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general description the aat3143 is a low noise, constant frequency charge pump dc/dc converter that uses a tri- mode load switch (1x), fractional (1.5x), and dou- bling (2x) conversion to maximize efficiency for white led applications. the aat3143 can deliver current levels up to 80ma to drive white leds con- nected to the four current source outputs from a 2.7v to 5.5v input. the current source outputs may source up to 20ma each and may be operated indi- vidually or in parallel for driving higher-current leds. a low external parts count (two 1f flying capacitors and two small 1f capacitors at v in and v out ) makes the aat3143 ideally suited for small battery-powered applications. output current, and therefore brightness, is con- trolled via externally applied pulse width modulation (pwm) control. typically, pwm frequencies of up to 50khz can be applied. the aat3143 has a thermal management system to protect the device in the event of a short-circuit con- dition at the voltage output pin. built-in soft-start cir- cuitry prevents excessive inrush current during start- up. a high charge pump switching frequency allows the use of very small external capacitors. a low cur- rent shutdown feature disconnects the load from v in and reduces quiescent current to less than 1a. the aat3143 is available in a pb-free, space-sav- ing, 2.85x3.0mm 12-pin tsopjw package. features ? input voltage range: 2.7v to 5.5v ? pwm brightness control ? tri-mode 1x, 1.5x, and 2x charge pump for maximum efficiency and v f coverage ? drives four low- or high-v f type leds ? up to 20ma led current per channel ? no inductors ? 1mhz switching frequency ? small application circuit ? autobias? technology ?i q <1a in shutdown ? 2.85x3.0mm tsopjw-12 package applications ? programmable current sources ? white led backlighting ? white photo flash for digital still cameras aat3143 high efficiency 1x/1.5x/2x charge pump with pwm control for white led applications typical application 3143.2006.05.1.0 1 chargepump ? c1 1f c2 1f d1 d2 d3 c out 1f c in 1f 2.7v to 5.5v pwm/en in en/pwm c1+ c1- c2+ c2- cp d1 d2 d3 gnd aat3143 d4 d4
pin descriptions pin configuration tsopjw-12 (top view) pin # symbol function 1 c2+ flying capacitor 2 positive terminal. connect a 1f capacitor between c2+ and c2-. 2 cp charge pump output. requires 1f capacitor connected between this pin and ground. 3 c1- flying capacitor 1 negative terminal. 4 c1+ flying capacitor 1 positive terminal. connect a 1f capacitor between c1+ and c1-. 5 d3 current source output #3. 6 d2 current source output #2. 7 d4 current source output #4. 8 d1 current source output #1. 9 en/pwm enable/pwm control pin. 10 in input power supply. requires 1f capacitor connected between this pin and ground. 11 gnd ground. 12 c2- flying capacitor 2 negative terminal. aat3143 high efficiency 1x/1.5x/2x charge pump with pwm control for white led applications 2 3143.2006.05.1.0 1 2 3 4 5 6 12 11 10 9 8 7 c2+ cp c1- c1+ d3 d2 c2- gnd in en/pwm d1 d4
absolute maximum ratings 1 thermal information 3 symbol description value units p d maximum power dissipation 4 0.625 w ja maximum thermal resistance 160 c/w symbol description value units v in input voltage -0.3 to 6 v v en/pwm en/pwm to gnd voltage -0.3 to v in + 0.3 v i out 2 maximum dc output current 80 ma t j operating junction temperature range -40 to 150 c t lead maximum soldering temperature (at leads, 10 sec) 300 c aat3143 high efficiency 1x/1.5x/2x charge pump with pwm control for white led applications 3143.2006.05.1.0 3 1. stresses above those listed in absolute maximum ratings may cause permanent damage to the device. functional operation at con ditions other than the operating conditions specified is not implied. only one absolute maximum rating should be applied at any one tim e. 2. based on long-term current density limitation. 3. mounted on an fr4 board. 4. derate 6.25 mw/c above 25c.
electrical characteristics 1 c in = c cp = c 1 = c 2 = 1.0f; t a = -40c to +85c, unless otherwise noted. typical values are t a = 25c, v in = 3.5v. symbol description conditions min typ max units input power supply v in operation range 2.7 5.5 v i cc operating current vd1:d4 = 2.0v, cp = 1x 550 a no load current, cp = 1.5x 3 5 i shdn shutdown current en/pwm = 0 1 a i dx output current accuracy i out = 20ma, t a = 25c, v in = 3.5v 18 20 22 ma i (d-match) current matching 2 vd1:d4 = 3.6v, v in = 3.5v -3 0.5 3 % cp charge pump efficiency v in = 3.5v, i out(total) = 80ma, 93 % measured from in to cp charge pump section f clk clock frequency 1000 khz en/pwm v en(l) enable threshold low 0.4 v v en(h) enable threshold high 1.4 v f pwm maximum pwm frequency 50 khz t on(min) minimum pulse width 2 s aat3143 high efficiency 1x/1.5x/2x charge pump with pwm control for white led applications 4 3143.2006.05.1.0 1. the aat3143 is guaranteed to meet performance specifications over the -40c to +85c operating temperature range and is assu red by design, characterization, and correlation with statistical process controls. 2. current matching is defined as i (d-match) = (i d - i ave )/i ave .
