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RT8560 1 ds8560-01 april 2011 www.richtek.com high voltage 4 channel led driver marking information for marking information, contact our sales representative directly or through a richtek distributor located in your area. applications z umpc and notebook computer backlight z gps, portable dvd backlight z desk lights and room lighting general description the RT8560 is a 60v 4-channel led driver capable of delivering 30ma to each channel with 15 leds (3.6v per diode) total 60 leds with one driver. the RT8560 is a current mode boost converter opearated at 1mhz switching frequency, wide v in range covers from 7v to 40v and the on-chip current switch is rated at 1.5a. the pwm output voltage loop selects and regulates the led pin with the highest voltage string to 0.9v allowing voltage mismatches between led strings. the RT8560 automatically detects and disconnects any unconnected and/or broken strings during operation from pwm loop to prevent v out from over voltage. the 3% matched led currents on all channels are simply programmed with a resistor or a current sink. both analog dimming and digitally controlled pwm dimming are supported by RT8560. analog dimming is linearly controlled by an external voltage. with an on-chip output clampping amplifier and a 200k resistor, pwm dimming signal is easily low-pass filtered to an analog dimming signal with one external capacitor for noise-free pwm dimming. a very high contrast ratio true digital pwm dimming can be achieved by driving en pin to pwm shutdown the chip or by driving actl pin. other protecting features include programmable pwm output over voltage protection, led curren limit, pwm switch current limit and thermal shutdown. the RT8560 is packaged with a tiny footprint package of wqfn-20l 4x4 packages. features z z z z z high voltage : v in up to 40v, v out up to 60v, driving up to 60 x 3.6v leds (15 each channel) z z z z z channel current programmabe 4ma to 30ma and matched to 3% accuracy z z z z z current mode pwm 1mhz boost converter z z z z z easy analog and digital dimming control z z z z z programmable soft start z z z z z automatic detecting unconnected and/or broken channel z z z z z programmable over voltage protection z z z z z disconnects led in digital dimming : providing high accuracy digital dimming by pwm at actl pin or en pin z z z z z v in under voltage lockout z z z z z over temperature protection z z z z z current limiting protection z z z z z small 20-lead wqfn package z z z z z rohs compliant and halogen free pin configurations (top view) wqfn-20l 4x4 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. 1 2 3 4 5 15 14 13 12 11 6 7 8910 20 19 18 16 17 vcc1 gnd led4 gnd gnd gnd gnd sw sw vcc2 riset actl dctl en ovp ss vc gnd led3 led2 led1 21 package type qw : wqfn-20l 4x4 (w-type) RT8560 lead plating system g : green (halogen free and pb free)
RT8560 2 ds8560-01 april 2011 www.richtek.com typical application circuit figure 2. 1mhz, 20ma full scale current analog dimming control figure 1. 1mhz, 20ma full scale current digital pwm dimming control led1 led2 led3 led4 dctl ss vc en ovp vcc1 v out 1.8k 3.9nf 0.1f sw 10h v out 60v max v in 7v to 40v 5.36k 15 led string : : : : : : : : : : : : : : : : actl riset 1f 10f pwm signal vcc2 led iset 5.36k i = 20ma r r1 r2 c out1 c out2 4, 5 c vin l c out3 d 10 r vcc1 c vcc1 1f 5v 1k r3 v in r vcc2 10 c vcc2 1f r iset r vc c vc 1, 2, 3, 19, 20, exposed pad (21) gnd 15 14 13 12 11 6 7 8 9 10 18 16 17 RT8560 1k r4 r5 c1 c2 led1 led2 led3 led4 dctl ss vc en ovp vcc1 v out 1.8k 3.9nf 0.1f sw 10h v out 60v max v in 7v to 40v 5.36k 15 led string : : : : : : : : : : : : : : : : actl riset 1f 10f vcc2 led iset 5.36k i = 20ma r r1 r2 c out1 c out2 4, 5 c vin l c out3 d 10 r vcc1 c vcc1 1f 5v 1k r3 v in r vcc2 10 c vcc2 1f r iset r vc c vc 1, 2, 3, 19, 20, exposed pad (21) gnd 15 14 13 12 11 6 7 8 9 10 18 16 17 RT8560 analog dimming 1k r4 c2 r5 c1
