2010/04/10 ver.2 page 1 SP1821 four channels constant current led driver description applications the SP1821 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 device can drive up to 25ma load current per string with an external resistor. the SP1821 can provide lowest cost for various applications. internal thermal protection automatically turns off led current to prevent overheating. the dimming can be achieved by controlling the i set input or by feeding a pwm signal to the en pin. the device can be shut down by setting enable low. z mr16 and other decoration light source z general reading lighting z display backlight z 12v battery powered devices features pin configuration(sop ? 8p) part marking z low cost led driver z constant current output z four channels led driver provides matching led current z low quiescent current z disconnects leds in shutdown mode z thermal shut down protection z current adjustable via external resistor z dimming control thru either enable or iset
2010/04/10 ver.2 page 2 SP1821 four channels constant current led driver typical applcation circuit pin description pin symbol description 1 vcc supply voltage input 2 gnd ground 3 en high enable pin 4 i set current set input 5 led1 led 1 6 led2 led 2 7 led3 led 3 8 led4 led 4 ordering information part number package part marking SP1821s8rgb sop- 8p SP1821 SP1821s8rgb : 13? tape reel ; pb ? free ; halogen ? free
2010/04/10 ver.2 page 3 SP1821 four channels constant current led driver block diagram absoulte maximum ratings (t a =25 unless otherwise specified) parameter symbol value unit dc supply voltage v cc 12 v output led current i led 25 ma operating temperature t opr -40 85 maximum junction temperature t j(max) 125 storage temperature t s -65 150 the ic has a protection circuit against static electricity. do not apply high static electricity or high voltage that exceeds the performance of the protection circuit to the ic.
2010/04/10 ver.2 page 4 SP1821 four channels constant current led driver electrical characteristics (t a =25 , v in =12v, r set =31.6kohm, v led =12v, unless otherwise specified) parameter conditions min. typ. max. unit operating voltage 10.5 12 v led current 22.5 25 27.5 ma current matching ch to ch +/-1.5 +/-3.5 % quiescent current iled = 0a, rset = open 700 800 900 a line regulation iled change per volt vcc change 5 6 %/v i set voltage 1.5 v enable voltage high 10.5v vin 12v 4.5 5 5.5 v enable voltage low 10.5v vin 12v 0.4 v thermal shutdown threshold 130 thermal shutdown hysteresis 20 current off mode 600 700 800 ua
2010/04/10 ver.2 page 5 SP1821 four channels constant current led driver performance characteristics (t a =25 , unless otherwise specified.) iled vs. vcc 0 3 6 9 12 15 18 21 24 27 10.5 11 11.5 12 vcc(v) iled(ma) iled1(ma) iled2(ma) iled3(ma) iled4(ma) rset vs. iled 0 2 4 6 8 10 12 14 16 18 20 22 24 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 rset(k ? ) iled ( ma ) application information circuit description SP1821 is a four channels white-led driver with matching current output. the matching current regulator has a 460:1 ratio between iled and i set . SP1821 is capable to supply 25ma for each channel with proper selection of external resistor. the design has a band gap regulator , voltage to current converter and mirror drivers. thermal protection SP1821 has a thermal comparator to shut down th e device when the internal temperature reaches 150 . it will remain shut down until the temperature drops to 130 . enable SP1821 has an enable pin that is designed for ttl input. the device will be active at voltage high. this pin can also be used to control the brightness of led with a pw m signal. the brightness is proportional to the duty cycle of the pwm signal. when duty cycle is zero, leds are tu rned off. for 50% duty cycl e, it will result an average iled to be half the programmed led current which is set by r set. iset the i set pin is a voltage input to set the current of led. an ex ternal resistor is used to set the output current, as approximated with the following equation: r set = 460 * (1.3v/iled) however, the r set shall not be selected to exceed the maximum cu rrent delivery capability of the device, 25ma. a pwm signal or analog signal can also be applied at i set pin to control the led brightness.
2010/04/10 ver.2 page 6 SP1821 four channels constant current led driver sop- 8 package outline
2010/04/10 ver.2 page 7 SP1821 four channels constant current led driver information provided is alleged to be exact and consistent. sync power corporation presumes no responsibility for the penalties of use of such information or for any violation of pa tents or other rights of third parties which may result from its use. no license is granted by allegation or otherwise under any pate nt or patent rights of sync power corporation. conditions mentioned in this publication ar e subject to change without notice. this p ublication surpasses and replaces all information previously supplied. sync power corporation products are not authorized for use as critical components in life support devices or systems without express written approval of sync power corporation. ?the sync power logo is a registered trademark of sync power corporation ?2004 sync power corporation ? printed in taiwan ? all rights reserved sync power corporation 7f-2, no.3-1, park street nankang district (nksp), taipei, taiwan 115 phone: 886-2-2655-8178 fax: 886-2-2655-8468 http://www.syncpower.com
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