typical characteristics v in = 3.5v, c in = c cp = c 1 = c 2 = 1f, t a = 25c, unless otherwise noted. aat3143 high efficiency 1x/1.5x/2x charge pump with pwm control for white led applications 3143.2006.05.1.0 5 led turn-on delay (pwm frequency = 5khz) time (1s/div) v en (2v/div) v led (2v/div) i led (10ma/div) led turn-on delay (pwm frequency = 500hz) time (5s/div) v en (2v/div) v led (2v/div) i led (10ma/div) turn-on to 2x mode (v in = 2.7v) time (50s/div) v en (1v/div) v cp (2v/div) v led (2v/div) i in (50ma/div) turn-on to 1.5x mode (v in = 3.5v) time (50s/div) v en (1v/div) v cp (2v/div) v led (2v/div) i in (50ma/div) turn-on to 1x mode (v in = 4.2v) time (50s/div) v en (1v/div) v cp (2v/div) v led (2v/div) i in (100ma/div) efficiency (100% duty cycle, 4x20ma/channel) input voltage (v) efficiency (%) 30 40 50 60 70 80 90 100 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2
typical characteristics v in = 3.5v, c in = c cp = c 1 = c 2 = 1f, t a = 25c, unless otherwise noted. aat3143 high efficiency 1x/1.5x/2x charge pump with pwm control for white led applications 6 3143.2006.05.1.0 input voltage (v) input current (ma) input current vs. input voltage (4x10ma) 0 10 20 30 40 50 60 70 80 90 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 v diode = 3.4v v diode = 3.0v load characteristics (1.5x mode, 4x15ma load) time (1s/div) v f (20mv/div) i in (10ma/div) v cp (20mv/div) line response (1.5x mode, 4x19ma load) time (1ms/div) v in (0.5v/div) v led (20mv/div) v cp (0.5v/div) i d (10ma/div) line response (1x mode, 4x19ma load) time (1ms/div) v in (0.5v/div) v led (20mv/div) v cp (0.5v/div) i d (10ma/div) pwm duty cycle vs. led current duty cycle (%) led current (ma) 0 2 4 6 8 10 12 14 16 18 20 0 102030405060708090100 100hz 10khz 1khz 1.5x mode pwm characteristic (5khz at 50% duty cycle) time (50s/div) v en (2v/div) v led (2v/div) i in (100ma/div) i led (20ma/div)
aat3143 high efficiency 1x/1.5x/2x charge pump with pwm control for white led applications 3143.2006.05.1.0 7 typical characteristics v in = 3.5v, c in = c cp = c 1 = c 2 = 1f, t a = 25c, unless otherwise noted. v ih and v il vs. v in input voltage (v) 0.600 0.625 0.650 0.675 0.700 0.725 0.750 0.775 0.800 0.825 0.850 2.5 3.0 3.5 4.0 4.5 5.0 5.5 v ih v il
aat3143 high efficiency 1x/1.5x/2x charge pump with pwm control for white led applications 8 3143.2006.05.1.0 functional block diagram functional description the aat3143 is a tri-mode load switch (1x) and high efficiency (1.5x or 2x) charge pump device intended for white led backlight applications. to maximize power conversion efficiency, an internal sensing circuit monitors the voltage required on each constant current source output and sets the load switch and charge pump modes based on the input battery voltage and the current source output voltage. as the battery discharges over time, the aat3143 charge pump is enabled when any of the four current source outputs nears dropout. the charge pump initially starts in 1.5x mode. if the charge pump output drops enough for any current source output to become close to dropout, the charge pump will automatically transition to 2x mode. the aat3143 requires only four external components: two 1f ceramic capacitors for the charge pump flying capacitors (c 1 and c 2 ), one 1f ceramic input capacitor (c in ), and one 0.33f to 1f ceramic charge pump output capacitor (c out ). the four constant current source outputs (d1 to d4) can drive four individual leds with a maximum current of 20ma each. the unused source outputs must be connected to gnd, otherwise the part will operate only in 2x charge pump mode. the en/pwm input allows the user to control the bright- ness of the four leds by pwming up to 50khz. 1x/1.5x/2x charge pump d/a d/a d/a en/pwm soft-start control 1mhz oscillator voltage reference in en/pwm gnd d4 d3 d2 d1 cp c1+ c1- c2+ c2- d/a
aat3143 high efficiency 1x/1.5x/2x charge pump with pwm control for white led applications 3143.2006.05.1.0 9 applications information en/pwm dimming control led brightness is controlled with the en/pwm pin. by driving the pin with a pwm signal, a correspon- ding pulse-width modulated current will be driven through the leds. in this way, the duty cycle sets the led brightness level. the resulting average current that flows through the led is calculated as follows: the en/pwm pin can be driven with a wide range of pwm frequencies. because of the short turn-on delay during high frequency pwm, a frequency as high as 50khz can be used. a low pwm frequency can also be used without complication. one should consider that below 50hz, the human eye can begin to see led flicker, so it is recommended that users choose an adequate pwm frequency exceeding 50hz. led selection although the aat3143 is specifically intended for driving white leds, the device can also be used to drive most types of leds with forward voltage spec- ifications ranging from 2.0v to 4.7v. led applica- tions may include main and sub-lcd display back- lighting, camera photo-flash applications, infrared (ir) diodes for remotes, and other loads benefiting from a controlled output current generated from a varying input voltage. since the d1 to d4 input cur- rent sources are matched with negligible voltage dependence, the led