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AAT3155 high efficiency 1x/1.5x/2x charge pump for white led applications 3155.2006.05.1.1 1 chargepump ? general description the AAT3155 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 AAT3155 is capable of driving up to four channels of leds at 20ma per channel from a 2.7v to 5.5v input. the current sinks may be operated individually or in parallel for driving higher current leds. a low external parts count (two 1f flying capacitors and two small 1f capacitors at in and outcp) make this part ideal- ly suited for small, battery-powered applications. analogictech's s 2 cwire ? (simple serial control ? ) serial digital input is used to enable, disable, and set current for each led with 16 settings down to 50 a. the low-current mode supply current can be as low as 50 a to save power. each output of the AAT3155 is equipped with built- in protection for output short-circuit and auto-dis- able for load short-circuit conditions. built-in soft- start circuitry prevents excessive inrush current during start-up. a low-current shutdown feature dis- connects the load from the input and reduces qui- escent current to less than 1 a. the AAT3155 is available in a pb-free, space-sav- ing 2.85x3.0mm 12-pin tsopjw package. features ?v in range: 2.7v to 5.5v ? fully programmable current with single wire ? 16 current levels ? four low current settings down to 50a ? low i q (50a) for low current mode ? tri-mode 1x, 1.5x, and 2x charge pump for maximum efficiency and v f coverage ? drives up to four channels of leds ? no inductors, low noise operation ? 1mhz constant switching frequency ? small application circuit ? built-in thermal protection ? automatic soft start ?i q <1a in shutdown ? 2.85x3.0mm tsopjw-12 package applications ? color (rgb) lighting ? programmable current sinks ? white led backlighting ? white photo flash for digital still cameras typical application 2.7v to 5.5v en/set in en/set c2+ c2- c1+ c1- outcp d1 d2 d3 gnd AAT3155 d1 c1 1f c2 1f c in 1f c ou t 1f d2 d3 d4 d4
pin descriptions pin configuration tsopjw-12 (top view) pin # symbol function 1 d3 current sink input #3. 2 d2 current sink input #2. 3 d1 current sink input #1. 4 gnd ground. 5 in input power supply. requires 1f capacitor connected between this pin and ground. 6 c2- flying capacitor 2 negative terminal. 7 c2+ flying capacitor 2 positive terminal. connect a 1f capacitor between c2+ and c2-. 8 outcp charge pump output to drive load circuit. requires 1 f capacitor connected between this pin and ground. 9 c1- flying capacitor 1 negative terminal. 10 c1+ flying capacitor 1 positive terminal. connect a 1 f capacitor between c1+ and c1-. 11 en/set s 2 cwire serial interface control pin. 12 d4 current sink input #4. AAT3155 high efficiency 1x/1.5x/2x charge pump for white led applications 2 3155.2006.05.1.1 1 2 3 4 5 6 12 11 10 9 8 7 d3 d2 d1 gnd in c2- d4 en/set c1+ c1- outcp c2+
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 to gnd -0.3 to 6 v v en/set en/set voltage to gnd -0.3 to v in + 0.3 v i out 2 maximum dc output current 150 ma t j operating junction temperature range -40 to 150 c t lead maximum soldering temperature (at leads, 10 sec) 300 c AAT3155 high efficiency 1x/1.5x/2x charge pump for white led applications 3155.2006.05.1.1 3 1. stresses above those listed in absolute maximum ratings may cause permanent damage to the device. functional operation at co ndi- tions other than the operating conditions specified is not implied. only one absolute maximum rating should be applied at any o ne time. 2. based on long-term current density limitation. 3. mounted on an fr4 board. 4. derate 6.25mw/c above 25c.
electrical characteristics 1 c in = c out = c 1 = c 2 = 1.0f; t a = -40c to +85c, unless otherwise noted. typical values are t a = 25c, v in = 3.6v. symbol description conditions min typ max units input power supply v in operation range 2.7 5.5 v 1x mode, 3.0 v in 5.5, active, 0.3 1 no load current 1.5x mode, 3.0 v in 5.5, active, 1 3 ma i cc operating current no load current 2x mode, 3.0 v in 5.5, active, 1 no load current 50a setting, 1x mode 50 a i shdn shutdown current v en/set = 0v 1 a i dx i sink average current accuracy i set = 20ma, t a = 25c 18 20 22 ma i (d-match) current matching 2 v f :d1:d4=3.6v 0.5 1 % v th 1x to 1.5x or 1.5x to 2x transition 150 mv threshold at any i sink pin charge pump section t ss soft-start time 100 s f clk clock frequency 1000 khz en/set v en(l) enable threshold low v in = 2.7v 0.4 v v en(h) enable threshold high v in = 5.5v 1.4 v t en/set lo en/set low time 0.3 75 s t en/set _ hi _ min minimum en/set high time 50 ns t en/set _ hi _ max maximum en/set high time 75 s t off en/set off timeout 500 s t lat en/set latch timeout 500 s i en/set en/set input leakage -1 1 a AAT3155 high efficiency 1x/1.5x/2x charge pump for white led applications 4 3155.2006.05.1.1 1. the AAT3155 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 the deviation of any sink current from the average of all active channels.
