SP7615

SP7615 Four Channel Constant Current LED Driver FEATURES VCC 1 8 LED1 ■ Cost Effective LED driver SP7615 7 LED2 EN 2 ■ Constant current output ideal for Driving LED strings 6 LED3 GND 3 8 Pin DFN ■ Four Channel LED Driver provides matched LED ISET 4 5 LED4 current ■ 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 EN C1 1n GND Oct 23-06 VCC EN GND SP7615 LED1 ® LED2 LED3 LED4 R1 ISET SP7615 Four Channel Constant Current LED Driver © Copyright 2006 Sipex Corporation 1 ABSOLUTE MAXIMUM RATINGS Vcc, VLED1, VLED2, VLED3, VLED4, Voltage to GND .......................................0.3V to 16V EN Voltage to GND..................................... 0 to (Vcc + 0.3V) ISET Voltage to GND...................................0 to (Vcc + 0.3V) or 6V, whichever is lower Output Current per LED (IOUT) ................................. 150mA Power Dissipation per Package 8-pin DFN at TA = 85ºC ...........................… 1.1W Junction Temperature ..............................................+150ºC Storage Temperature ............................... -55ºC to +150ºC ESD Level. ....................................................... 2kV HBM DFN Thermal Resistance......................................59ºC/W These are stress ratings only and functional operation of the device at these ratings or any other above those indicated in the operation sections of the specifications below is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. ELECTRICAL CHARACTERISTICS 4.5V < VCC 80mA Note 2. ENABLE "OFF" is VEN for which ILED < 1uA@ VLED1 > 1.0V Oct 23-06 SP7615 Four Channel Constant Current LED Driver © Copyright 2006 Sipex Corporation 2 BLOCK DIAGRAM LED1 VCC Thermal Shutdown GND Bias Driver LED3 EN V to I Converter LED4 LED2 Figure 1: SP7615 Block Diagram 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. Thermal Shutdown 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 VCCpin so levels up to VCCare 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. The EN pin is internally pulled down with an approximately 80kOhm resistor. The SP7615 will remain in shutdown mode if this pin is left open. Oct 23-06 SP7615 Four Channel Constant Current LED Driver © Copyright 2006 Sipex Corporation 3 THEORY OF OPERATION VCC EN C1 1n R1 VCC EN GND ISET SP7615 LED1 ® LED2 LED3 LED4 VCC EN GND SP7615 LED1 ® LED2 LED3 LED4 GND R2 ISET Current sharing capabilities allow two SP7615s to run in parallel for twice as much current through the LEDs. 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 power dissipated by one LED driver output is 125mA * 500mV = 62.5mW. The charts in t he following pages 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 derated to 530mW at 85ºC. 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. Oct 23-06 SP7615 Four Channel Constant Current LED Driver © Copyright 2006 Sipex Corporation 4 THEORY OF OPERATION D1 LED VCC EN C1 1n VMOD GND R1 VCC EN GND ISET SP7615 LED1 ® LED2 LED3 LED4 ISET Pin The ISET pin is the servo point of an amplifier configured as a voltage-to-current converter. The voltage at this pin servos to the internal bandgap potential. A set resistor can be connected from the Iset pin to the 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 be used also for LED current adjustment with external voltage from ambient light, optical feedback sensors or other voltage source. This voltage should not exceed 1.25V. The RSET value may be determined as RSET = (1.26 - V MOD) * 1000/IOUT kΩ, where 1.26 is a typical ISET pin voltage, VMOD is an adjustment voltage (V), 1000 is a typical current multiplication ratio, IOUT is a required LED current in mA/channel. If adjustment voltage V MOD isn’t used, RSET resistor should be connected to the ground. Oct 23-06 SP7615 Four Channel Constant Current LED Driver © Copyright 2006 Sipex Corporation 5 TYPICAL PERFORMANCE CHARACTERISTICS 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 = 500mV Oct 23-06 SP7615 Four Channel Constant Current LED Driver © Copyright 2006 Sipex Corporation 6 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 Oct 23-06 SP7615 Four Channel Constant Current LED Driver © Copyright 2006 Sipex Corporation 7 TYPICAL PERFORMANCE CHARACTERISTICS Figure 6 – LED Current versus Temperature with Thermal Shutdown Figure 7 – ISET Voltage versus Temperature Oct 23-06 SP7615 Four Channel Constant Current LED Driver © Copyright 2006 Sipex Corporation 8 TYPICAL PERFORMANCE CHARACTERISTICS Figure 8 –PWM Signal Applied To The Enable Pin, Amplitude=5V, Duty Cycle=50% 140 120 100 80 60 40 20 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Vm od, V Rset = 51k Rset = 20k Rset = 30k Rset = 15k Rset = 24k Rset = 10k Figure 9 -- Iout current (mA per channel) vs. VMOD voltage Oct 23-06 SP7615 Four Channel Constant Current LED Driver © Copyright 2006 Sipex Corporation 9 PACKAGE: 8 PIN DFN D D/2 5 6 D2 D2/2 7 8 E/2 E2/2 E E2 L 4 3 2 1 K e b INDEX AREA (D/2 x E/2) Pin1 Designator to be within this INDEX AREA (D/2 x E/2) TOP VIEW BOTTOM VIEW ø A (A3) A1 Seating Plane SIDE VIEW 2x3 8 Pin DFN SYMBOL JEDEC MO-229 VARIATION VCED-2 Dimensions in Inches Conversion Factor: 1 Inch = 25.40 mm MIN 0.032 0.000 0.008 0º 0.008 0.059 0.063 0.012 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 14º 0.012 0.069 0.075 0.020 Dimensions in Millimeters: Controlling Dimension MIN 0.80 0.00 0.20 0º 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 MAX 1.00 0.05 14º 0.30 1.75 1.90 0.50 A A1 A3 K ø b D D2 E E2 e L SIPEX Pkg Signoff Date/Rev: JL Aug18-05 / RevA Oct 23-06 SP7615 Four Channel Constant Current LED Driver © Copyright 2006 Sipex Corporation 10 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. 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. Oct 23-06 SP7615 Four Channel Constant Current LED Driver © Copyright 2006 Sipex Corporation 11