAX ILED (Average) = 0.3 x ILED-MAX ILED 0mA PWM Control Once RSET is chosen to set maximum LED current (ILED_MAX), PWM modes can be used for brightness control. By turning the ENABLE pin ON and OFF, the current can be modulated between 0 to ILED_MAX to achieve any IAverage value. In PWM mode, the modulating frequency has to be set sufficiently high in order to avoid a flickering effect (50Hz to 100Hz). The best LED to LED matching and the purest white light are achieved over the entire range of average current settings, when the PWM brightness control is used to modulate the LED current between zero and the maximum value. Application Information Brightness Control ss OFF VEXT R2 R1 ISET FAN5607 Figure 5. DC Voltage Control The FAN5607 internal circuit maintains a constant ISET voltage = 0.5V. Adjusting VEXT changes the ISET and ILED accordingly. Selecting different values for R1, R2 and VEXT range, the ILED variation range can be changed according to the relation: 250 ( 250 – 500 × V EXT ) I LED = ---------- + --------------------------------------------------- mA R2 R1 1. Dimming Using PWM at EN Pin A PWM signal applied to EN can control the LED brightness in direct dependence on the duty cycle. The recommended PWM signal frequency is 100Hz to ensure a good match between the input signal duty cycle and the LED average current. If this ripple frequency is too low for a particular noise sensitive application, then DC-based dimming control circuits or higher-frequency-filtered PWM signals may be used. Where 0V < VEXT < 0.5V and R1 and R2 are in KΩ. 2. Dimming with DC Voltage The brightness control using a variable DC voltage is shown in Figure 5. If R1=125kΩ, R2=13.9kΩ, adjusting VEXT in the (0V to 0.5V) range results in dimming the LED current from 20mA to 2mA. R3 10 3. Dimming Using a Filtered PWM Signal The external PWM signal is filtered by an R3C network resulting in a DC component dependent on the PWM signal duty cycle as shown in Figure 6. The resistor R3 needs to be much smaller than R2 and the corner frequency of R3C group is much smaller than the PWM signal frequency. R2 C R1 ISET FAN5607 Figure 6. Filtered PWM Control REV. 1.0.0 6/22/04 PRODUCT SPECIFICATION FAN5607 Selecting Capacitors It is important to select the appropriate capacitor types and the values for use with the FAN5607. These capacitors determine parameters such as power efficiency, maximum sustainable load current by the charge pump, input and output ripple and start-up process. through the RC input filter, as shown in Figure 7. Two low ESR bucket capacitors of value between 0.1µF to 1µF, should be used for best efficiency in boost mode. The bucket capacitor, CAP1 = CAP2 = 1µF is recommended, if the FAN5607 is required to start at battery voltage lower than 3V. PC Board Layout 0.22Ω Input Power Supply VIN 10µF 4.7µF FAN5607 GND For best performance, a solid ground plane is recommended on the back side of the PCB. The ground tails of CIN and COUT should be connected together close to the GND pin of IC. Figure 7. Battery Ripple Reduction In order to reduce ripple, both CIN and COUT should be low ESR capacitors. Increasing the COUT capacitor reduces the output ripple voltage. However this will increase the poweron time. The CIN value controls input ripple. If necessary, this ripple can be further reduced by powering the FAN5607 REV. 1.0.0 6/22/04 11 FAN5607 PRODUCT SPECIFICATION Mechanical Dimensions 4x4mm 16-Lead MLP Package 12 REV. 1.0.0 6/22/04 FAN5607 PRODUCT SPECIFICATION Ordering Information Product Number Package Type Order Code FAN5607 4x4mm 16-Lead MLP FAN5607HMPX 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 6/22/04 0.0m 001 Stock#DS505607 2004 Fairchild Semiconductor Corporation