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RT9373A 1 ds9373a-04 april 2011 www.richtek.com 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. general description the RT9373A is a high efficiency and cost effective charge pump white led driver. it supports up to 3 white leds with regulated constant current for uniform intensity. the RT9373A maintains the highest efficiency by utilizing a x1/x1.5/x2 charge pump and low dropout current regulators. user can easily configure each led current from 1.25ma to 20ma by a pulse dimming control. the dimming of white leds current can be achieved by applying a pulse signal to the en pin. there are totally 16 steps of current could be set by users. RT9373A is available in a wqfn3x3-16l package. features z z z z z very high efficiency over 80% of battery life z z z z z support up to 3 white leds z z z z z support up to 60ma output current z z z z z 1% typical led current matching z z z z z soft start function z z z z z auto charge pump mode selection z z z z z 250khz fixed frequency oscillator z z z z z output over voltage protection z z z z z 16 steps brightness control z z z z z low input noise and emi z z z z z rohs compliant and 100% lead (pb)-free 3-channel charge pump white led driver with low dropout current source applications z mobile phone, dsc, mp3 z white led backlighting z lcd display supply pin configurations (top view) wqfn-16l 3x3 marking information for marking information, contact our sales representative directly or through a richtek distributor located in your area. nc en 12 11 10 9 13 14 15 16 1 2 3 4 8 7 6 5 c1p gnd nc c2p gnd nc vout vin c2n c1n vin led3 led2 led1 17 RT9373A package type qw : wqfn-16l 3x3 (w-type) lead plating system p : pb free g : green (halogen free and pb free)
RT9373A 2 ds9373a-04 april 2011 www.richtek.com typical application circuit figure 1. for 3-wleds application circuit figure 2. for 2-wleds application circuit vout led2 led1 led3 en vin c1n c2p c2n c out c in v cc RT9373A gnd 2.2uf c1p c pump2 1uf c pump1 1uf 2.2uf 2.8v to 5.5v gpio 12 3, 10 5, 13 9 47 6 14 15 16 8 vout led2 led1 led3 en vin c1n c2p c2n c out c in v cc RT9373A gnd 2.2uf c1p c pump2 1uf c pump1 1uf 2.2uf 2.8v to 5.5v gpio 12 9 14 15 16 3, 10 4 8 76 5, 13
RT9373A 3 ds9373a-04 april 2011 www.richtek.com functional pin description pin no. pin name pin function 1, 2, 11, 17 (exposed pad) nc no internal connection. 3 gnd ground. 4 c1p positive terminal of bucket capacitor 1 5 vin power input voltage. 6 c2n negative terminal of bucket capacitor 2. 7 c1n negative terminal of bucket capacitor 1. 8 vout output voltage source. 9 c2p positive terminal of bucket capacitor 2. 10 gnd ground. 12 en chip enable (active high). note that this pin is high impedance. 13 vin power input voltage. 14 led 1 output current for led1. (if not in use, pin should be connected to gnd). 15 led 2 output current for led2. (if not in use, pin should be connected to gnd). 16 led 3 output current for led3. (if not in use, pin should be connected to gnd). function block diagram vin led1 led2 led3 vout c1p en c2p c1n c2n current limitation soft start circuit 16 steps pulse dimming controller uvlo x1/x1.5/x2 charge pump low drop out current source (pmos) shut down delay (2ms) gnd
RT9373A 4 ds9373a-04 april 2011 www.richtek.com electrical characteristics (v in = 2.5v to 5.5v, c in = c out = c fly = 1uf (esr = 30m ), t a = 25 c, unless otherwise specification) to be continued absolute maximum ratings (note 1) z supply input voltage ------------------------------------------------------------------------------------------------------ ? 0.3v to 6v z other i/o pin voltage ----------------------------------------------------------------------------------------------------- ? 0.3v to 6v z power dissipation, pd @ t a = 25 c wqfn-16l 3x3 ------------------------------------------------------------------------------------------------------------ 1.47w z package thermal resistance (note 2) wqfn-16l 3x3, ja ------------------------------------------------------------------------------------------------------- 68 c/w z junction temperature ----------------------------------------------------------------------------------------------------- 150 c z lead temperature (soldering, 10 se c.) ------------------------------------------------------------------------------- 260 c z storage temperature range -------------------------------------------------------------------------------------------- ? 