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austriamicrosystems ag is now ams ag the technical content of this austriamicrosystems datasheet is still valid. contact information: headquarters: ams ag tobelbaderstrasse 30 8141 unterpremstaetten, austria tel: +43 (0) 3136 500 0 e - mail: ams_sales @ams.com please visit our website at www.ams.com
AS3490 highly efficient 2-6 leds backlight driver with pwm input www.austriamicrosystems.com/AS3490 1.2 1 - 18 (ptr) datasheet 1 general description the AS3490 is an inductive highly efficient dcdc boost converter. the dcdc converte r operates at a fixed fre- quency of 2mhz and includes soft startup to allow easy integration into noise sens itive rf systems. a predict- able startup is guaranteed even with very low duty cycle pwm input signals. the voltage on the output capacitor is controlled to minimize ripple and to avoid any acoustic effects for low frequency pwm input signals. the output of the dcdc converter is used for five cur- rent sources connected to up to 6 leds. if a current source is not required, it sh all be connected to vout or gnd - the AS3490 detects this condition and disables this current source automatically; this keeps the effi- ciency of the system constantly high. the AS3490 is controlled by one enable input, on. this input can also be used to connect a pwm input (like dls or dbc). the AS3490 includes several protection functions like undervoltage lockout, overcurrent and overtemperature. no microvias are required to assemble the AS3490. the AS3490 is available in a space-saving wl-csp package measuring only 1. 7x1.4x0.5mm and operates over the -30oc to + 85oc temperature range. figure 1. AS3490 typical operating circuit 2 key features ?? 2 mhz dcdc boost converter - small 4.7h external coil - very high system efficiency of 86% (dcdc and current sources combined) - very low voltage changes on output to avoid acoustic noise on output capacitor even with pwm - smooth startup even under low duty cycle pwm conditions ?? three current sources up to 25ma - low voltage compliance (150mv) - high side current source to simplify layout and thermal management of the leds - automatically detect and di sable failing or not used leds to keep efficiency high - current matching <4% - current accuracy <7.5% ?? excellent led current output ripple <500a ?? support dls (dynamic luminance scaling or dbc) ?? undervoltage lockout and overcurrent protection ?? overtemperature protection ?? available in a tiny wl-csp package - 3x4 balls, 0.4mm pitch, 1.7x1.4x0.5mm 3 applications display backlight driver for mobile phones, digital cam- eras, pnd and pmps. AS3490 ams ag technical content still valid
www.austriamicrosystems.com/AS3490 1.2 2 - 18 AS3490 datasheet - pinout 4 pinout pin assignment figure 2. pin assignments (top view) pin description table 1. wl-csp12 pin description pin number pin name description a1 vin positive supply voltage input - connect to supply and make a short connection to input capacitor c vin a2 iset external current set resistor, forced to 1.25v in operation - led current typically 400xiset current a3 led1 current source output 1 - controlled by on b1 on digital input pin - enable input active high for current sources d1...d3 1 1. if on is low low, the AS3490 enters shutdown. b2 gnd supply ground - connect to ground supply b3 led2 current source output 2 - controlled by on c1 gnd supply ground - connect to supply and make a short connection to input capacitor c vin and c vout c2 gnd supply ground - connect to ground supply c3 led3 current source output 3 - controlled by on d1 sw dcdc converter switching node d2 vout dcdc converter output - make a short connection to capacitor c out d3 vout connect directly to ball d2

