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aat3142 high efficiency 1x/1.5x/2x charge pump for white led applications 3142.2005.12.1.1 1 chargepump ? general description the aat3142 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 device produces cur- rent levels up to 30ma on each of its three current source outputs to drive various arrangements of leds from a 2.7v to 5.5v input. outputs may be operated individually or in parallel for driving high- er-current leds. a low external parts count (two 1f flying capacitors and two small 1f capacitors at v in and cp) make the aat3142 ideally suited for small battery-powered applications. analogictech's simple serial control? (s 2 cwire?) digital input is used to enable, disable, and set the led drive current with a 32-level logarithmic scale led brightness control. the aat3142 has a thermal management system to protect the device in the event of a short-circuit condition at an output pin. built-in soft-start circuitry prevents excessive inrush current during start-up. a high charge pump switch- ing frequency enables the use of very small external capacitors. in shutdown mode, the device discon- nects the load from v in and reduces quiescent cur- rent to less than 1a. the aat3142 is available in the very small, pb-free 12-pin tsopjw package. features ?v in range: 2.7v to 5.5v ? tri-mode 1x, 1.5x, and 2x charge pump for maximum efficiency and v f coverage ? drives low-v f and high-v f type leds ? up to three 30ma outputs ? 32-position logarithmic scale with digital control ? low noise constant frequency operation ? 1mhz switching frequency ? small application circuit ? regulated output current ? automatic soft start ? no inductors ?i q < 1a in shutdown ? 12-pin tsopjw package applications ? color (rgb) lighting ? programmable current sources ? white led backlighting ? white photo flash for digital still cameras typical application c in 1 f v battery c cp 1 f en/set c1 1 f c2 1 f d3 d2 d1 vin cp c1+ c1- c2+ c2- d1 d2 d3 en/set gnd aat3142
pin descriptions pin configuration tsopjw-12 (top view) 1 2 3 4 5 6 12 11 10 9 8 7 c2+ cp c1- c1+ d3 d2 c2- gnd in en/se t d1 gnd 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 gnd ground pin; must be connected to pin 11. 8 d1 current source output #1. 9 en/set s 2 cwire serial interface control pin. 10 in input power supply. requires 1f capacitor connected between this pin and ground. 11 gnd ground pin; must be connected to pin 7. 12 c2- flying capacitor 2 negative terminal. aat3142 high efficiency 1x/1.5x/2x charge pump for white led applications 2 3142.2005.12.1.1
absolute maximum ratings 1 thermal information 3 symbol description value units p d maximum power dissipation 4 625 mw ja thermal resistance 160 c/w symbol description value units v in input voltage -0.3 to 6 v v en/set en/set to gnd voltage -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 aat3142 high efficiency 1x/1.5x/2x charge pump for white led applications 3142.2005.12.1.1 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 cp = c 1 = c 2 = 1.0f; t a = -40c to +85c, unless otherwise noted. typical values are at 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:d3 = 2.0v, cp = 1x 550 a no load current, cp = 1.5x 3 5 ma i shdn shutdown current v in = 3.5v, en/set = 0 1 a i dx output current accuracy 2 v in = 3.5v, t a = 25c -10 10 % i (d-match) current matching 3 vd1:d3 = 3.6v, v in = 3.5v -3 0.5 3 % cp charge pump section efficiency v in = 3.5v, i out(total) = 90ma, 93 % measured from in to cp charge pump section t ss soft-start time 50 s f clk clock frequency 1 mhz 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 v en/set = 5.5v, v in = 5.5v -1 1 a aat3142 high efficiency 1x/1.5x/2x charge pump for white led applications 4 3142.2005.12.1.1 1. the aat3142 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. codes 2 through 7 are guaranteed to be within 15% of stated current level. 3. current matching is defined as i (d-match) = (i d - i ave )/i ave .
