Four Channel Constant Current LED Driver EC4101 FEATURES z z z z z z z z z z Package type SOP-8 Cost Effective LED driver Constant current output ideal for Driving Led strings Four Channel LED Driver provides matched LED current Current adjusted via an external resistor PWM dimming possible by using either the ENABLE Small SOP-8 package Outputs can be connected in parallel to increase drive Constant current for wide cathode voltage range (4.5V to 18V) Highly integrated design, minimal components Thermal shutdown protects the driver APPLICATIONS z z z z z z Next Generation Mobile Phones PDA, DSC, MP3 Players Handheld Computers LCD Display Modules Keyboard Backlight LED Displays DESCRIPTION The EC4101 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 voltage. The EC4101 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 flickering. The built-in thermal protection automatically adjusts LED current to prevent overheating. P 1 / 6 DR18EC070105-VER1.0 Four Channel Constant Current LED Driver EC4101 ABSOLUTE MAXIMUM RATINGS Vcc, VLED1, VLED2, VLED3, VLED4 Voltage to GND 0.3V to 18V ISET and EN Voltage to GND..................................... 6V These are stress ratings only and functional operation Output Current per LED (IOUT) ............................. 125mA 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 SOP at TA = 85℃ ......................… 1.1W below is not implied. Exposure to absolute maximum Junction Temperature ..........................................+150ºC rating conditions for extended periods of time may Storage Temperature ........................... -55ºC to +150ºC affect reliability. ESD Level. ....................................................... 1.5kV HBM ELECTRICAL CHARACTERISTICS 4.5V < VCC <18V , VEN = 5V, VLED1 =VLED2 =VLED3 =VLED4 =1.0V, RSET =10k or ISET=125uA, -40 < TA < 85ºC, Unless otherwise noted. PARAMETER MIN. TYP. Supply Voltage 4.5 5 18 V 0.4 0.5 mA 1200 1400 Quiescent Supply Current Output/ISET Current Multiplication 1000 MAX. UNITS CONDITIONS ILED1=ILED2=ILED3=ILED4 VCH = 1V Ratio LED Current (per diode ) CH to CH Current Matching 125 -5% LED Current Line Voltage Regulation 0.15 LED Current Load Voltage Regulation 9 LED Current Thermal Regulation ISET Pin Voltage mA +5% % 0.6 %/V IOUT change per volt Vcc change %/V 1.0V < VLED <5V, ILED = 125mA %/℃ ILED =125mA 0.1 1.4 1.5 1.6 V Thermal Shutdown Threshold 130 ℃ Thermal Shutdown Hysteresis 20 ℃ Current OFF Mode 0.5 mA Min. ENABLE “ ON Voltage “ (Note1) 1.6 V Max. ENABLE “ OFF Voltage “ (Note2) VEN = 0V V 0.4 Note 1. ENABLE "ON" is VEN for which ILED > 80mA Note 2. ENABLE "OFF" is VEN for which ILED < 1uA@ VLED1 > 1.0V P 2 / 6 DR18EC070105-VER1.0 Four Channel Constant Current LED Driver EC4101 BLOCK DIAGRAM THEORY OF OPERATION Introduction The EC4101 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 EC4101 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 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 EC4101 responds in less than 10us to PWM signals applied to this pin. P 3 / 6 DR18EC070105-VER1.0 Four Channel Constant Current LED Driver EC4101 ISET Pin The ISET pin is the servo point of an amplifier configured as a voltage to current converter. The voltage at this pins 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. The RSET value may be determined as RSET = 1.5 * 1200/IOUT, kΩ where 1.5 is a typical ISET pin voltage, 1200 is a typical current multiplication ratio, and IOUT is a required LED current in mA. Cathode Voltage, Supply Voltage and Power Dissipation The voltage applied to the cathode of each LED determines the overall efficiency of the EC4101 circuit. The EC4101 is designed to be able to sink 125mA at each of its four outputs; LED1 - 4. The EC4101 is also designed to be able to handle up to 18V on these pins. This voltage handling capability assumes the total power can be dissipated by the EC4101. The power dissipation inside the EC4101 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 following charts show the power dissipation of the EC4101 under various conditions. The power dissipation should be kept below 1.3W for safe operation and long term reliability at room P 4 / 6 DR18EC070105-VER1.0 Four Channel Constant Current LED Driver EC4101 temperature and dartle 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. ORDERING INFORMATION PART NUMBER TOP MARK PACKAGE EC4101N-F EC4101-F Lead free 8-pin SOP EC4101N-G EC4101-G Green Mode 8-pin SOP P 5 / 6 DR18EC070105-VER1.0 Four Channel Constant Current LED Driver EC4101 PACKAGE TYPE SOP8 : P 6 / 6 DR18EC070105-VER1.0