brightness will be matched regardless of the specific led forward voltage (v f ) levels. in some instances (e.g., in high luminous output applications such as photo flash), it may be necessary to drive high-v f type leds. the low dropout current sources in the aat3143 make it capable of driving leds with forward voltages as high as 4.7v at full current from an input supply as low as 3.0v. outputs can be paralleled to drive high- current leds without complication. capacitor selection careful selection of the four external capacitors c in , c 1 , c 2 , and c out is important because they will affect turn-on time, output ripple, and transient per- formance. optimum performance will be obtained when low equivalent series resistance (esr) ceramic capacitors are used; in general, low esr may be defined as less than 100m . a value of 1f for all four capacitors is a good starting point when choosing capacitors. if the led current sources are only programmed for light current lev- els, then capacitor size may be decreased. capacitor characteristics ceramic composition capacitors are highly recom- mended over all other types of capacitors for use with the aat3143. ceramic capacitors offer many advantages over their tantalum and aluminum elec- trolytic counterparts. a ceramic capacitor typically has very low esr, is lowest cost, has a smaller pcb footprint, and is non-polarized. low-esr ceramic capacitors help maximize charge pump transient response. since ceramic capacitors are non-polarized, they are not prone to incorrect con- nection damage. equivalent series resistance esr is an important characteristic to consider when selecting a capacitor. esr is a resistance internal to a capacitor that is caused by the leads, internal connections, size or area, material composition, and ambient temperature. capacitor esr is typi- cally measured in milliohms for ceramic capacitors and can range to more than several ohms for tanta- lum or aluminum electrolytic capacitors. ceramic capacitor materials ceramic capacitors less than 0.1f are typically made from npo or c0g materials. npo and c0g materials generally have tight tolerance and are very stable over temperature. larger capacitor val- ues are usually composed of x7r, x5r, z5u, or y5v dielectric materials. large ceramic capacitors (i.e., greater than 2.2f) are often available in low- cost y5v and z5u dielectrics, but capacitors greater than 1f are not typically required for aat3143 applications. i led = dc 20m a
aat3143 high efficiency 1x/1.5x/2x charge pump with pwm control for white led applications 10 3143.2006.05.1.0 capacitor area is another contributor to esr. capacitors that are physically large will have a lower esr when compared to an equivalent material smaller capacitor. these larger devices can improve circuit transient response when compared to an equal value capacitor in a smaller package size. thermal protection the aat3143 has a built-in thermal protection cir- cuit that will shut down the charge pump if the die temperature rises above the thermal limit, as is the case during a short-circuit of the cp pin.
aat3143 high efficiency 1x/1.5x/2x charge pump with pwm control for white led applications 3143.2006.05.1.0 11 ordering information package information tsopjw-12 all dimensions in millimeters. package marking 1 part number (tape and reel) 2 tsopjw-12 roxyy AAT3143ITP-T1 advanced analogic technologies, inc. 830 e. arques avenue, sunnyvale, ca 94085 phone (408) 737-4600 fax (408) 737-4611 1. xyy = assembly and date code. 2. sample stock is generally held on part numbers listed in bold . ? advanced analogic technologies, inc. analogictech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an analogictech pr oduct. no circuit patent licenses, copyrights, mask work rights, or other intellectual property rights are implied. analogictech reserves the right to make changes to their products or specifi cations or to discontinue any product or service without notice. customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information b eing relied on is current and complete. all products are sold sub- ject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. analogictech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with anal ogictech?s standard warranty. testing and other quality con- trol techniques are utilized to the extent analogictech deems necessary to support this warranty. specific testing of all param eters of each device is not necessarily performed. analogictech and the analogictech logo are trademarks of advanced analogic technologies incorporated. all other brand and produ ct names appearing in this document are regis- tered trademarks or trademarks of their respective holders. 0.20 + 0.10 - 0.05 0.055 0.045 0.45 0.15 7 nom 4 4 3.00 0.10 2.40 0.10 2.85 0.20 0.50 bsc 0.50 bsc 0.50 bsc 0.50 bsc 0.50 bsc 0.15 0.05 0.9625 0.0375 1.00 + 0.10 - 0.065 0.04 ref 0.010 2.75 0.25 all analogictech products are offered in pb-free packaging. the term ?pb-free? means semiconductor products that are in compliance with current rohs standards, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. for more information, please visit our website at http://www.analogictech.com/pbfree.

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