rt9302 1 ds9302-04 april 2011 www.richtek.com marking information for marking information, contact our sales representative directly or through a richtek distributor located in your area. 60ma 3-channel pulse dimming current source led driver features z z z z z support up to 3 white leds z z z z z output current up to 20ma each channel z z z z z support pulse and pwm dimming z z z z z 40mv typical current source dropout z z z z z 1% typical led current accuracy z z z z z 0.7% typical led current matching z z z z z 16-step brightness control z z z z z low noise and emi z z z z z low shutdown current 4 a typical z z z z z rohs compliant and 100% lead (pb)-free applications z mobile phone, dsc, mp3 z white led backlighting z lcd display supply general description the rt9302 is a high performance constant current driver for white led. it supports up to 3 white leds and regulates a constant current for uniform intensity. each channel supports up to 20ma output current with 1% typical current accuracy and 0.7% typical current matching. the rt9302 provides a 16-step brightness dimming control. the led current can be easily configured from 1.25ma to 20ma. the dimming of white leds' current can be achieved by applying a pulse signal to the en pin. the led current can be turned off by en pin with pull low for 20 s or longer. the typical leakage curren t is 4 a wh ile shutdown condition. rt9302 is available in a tsot-23-8 package (1.0mm maximum height). ordering information note : richtek products are : ` rohs compliant and compatible with the current require- ments of ipc/jedec j-std-020. ` suitable for use in snpb or pb-free soldering processes. (top view) tsot-23-8 pin configurations led3 gnd vin led2 en nc nc led1 5 34 6 8 2 7 rt9302 package type j8 : tsot-23-8 lead plating system p : pb free g : green (halogen free and pb free)
rt9302 2 ds9302-04 april 2011 www.richtek.com typical application circuit figure 1. for 3-wleds application circuit figure 2. for 2-wleds application circuit figure 3. brightness control by pulse dimming. rt9302 implements 16 steps brightness control 0.5us < t lo < 10us 0.5us < t hi 20us < t shdn 15/16 14/16 13/16 12/16 3/16 1/16 2/16 100% 100% 15/16 0 12345 14 15 01 en i ledx shutdown shutdown vin led3 rt9302 gnd c in 4.7uf led1 led2 en v in 2.8 to 5.5v 3 7 8 1 4 6 vin led3 rt9302 gnd c in 4.7uf led1 led2 en v in 2.8 to 5.5v 3 7 8 1 4 6
rt9302 3 ds9302-04 april 2011 www.richtek.com functional pin description pin number pin name pin function 1 led3 current sink for led3. (if not in use, this pin must be connected to v in ) 2, 5 nc no internal connection. 3 gnd power ground. 4 vin input voltage. 6 en chip enable. 7 led1 current sink for led1. (if not in use, this pin must be connected to v in ) 8 led2 current sink for led2. (if not in use, this pin must be connected to v in ) function block diagram 1mhz oscillator 16 steps pulse dimming controller shut down delay uvlo low dropout current source en gnd vin led1 led2 led3
rt9302 4 ds9302-04 april 2011 www.richtek.com electrical characteristics parameter symbol test conditions min typ max unit input input supply voltage v in 2.8 -- 5.5 v under voltage lockout threshold v in falling -- 2.0 -- v under voltage lockout hysteresis -- 200 -- mv shutdown current i shdn v en = 0v -- 4 10 a quiescent current i q v en = high, i out = 0 -- 0.4 -- ma output output current i led 100% setting, v led = 1v 18.4 20 21.6 ma current matching i led -led 100% setting, v led = 1v ? 5 0 +5 % dropout voltage v led 90% of full output current -- 40 150 mv enable logic-high v ih 1.5 -- -- en threshold voltage logic-low v il -- -- 0.4 v logic-high t hi duration of en logic high for pulse dimming 0.5 -- -- time of en logic logic-low t lo duration of en logic low for pulse dimming 0.5 -- 10 s shutdown delay t shdn from en low to shutdown 10 16 20 s en input current i en v en = 1.8v -- 1 -- a absolute maximum rating s (note 1) z supply input voltage ------------------------------------------------------------------------------------------------------ ? 0.3v to 6v z other i/o pin v oltages --------------------------------------------------------------------------------------------------- ? 0.3v to 6v z vin, en to gnd ------------------------------------------------------------------------------------------------------------ 6v z power dissipation, p d @ t a = 25 c tsot-23-8 ------------------------------------------------------------------------------------------------------------------- 0.455w z package thermal resistance (note 2) tsot-23-8, ja ------------------------------------------------------------------------------------------------------------- 220 c/w z lead temperature (soldering, 10 sec.) ------------------------------------------------------------------------------- 260 c z junction temperature ----------------------------------------------------------------------------------------------------- 150 c z storage temperature range -------------------------------------------------------------------------------------------- ? 65 c to 150 c z esd susceptibility (note 3) hbm (human body mode) ---------------------------------------------------------------------------------------------- 2kv mm (ma chine mode) ------------------------------------------------------------------------------------------------------ 200v recommended operating conditions (note 4) z junction temperature range -------------------------------------------------------------------------------------------- ? 40 c to 125 c z ambient temperature range -------------------------------------------------------------------------------------------- ? 40 c to 85 c (v in = 3.6v, c in = 1uf, esr = 0.03 , v f = 3.4v, i led1 = i led2 = i led3 = 20ma, t a = 25 c, unless otherwise specified)
rt9302 5 ds9302-04 april 2011 www.richtek.com note 1. stresses listed as the above ? absolute maximum ratings ? may cause permanent damage to the device. these are for stress ratings. functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may remain possibility to affect device reliability. note 2. ja is measured in the natural convection at t a = 25 c on a low effective thermal conductivity test board of jedec 51-3 thermal measurement standard. note 3. devices are esd sensitive. handling precaution recommended. note 4. the device is not guaranteed to function outside its operating conditions.