40 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 parameter symbol test condition min typ max units input input supply voltage v in 2.8 -- 5.0 v under-voltage lockout threshold v in rising 1.6 2.1 2.5 v under-voltage lockout hysteresis -- 100 -- mv quiescent of x1 mode i q_x1 x1 mode, no load, all led pins connected to gnd, v in = 4v 0.5 1 2 ma quiescent of x2 mode i q_x2 x2 mode, no load, all led pins floating, v in = 3.5v 1.5 2.5 5 ma shutdown current enable = 0.4v, v in = 2.8v to 5.5v 0 0.1 10 ua x1 mode to x1.5 mode transition voltage (v in falli ng) v ts_x1.5 v f = 3.5v, i ou t = 80ma, i ledx = 20ma -- 3.75 -- v x1.5 mode to x2 mode transition voltage (v in falli ng) v ts_x2 v f = 3.5v, i ou t = 80ma, i ledx = 20ma -- 3.0 -- v hysteresis of mode transition -- 150 -- mv output current range of i led x 2.8 < v in < 5.5@v f = 3.2, i out = 60ma 1.25 -- 20 ma i ledx accuracy i led-err 100% setting ? 8 -- +8 % current matching 100% setting ? 5 -- +5 % enable logic-high voltage v ih 1.5 -- -- v en threshold logic-low voltage v il -- -- 0.4 v
RT9373A 5 ds9373a-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 is highly recommended. note 4. the device is not guaranteed to function outside its operating conditions. parameter symbol test condition min typ max units en low time for dimming t il 0.5 -- 500 us en high time for dimming t ih 0.5 -- -- us high current i ih v ih = v in -- 1 10 ua en current low current i il v il = gnd -- 1 10 ua en low time for shut down t shd n pulse dimming -- 2 -- ms frequency oscillator fr equency f osc -- 250 -- khz
RT9373A 6 ds9373a-04 april 2011 www.richtek.com quiescent current vs. input voltage 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 2.6 3.1 3.6 4.1 4.6 5.1 5.6 input voltage (v) quiescent current (ma ) x2 mode x1 mode typical operating characteristics shutdown current vs. input voltage 0 0.3 0.6 0.9 1.2 1.5 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) shutdown current (ua ) oscillator frequency v s. input voltage 0 50 100 150 200 250 300 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) oscillator frequency (khz ) enable voltage v s. input voltage 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) en voltage threshold (v ) efficiency vs. input voltage 50 55 60 65 70 75 80 85 90 95 2.6 3 3.4 3.8 4.2 4.6 5 5.4 5.8 input voltage (v) efficiency (%) v f = 3.3v rising falling led current vs. input voltage 18.0 18.5 19.0 19.5 20.0 20.5 21.0 2.533.544.5 55.5 input voltage (v) led current (ma) led2 led3 led1 v f = 3.2v
RT9373A 7 ds9373a-04 april 2011 www.richtek.com v in = 3.6v dimming operation v in (2v/div) time (1ms/div) v out (2v/div) en (2v/div) i led (20ma/div) v in = 3.3v dimming operation v in (2v/div) time (1ms/div) v out (2v/div) en (2v/div) i led (20ma/div) x2 mode inrush current response v in (2v/div) time (100us/div) v out (5v/div) en (2v/div) i in (500ma/div) v in = 3v, c in = c out = 2.2uf, c pump = 1uf x2 mode en pin shutdown response c2n (2v/div) time (500us/div) v out (5v/div) en (2v/div) i led (500ma/div) c in = c out = 2.2uf, c pump = 1uf x1.5 mode inrush current response v in (2v/div) time (100us/div) v out (5v/div) en (2v/div) i in (500ma/div) v in = 3.7v, c in = c out = 2.2uf, c pump = 1uf x1 mode inrush current response v in (2v/div) time (25us/div) v out (5v/div) en (2v/div) i in (500ma/div) v in = 4.2v, c in = c out = 2.2uf, c pump = 1uf
RT9373A 8 ds9373a-04 april 2011 www.richtek.com v in = 3.0v, c in = c out = 2.2 f x2 mode ripple & spike v in ac (100mv/div) time (1us/div) v out ac (200mv/div) c2n (2v/div) v in = 3.3v, c in = c out = 2.2 f x1.5 mode ripple & spike v in ac (100mv/div) time (1us/div) v out ac (200mv/div) c2n (2v/div)
RT9373A 9 ds9373a-04 april 2011 www.richtek.com applications information the RT9373A is a high efficiency charge pump white led driver. it provides 3 channels low dropout voltage current source to regulated 3 white leds current. for high efficiency, the RT9373A implements a smart mode transition for charge pump operation. the RT9373A provides pulse dimming function for led brightness control. soft start the RT9373A includes a soft start circuit to limit the inrush current at power on and mode switching. soft start circuit limits the input current before output voltage reaching a desired voltage level. when the soft start off, the RT9373A won't sink spike current from v in . mode decision the RT9373A uses a smart mode decision method to select the working mode for maximum efficiency. the charg pump can operation at x1, x1.5 or x2 mode. the mode decision