® Preliminary SP7615 Four Channel Constant Current LED Driver FEATURES ■ Cost Effective LED driver VCC 1 8 LED1 ■ Constant current output ideal for Driving LED strings SP7615 7 LED2 EN 2 ■ Four Channel LED Driver provides matched LED 6 LED3 GND 3 8 Pin DFN current ISET 4 5 LED4 ■ Current adjusted via an external resistor ■ PWM dimming possible Now Available in Lead Free Packaging ■ Small 2mm x 3mm DFN package ■ Outputs can be connected in parallel to APPLICATIONS increase drive ■ Constant current for wide cathode voltage range ■ Next Generation Mobile Phones (1.0V to 16V) ■ PDA, DSC, MP3 Players ■ Highly integrated design, minimal components ■ Handheld Computers ■ LCD Display Modules ■ Thermal shutdown protects the driver ■ Keyboard Backlight ■ LED Displays DESCRIPTION The SP7615 is a linear constant current driver designed to drive multiple LEDs in series from a high input voltage rail. The driver acts as a high current matched, four-channel current source ensuring constant LED current for a range of input voltages. The SP7615 allows implementing the lowest cost LED driver for a variety of applications. Internal circuitry maintains the pre-set constant current output for a wide voltage range at the LED outputs (LED1,2,3,4). LED current can be adjusted up to 125mA per string with an external resistor. The dimming can be achieved by controlling the ISET input or by feeding a PWM signal to the EN pin. Fast EN turn-on and turn-off time allows for very fast PWM dimming frequencies, completely eliminating flicker. The built-in thermal protection automatically adjusts LED current to prevent overheating. TYPICAL APPLICATION SCHEMATIC VCC VCC EN EN GND C1 1n R1 LED1 ® LED2 SP7615 LED3 ISET LED4 GND Date: 08/31/05 SP7615 Four Channel Constant Current LED Driver 1 © Copyright 2005 Sipex Corporation ABSOLUTE MAXIMUM RATINGS Vcc, VLED1, VLED2, VLED3, VLED4 Voltage to GND 0.3V to 16V ISET and EN Voltage to GND..................................... 6V These are stress ratings only and functional operation Output Current per LED (IOUT) ............................. 150mA of the device at these ratings or any other above those Power Dissipation per Package indicated in the operation sections of the specifications 8-pin DFN at TA = 85ºC ......................… 1.1W below is not implied. Exposure to absolute maximum Junction Temperature ..........................................+150ºC rating conditions for extended periods of time may affect Storage Temperature ........................... -55ºC to +150ºC reliability. ESD Level. ....................................................... 2kV HBM DFN Thermal Resistance......................................59ºC/W ELECTRICAL CHARACTERISTICS 4.5V < VCC <16V , VEN = 5V, VLED1 =VLED2 =VLED3 =VLED4 =1.0V, RSET =10kΩ or ISET=126µA, -40 < TA < 85ºC, Unless otherwise noted. Typical numbers are for TA = 25ºC. PARAMETER MIN. TYP. MAX. UNITS Supply Voltage 4.5 5 16 V 20 39 mA 1000 1200 Quiescent Supply Current Output/I SET Current Multiplication Ratio 700 LED Current (per diode) LED to LED Current Matching 126 -5 LED Current Line Voltage Regulation LED Current Load Voltage Regulation LED Current Thermal Regulation ISET Pin Voltage 1.17 ILED1 = ILED2 = ILED3= ILED4 =126mA mA 5 % 0.15 0.6 %/V 2 4 IOUT change per volt VCC change %/V 0.4V < VLED < 5V, ILED = 25mA 9 %/V 1.0V < VLED < 5V, ILED = 126mA 0.1 %/ºC ILED = 126mA 1.26 1.39 V Thermal Shutdown Threshold 150 ºC Thermal Shutdown Hysteresis 20 ºC Current in OFF Mode Min. ENABLE “ON Voltage” (Note1) Max. ENABLE “OFF Voltage” (Note 2) CONDITIONS 1 µA 1.6 V 0.4 ISET = 1µA VEN = ZeroV V Note 1. ENABLE "ON" is VEN for which ILED > 80mA Note 2. ENABLE "OFF" is VEN for which ILED < 1uA@ VLED1 > 1.0V Date: 08/31/05 SP7615 Four Channel Constant Current LED Driver 2 © Copyright 2005 Sipex Corporation BLOCK DIAGRAM LED1 VCC Thermal Shutdown GND LED2 Bias Driver LED3 EN V to I Converter Figure 1. SP7615 Block Diagram LED4 ISET THEORY OF OPERATION Introduction The SP7615 is a four channel constant current source LED driver with programmable output current level. The design consists of a regulator bandgap, voltage to current converter, and output mirror drivers. The bandgap ensures good performance over voltage and temperature. The four outputs are tightly coupled allowing for excellent channel matching. acceptable. The enable pin can also be used to control the LED brightness with a pulse width modulated control signal. Duty Cycle or PWM control of the LED current maintains constant LED color while brightness is changing. The SP7615 responds in less than 10µs to PWM signals applied to this pin. Thermal Shutdown The ISET pin is the servo point of an amplifier configured as a voltage to current converter. The voltage at this pin trips servos to the internal bandgap potential. A set resistor can be connected from the ISET pin to ground to generate a reference current for the following current gain stages. A current could alternately be applied