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www.austriamicrosystems.com/AS3490 1.2 3 - 18 AS3490 datasheet - absolute maximum ratings 5 absolute maximum ratings stresses beyond those listed in table 2 may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other cond itions beyond those indicated in table 3, ?electrical characteristics,? on page 4 is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. table 2. absolute maximum ratings parameter min max units comments vin, on and iset to gnd -0.3 +7.0 v on and iset to vin +0.3 v internal protection diodes to vin sw, vout, led1...led3 to gnd -0.3 11 v sw, led1...led3 to vout +0.3 v internal protection diodes to vout input pin current without causing latchup -100 +100 +i in ma norm: eia/jesd78 continuous power dissipation (t a = +70oc) continuous power dissipation 870 mw p t 1 at t amb =70oc 1. depending on actual pcb layout and pcb used continuous power dissipation derating factor 11.67 mw/oc p derate 2 2. p derate derating factor changes the total continuous power dissipation (p t ) if the ambient te mperature is not 70oc. therefore for e.g. t amb =85oc calculate p t at 85oc = p t - p derate * (85oc - 70oc) electrostatic discharge esd hbm 2000 v norm: jedec jesd22-a114f esd cdm 500 v norm: jedec jesd 22-c101e esd mm 100 v norm: jedec jesd 22-a115-b temperature ranges and storage conditions junction temperature +125 oc storage temperature range -55 +125 oc humidity 5 85 % non condensing body temperature during soldering +260 oc according to ipc/jedec j-std-020 moisture sensitivity level (msl) msl 1 represents a max. floor life time of unlimited ams ag technical content still valid
www.austriamicrosystems.com/AS3490 1.2 4 - 18 AS3490 datasheet - electrical characteristics 6 electrical characteristics v vin = +2.5v to +5.5v, t amb = -30oc to +85oc, unless otherwise specified. typical values are at v vin = +3.7v, t amb = +25oc, unless otherwise specified. table 3. electrical characteristics symbol parameter condition min typ max unit general operating conditions v vin supply voltage 2.5 3.7 5.5 v v vin _ reduc ed supply voltage reduced performance not all parameters within specification 2.3 v i shutdown shutdown current on=0v 0.5 2.0 a i vin operating current no load, pwm normal mode 250 a t amb operating temperature -30 25 85 oc dcdc converter parameters v vout output voltage vout automatically regulated v vin + 0.3v v vout _max v all other conditions with on13=on45 140 v vout _ ripp le_pwm voltage vout due to pwm signal dcdc not in pulseskip or current limit 70 mv i load load current vout<7.5v 0.0 100 ma ? overall efficiency v vin =3.7v, t amb = +25oc, led mismatch <= 30mv, v led =3.0v i load =50ma 86 % i load =75ma 85 86 i load =100ma 86 f clk operating frequency all internal timings are derived from this oscillator -10% 2.0 +10% mhz t min_on minimum on-time 60 ns mdc maximum duty cycle 90 % r sw_p dcdc switch sw - vout 0.5 ? r sw_n dcdc switch sw - gnd 0.5 ? output voltage soft start t vout_start softstart time measured from first high signal on on 1.2 ms v vout_ start vout startup voltage 7.0 v t pwm_start _max startup with pwm maximum duration between pwm pulses during startup; see figure 17 on page 11 10 11 12 ms t timeout dcdc timeout time if on=0 for t timeout , the dcdc is stopped and the AS3490 enters shutdown 29 48 ms current sources v led1..3 led1...led3 output voltage range 2.6 x2 3.3 x2 3.9 x2 v i led1..3 led1...led3 output current range 0.0 25.0 ma i led1..3 ? led1...led3 current source accuracy 1 i led1..3 =20ma -7.5 +7.5 % ams ag technical content still valid
www.austriamicrosystems.com/AS3490 1.2 5 - 18 AS3490 datasheet - electrical characteristics i led1..3 match led1...led3 current source matching i led1..3 = 20ma -4.0 +4.0 % i led1..3 ripple led1...led3 ripple current bw=10mhz i led > 5ma 10 % of i led i led < 5ma 500 a i led1..3 pwmlin led1...led3 linearity 2 i led =20ma, pwm frequency 300hz pwm>=25/255 -2 +2 % 25/255> pwm>=1/255 -10 +10 % f pwm pwm input frequency on pin on 100 300 800 hz i led1..3 leakage led1...led3 leakage current current source off, t amb < +50oc -0.5 0 +0.5 a v iled_comp led1...led3 current source voltage compliance minimum voltage between pin vout and led1...led3, i led <20ma 3 100 