RT8560 3 ds8560-01 april 2011 www.richtek.com figure 3. 1mhz, 20ma full scale current pwm to analog dimming control led1 led2 led3 led4 dctl ss vc en ovp vcc1 v out 1.8k 3.9nf 0.1f sw 10h v out 60v max v in 7v to 40v 5.36k 15 led string : : : : : : : : : : : : : : : : actl riset 1f 10f pwm signal vcc2 led iset 5.36k i = 20ma r r1 r2 c out1 c out2 4, 5 c vin l c out3 d 10 r vcc1 c vcc1 1f 5v 1k r3 v in r vcc2 10 c vcc2 1f r iset r vc c vc 1, 2, 3, 19, 20, exposed pad (21) gnd 15 14 13 12 11 6 7 8 9 10 18 16 17 RT8560 0.1f 1k r4 c3 r5 c1 c2 figure 4. wide range vin application by connecting vcc1 to lcd driver power avdd led1 led2 led3 led4 dctl ss vc en ovp vcc1 v out 1.8k 3.9nf 0.1f sw 10h v out 60v max v avdd 7v to 40v 5.36k 15 led string : : : : : : : : : : : : : : : : actl riset 1f 10f pwm signal vcc2 led iset 5.36k i = 20ma r r1 r2 c out1 c out2 4, 5 c vin l c out3 d 10 r vcc1 c vcc1 2.2f 5v 1k r3 v in r vcc2 10 c vcc2 1f r iset r vc c vc 1, 2, 3, 19, 20, exposed pad (21) gnd 15 14 13 12 11 6 7 8 9 10 18 16 17 RT8560 v in 4v to 40v 1k r4 c2 r5 c1
RT8560 4 ds8560-01 april 2011 www.richtek.com function block diagram + - + - + - + - r r s + - + - + - 6.2v 2.5v 6ua + - 2v shutdown + - 5v + - led1 led2 led3 led4 dctl ss vc en ovp vcc1 osc sw 200k actl riset 1.2v 1.2v vcc2 v out regulation unit
RT8560 5 ds8560-01 april 2011 www.richtek.com pin number pin name pin function 1, 2, 3, 19, 20, 21 (exposed pad) gnd ground pin of the chip. the exposed pad must be soldered to a large pcb and connected to gnd for maximum power dissipation. 4, 5 sw pwm boost converter switch node. 6 v cc2 bipolar power switch base current supply. typical beta of the power npn switch is approximately 70. vcc2 can be connected either to vcc1 or to a separate lower voltage, as low as 3v, for better system efficiency and/or heat concern. a good bypass is necessary. 7 v cc1 power supply of the chip. for good bypass, a low esr capacitor is required. 8 ris et a resistor or a current from dac on this pin programs the full led current. 9 a ctl analog/digital dimming control. when using analog dimming, led actl iset 5.36k i = 20ma for v 1.2v. r 10 dc tl by adding a 0.1uf filtering capacitor on actl pin, the pwm dimming signal on dctl pin will be averaged out and converted into analog dimming signal on actl pin. 11 e n chip enable pin, when low chip is in shutdown mode. 12 ov p over voltage protection. pwm boost converter turns off when v ovp goes higher than 2.5v. 13 s s soft start pin, a capacitor of at least 10nf is required for soft start. 14 v c pwm boost converter loop compensation node. 18, 17, 16, 15 led1, led2, led3, led4 channel 1 to channel 4 led current sink. leave the pin unconnected if not us ed. functional pin description
RT8560 6 ds8560-01 april 2011 www.richtek.com absolute maximum ratings (note 1) z supply voltage, vcc1, vcc2 ------------------------------------------------------------------------------------------ 42v z sw pin voltage at switching off -------------------------------------------------------------------------------------- 65v z led1, led2, led3, led4 pin ----------------------------------------------------------------------------------------- 25v z en pin v oltage ------------------------------------------------------------------------------------------------------------- 20v z riset pin v oltage -------------------------------------------------------------------------------------------------------- 4v z actl, dctl, ovp, ss, vc pin v oltage ----------------------------------------------------------------------------- 8v z power dissipation, p d @ t a = 25 c wqfn-20l 4x4 ------------------------------------------------------------------------------------------------------------ 1.852w z package thermal resistance (note 2) wqfn-20l 4x4, ja ------------------------------------------------------------------------------------------------------- 54 c/w wqfn-20l 4x4, jc ------------------------------------------------------------------------------------------------------ 7 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 recommended operating conditions (note 4) z supply input voltage, vcc1, vcc2 ---------------------------------------------------------------------------------- 7v to 40v z junction temperature range -------------------------------------------------------------------------------------------- ? 40 c to 125 c z ambient temperature range -------------------------------------------------------------------------------------------- ? 40 c to 85 c electrical characteristics (v cc1 = 17v, t a = 25 c, unless otherwise specified) parameter symbol test conditions min typ max unit v cc1 uvlo threshold v uvlo v cc1 rising -- 6.2 6.5 v supply current i vcc1 vc 0.4v (switching off) -- 4 7 ma shutdown current i shdn v en 0.7v -- 12 -- a logic-high voltage v en_h 2 -- 5 en threshold logic-low voltage v en_l -- -- 0.8 v logic-high voltage v actl_h 2 -- 5 actl threshold logic-low voltage v actl_l -- -- 0.15 v en pin input current i en v en 5v -- -- 2 a led current programming led current i led 2v > v led > 0.7v, r iset = 5.36k , v actl >1.28v 19 20 21 ma leds current matching 2v > v led > 0.7v, r iset = 5.36k , v actl >1.28v, calculating (i (max) ? i (mi n) / i average x 100%) -- -- 3 % riset pin voltage v riset r iset = 5.36k , v actl > 1.28v -- 1.21 -- v input current of actl i actl 0.3v v actl 1.2v -- -- 2 a to be continued
