RT9385 1 ds9385-01 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. marking information for marking information, contact our sales representative directly or through a richtek distributor located in your area. pin configurations (top view) wqfn-16l 2x3 5 channels 125ma x1/x1.5/x2 charge pump white led driver general description the RT9385 is a 5 channel wled driver with auto mode selection of x1, x1.5 and x2 mode with low dropout voltage in current sources. the RT9385 can power up to 5 white leds with regulated constant current for uniform intensity. each channel (led1 to led5) can support up to 25ma. the part maintains highest efficiency by utilizing x1/x1.5/ x2 fractional charge pump and low dropout current regulators. for the brightness control, user can easily use a pwm signal generated from gpio to control the brightness of wleds. the RT9385 is available in a wqfn-16l 2x3 package. small 1 f capacitors can be used for fly capacitors. it provides the best backlighting solution with high efficiency and smallest board space for portable application. features z z z z z 85% average efficiency over li-ion battery discharge z z z z z support up to 5 white leds z z z z z support up to 25ma/per channel z z z z z pwm brightness control z z z z z 60mv current source dropout z z z z z 1% led current accuracy z z z z z 0.7% led current matching z z z z z automatic x1/x1.5/x2 charge pump mode transition z z z z z low input noise and emi z z z z z over voltage protection z z z z z power on/mode transition inrush protection z z z z z 1mhz switching frequency z z z z z 0.4 a low shutdown current z z z z z rohs compliant and halogen free applications z camera phone, smart phone z white led backlighting led3 agnd vout led5 led4 en vin cf c2n c1n c1p led2 led1 vin pgnd c2p 13 12 11 10 14 15 16 1 2 3 4 8 7 6 17 gnd 9 5 RT9385 package type qw : wqfn-16l 2x3 (w-type) lead plating system g : green (halogen free and pb free)
RT9385 2 ds9385-01 april 2011 www.richtek.com functional pin description pin no. pin name pin function 1 led3 current sink for led3. (if not in use, this pin should be connected to vin) 2 led4 current sink for led4. (if not in use, this pin should be connected to vin) 3 led5 current sink for led5. (if not in use, this pin should be connected to vin) 4 vout charge pump output. 5 pgnd ground. 6 c2n fly capacitor 2 negative connection. 7 c1n fly capacitor 1 negative connection. 8 c1p fly capacitor 1 positive connection. 9 c2p fly capacitor 2 positive connection. 10 en chip enable (active high). 11, 14 vin power input. 12 cf pwm filter capacitor connection, no connection if this pin is not in use. 13 agnd ground. 15 led1 current sink for led1. (if not in use, this pin should be connected to vin) 16 led2 current sink for led2. (if not in use, this pin should connected to vin) 17 (exposed pad) gnd the exposed pad must be soldered to a large pcb and connected to gnd for maximum power dissipation. typical application circuit c2n led4 pgnd c out vin c1p c1n c2p RT9385 en vout led3 led2 led1 c fly2 1f c fly1 1f c in 1f 1 0 1 3 8 1 4 , 1 1 4 agnd 7 6 9 5 1 5 1 6 1 2 1f pwm input 3 led5 c cf cf 1 2 0.1f
RT9385 3 ds9385-01 april 2011 www.richtek.com function block diagram en led2 led5 led3 led4 1mhz osc pwm dimming controller soft start circuit current source shutdown delay vin vout gate driver uvlo ovp c1p c2p c2n c1n mode decision current bias pgnd agnd led1 cf
RT9385 4 ds9385-01 april 2011 www.richtek.com absolute maximum ratings (note 1) z supply input voltage, v in ------------------------------------------------------------------------------------------------ ? 0.3v to 5v z power dissipation, p d @ t a = 25 c wqf n-16l 2x3 ------------------------------------------------------------------------------------------------------------ 1.111w z package thermal resistance (note 2) wqfn-16l 2x3, ja ------------------------------------------------------------------------------------------------------- 90 c/w wqfn-16l 2x3, jc ------------------------------------------------------------------------------------------------------ 15 c/w z junction temperature ----------------------------------------------------------------------------------------------------- 150 c z lead temperature (soldering, 10 se c.) ------------------------------------------------------------------------------- 260 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 (v in = 3.6v, v f = 3.5v, c in = c out = 1uf, c fly1 = c fly2 = 1 f, i led1 to led5 = 25ma, t a = 25 c, unless otherwise specified) parameter symbol test conditions min typ max unit input power supply input supply voltage v in 2.8 -- 4.5 v under-voltage lockout threshold v uvlo v in rising 1.8 2 2.5 v under-voltage lockout hysteresis v uvlo -- 100 -- mv quiescent current i q x1 mode -- 1 2 ma shutdown current i shdn v in = 4.5v -- 0.4 2 a led current led current accuracy i ledx i ledx = 25ma ? 