mv current reference (pin iset) v iset iset voltage 1.25 v i led2iset led current to isetcurrent 400 a/a protection functions (see page 12) v vout_max vout overvoltage protection 8.6 10.0 v v vout_ope nled vout open led detection threshold voltage level on vout where open led detection is performed 8.0 8.5 8.8 v v led_open v vled1..3 open detection an open led is assumed if the voltage on the current source is less than v led_open and vout=v vout_openled 92 125 mv v led_short v led1..3 short detection voltage on led1..3 where a shorted led is assumed 0.95 v t led_error _deb_open v led1..3 open debounce time open led detection debounce time 4.8 s t led_error _deb_short v led1..3 short debounce time short led detection debounce time 4 9.0 s i limit current limit for coil l sw (pin sw) 510 600 685 ma t ovtemp overtemperature protection junction temperature 144 oc t ovtemphy st overtemperature hysteresis 5oc v uvlo undervoltage lockout falling v vin 1.8 1.9 2.1 v rising v vin v uvlo +0.05 2.2 2.3 v digital interface v ih high level input voltage 1.07 v vin v v il low level input voltage 0.0 0.68 v r pulldown pulldown resistor 1.8v on pad 90 250 k ? 1. excluding variation of external resistor r iset ; voltage difference between any set of drivers less than 200mv table 3. electrical characteristics (continued) symbol parameter condition min typ max unit ams ag technical content still valid
www.austriamicrosystems.com/AS3490 1.2 6 - 18 AS3490 datasheet - electrical characteristics 2. note: it is not recommend ed to operate the cu rrent sources at minimum duty cycle with low led currents. 3. the dcdc output voltage vout is regulated to 150m v above the maximum led voltage (led1...led3) to guar- antee proper operation of the current with output voltage ripple and undershoots (e.g. due to pwm or supply voltage changes) 4. the short led detection debounce time is longer than the open led detection debounce time to allow the par- asitic capacitance of the led to charge above v led_short within this time and avoid wrong triggering of short led detection. ams ag technical content still valid
www.austriamicrosystems.com/AS3490 1.2 7 - 18 AS3490 datasheet - typical operating characteristics 7 typical operating characteristics v bat = 3.7v, t a = +25oc (unless otherwise specified). figure 3. dcdc efficiency vs. vbat figure 4. led efficiency vs. vbat 55 60 65 70 75 80 85 90 95 2,5 2,9 3,3 3,7 4,1 4,5 4,9 5,3 % input voltage (v) vled=7.5v, ileds=73.5ma vled=7.5v, ileds=49ma 55 60 65 70 75 80 85 90 95 2,5 2,9 3,3 3,7 4,1 4,5 4,9 5,3 % input voltage (v) vled=7.5v, ileds=73.5ma vled=7.5v, ileds=49ma figure 5. efficiency vs. load current figure 6. startup with pwm, 20% duty cycle 55 60 65 70 75 80 85 90 95 0255075 e f f i c i e n c y ( % ) iled(s) (ma) - combined led efficiency (pled/pvin) dcdc efficiency (pdcdc/pvin) figure 7. startup with pwm, 70% duty cycle figure 8. dcdc switching waveforms ams ag technical content still valid
www.austriamicrosystems.com/AS3490 1.2 8 - 18 AS3490 datasheet - typical operating characteristics figure 9. open led detection waveform figure 10. vin line transient 10 s (i load =100ma) figure 11. vout ripple with pwm figure 12. i led ripple (i load =100ma) figure 13. iled vs. r iset figure 14. fosc vs.vin 0 5 10 15 20 25 0 25 50 75 100 125 150 175 200 iled ma riset [kohm] iled [ma] i led =v iset /r iset *i led2iset 1,950 1,975 2,000 2,025 2,050 2,3 2,7 3,1 3,5 3,9 4,3 4,7 5,1 5,5 fosc [mhz] input voltage (v) -30deg 85deg 25deg ams ag technical content still valid
www.austriamicrosystems.com/AS3490 1.2 9 - 18 AS3490 datasheet - typical operating characteristics figure 15. current error vs. duty cycle (i led =25ma) -1 0 1 2 3 4 0 102030405060708090100 error [%] pwm duty cycle [%] ams ag technical content still valid