RT8560 7 ds8560-01 april 2011 www.richtek.com parameter symbol test conditions min typ max unit threshold of actl v actl led current off -- 0.2 -- v input current of dctl i dctl 0.3v v dctl 6v -- -- 1 a pwm boost converter switching frequency 840 1000 1160 khz maximum duty cycle -- 88 -- % minimum on time -- 200 -- ns regulated v led highest voltage led string -- 0.9 -- v amplifier gm gm -- 220 -- a/v amplifier (gm) output current 2.4v > v c > 0.2v -- 30 -- a vc threshold pwm switch off -- 0.7 -- v sw on voltage i sw = 0.5a -- 0.4 -- v sw current limit i lim 1.2 1.5 -- a ovp & soft start ovp threshold v ovp -- 2.5 -- v ovp input current i ov p v ovp 2.5v -- -- 50 na soft start current i ss v ss = 0v -- 7 -- a 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 expose pad for the wqfn package. note 3. devices are esd sensitive. handling precaution is recommended. note 4. the device is not guaranteed to function outside its operating conditions.
RT8560 8 ds8560-01 april 2011 www.richtek.com typical operating characteristics v riset vs. temperature 1.10 1.12 1.14 1.16 1.18 1.20 1.22 1.24 -40 -20 0 20 40 60 80 100 120 temperature v riset (v) ( c) v in = 12v led current vs. temperature 16 17 18 19 20 21 22 23 24 -40 -15 10 35 60 85 110 135 temperature led current (ma) ( c) v in = 12v v riset v s. input voltage 1.15 1.16 1.17 1.18 1.19 1.20 1.21 1.22 1.23 1.24 1.25 8 1216202428323640 input voltage (v) v riset (v) led current vs. input voltage 10 12 14 16 18 20 22 24 26 8 1216202428323640 input voltage (v) led current (ma) led1 led2 led3 led4 efficiency vs. input voltage 0 10 20 30 40 50 60 70 80 90 100 8 1216202428323640 input voltage (v) efficiency (%) 60leds led current vs. actl pwm duty cycle 0 2 4 6 8 10 12 14 16 18 20 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100 % duty cycle (%) led current (ma) actl = 200hz actl = 1khz actl = 10khz actl = 20khz actl = 30khz actl = 0v to 3v, v in = 12v 0 10 20 30 40 50 60 70 80 90 100
RT8560 9 ds8560-01 april 2011 www.richtek.com frequency vs. input voltage 0.90 0.92 0.94 0.96 0.98 1.00 1.02 1.04 1.06 1.08 1.10 8 1012141618202224 input voltage (v) frequency (mhz) led current vs. dctl pwm duty cycle 0 5 10 15 20 25 20 30 40 50 60 70 80 90 100 duty cycle (%) led current (ma) dctl = 200hz dctl = 1khz dctl = 10khz dctl = 0v to 3v, v in = 12v led current vs. actl voltage 0 5 10 15 20 25 0 0.25 0.5 0.75 1 1.25 1.5 actl voltage (v) led current (ma) v in = 12v shutdown current vs. input voltage 0 5 10 15 20 25 30 35 40 8 1216202428323640 input voltage (v) shutdown current (ua) v en = 0v switch off current vs. input voltage 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5.0 8 1216202428323640 input voltage (v) switch off current (ma) vc = 0v ss current vs. temperature 0 1 2 3 4 5 6 7 8 9 10 -40 -20 0 20 40 60 80 100 120 temperature ss current (ua) ( c) v in = 12v, c ss = 0.1uf
RT8560 10 ds8560-01 april 2011 www.richtek.com limit current vs. input voltage 0.0 0.5 1.0 1.5 2.0 2.5 8 101214161820222426283032 input voltage (v) limit current (a) power on from en time (5ms/div) i in (500madiv) v out (20v/div) v en (2v/div) v in = 12v, c ss = 0.1uf actl voltage vs. temperature 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 -40 -20 0 20 40 60 80 100 120 temperature actl voltage (v) ( c) v in = 12v ovp voltage v s. input voltage 2.2 2.3 2.4 2.5 2.6 2.7 2.8 8 1216202428323640 input voltage (v) ovp voltage (v) ovp voltage vs. temperature 2.30 2.32 2.34 2.36 2.38 2.40 2.42 2.44 2.46 2.48 2.50 -40 -20 0 20 40 60 80 100 120 temperature ovp voltage (v) ( c) v in = 12v ss current vs. input voltage 0 1 2 3 4 5 6 7 8 9 10 8 1216202428323640 input voltage (v) ss current (ua) c ss = 0.1uf
RT8560 11 ds8560-01 april 2011 www.richtek.com ovp time (2.5ms/div) sw (20v/div) v in (5v/div) v in = 12v, all led pin open v out (20v/div) line transient response time (50ms/div) i out (50ma/div) v in (5v/div) v in = 10.8v to 13.2v, riset = 4.8k
