Preliminary WS2801 3-Channel Constant Current LED Driver With Programmable PWM Outputs Features Applications Supports both constant voltage and constant current drive mode LED decorative lighting Programmable constant LED drive current Indoor/Outdoor LED video or massage display Wide constant output current range 5~150mA PWM signal generator Build in PWM dimming scheme for each output channel, LCD TV back lighting supports free-run, especially suitable for low cost controller application PWM free-run capability(refresh rate(2.5KHz) Build in buffers to cascading data and clock to the next driver Output polarity reverse function Support hot swap Maximum input clock frequency 25MHz Power supply voltage 3.3~5.5V General Description The WS2801 is a constant current LED driver. It is designed for indoor/ outdoor LED displays and decorative LED lighting system. It is suitable for LED cascading applications. The WS2801ownes 3 output channels, each channel can drive a constant current up to 30mA. WS2081 contains serial shift registers, data latches, output registers, band gap reference voltage generator, internal oscillator, and programmable constant output current drivers. The serial data is read into the shift registers at the rise edge of the external clock. The data and clock output buffers are designed for cascading another chip. The output polarity reverse function is designed for driving high power LED by adapting the application circuitry. The WS2801 adopts the reliable 2-wire scheme, which features low EMI transport, very strong anti-interference ability, and support hot-swap. The 2-wire control scheme can reduce the system cost it is very suitable for low cost LED decorative LED lighting systems. WS2801 is available in both SOP-14 and DIP-14 packages, the operating temperature is -40~85 Pin Configurations Typical Application Circuit Fig1.a SOP-14 package Fig1.b DIP-14 package 1 /15 WS-Preliminary-V0.3 Preliminary WS2801 3-Channel Constant Current LED Driver With Programmable PWM Outputs Absolute Maximum Ratings Parameter Symbol Ratings Unit Power Supply Voltage VCC -0.3 to 6V V Input Voltage V -0.3 to VCC+0.3V V IN Output Voltage V -0.4 to 7V V OUT Output Pin Voltage V -0.3 to 7V V XOUT Output Current Constant Current Drive Mode I 0 to 50 mA OUTCC Constant Voltage Drive Mode I 0 to 100 OUTCV Output Current Deviation (Constant Current Driving Mode) Between output channels D 1 % IOI Between chips D 3 IOE Input Clock Frequency F 25 MHz CLK Maximum Power Dissipation P 600 mW D Operating Junction Temperature Topr -40 to + 150 Storage Temperature Range Tstg -55 to + 150 Lead Temperature (Soldering, 10 seconds) Tsolder 300 ESD susceptibility 4000 V Note: If the voltage on the pins exceeds the maximum ratings may cause permanent damage to the device. Electrical Characteristics (VCC=5V, TA= 25 , unless otherwise specified.) Parameter SymbolConditions Min Typ Max Units Power Supply Voltage Range V 3.3 -- 5.5 V CC Output Voltage VOUT IOUT=1uA -0.3 -- 7.0 V Constant Current Output 5 -- 30 mA I outH Constant Voltage Output -- -- 50 mA Output Current I Output Cut Off -- 0.1 1 uA outL Other Output -- 1 -- mA I SOURCE I Other Output -- -1 -- mA SINK Standby Supply Current I B R/G/BOUT Floating -- 1 1.5 mA STB V V or V , IN IH IL Minimum Constant Current Output Time I -- 14 -- uS OH I =20mA OUT PINCKISDI -- -- 1 uA V VDD or GND IN Input Current I IN PINCKMPOL -- 10 20 uA V VDD or GND IN V 0.8*VDD -- VDD V IH Input Voltage Level TA-40125 V GND -- 0.2*VDD V IL Constant Current Feed Back Voltage V B R =20B 0.582 0.6 0.618 V XFB R/G/BFB Output Saturation Voltage V IOUT=20mA -- 0.4 0.6 V SAT 2 /15 WS-Preliminary-V0.3