www.austriamicrosystems. com/AS3490 1.2 10 - 18 AS3490 datasheet - detailed description 8 detailed description the AS3490 is a high performance dcdc step up converter and three current sources in a small wl-csp12 package. the led configuration is done in up to three strings 1 , each strings using two leds in series 2 . this configuration results in excellent application efficiency even using very small external components (capacitors and coil). the device is con- trolled by on. a high levels on this input enables the d cdc and the current sources. on can be used as pwm input 3 to accurately control the led brightness. the target application is to use the AS3490 for highly effi cient backlight driver (displ ay and/or keypad backlight). internal circuit figure 16. AS3490 internal circuit the AS3490 includes a fixed frequency dcdc step-up with accurate startup control. it is enabled by the input pin on and controls the led current with five current sources. th ese input can be used as pwm inputs to control the bright- ness: - a high level on on enables led1, led2 and led3 the current is adjustable by an external resistor r iset . 1. unused strings shall be connected to vout or gnd. 2. single led strings can be mixed with dual led strings as long as one string has two leds in series - it will reduce application efficiency. 3. using the pwm inputs, the AS3490 supports dls, dynamic luminance scaling, also called cabc, content adaptive backlight control or db c, dynamic backlight control.

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www.austriamicrosystems. com/AS3490 1.2 11 - 18 AS3490 datasheet - detailed description startup in order to avoid inrush-current during startup the supplies are smoothly ramped up according to figure 17 even under low pwm duty cycle conditi ons. this allows the easy integration into mobile battery powered systems: figure 17. startup procedure open and short led detection after the startup is finished, the AS3490 continuously monitors open and shorted leds. if an open or shorted led string is detected, this led st ring is disabled and the driver continuous its normal operation. the driver is disabled to keep the efficiency of AS3490 for different led configurations high. the error is cleared once the AS3490 enters shut- down 4 . shorted led after startup is finished, for any led, enabled by the inputs on, is below v led_short , for at least t led_error_deb_short , a shorted led is assumed. open led led outputs (led1...led5) which are not used by the application shall be connected permanently to vout or gnd. the AS3490 detect this condition upon st artup and automatically disables the current sources for these leds - see figure 18 and figure 19 , immediately after the rising edged of on. for leds, which are open during operation of the device, following procedure of the AS3490 is used for detection: after startup is finished, if the voltage on vout=v vout_openled 5 and the voltage across any current source, enabled by the inputs on, is below v led_open (vout-led1...3), for at least t led_error_deb_open , an open led is assumed. figure 18 shows the waveform for the detection of a single open led, figure 19 for all leds open. 4. the error is automatically cleared as the open/short led error might be temporarily (e.g. bouncing of the connections to the led) 5. if the current limit of the coil (i limit ) is reached before vout=v vout_openled , an open led is not detected. &'

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www.austriamicrosystems. com/AS3490 1.2 12 - 18 AS3490 datasheet - detailed description figure 18. single open led detection figure 19. all leds open protection and fault detection functions the protection functions protect t he AS3490, its external components and connected leds against physical damage. overvoltage protection the voltage on vout is kept below or at v vout_max under every operating condition 6 . if the voltage on vout is at v vout_max for more than 70ms 7 , the dcdc will shutdown. it can be re-enabled by setting on to low for more than t timeout . 6. when reaching vout=v vout_openled , the open led detection is performed. 7. the duration can vary from 55ms to 85ms within a single AS3490.