RT8560 12 ds8560-01 april 2011 www.richtek.com applications information the RT8560 is a current mode boost converter operated at 1mhz to power up to 60 white leds with a programmable current for uniform intensity. the part integrates current sources, soft-start, and easy analog and digital dimming control. the protection block provides the circuitry for over-temperature, over-voltage and current- limit protection features. input uvlo the input operating voltage range of the RT8560 is 7v to 40v. an input capacitor at the vcc1 and vcc2 pin can reduce ripple voltage. it is recommended to use a ceramic 10uf or larger capacitance as the input capacitor. this ic provides an under voltage lockout (uvlo) function to enhance the stability when startup. the uvlo threshold of input rising voltage is around 6.2v. power sequence please refer to the below figure 5 and 7. the recommended power-on sequence is that the pwm ready before en and/or vin ready. if not, the soft-start function will be disabled. as to power-off sequence, the en/vin must be pulled low within 10ms to prevent ? hard-start ? shown as figure 7. led iset 5.36k i = 20ma r soft start the RT8560 employs a soft start feature to limit the inrush current. the soft-start circuit prevents the excessive inrush current and input voltage droop. the soft-start time is determined by capacitor c ss connected to ss with a 7ua constant current to charge c ss . the value of capacitor c ss is user-defined to satisfy designer' requirement. led connection the RT8560 equips 4 channel led divers and each channel supports up to 15 leds. the 4 led strings are connected from vout to pin 15, 16, 17 and 18 respectively. if one of the led channel is not used, the led pin should be opened directly. setting and regulation of led current the led current can be calculated by the following equation : en must be turned on late than vin and pwm signal en must be turned off early than vin and pwm signal power-on sequence en vin pwm power-off sequence uvlo vout soft-start no soft-start abnormal power- on sequence if pwm turns on late figure 5. power-on sequence control by en vin must be turned on late than en and pwm signal vin must be turned off early than en and pwm signal power-on sequence en vin pwm power-off sequence uvlo vout soft-start no soft-start abnormal power- on sequence if pwm turns on late figure 6. power-on sequence control by vin pwm en/vin en and/or vin should be pulled low once pwm pull low for over 10ms 10ms figure 7. to prevent ? hard-start ? sequence
RT8560 13 ds8560-01 april 2011 www.richtek.com where, v riset is the voltage of the riset pin (1.21v typ.) and the r iset is the resister between riset pin and gnd. this setting is the reference for the led current at led1- 4 and represents the sensed led current for each string. the dc/dc converter regulates the led current according to the setting. brightness control the RT8560 features both analog and digital dimming control. analog dimming is linearly controlled by an external voltage (0.3v < v actl < 1.2v). with an on-chip output clamping amplifier and a 200k resistor, pwm dimming signal is easily low-pass filtered to an analog dimming signal with one external capacitor for noise-free pwm dimming. a very high contrast ratio true digital pwm dimming can be achieved by driving actl pin with a pwm signal and suggest pwm frequency is from 200hz to 10khz. refer to figure 8, the minimum dimming duty can be as low as 1% for the frequency range from 100hz to 300hz. for the dimming frequency from 300hz to 1khz, the duty is about 5%. if the frequency is increased to 1khz to 30khz, the duty will be about 10%. led current vs. actl pwm duty cycle 0 2 4 6 8 10 12 14 16 18 20 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100 % duty cycle (%) led current (ma) actl = 200hz actl = 1khz actl = 10khz actl = 20khz actl = 30khz actl = 0v to 3v, v in = 12v 0 10 20 30 40 50 60 70 80 90 100 figure 8. led current vs. pwm dimming duty cycle over voltage protection the RT8560 equips over voltage protection (ovp) function. when the voltage at ovp pin reaches a threshold of approximately 2.5v, the mosfet drive output (sw) will turn ? off ? . the mosfet drive output (sw) will turn ? on ? again once the voltage at ovp drops below the threshold of approximately 2.5v. so, the output voltage can be clamped at a certain voltage level and it can be calculated by the following equation : out, ovp r1 v = 2.51+ r2 ?? ?? ?? where, r1 and r2 are the voltage divider connected to ovp pin. if at least one string is in normal operation, the