rt9300a/b 1 ds9300a/b-05 april 2011 www.richtek.com features z z z z z low 60/45mv dropout at 20/15ma z z z z z 5% led current matching z z z z z simple led brightness control z z z z z 2.5v to 5.5v supply voltage range z z z z z thermal shutdown protection z z z z z rohs compliant and 100% lead (pb)-free applications z next-generation wireless handsets z pdas, palmtops, and handy terminals z digital cameras, camcorders z battery-powered equipment tiny package, low dropout current source ordering information general description the rt9300a/b low-dropout bias supply for white leds is a high-performance alternative to the simple ballast resistors used in conventional white led designs. the rt9300a/b uses an internal resistor to set the bias current for four leds, which are matched to 5%. the rt9300a/b's advantages over ballast resistors include much lower bias variation with supply voltage variation, significantly lower dropout voltage, and in some applications, significantly improved efficiency. the rt9300a/b requires only a 60/45mv dropout voltage at a 20/15ma load on each output to match the led brightness. (top view) sot-23-6 typical application circuit pin configurations figure 1. application circuit for backlight. 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. marking information for marking information, contact our sales representative directly or through a richtek distributor located in your area. led4 led3 led2 led1 gnd en enable v in 6 5 43 1 2 rt9300a/b c 0.1uf en gnd led4 led1 led2 led3 4 23 5 6 rt9300a/b package type e : sot-23-6 lead plating system p : pb free g : green (halogen free and pb free) sink current a : 20ma b : 15ma
rt9300a/b 2 ds9300a/b-05 april 2011 www.richtek.com function block diagram functional pin description pin name function 1 en chip enable (active high). 2 gnd ground 3 led4 led4 cathode connection. current flowing into led4 is constant. (20ma/15 ma) led4 is high impedance when en is low. 4 led3 led3 cathode connection. current flowing into led3 is constant. (20ma/15 ma) led3 is high impedance when en is low. 5 led2 led2 cathode connection. current flowing into led2 is constant. (20ma/15 ma) led2 is high impedance when en is low. 6 led1 led1 cathode connection. current flowing into led1 is constant. (20ma/15 ma) led1 is high impedance when en is low. + - current source uvlo bandgap otp led1 led2 led3 led4 en i ref v ref figure 2. application circuit for keypad. led4 led3 led2 led1 gnd en pwm v in 6 5 43 1 2 rt9300a/b c 0.1uf keypad led
rt9300a/b 3 ds9300a/b-05 april 2011 www.richtek.com absolute maximum ratings (note 1) z supply input voltage, v in ------------------------------------------------------------------------------------------------ ? 0.3v to 6v z the other pins -------------------------------------------------------------------------------------------------------------- ? 0.3v to 6v z power dissipation, p d @ t a = 25 c sot-23-6 -------------------------------------------------------------------------------------------------------------------- 0.4w z package thermal resistance (note 2) sot-23-6, ja --------------------------------------------------------------------------------------------------------------- 250 c/w z lead temperature (soldering, 10 sec.) ------------------------------------------------------------------------------- 260 c z operation temperature range ----------------------------------------------------------------------------------------- ? 40 c to 85 c z junction te mperature ----------------------------------------------------------------------------------------------------- 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 electrical characteristics parameter symbol test conditions min typ max unit system supply input operation voltage range v en 2.5 -- 5.5 v under voltage lock out v(uvlo) falling -- 2.1 -- v uvlo hysteresis -- 100 -- mv rt9300a 18 20 22 led sink current rt9300b 13.5 15 16.5 ma quiescent current i en i led = 0 -- -- 600 ua i led = 20ma -- 60 -- led dropout voltage i led = 15ma -- 45 -- mv led current deviation matching -- -- 5 % en high-level input voltage v en _h 2.5 -- -- v en low-level input voltage v en _l -- -- 0.7 v otp -- 170 -- c otp hysteresis -- 10 -- c shutdown current i shdn v en < 0.4v -- -- 1 ua (v in = 3.7v, t a = 25 c, unless otherwise specification) recommended operating conditions (note 4) z junction temperature range -------------------------------------------------------------------------------------------- ? 40 c to 125 c z ambient temperature range -------------------------------------------------------------------------------------------- ? 40 c to 85 c
rt9300a/b 4 ds9300a/b-05 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 single layer thermal conductivity test board of jedec 51-3 thermal measurement standard. note 3. devices are esd sensitive. handling precaution is recommended. note 4. the device is not guaranteed to function outside its operating conditions. note 5. floating connection or pull low to disable this function.