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www.austriamicrosystems. com/AS3490 1.2 13 - 18 AS3490 datasheet - detailed description dcdc inductor peak current limitation to limit the maximum current from the battery, the dcdc converter limits its current through the coil to i limit on a cycle by cycle basis. overtemperature protection the junction temperature of the AS3490 is contin uously monitored. if the temperature exceeds t ovtemp , the dcdc is stopped. the driver is automatically re-enabled once the junction temperature drops below t ovtemp -t ovtemphyst . supply undervoltage protection if the voltage on the pin vin is or falls below v uvlo , the AS3490 is kept in shutdown. ams ag technical content still valid
www.austriamicrosystems. com/AS3490 1.2 14 - 18 AS3490 datasheet - application information 9 application information external components input capacitor c vin low esr input capacitors reduce input switching noise and reduce the peak current drawn from the battery. ceramic capacitors are required for input decoupling and should be located as close to the device as is practical. if a different input capacitor is chosen, ensure similar esr value and at least 0.6f capacitance at the maximum input supply voltage. larger capacitor val ues (c) may be used without limitations. output capacitors c out low esr capacitors should be used to minimize vout ripple. multi-layer ceramic capacitors are recommended since they have low esr and are available in sm all footprints. the capacitor should be located as close to the device as is practical. x5r dielectric material is recommended due to their ability to maintain capacitance over wide voltage and temperature range. if a different output capacitor is chosen, ensure simila r esr values and at least 4.2f @ 5.6v and maximum 20f capacitance. table 4. recommended input capacitor part number c tc code esr rated voltage size manufacturer grm155r60j225me15 2.2f +/-20% x5r 6v3 0402 (1.0x0.5x 0.5mm) murata www.murata.com grm155r60j155m---d 1.5f x5r 6v3 ecj0mbfj185v x5r 0402 (1.0x0.5x 0.5mm) panasonic matsushita www.panasonic.com jdk105bj155mvnf x5r 0402 (1.0x0.5x 0.5mm) ta i y o yu d e n www.taiyo-yuden.com table 5. recommended output capacitor c out part number c tc code esr rated voltage size manufacturer grm219r61a116ue82l 10f x5r 120m ? 10v 0805 (2x1.25x 0.85mm) murata www.murata.com ldk212bj106mdnt 10f x5r 10v 0805 (2x1.25x 0.85mm) ta i y o yu d e n www.taiyo-yuden.com ams ag technical content still valid
www.austriamicrosystems. com/AS3490 1.2 15 - 18 AS3490 datasheet - application information inductor l sw the fast switching frequency (2mhz) of the AS3490 allows fo r the use of small smds for the external inductor. the inductor should have low dc resistance (dcr) to reduce the i 2 r power losses - high dcr values will reduce effi- ciency. if a different inductor is chosen, ensure similar dcr values and at least 2.45h inductance at maximum peak input current. pcb layout guideline the high speed operation requires proper layout for optimum per formance. route the power traces first and try to min- imize the area and wire length of the three high frequency/high current loops: loop1: pin gnd - c vin - l sw - pin sw - pin gnd loop2: pin gnd - c vin - l sw - pin sw - pin vout - c vout - pin gnd at the pin gnd a single via (or more vias, which are closely combined) connects to the common ground plane. this via(s) will isolate the dcdc high frequency currents from th e common ground (as most high frequency current will flow between loop1 and loop2 and will not pass the ground plane) - see the ?island? at the two through ground vias in figure 20 : figure 20. layout recommendation note: if component placement rules allow, move all components close to the AS3490 to reduce the area and length of loop1 and loop2 table 6. recommended inductor part number l dcr size manufacturer lqm2hpn4r7mgc 4.7h; >2.45h @ 0.5a 160m ? 2.5x2.0x0.9mm max height 1.0mm murata www.murata.com cig32k1r0saf 4.57h; >2.45h @ 0.5a <300m ? 2.0x1.25x0.9mm max height 1.0mm samsung electro- mechancs www.sem.samsung.co.kr

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www.austriamicrosystems. com/AS3490 1.2 16 - 18 AS3490 datasheet - package drawings and markings 10 package drawings and markings figure 21. 12pin wl-csp12 1.7x1.4x0.5mm marking note: line 1: austriamicrosystems logo line 2: AS3490 line 3:

 encoded datecode (4 characters) figure 22.  12pin wl-csp12  1.7x1.4x0.5mm package dimensions the coplanarity of the balls is 40m. 	