controller will automatically ignore the open strings and continue to regulate the current for the string(s) in normal operation. current-limit protection the RT8560 can limit the peak current to achieve over current protection. the RT8560 senses the inductor current of on period that flows through sw pin. the duty cycle depend on current signal and internal slope compensation compared with error signal. the internal n-mosfet will be turned off when the current signal is large than internal slope compensation. in the off period, the inductor current will be descended until the internal n-mosfet is on by the oscillator. over temperature protection the RT8560 has over temperature protection (otp) function to prevent the excessive power dissipation from overheating. otp will shut down the ic while junction temperature exceeds 150 c. main converter starts switching once the junction temperature is cooled approximately 20 c. inductor selection the value of the output inductor (l), where the transition from discontinuous to continuous mode occurs is approximated by the following equation : ) 2 2 out in in out out (v v v l = 2i f v ?
RT8560 14 ds8560-01 april 2011 www.richtek.com ) out in out out ripple out (v v i c = vvf ? layout guideline pcb layout is very important for designing power switching converter circuits. some recommended layout guides that should be strictly be followed are shown as follows : ` the power components l, d, c vin , c out1 and c out2 must be placed as close as possible to reduce the ac current loop. the pcb trace between power components must be as short and wide as possible due to large current stream flows through these traces during operation. ` place l and d connected to sw pin as close as possible. the trace should be short and wide as possible. ` it is recommended to place c vcc1 and c vcc2 close to v cc1 and v cc2 pins. ` pin14 is the compensation point to adjust system stability. place the compensation components to pin14 as close as possible, no matter the compensation is rc or capacitance. figure 9. pcb layout out out in out in peak in out vi vtv v i = v2lv ? ?? + ?? ?? where, v out = maximum output voltage. v in = minimum input voltage. f = operating frequency. i out = sum of current from all led strings. the boost converter operates in discontinuous mode over the entire input voltage range when the l1 inductor value is less than this value l. with an inductance greater than l, the converter operates in continuous mode at the minimum input voltage and may be discontinuous at higher voltages. the inductor must be selected with a saturated current rating that is greater than the peak current provided by the following equation : where, is the efficiency of the power converter. diode selection schottky diode is a good choice for an asynchronous boost converter due to the small forward voltage. however, power dissipation, reverse voltage rating and pulsating peak current are the important parameters for schottky diode selection. choose a suitable diode whose reverse voltage rating is greater than the maximum output voltage. capacitor selection the input capacitor reduces current spikes from the input supply and minimizes noise injection to the converter. for most applications, a 10uf ceramic capacitor is sufficient. a value higher or lower may be used depending on the noise level from the input supply and the input current to the converter. it is recommended to choose a ceramic capacitor bases on the output voltage ripple requirements. the minimum value of the output capacitor c out is approximately given by the following equation : 1 2 3 4 5 15 14 13 12 11 6 7 8910 20 19 18 16 17 vcc1 gnd led4 gnd gnd gnd gnd sw sw vcc2 riset actl dctl en ovp ss vc gnd led3 led2 led1 21 c out1 c out2 d v out c out3 gnd gnd c vin l c vcc1 c vcc2 r vcc2 r vcc1 gnd r vc c vc1 c vc2 v in place these components as close as possible. locate the c vcc1 and c vcc2 as close as possible to v cc1 and v cc2 pin. locate the compensation components to vc pin as close as possible.
RT8560 15 ds8560-01 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 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 0.300 0.006 0.012 d 3.950 4.050 0.156 0.159 d2 2.650 2.750 0.104 0.108 e 3.950 4.050 0.156 0.159 e2 2.650 2.750 0.104 0.108 e 0.500 0.020 l 0.350 0.450 0.014 0.018 w-type 20l qfn 4x4 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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