18V/1A High Brightness LED Driver CS8801 Revision History Rev. No. History Issue Date 1.0 New issue May 17, 2010 1.1 Update MR16 diagram Aug. 27, 2010 1.2 Format modify Oct. 21, 2010 1 Chiplus reserves the right to change product or specification without notice. Rev. 1.2 18V/1A High Brightness LED Driver CS8801 CS8801(NP) 18V/1A High Brightness Constant Current LED Driver Description The chip is a constant current output floating buck switching converter designed to provide constant current to high power LEDs with high efficiency. The device is ideal for architectural, industrial and ambient lighting applications. The chip delivers constant current within ±5% accuracy to a wide variety and number of series connected LEDs. Output current is adjusted with an external current sensing resistor to drive high power LEDs in excess of 1A. For improved accuracy and efficiency, the chip features dual-side hysteresis, and short propagation delay. Additional features a dimming input to enable LED brightness control by Pulse Width Modulation (PWM). Additional features include a +5V regulated output with 10mA output current ability. Feature Input operating range of 6V ~ 18V Constant current output with ±5% accuracy in excess of 1A Maximum efficiency over 90% Hysteretic control for speed and simplicity High speed COMS compatible PWM dimming (Up to 20kHz) Input Under Voltage Lock Out (UVLO) Over Temperature protection (OTP) 5V, 10mA On-Board Regulator -40°C to +125°C Operating Temperature Range Applications High Power LED Driver Automotive, general illumination, and industrial lighting Lighting such as MR16, AR111 or Other LED Bulbs Product Family CS8801NP ------- 8SOP (150mil, 1.27mm lead-pitch) 2 Chiplus reserves the right to change product or specification without notice. Rev. 1.2 18V/1A High Brightness LED Driver CS8801 Pin Assignment Pin No. Pin Name Function 1 LX N-MOSFET switch 2 DIM PWM dimming input pin 3 GND Ground pin 4 VDD Internal regulator output pin 5 CS LED current sense pin 6 GND Ground pin 7 VIN Power supply input pin 8 GND Ground pin Block Diagram VIN CS Current sensing VIN Current limiting Thermal shutdown VDD regulator VDD SD VREF Error Comparator LX VDD 3.6V UVLO GND DIM Absolute Maximum Ratings VIN, CS to GND ….............................-0.3V to +20V Operating Temperature Range VDD, LX, DIM to GND .........................-0.3V to +9V ………………...................................-40°C to +125°C CS to VIN.................................................-1V to +1V Junction Temperature....................................+150°C Maximum Current into Any Pin Storage Temperature......................-65°C to + 125°C (except VIN, LX, and VDD).........................±20mA 3 Chiplus reserves the right to change product or specification without notice. Rev. 1.2 18V/1A High Brightness LED Driver CS8801 Electrical Characteristics (VIN = 12V, CVIN1 = 10µF, CVIN2 = 1µF, CVDD = 1µF, RSEN = 0.5Ω, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) Characteristics Symbol Input Voltage Range VIN Supply Current IVIN Internal Regulator Voltage Condition Min Typ 6 VDIM = 0V, LX open VDD Max Unit 18 V 400 uA 5 V 5.5 V 3.3 V 2.2 V Under Voltage Lockout (UVLO) VCS = VIN, VIN rising until LX on Undervoltage Lockout UVLO VCS = VIN, VIN falling until LX off Undervoltage-Lockout Hysteresis Sense Comparator Sense Voltage Threshold High VSNSHI (VIN - VCS) rising until LX off 560 mV Sense Voltage Threshold Low VSNSLO (VIN - VCS) falling until LX on 420 mV VIN = VCS 5.8 uA VIN = VCS = 18V, ILX = 1A 0.10 Ω CS Input Current ICSIN Internal N-MOSFET Drain-to-Source Resistance RDSON DIM Input Maximum DIM Frequency fDIM DIM Input-Voltage High VIH DIM Input-Voltage Low VIL 20 VCS = VIN, increase DIM until LX on 2.1 kHz V VCS = VIN, decrease DIM until LX off 1.3 V 165 ºC Thermal Shutdown Temperature rising Thermal-Shutdown Threshold Temperature falling 130 VDD Regulator Regulator Output Voltage VDD Current Ability for External Circuitry VDD 5 IVDD V 10 4 Chiplus reserves the right to change product or specification without notice. mA Rev. 1.2 18V/1A High Brightness LED Driver CS8801 Typical Operating Circuit D5 L R SEN LEDs LX DIM VD D D1 GND CHIPLUS DIM VIN CS8801 GND GND VDD CS D2 CVIN1 AC or DC INPUT CVIN2 D3 CVDD D4 Reference Component Table Designator Component Description D1 ~ D5 Schottky >20V, >2A RSEN Resistor 0.5Ω, ±1%, >0.5W L Inductor 22uH, >2A CVDD Capacitor 1uF, >6V CVIN1 Capacitor >10uF, >20V CVIN2 Capacitor 1uF, >20V 5 Chiplus reserves the right to change product or specification without notice. Rev. 1.2 18V/1A High Brightness LED Driver CS8801 Typical Operating Characteristics (VIN = 12V, CVIN1 = 10µF, CVIN2 = 1µF, CVDD = 1µF, RSEN = 0.5Ω, L = 22uH. Typical values are at TA = +25°C, unless otherwise noted.) CS8801 Input Voltage vs. Efficiency (LEDs=3) CS8801 Input Voltage vs. LED Current (LEDs=3) 1200 100% 90% 1000 80% LED_current(mA) 70% efficiency 60% 50% 40% 30% 20% 800 600 400 200 10% 0% 0 11 13 15 17 19 21 0 5 input_voltage(V) 10 15 20 input_voltage(V) CS8801 Input Voltage vs. Switch Frequence (LEDs=3) CS8801 Input Voltage vs. VDD (LEDs=3) 6 700 650 5 600 550 freq.(kHz) VDD(V) 4 3 2 500 450 400 350 300 1 250 0 200 0 5 10 15 20 12 input_voltage(V) 14 16 18 20 22 input_voltage(V) 6 Chiplus reserves the right to change product or specification without notice. Rev. 1.2 18V/1A High Brightness LED Driver CS8801 Applications Information Output Current Setting The LED average current is programmed using a resistor between VIN and CS, show as RSEN in the typical application schematic. Use the following equation to calculate the value of this resistor: RSEN = VSEN I LED Where VSEN is 500mV typically, and ILED is the DC average LED current. Switching Frequency Although hysteretic control is a simple control method, the switching frequency depends on application conditions and components. Use the following equation to determine the operating frequency: f SW = (VIN − n ⋅VLED ) ⋅ n ⋅ VLED ⋅ RSEN VIN ⋅ ∆V ⋅ L Where n is the number of LEDs, VLED is the forward voltage drop of 1 LED, and ∆V is 50mV. Inductor Selection The inductor value can be calculated from a known frequency by re-arranging the same equation: L= (VIN − n ⋅ VLED ) ⋅ n ⋅VLED ⋅ RSEN VIN ⋅ ∆V ⋅ f SW Diode Selection The forward voltage of the diode should be as low as possible for better efficiency. A Schottky diode is a good choice as long as the breakdown voltage is high enough to withstand the maximum operating voltage. The forward current rating of the diode must be at least equal to the maximum LED current. Order Information Part No. Package Type Lead Pitch CS8801NP 8SOP(mil) 1.27mm 7 Chiplus reserves the right to change product or specification without notice. Rev. 1.2 18V/1A High Brightness LED Driver CS8801 8 Chiplus reserves the right to change product or specification without notice. Rev. 1.2 18V/1A High Brightness LED Driver CS8801 9 Chiplus reserves the right to change product or specification without notice. Rev. 1.2