AAT3155 high efficiency 1x/1.5x/2x charge pump for white led applications 3155.2006.05.1.1 5 typical characteristics c in = c out = c 1 = c 2 = 1.0f; t a = 25c, v in = 3.6v, unless otherwise noted. diode current vs. temperature (20ma/channel) temperature ( c) diode current (ma) 18.0 18.5 19.0 19.5 20.0 20.5 21.0 21.5 22.0 -40 -25 -10 5 20 35 50 65 80 95 i d1 i d2 i d4 i d3 turn-off from 1.5x mode (v in = 3.5v; 20ma load) time (200 s/div) en (2v/div) v f (1v/div) i in (100ma/div) turn-on to 2x mode (v in = 2.8v; 20ma load) time (200 s/div) en (2v/div) v out (2v/div) i in (200ma/div) v sink (500mv/div) turn-on to 1.5x mode (v in = 3.5v; 20ma load) time (200 s/div) en (2v/div) v out (2v/div) i in (200ma/div) v sink (1v/div) turn-on to 1x mode (v in = 4.2v; 20ma load) time (200 s/div) en (2v/div) v out (2v/div) i in (100ma/div) v sink (1v/div) efficiency vs. supply voltage supply voltage (v) efficiency (%) 30 40 50 60 70 80 90 100 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 5ma/ch v f = 3v 20ma/ch v f = 3.4v 500a/ch v f = 2.7v
typical characteristics c in = c out = c 1 = c 2 = 1.0f; t a = 25c, v in = 3.6v, unless otherwise noted. AAT3155 high efficiency 1x/1.5x/2x charge pump for white led applications 6 3155.2006.05.1.1 en/set latch timeout vs. input voltage input voltage (v) en/set latch timeout ( s) 0 50 100 150 200 250 300 350 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 -40 c 25 c 85 c input ripple vs. input voltage input voltage (v) input ripple (mv) 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 20ma/channel 14ma/channel 10ma/ channel load characteristics (v in = 2.9v; 2x mode; 14ma load) time (500ns/div) v in (40mv/div) v sink (40mv/div) v cp (40mv/div) load characteristics (v in = 2.9v; 2x mode; 20ma load) time (500ns/div) v in (40mv/div) v sink (40mv/div) v cp (40mv/div) load characteristics (v in = 3.9v; 1.5x mode; 14ma load) time (500ns/div) v in (40mv/div) v sink (20mv/div) v cp (20mv/div) load characteristics (v in = 3.9v; 1.5x mode; 20ma load) time (500ns/div) v in (40mv/div) v sink (20mv/div) v cp (40mv/div)
typical characteristics c in = c out = c 1 = c 2 = 1.0f; t a = 25c, v in = 3.6v, unless otherwise noted. AAT3155 high efficiency 1x/1.5x/2x charge pump for white led applications 3155.2006.05.1.1 7 enable threshold low vs. input voltage input voltage (v) enable threshold low (v) 0.4 0.6 0.8 1.0 1.2 1.4 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 -40 c 25 c 85 c enable threshold high vs. input voltage input voltage (v) enable threshold high (v) 0.4 0.6 0.8 1.0 1.2 1.4 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5. 5 -40 c 25 c 85 c en/set off timeout vs. input voltage input voltage (v) en/set off timeout ( s) 0 50 100 150 200 250 300 350 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 -40 c 25 c 85 c
AAT3155 high efficiency 1x/1.5x/2x charge pump for white led applications 8 3155.2006.05.1.1 functional block diagram functional description the AAT3155 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 sink input and sets the load switch and charge pump modes based on the input battery voltage and the current sink input voltage. as the battery discharges over time, the AAT3155 charge pump is enabled when any of the four cur- rent sink inputs nears dropout. the charge pump initially starts in 1.5x mode. if the charge pump output droops enough for any current source out- put to become close to dropout, the charge pump will automatically transition to 2x mode. the AAT3155 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 sink inputs (d1 to d4) can drive four individual leds with a maximum cur- rent of 20ma each. the unused sink inputs must be connected to outcp, otherwise the part will oper- ate only in 2x charge pump mode. the s 2 cwire serial interface enables the AAT3155 and sets the current sink magnitudes. constant current output level settings the constant current sink levels for d1 to d4 are set via the serial interface according to a logarithmic scale for the first 12 codes and a separate low-cur- rent scale for the last four codes. for the first 12 codes, each code is approximately 1.5db lower than the previous code. in this manner, led brightness appears linear with each increasing code count. because the inputs d1 to d4 are true independent constant current sinks, the voltage observed on any single given input will be determined by the actual forward voltage (v f ) for the led being driven. since the input current sinks of the AAT3155 are programmable, no pwm (pulse width modulation) or 1x, 1.5x, 2x charge pump d/a d/a d/a d/a 6 x 16 bit rom s 2 cwire interface soft-start control 1mhz oscillator voltage reference in en/set d4 gnd d3 d2 d1 outcp c1+ c1- c2+ c2-