5 0 +5 % current matching i ledx = 25ma ? 2 0 +2 % charge pump oscillator frequency f os c -- 1000 -- khz pwm dimming frequency 1 -- 200 khz internal cf resistance -- 160 -- k mode decision x1 mode to x1.5 mode transition voltage (v in falling) i out = 125ma, i ledx = 25ma. -- 3.65 3.8 v mode transition hystersis i out = 125ma, i ledx = 25ma. -- 200 -- mv recommended operating conditions (note 4) z junction temperature range -------------------------------------------------------------------------------------------- ? 40 c to 125 c z ambient temperature range -------------------------------------------------------------------------------------------- ? 40 c to 85 c to be continued
RT9385 5 ds9385-01 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 high effective four layers thermal conductivity test board of jedec 51-7 thermal measurement standard. the case point of jc is on the exposed pad for the package. note 3. devices are esd sensitive. handling precaution is recommended. note 4. the device is not guaranteed to function outside its operating conditions. parameter symbol test conditions min typ max unit protection ovp v in ? v out 4.5 5 5.5 v enable en low time for shutdown 3 -- -- ms logic-low voltage v il -- -- 0.2 en threshold logic-high voltage v ih 1 -- 4.5 v en pull low current -- 2 -- a
RT9385 6 ds9385-01 april 2011 www.richtek.com typical operating characteristics x1 mode quiescent current vs. input voltage 1.00 1.05 1.10 1.15 1.20 1.25 1.30 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5 input voltage (v) quiescent current (ma) x2 mode quiescent current vs. input voltage 2.0 2.5 3.0 3.5 4.0 4.5 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5 input voltage (v) quiescent current (ma) efficiency vs. input voltage 0 10 20 30 40 50 60 70 80 90 100 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5 input voltage (v) efficiency (%) led v f = 3.02v led current vs. input voltage 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5 input voltage (v) led current (ma) led1 led2 led3 led4 led5 led v f = 3.02v shutdown current vs. input voltage 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5 input voltage (v) shutdown current ( a ) v in = 3.2v time (100 s/div) c2p (2v/div) v out (1v/div) en (5v/div) i in (200ma/div) x1 mode inrush current response
RT9385 7 ds9385-01 april 2011 www.richtek.com v in = 3.1v ripple & spike time (1 s/div) c2p (5v/div) v out (50mv/div) i in (200ma/div) v in (50mv/div) v in = 3.7v, c cf = 56nf, duty = 50%, f = 10khz pwm dimming operation time (250 s/div) en (2v/div) i led (10ma/div) v in = 3.1v x2 mode inrush current response time (100 s/div) c2p (2v/div) v out (1v/div) en (5v/div) i in (200ma/div) v in = 3.15v x1.5 mode inrush current response time (100 s/div) c2p (2v/div) v out (1v/div) en (5v/div) i in (200ma/div)
RT9385 8 ds9385-01 april 2011 www.richtek.com applications information the RT9385 uses a fractional switched capacitor charge pump to power up to five white leds with a programmable current for uniform intensity. the part integrates current sources and automatic mode selection charge pump. it maintains the high efficiency by utilizing an x1/x1.5/x2 fractional charge pump and current sources. the small equivalent x1 mode open loop resistance and ultra-low dropout voltage of current source extend the operating time of x1 mode and optimize the efficiency in white led applications. input uvlo the input operating voltage range of the led driver is from 2.8v to 4.5v. 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. the RT9385 provides an under voltage lockout (uvlo) function to prevent it from unstable issue when startup. the uvlo threshold of input rising voltage is set at 2v typically with a hysteresis of 100mv. soft start the charge pump employs a soft start feature to limit the inrush current. the soft-start circuit prevents the excessive inrush current and input voltage drop. the soft-start clamps the input current in a typical period of 50 s. mode decision the RT9385 uses a smart mode selection method to decide the working mode for optimizing the efficiency. mode decision circuit senses the output and led voltage for up/down selection. the RT9385 automatically switches to x1.5 or x2 mode whenever the dropout condition is detected from the current source and returns to x1 mode whenever the dropout condition releases. led connection the RT9385 supports up to 5 white leds. the 5 leds are connected from vin to pin1, 2, 3, 15 and 16 respectively. if the led is not used, the led pin should be connected to vin directly. capacitors selection to get the better performance of the RT9385, the selection of peripherally appropriate capacitor and value is very important. these capacitors determine some parameters such as input/output ripple voltage, power efficiency and maximum supply current by charge pump. to reduce the input and output ripple effectively, the low esr ceramic capacitors are recommended. 