circuit senses the output and led voltage for up/down selection. brightness control the RT9373A implements the pulse dimming method being used to control the brightness of white leds. the part implements a 4-bit dac for brightness control. users can easily configure the led current from 1.25ma to 20ma by a serial pulse. the maximum led current is up to 20ma that is sufficient for most application in backlight. the dimming of white leds' current can be achieved by applying a pulse signal to the en pin. there are totally 16 steps of current could be set by users. the detail operation of brightness dimming is showed in the figure 3. selecting capacitors to get the better performance of RT9373A, the selecting of peripherally appropriate capacitor and value is very important. these capacitors determine some parameters such as input and output ripple, power efficiency, maximum supply current by charge pump, and start-up time. to reduce the input and output ripple effectively, the low esr ceramic capacitors are recommended. generally, to reduce the output ripple, increasing the output capacitance c out is necessary. however, this will increase the start- up time of output voltage. for led driver applications, the input voltage ripple is more important than output ripple. input ripple is controlled by input capacitor c in , increasing the value of input capacitance can further reduce the ripple. practically, the input voltage ripple depends on the power supply ? s impedance. if a single input capacitor c in cannot satisfy the requirement of application, it is necessary to add a low-pass filter. c-r-c filter used to reduce input ripple. the flying capacitor c pump1 and c pump2 determine the supply current capability of the charge pump. the lower value will limit the led ? s current at low input voltage. 0.5us < t lo < 500us 30us < t ready 2ms < t shdn 15/16 14/16 13/16 12/16 1/16 2/16 100% 100% 15/16 0 1234 5 14 15 0 1 en iledx shutdown shutdown 0.5us < t hi figure 3. brightness control by pulse dimming. RT9373A implements 16 steps brightness control
RT9373A 10 ds9373a-04 april 2011 www.richtek.com figure 4. pcb layout guide layout consideration the RT9373A is a low dropout current source for white led driver. careful pcb layout is necessary. for best performance, place all peripheral components 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 RT9373A. 1. all the traces of led pins 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 v in (pin 5) and connected to ground plane. the trace of v in in the pcb should be placed far away the sensitive devices or shielded by the ground. 3. the gnd should be connected to a strong ground plane for heat sinking and noise protection. 4. output capacitor (c out ) should be placed close to v out and connected to ground plane to reduce noise coupling from charge pump to leds. 5. the traces running from pins to flying capacitor should be short and wide to reduce parasitic resistance and prevent noise radiation. c in c2 battery ground plane 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 c out nc gnd c1p c2p gnd nc en c2n c1n vout vin led3 led2 led1 vin c1 all the traces of led pins 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 (pin 5) and connected to ground plane. the trace of v in in the pcb should be placed far away the sensitive devices or shielded by the ground. the gnd should be connected to a strong ground plane for heat sinking and noise protection. output capacitor (c out ) should be placed close to v out and connected to ground plane to reduce noise coupling from charge pump to leds. the traces running from pins to flying capacitor should be short and wide to reduce parasitic resistance and prevent noise radiation. nc
RT9373A 11 ds9373a-04 april 2011 www.richtek.com 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 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. outline dimension a a1 a3 d e 1 d2 e2 l b e see detail a dimensions in millimeters dimensions in inches symbol min max min max a 0.700 0.800 0.028 0.031 a1 0.000 0.050 0.000 0.002 a3 0.175 0.250 0.007 0.010 b 0.180 0.300 0.007 0.012 d 2.950 3.050 0.116 0.120 d2 1.300 1.750 0.051 0.069 e 2.950 3.050 0.116 0.120 e2 1.300 1.750 0.051 0.069 e 0.500 0.020 l 0.350 0.450 0.014 0.018 w-type 16l qfn 3x3 package note : the configuration of the pin #1 identifier is optional, but must be located within the zone indicated. det ail a pin #1 id and tie bar mark options 1 1 2 2

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