AAT3155 high efficiency 1x/1.5x/2x charge pump for white led applications 3155.2006.05.1.1 9 additional control circuitry is needed to control led brightness. this feature greatly reduces the burden on a microcontroller or system ic to manage led or display brightness, allowing the user to "set it and forget it." with its high-speed serial interface (1mhz data rate), the input sink current of the AAT3155 can be changed successively to brighten or dim leds, in smooth transitions (e.g., to fade-out) or in abrupt steps, giving the user complete programmability and real-time control of led brightness. s 2 cwire serial interface the current level magnitude is controlled by analogictech's simple serial control (s 2 cwire) serial interface. the interface records rising edges of the en/set pin and decodes them into 16 differ- ent states. the 16 current level settings available are indicated in table 1. table 1: current level settings. the s 2 cwire serial interface has flexible timing. data can be clocked-in at speeds greater than 1mhz, or much slower, such as 15khz. after data is submitted, en/set is held high to latch the data. once en/set has been held in the logic high state for time t lat , the programmed current becomes active and the internal data register is reset to zero. for subsequent current level programming, the number of rising edges corresponding to the desired code must be entered on the en/set pin. when en/set is held low for an amount of time greater than t off , the AAT3155 enters into shutdown mode and draws less than 1a from v in . the internal data register is reset to zero during shutdown. auto-disable feature the AAT3155 is equipped with an auto-disable fea- ture for each led channel. after the ic is enabled and started up, a test current of 100 a (typical) is forced through each sink channel. the channel will be disabled if the voltage of that particular sink pin does not drop to a certain threshold. this feature is very convenient for disabling an unused channel or during an led fail-short event. thermal protection the AAT3155 has a thermal protection circuit that will shut down the charge pump if the die tempera- ture rises above the thermal limit, as would be the case during a short circuit of the outcp pin. output output data (ma/ch) data (ma/ch) 1 20.0 9 5.0 2 17.0 10 4.2 3 14.0 11 3.4 4 12.0 12 2.8 5 10.0 13 1.0 6 8.6 14 0.5 7 7.0 15 0.1 8 6.0 16 0.05 s 2 cwire serial interface timing 1 en/set 2 n n <= 16 data reg 1n 0 t hi t lo t lat t off
AAT3155 high efficiency 1x/1.5x/2x charge pump for white led applications 10 3155.2006.05.1.1 applications information although the AAT3155 is designed for driving white leds, the device also can be used to drive most types of leds with forward voltage specifications ranging from 2.0v to 4.7v. led applications may include main and sub-lcd display backlighting, camera photo-flash applications, color (rgb) leds, 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 current sinks are matched with neg- ligible 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-sinks in the AAT3155 make it capable of driving leds with forward volt- ages 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. device switching noise performance the AAT3155 operates at a fixed frequency of approximately 1mhz to control noise and limit har- monics that can interfere with the rf operation of cellular telephone handsets or other communica- tion devices. back-injected noise appearing on the input pin of the charge pump is 20mv peak-to- peak, typically ten times less than inductor-based dc/dc boost converter white led backlight solu- tions. the AAT3155 soft-start feature prevents noise transient effects associated with inrush cur- rents during start-up of the charge pump circuit. 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 1 f for all four capacitors is a good starting point when choosing capacitors. if the led current sources are programmed only for light current lev- els, then the capacitor size may be decreased. capacitor characteristics ceramic composition capacitors are highly recom- mended over all other types of capacitors for use with the AAT3155. ceramic capacitors offer many advantages over their tantalum and aluminum electrolytic counterparts. a ceramic capacitor typi- cally has very low esr, is lowest cost, has a small- er pcb footprint, and is non-polarized. low esr ceramic capacitors help to 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 tan- talum 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 AAT3155 applications. 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.
AAT3155 high efficiency 1x/1.5x/2x charge pump for white led applications 3155.2006.05.1.1 11 advanced analogic technologies, inc. 830 e. arques avenue, sunnyvale, ca 94085 phone (408) 737-4600 fax (408) 737-4611 ordering information package information tsopjw-12 all dimensions in millimeters. package marking 1 part number (tape and reel) 2 tsopjw-12 qoxyy AAT3155itp-t1 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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