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 impedance. the flying capacitor c fly1 and c fly2 determine the supply current capability of the charge pump to influence the overall efficiency of the system. the lower value will improve efficiency. however, it will limit the led's current at low input voltage. for 5x25ma load over the entire input range of 2.8v to 4.5v, it is recommended to use a 1 f ceramic capacitor on the flying capacitor c fly1 and c fly2 . brightness control the RT9385 implements a pwm dimming method to control the brightness of white leds. when an external pwm signal is connected to the en pin, brightness of white led is adjusted by the duty cycle. the suggested pwm dimming frequency range is from 1khz to 200khz. thermal considerations for continuous operation, do not exceed absolute maximum operation junction temperature. 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, t a is the ambient temperature and the ja is the junction to ambient thermal resistance. for recommended operating conditions specification of
RT9385 9 ds9385-01 april 2011 www.richtek.com the RT9385, the maximum junction temperature is 125 c. the junction to ambient thermal resistance ja is layout dependent. for wqfn-16l 2x3 package, the thermal resistance ja is 90 c/w on the standard jedec 51-7 four layers 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) / (90 c/w) = 1.111w for wqfn-16l 2x3 package the maximum power dissipation depends on operating ambient temperature for fixed t j(max) and thermal resistance ja . for RT9385 package, the figure 1 of derating curve allows the designer to see the effect of rising ambient temperature on the maximum power dissipation allowed. figure 1. derating curve for RT9385 package 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 0 25 50 75 100 125 ambient temperature (c) maximum power dissipation (w) four layers pcb wqfn-16l 2x3 figure 2. pcb layout guide layout considerations for best performance of the RT9385, the following layout guidelines should be strictly followed : ` output capacitor (c out ) should be placed close to vout and connected to ground plane to reduce noise coupling from charge pump to leds. ` all the traces of led pins running from chip to led's should be wide and short to reduce the parasitic connection resistance. ` the trace from cf pin to external capacitance should be as short as possible. ` input capacitor (c in ) should be placed close to vin and connected to ground plane. the trace of vin in the pcb should be placed far away from the sensitive devices or shielded by the ground. ` the traces running from pins to flying capacitor should be short and wide to reduce parasitic resistance and prevent noise radiation. battery gnd led3 agnd vout led5 led4 en vin cf c2n c1n c1p led2 led1 vin pgnd c2p 13 12 11 10 14 15 16 1 2 3 4 8 7 6 17 gnd 9 5 gnd all the traces of led pins running from chip to leds should be wide and short to reduce the parasitic co nnection resistance. the trace from cf pin to external capacitance should be as short as possible. the traces running from pi ns to flying capacitor should be short and wide to reduce parasitic resistance and prevent noise radiation. output capacitor (c out ) should be placed close to vout and connected to ground plane to reduce noise coupling from charge pump to leds. input capacitor (c in ) should be placed close to vin and connected to ground plane. the trace of vin in the pcb should be placed far away from the sensitive devices or shielded by the ground.
RT9385 10 ds9385-01 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 d e l d2 e2 a3 a a1 b see detail a e 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 0.150 0.250 0.006 0.010 d 1.900 2.100 0.075 0.083 d2 0.700 0.800 0.028 0.031 e 2.900 3.100 0.114 0.122 e2 1.700 1.800 0.067 0.071 e 0.400 0.016 l 0.325 0.425 0.013 0.017 w-type 16l qfn 2x3 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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