to this pin in the form of a current source or current output DAC. This pin can also have a PWM signal applied to control the LED brightness. ISET Pin The SP7615 uses a thermal comparator to monitor the system temperature shutting the device down if the internal temperature reaches 150ºC. The device will remain off until the internal temperature drops below 130ºC. Enable The device has an enable function that is designed for TTL level inputs. This input will also track the VCC pin so levels up to VCC are Date: 08/31/05 SP7615 Four Channel Constant Current LED Driver 3 © Copyright 2005 Sipex Corporation THEORY OF OPERATION The RSET value may be determined as RSET = 1.26 * 1000/IOUT, kΩ where 1.26 is a typical ISET pin voltage, 1000 is a typical current multiplication ratio, and IOUT is a required LED current in mA. D1 LED VCC VCC EN EN LED2 GND C1 1n R1 LED1 ® ISET SP7615 LED3 LED4 GND VCC VCC EN EN GND C1 1n LED1 ® LED2 SP7615 LED3 ISET R1 LED4 VCC LED1 ® EN GND GND R2 LED2 SP7615 ISET LED3 LED4 CATHODE VOLTAGE, SUPPLY VOLTAGE AND POWER DISSIPATION The voltage applied to the cathode of each LED determines the overall efficiency of the SP7615 circuit. The SP7615 is designed to be able to sink 125mA at each of its four outputs; LED1 - 4. The SP7615 is also designed to be able to handle up to 16V on these pins. This voltage handling capability assumes the total power can be dissipated by the SP7615. The power dissipation inside the SP7615 will de directly related to the voltage and current applied to these pins. For example, the typical operating cathode voltage is 500mV. At maximum current the Date: 08/31/05 power dissipated by one LED driver output is 125mA * 500mV = 62.5mW. The following charts show the power dissipation of the SP7615 under various conditions. The power dissipation should be kept below 1.3W for safe operation and long term reliability at room temperature and derates to 530mW at 85 ºC. While the above operating conditions are recommended, the part cannot be damaged due to internal temperature control as described above in the thermal shutdown section. SP7615 Four Channel Constant Current LED Driver 4 © Copyright 2005 Sipex Corporation PERFORMANCE GRAPHS Figure 2 – Four Channel Total Power Dissipation versus Cathode Voltage at VCC = 5V Figure 3 – Four Channel Total Power Dissipation versus Supply Voltage at Vcathode = 500mW Date: 08/31/05 SP7615 Four Channel Constant Current LED Driver 5 © Copyright 2005 Sipex Corporation TYPICAL PERFORMANCE CHARACTERISTICS Figure 4 – LED Current versus ISET Current and Cathode Voltage, Vcc=5V, T= 27°C Figure 5 – LED Current versus RSET Value Date: 08/31/05 SP7615 Four Channel Constant Current LED Driver 6 © Copyright 2005 Sipex Corporation TYPICAL PERFORMANCE CHARACTERISTICS Figure 6 – LED Current versus Temperature with Thermal Shutdown Figure 7 – ISET Voltage versus Temperature Date: 08/31/05 SP7615 Four Channel Constant Current LED Driver 7 © Copyright 2005 Sipex Corporation TYPICAL PERFORMANCE CHARACTERISTICS Figure 8 –PWM Signal Applied To The Enable Pin, Amplitude=5V, Duty Cycle=50% Date: 08/31/05 SP7615 Four Channel Constant Current LED Driver 8 © Copyright 2005 Sipex Corporation PACKAGE: 8 PIN DFN D2 D D/2 D2/2 5 6 7 8 E/2 E2/2 E E2 K L 4 Pin1 Designator to be within this INDEX AREA (D/2 x E/2) 3 2 e TOP VIEW 1 b INDEX AREA (D/2 x E/2) BOTTOM VIEW ø A (A3) A1 Seating Plane SIDE VIEW 2x3 8 Pin DFN SYMBOL Dimensions in Millimeters: Controlling Dimension MIN 0.80 0.00 A A1 A3 K ¿ b D D2 E E2 e L JEDEC MO-229 0.20 0… 0.18 1.50 1.60 0.30 NOM 0.90 0.02 0.20 REF 0.25 2.00 BSC 3.00 BSC 0.50 BSC 0.40 Dimensions in Inches Conversion Factor: 1 Inch = 25.40 mm MAX 1.00 0.05 MIN 0.032 0.000 14… 0.30 0.008 0… 0.008 1.75 0.059 1.90 0.063 0.50 0.012 SIPEX Pkg Signoff Date/Rev: Date: 08/31/05 VARIATION VCED-2 NOM 0.036 0.001 0.008 REF 0.010 0.079 BSC 0.118 BSC 0.020 BSC 0.016 MAX 0.039 0.002 14… 0.012 0.069 0.075 0.020 JL Aug18-05 / RevA SP7615 Four Channel Constant Current LED Driver 9 © Copyright 2005 Sipex Corporation ORDERING INFORMATION Part Number Operating Temperature Range Package Type SP7615ER .................................................. -40°C to +85°C ............................................ 8 Pin DFN (2 x 3mm) SP7615ER/TR ............................................ -40°C to +85°C ............................................ 8 Pin DFN (2 x 3mm) Available in lead free packaging. To order add "-L" suffix to part number. Example: SP7615ER/TR = standard; SP7615ER-L/TR = lead free /TR = Tape and Reel Pack quantity is 3000 for DFN. Corporation ANALOG EXCELLENCE Sipex Corporation Headquarters and Sales Office 233 South Hillview Drive Milpitas, CA 95035 TEL: (408) 934-7500 FAX: (408) 935-7600 Sipex Corporation reserves the right to make changes to any products described herein. Sipex 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. Date: 08/31/05 SP7615 Four Channel Constant Current LED Driver 10 © Copyright 2005 Sipex Corporation