rt9302 6 ds9302-04 april 2011 www.richtek.com typical operating characteristics led current vs. temperature 17 17.5 18 18.5 19 19.5 20 20.5 21 21.5 22 -40-30-20-10 0 102030405060708090 temperature led current (ma) ( c) dimming operation time (25 s/div) v in = 3.7v en (5v/div) i led (5ma/div) dimming operation time (100 s/div) v in = 3.7v en (2v/div) i led (5ma/div) shutdown current vs. input voltage 0 1 2 3 4 5 6 7 8 9 2.6 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5 5.2 input voltage (v) shutdown current (ua) 25 c 85 c -40 c led current vs. input voltage 0 2.5 5 7.5 10 12.5 15 17.5 20 22.5 25 2.7 2.95 3.2 3.45 3.7 3.95 4.2 4.45 4.7 4.95 5.2 input voltage (v) led current (ma) led1 v f = 3.124v led2 v f = 3.224v led3 v f = 3.143v quiescent current vs. input voltage 0.36 0.37 0.38 0.39 0.4 0.41 0.42 0.43 0.44 2.6 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5 5.2 input voltage (v) quiescent current (ma) 25 c 85 c -40 c
rt9302 7 ds9302-04 april 2011 www.richtek.com turn-off time (5 s/div) v in = 3.7v en (2v/div) i led (10ma/div) i in (50ma/div) turn-on time (5 s/div) v in = 3.7v en (2v/div) i led (10ma/div) i in (50ma/div) dimming operation time (10 s/div) v in = 3.7v en (2v/div) i led (5ma/div)
rt9302 8 ds9302-04 april 2011 www.richtek.com application information input uvlo the input operating voltage range of the rt9302 is 2.8v to 5.5v. an input capacitor at the vin pin could reduce ripple voltage. it is recommended to use a ceramic 1 f or larger capacitance as the input capacitor. this ic provides an under voltage lockout (uvlo) function to prevent it from unstable issue when startup. the uvlo threshold of input falling voltage is set at 2v typically with a hysteresis 0.2v. output current rt9302 provides a constant output current for white led. figure 1 shows a typical application circuit for 3 white leds. each channel supports up to 20ma output current and regulates a constant current for uniform intensity. for two or one led application, the non-used channel must be connected to v in as shown in fig ure 2. brightness dimming control the rt9302 provides a 16-step brightness dimming control. the led current can be easily configured from 1.25ma to 20ma. the dimming of white leds' current can be achieved by applying a pulse signal to the en pin. figure 3 shows the configuration of the 16-step pulse dimming control operation. the output current is set at 10 0% of 20ma typical output current when en pin pull high initi ally from shutdown condition. the step change of pulse dimming can be implemented by en pin changing with a logic low pulse. each step change 1/16 of full output current setting. the output current change of pulse dimming is designed in decreasing sequence in terms of (16/16, 15/16, ....., 1/16) and then (16/16, 15/16, .....) cycle by cycle. the duration of logic low pulse is between 0.5us and 10 s. the duration of en logic high pulse should be longer than 0.5 s. the led current can be turned off by en pin with pulling low for 20 s or longer. the typical leakage current i s 4 a while shutdown condition. layout consideration for best performance, careful pcb layout is necessary. all peripheral components should be placed as close to the ic as possible. a short connection is highly recommended. the following guidelines should be strictly followed when designing a pcb layout for the rt9302. 1. all the traces of led and v in running from chip to leds should be wide and short to reduce the parasitic connection resistance. 2. input capacitor (c in ) should be placed close to vin and connected to ground plane. the anodes of leds must be connected to c in , not battery directly. 3. the gnd should be connected to a strong ground plane for heat sinking and noise protection. battery ground plane c in gpio all the traces of led and v in running from chip to leds should be wide and short to reduce the parasitic connection resistance. input capacitor (c in ) should be placed close to v in and connected to ground plane. the anodes of leds must connect to c in , not battery directly. the gnd should be connected to a strong ground plane for heat sinking and noise protection. vin gnd nc led3 led2 led1 en nc 5 2 3 7 8 1 4 6 figure 4. pcb layout guide
rt9302 9 ds9302-04 april 2011 www.richtek.com information that is provided by richtek technology corporation is believed to be accurate and reliable. richtek reserves the ri ght to make any change in circuit design, specification or other related things if necessary without notice at any time. no third party intellectual property inf ringement of the applications should be guaranteed by users when integrating richtek products into any application. no legal responsibility for any said applications i s assumed by richtek. richtek technology corporation headquarter 5f, no. 20, taiyuen street, chupei city hsinchu, taiwan, r.o.c. tel: (8863)5526789 fax: (8863)5526611 richtek technology corporation taipei office (marketing) 5f, no. 95, minchiuan road, hsintien city taipei county, taiwan, r.o.c. tel: (8862)86672399 fax: (8862)86672377 email: marketing@richtek.com outline dimension tsot-23-8 surface mount package dimensions in millimeters dimensions in inches symbol min max min max a 0.700 1.000 0.028 0.039 a1 0.000 0.100 0.000 0.004 b 1.397 1.803 0.055 0.071 b 0.220 0.380 0.009 0.015 c 2.591 3.000 0.102 0.118 d 2.692 3.099 0.106 0.122 e 0.585 0.715 0.023 0.028 h 0.080 0.254 0.003 0.010 l 0.300 0.610 0.012 0.024 a a1 b d c h l b e
|