aat3142 high efficiency 1x/1.5x/2x charge pump for white led applications 3142.2005.12.1.1 5 typical characteristics v in = 3.5v, c in = c cp = c 1 = c 2 = 1f, t a = 25c, unless otherwise noted. input voltage (v) efficiency (%) efficiency vs. input voltage (d1-d2 = 3.5v, d3 = 3.2v) 30 40 50 60 70 80 90 100 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 code 32 code 28 code 26 efficiency vs. input voltage (d1 = 3.5v, d2 = 3.3v, d3 = 3.2v) input voltage (v) efficiency (%) 30 40 50 60 70 80 90 100 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 code 32 code 28 code 26 input voltage (v) efficiency (%) efficiency vs. input voltage (code 26) 30 40 50 60 70 80 90 100 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 3.5v f 3.0v f
typical characteristics v in = 3.5v, c in = c cp = c 1 = c 2 = 1f, t a = 25c, unless otherwise noted. turn-off from full-scale 2x mode time (200s/div) en/set (2v/div) v diode (2v/div) i in (200ma/div) turn-on to 1.5x mode (3x30ma load) time (100s/div) en/set (2v/div) v cp (4v/div) v diode (2v/div) i in (100ma/div) turn-on to 1.5x mode (3x19ma load) time (100s/div) en/set (2v/div) v cp (4v/div) v diode (2v/div) i in (100ma/div) turn-on to 1x mode (3x30ma load) time (100s/div) en/set (2v/div) v cp (4v/div) v diode (2v/div) i in (100ma/div) turn-on to 1x mode (3x19ma load) time (100s/div) en/set (2v/div) v cp (4v/div) v diode (2v/div) i in (100ma/div) aat3142 high efficiency 1x/1.5x/2x charge pump for white led applications 6 3142.2005.12.1.1
typical characteristics v in = 3.5v, c in = c cp = c 1 = c 2 = 1f, t a = 25c, unless otherwise noted. load switch to charge pump (1.5x mode, 3x30ma load) time (2ms/div) v in (1v/div) v cp (4v/div) v diode (500mv/div) i in (50ma/div) load switch to charge pump (1.5x mode, 3x19ma load) time (2ms/div) v in (1v/div) v cp (4v/div) v diode (500mv/div) i in (50ma/div) charge pump to load switch (2x mode, 3x30ma load) time (5ms/div) v in (500mv/div) v cp (1v/div) v diode (500mv/div) i in (50ma/div) charge pump to load switch (2x mode, 3x19ma load) time (5ms/div) v in (500mv/div) v cp (1v/div) v diode (500mv/div) i in (50ma/div) charge pump to load switch (1.5x mode, 3x30ma load) time (5ms/div) v in (500mv/div) v cp (1v/div) v diode (500mv/div) i in (50ma/div) charge pump to load switch (1.5x mode, 3x19ma load) time (5ms/div) v in (500mv/div) v cp (1v/div) v diode (500mv/div) i in (50ma/div) aat3142 high efficiency 1x/1.5x/2x charge pump for white led applications 3142.2005.12.1.1 7
typical characteristics v in = 3.5v, c in = c cp = c 1 = c 2 = 1f, t a = 25c, unless otherwise noted. load characteristics (1.5x mode, 3x30ma load) time (1s/div) v in (20mv/div) i in (10ma/div) v cp (20mv/div) load characteristics (1.5x mode, 3x15ma load) time (1s/div) v in (20mv/div) i in (10ma/div) v cp (20mv/div) line response (1x mode, 3x30ma load) time (1ms/div) v in (0.5v/div) v led (20mv/div) v cp (0.5v/div) i d (10ma/div) line response (1.5x mode, 3x19ma 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, 3x30ma 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, 3x19ma load) time (1ms/div) v in (0.5v/div) v led (20mv/div) v cp (0.5v/div) i d (10ma/div) aat3142 high efficiency 1x/1.5x/2x charge pump for white led applications 8 3142.2005.12.1.1
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 input voltage (v) i diode (ma) diode current vs. input voltage (30ma, 15ma settings) 10 15 20 25 30 35 40 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 v diode = 3.4v v diode = 3.4v input voltage (v) i in (ma) input current vs. input voltage (3x30ma) 0 20 40 60 80 100 120 140 160 180 200 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5. 5 v diode = 3.0v v diode = 3.4v input voltage (v) i in (ma) input current vs. input voltage (3x10ma) 0 10 20 30 40 50 60 70 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 v diode = 3.4v v diode = 3.0v aat3142 high efficiency 1x/1.5x/2x charge pump for white led applications 3142.2005.12.1.1 9
aat3142 high efficiency 1x/1.5x/2x charge pump for white led applications 10 3142.2005.12.1.1 functional block diagram 1x 1.5x 2x charge pump soft-start control 1mhz oscillator voltage reference 32 x 8 bit rom c1+ c1- c2+ c2- cp d1 d2 d3 gnd en/set vin s 2 cwire interface d/a d/a d/a functional description the aat3142 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 aat3142 charge pump is enabled when any of the three 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. each of the three current source outputs is independently switched between the battery input (1x) or the charge pump output (1.5x or 2x), depending on the voltage at the current source out- put. since the led-to-led forward voltage (v f ) can vary as much as 1v, this function significantly enhances overall device efficiency when the bat- tery input voltage level is greater than the voltage required at any current source output. the aat3142 requires only four external compo- nents: 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 cp ). the three constant current outputs (d1 to d3) drive three individual leds with a maximum current of 30ma each. the en/set s 2 cwire serial interface enables the aat3142 and sets the current source magnitudes.