rt9300a/b 5 ds9300a/b-05 april 2011 www.richtek.com typical operating characteristics led current vs. en voltage 0 2 4 6 8 10 12 14 16 18 1.5 1.75 2 2.25 2.5 2.75 3 3.25 3.5 en voltage (v) led current (ma) v in = 3.7v en current vs. en supply voltage 0 50 100 150 200 250 300 350 400 1.522.533.544.5 en supply voltage (v) en current (ua) v in = 3.5v led current vs. input voltage 0 2 4 6 8 10 12 14 16 18 22.533.544.55 input voltage (v) led current (ma) led 1 led 2 led 3 led 4 ( c) led current vs. temperature 15 15.1 15.2 15.3 15.4 15.5 -40-30-20-100 102030405060708090 temperature led current (ma) en pin dimming operation time (50us/div) (2v/div) (10ma/div) led current en pin voltage v en = 0v to 3v en pin shutdown response time (50us/div) en pin voltage led current (2v/div) (10ma/div) en current vs. en supply voltage en supply voltage (v) en current (ua) led current vs. en voltage en voltage (v) led current (ma)
rt9300a/b 6 ds9300a/b-05 april 2011 www.richtek.com v in = 3.2v to 3.7v line transient response time (100us/div) input voltage (1v/div) (25ma/div) led current
rt9300a/b 7 ds9300a/b-05 april 2011 www.richtek.com applications information the rt9300a/b is a 4-channel current source driver for white leds. enable input en powers the input of the rt9300a/b. 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 2.1v typically with a hysteresis 0.1v.drive en high to enable the device; drive en low to disable the device. when driven high, en draws 350ua to power the ic. driving en low forces led1, led2, led3, and led4 into a high-impedance state. led current rt9300a/b provides a constant current for white led. figure 1 shows a typical application circuit for 4 white leds. each channel supports up to 20ma/15ma current and regulates a constant current for uniform intensity. for keypad led application, the all channels must be connected to led as shown in figure 2. in order to maintain led constant current, the input voltage must provide the required led forward voltage and current source dropout voltage. if the forward voltage of white leds is 3.3v, the input voltage should be higher than 3.4v to provide enough voltage headroom for maintaining constant brightness. led brightness dimming control for controlling the led brightness, the rt9300a/b can perform the dimming control by applying a pwm signal to en pin. when an external pwm signal is connected to the en pin, brightness of white led is adjusted by the duty cycle. the average led current is proportional to the pwm signal duty cycle. the magnitude of the pwm signal must be higher than the minimum level of enable input high level, in order to let the dimming control perform correctly, the suggested pwm frequency range is 10khz to 200hz. thermal considerations for continuous operation, do not exceed absolute maximum operation junction temperature 125 c. the maximum power dissipation depends on the thermal resistance of ic package, pcb layout, the rate of surroundings airflow and temperature difference between junction to ambient. the maximum power dissipation can be calculated by following formula : p d(max) = ( t j(max) - t a ) / ja where t j(max) is the maximum operation junction temperature 125 c, t a is the ambient temperature and the ja is the junction to ambient thermal resistance. for recommended operating conditions specification of rt9300, where t j(max) is the maximum junction temperature of the die (125 c) and t a is the maximum ambient temperature. the junction to ambient thermal resistance ja is layout dependent. for sot-23-6 packages, the thermal resistance ja is 250 c/w on the standard jedec 51-3 single-layer thermal test board. the maximum power dissipation at t a = 25 c can be calculated by following formula : p d(max) = (125 c ? 25 c) / (250 c/w) = 0.4w for sot-23-6 packages the maximum power dissipation depends on operating ambient temperature for fixed t j(max) and thermal resistance ja . for rt9300 packages, the figure 1 of derating curves allows the designer to see the effect of rising ambient temperature on the maximum power allowed. figure 1. derating curves for rt9300 packages 0 50 100 150 200 250 300 350 400 450 500 0 255075100125 ambient temperature (c) maximum power dissipation (mw) sot-23-6 single layer pcb
rt9300a/b 8 ds9300a/b-05 april 2011 www.richtek.com layout considerations 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 rt9300a/ b. ` all the traces of led and vin running from chip to leds should be wide and short to reduce the parasitic connection resistance. ` the capacitor should be placed close to the anodes of leds and connected to ground plane. ` the gnd should be connected to a strong ground plane for heat sinking and noise protection. led3 led2 led1 led4 gnd en 4 23 5 6 1 pwm battery all the traces of led and vin running from chip to leds should be wide and short to reduce the parasitic connection resistance. the gnd should be connected to a strong ground plane for heat sinking and noise protection. gnd figure 2
rt9300a/b 9 ds9300a/b-05 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 infringemen t of the applications should be guaranteed by users when integrating richtek products into any application. no legal responsibility for any said applications is assumed b y 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 a a1 e b b d c h l sot-23-6 surface mount package dimensions in millimeters dimensions in inches symbol min max min max a 0.889 1.295 0.031 0.051 a1 0.000 0.152 0.000 0.006 b 1.397 1.803 0.055 0.071 b 0.250 0.560 0.010 0.022 c 2.591 2.997 0.102 0.118 d 2.692 3.099 0.106 0.122 e 0.838 1.041 0.033 0.041 h 0.080 0.254 0.003 0.010 l 0.300 0.610 0.012 0.024
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