 	
        
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 www.austriamicrosystems. com/AS3490 1.2 17 - 18 AS3490 datasheet - ordering information 11 ordering information the devices are available as the standard products shown in  table 7 . note: all products are rohs complian t and austriamicrosystems green. buy our products or get free samples online at icdirect:  http://www.austriamicr osystems.com/icdirect technical support is found at  http://www.austriamicrosystems.com/technical-support for further information and requests, please contact us  mailto:sales@austriamicrosystems.com or find your local distributor at  http://www.a ustriamicrosystems.com/distributor note: AS3490-zwlt AS3490- z temperature range: -30oc - 85oc wl wafer level chip scale pa ckage (wl-csp) 1.7x1.4x0.5mm t delivery form: tape & reel table 7.  ordering information model description delivery form package AS3490-zwlt highly efficient 2-6 leds backlight driver with   pwm input tape & reel 12-pin wl-csp (1.7x1.4x0.5mm) rohs compliant / pb-free /  green  ams  ag  technical  content  still  valid

 www.austriamicrosystems. com/AS3490 1.2 18 - 18 AS3490 datasheet - ordering information copyrights copyright ? 1997-2012, austriamicrosystems ag, schloss premstaetten, 8141 unterpremstaetten, austria-europe.  trademarks registered ?. all rights reserved. the material herei n may not be reproduced, adapted, merged, trans- lated, stored, or used without the  prior written consent of the copyright owner.  all products and companies mentioned are trademarks or registered trademarks of their respective companies. disclaimer devices sold by austriamicrosystems ag are covered by the warranty and patent indemnification provisions appearing  in its term of sale. austriamicrosystems ag makes no warranty, express, statutory, implied, or by description regarding  the information set  forth herein or regarding the freedom of the described devices from patent infringement. austriami- crosystems ag reserves the right to change specifications a nd prices at any time and  without notice. therefore, prior  to designing this product into a system, it is necessary to  check with austriamicrosystems ag for current information.  this product is intended for use in normal commercial a pplications. applications requiring extended temperature  range, unusual environmental requirements, or high reliability applications, such as military, medical life-support or life- sustaining equipment are specifically not recommended without additional  processing by austriamicrosystems ag for  each application. for shipments of less than 100 parts the manufacturing flow might show deviations from the standard  production flow, such as test flow or test location. the information furnished here by austriamicrosystems ag  is believed to be correct  and accurate. however,  austriamicrosystems ag shall not be liable to recipient or  any third party for any damages, in cluding but not limited to  personal injury, property damage, loss of profits, loss of  use, interruption of business or indirect, special, incidental or  consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the tech- nical data herein. no obligation or liability to recipie nt or any third party shall arise or flow out of  austriamicrosystems ag rendering of technical or other services.  contact information headquarters austriamicrosystems ag tobelbaderstrasse 30 schloss premstaetten a-8141 austria tel: +43 (0) 3136 500 0 fax: +43 (0) 3136 525 01 for sales offices, distributors and representatives, please visit:  http://www.austriamicrosystems.com/contact  ams  ag  technical  content  still  valid

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