aat3142 high efficiency 1x/1.5x/2x charge pump for white led applications 3142.2005.12.1.1 11 applications information constant current output level settings the constant current source amplitudes for d1 to d3 are set via the serial interface according to a loga- rithmic scale where each code is 1db greater than the previous code. in this manner, led brightness appears linear with each increasing code count. because the outputs d1 to d3 are true independent constant current sources, the voltage observed on any single given output will be determined by the actual forward voltage (v f ) for the led being driven. since the output current of the aat3142 is pro- grammable, no pwm (pulse width modulation) or additional control circuitry are 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 output current of the aat3142 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 programma- bility and real-time control of led brightness. the individual current level settings are each approximately 1db apart for settings above code 8 (see figure 1). the current level settings below code 8 are more than 1db apart and serve the needs of transmissive displays and other low-cur- rent applications. figure 1: normalized current level settings. figure 1: constant current source output nominal programming levels. i out (typ) i out (typ) i out (typ) i out (typ) code (ma) code (ma) code (ma) code (ma) 1 0.0 9 2.0 17 5.1 25 13 2 0.1 10 2.2 18 5.6 26 15 3 0.2 11 2.5 19 6 27 17 4 0.4 12 2.8 20 7 28 19 5 0.5 13 3.2 21 8 29 21 6 0.7 14 3.5 22 9 30 24 7 1.1 15 4.0 23 10 31 27 8 1.8 16 4.5 24 12 32 30 0.00 0.01 0.10 1.00 1234567891011121314151617181920212223242526272829303132 code current (ma)
aat3142 high efficiency 1x/1.5x/2x charge pump for white led applications 12 3142.2005.12.1.1 s 2 cwire serial interface the current source output magnitude is controlled by the en/set pin, using analogictech's s 2 cwire interface. the interface records rising edges of the en/set pin and decodes them into 32 individual current level settings with code 1 reserved for no current. once en/set has been held in the logic high state for time t lat , the programmed current is seen at the current source outputs, and the internal data register is reset to 0. for subsequent current level programming, the number of rising edges cor- responding 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 aat3142 enters into shut- down mode and draws less than 1a from v in . the internal data register is reset to 0 during shutdown. s 2 cwire serial interface timing 1 en/set 2 n-1 n <= 32 data reg 0n0 t hi t lo t lat t off led selection the aat3142 is specifically intended for driving white leds. however, the device design will allow the aat3142 to drive most types of leds with for- ward voltage specifications ranging from 2.0v to 4.3v. led applications may include main and sub- lcd display backlighting, camera photo-flash appli- cations, color (rgb) leds, infrared (ir) diodes for remotes, and other loads benefiting from a controlled output-current generated from a varying input-volt- age. since the d1 to d3 output current 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 neces- sary to drive high-v f type leds. the low-dropout current sources in the aat3142 make it capable of driving leds with forward voltages as high as 4.3v at full current from an input supply as low as 3.0v. outputs can be paralleled to drive high-current leds without complication. termination of unused current source outputs if any outputs (d1 to d3) are not used, they should be terminated by connecting the respective unused output directly to ground. this is required to assure correct charge pump mode operation. if a given unused output is not terminated to ground, it will appear to the respective output?s feedback control as an infinite impedance load and the unused con- stant current source will be set for a maximum volt- age. although no current flows from the unused current source, the voltage sensed at that node could force the charge pump control to activate the charge pump when it is not necessary. to prevent this effect, simply connect the unused constant current source outputs to ground. device switching noise performance the aat3142 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 communication
aat3142 high efficiency 1x/1.5x/2x charge pump for white led applications 3142.2005.12.1.1 13 devices. back-injected noise appearing on the input pin of the charge pump is 20mv peak-to-peak, typi- cally ten times less than inductor-based dc/dc boost converter white led backlight solutions. the aat3142 soft-start feature prevents noise transient effects associated with inrush currents during start- up of the charge pump circuit. power efficiency and device evaluation the charge pump efficiency discussion in the follow- ing sections only accounts for efficiency of the charge pump section itself. due to the unique circuit architecture and design of the aat3142, it is very dif- ficult to measure efficiency in terms of a percent value comparing input power over output power. since the aat3142 outputs are pure constant cur- rent sources and typically drive individual loads, it is difficult to measure the output voltage for a given output (d1 to d3) to derive an overall output power measurement. for any given application, white led forward voltage levels can differ, yet the out- put drive current will be maintained as a constant. this makes quantifying output power a difficult task when taken in the context of comparing to other white led driver circuit topologies. a better way to quantify total device efficiency is to observe the total input power to the device for a given led current drive level. the best white led driver for a given applica- tion should be based on trade-offs of size, external component count, reliability, operating range, and total energy usage... not just % efficiency. the aat3142 efficiency may be quantified under very specific conditions and is dependent upon the input voltage versus the output voltage seen across the loads applied to outputs d1 through d3 for a given constant current setting. depending upon the case of v in being greater than the specific voltage seen across the loads on d1 through d3, the device will operate in load switch mode. if the voltage seen on the constant current source output is less than v in , then the device will operate in 1.5x or 2x charge pump mode. each of these modes will yield differ- ent efficiency values. refer to the following two sec- tions for explanations of each operational mode. load switch mode efficiency the aat3142 load switch mode is operational at all times and functions alone to enhance device power conversion efficiency when v in is greater than volt- age across the load connected to the constant cur- rent source outputs. when in load switch mode, the voltage conversion efficiency is defined as out- put power divided by input power: the expression to define the ideal efficiency ( ) can be rewritten as: -or- charge pump section efficiency the aat3142 contains a fractional charge pump which will boost the input supply voltage when v in is less than the voltage required on the constant current source outputs. the efficiency ( ) can be simply defined as a linear voltage regulator with an effective output voltage that is equal to one and one half or two times the input voltage. efficiency ( ) for an ideal 1.5x charge pump can typically be expressed as the output power divided by the input power: = p ou t p in (%) = 100 v out v in ?? ?? = p out = v out i out = v out p in v in i out v in = p ou t p in
aat3142 high efficiency 1x/1.5x/2x charge pump for white led applications 14 3142.2005.12.1.1 in addition, with an ideal 1.5x charge pump, the output current may be expressed as 2/3 of the input current. the expression to define the ideal efficiency ( ) can be rewritten as: -or- for a charge pump with an output of 5v and a nom- inal input of 3.5v, the theoretical efficiency is 95%. due to internal switching losses and ic quiescent current consumption, the actual efficiency can be measured at 93%. these figures are in close agree- ment for output load conditions from 1ma to 100ma. efficiency will decrease as load current drops below 0.05ma or when the level of v in approaches v out . refer to the typical characteristics section of this datasheet for measured plots of efficiency versus input voltage and output load current for the given charge pump output voltage options. 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 levels, 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 aat3142. ceramic capacitors offer many advan- tages over their tantalum and aluminum electrolytic counterparts. a ceramic capacitor 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 connection 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 con- nections, size or area, material composition, and ambient temperature. capacitor esr is typically measured in milliohms for ceramic capacitors and can range to more than several ohms for tantalum 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 have tight tolerance and are stable over temperature. large capacitor values are typically composed of x7r, x5r, z5u, or y5v dielectric mate- rials. large ceramic capacitors, greater than 2.2f, are often available in low-cost y5v and z5u dielectrics, but capacitors greater than 1f are usu- ally not required for aat3142 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. thermal protection the aat3142 has a thermal protection circuit 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. charge pump compatibility the three-output aat3142 is pin-compatible with the aat3140, aat3123, and aat3113 in tsopjw- 12 packages. the aat3142 offers an improved overall efficiency, wider operating range, and the ability to drive high-v f type leds at full current. the aat3142 is well suited for battery-powered applications using single-cell lithium-ion/polymer batteries and 3-series connected dry cells (3.6v). (%) = 100 v out 1.5v in ?? ?? = p out = v out i out = v out p in v in 1.5i out 1.5v in
aat3142 high efficiency 1x/1.5x/2x charge pump for white led applications 3142.2005.12.1.1 15 ordering information package information tsopjw-12 all dimensions in millimeters. 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. package marking 1 part number (tape and reel) 2 tsopjw-12 pjxyy AAT3142ITP-T1 1. xyy = assembly and date code. 2. sample stock is generally held on part numbers listed in bold .
aat3142 high efficiency 1x/1.5x/2x charge pump for white led applications 16 3142.2005.12.1.1 advanced analogic technologies, inc. 830 e. arques avenue, sunnyvale, ca 94085 phone (408) 737-4600 fax (408) 737-4611 ? 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 subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warran ty, 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.

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