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general description the aat3175 is a low noise, constant frequency charge pump dc/dc converter that uses a tri-mode load switch (1x), fractional (1.5x), and doubling (2x) conversion to maximize efficiency for white led flash applications. the aat3175 is capable of driving up to three flash leds at 300ma total cur- rent from a 2.7v to 5.5v input. a low external parts count (two 1f flying capacitors and two small 1f capacitors at v in and v out ) make this part ideally 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 all leds with 16 level settings down to 0. the aat3175 is equipped with built-in protection for v out short-circuit condition and auto-disable for load short-circuit condition on any one of the chan- nels. built-in soft-start circuitry prevents excessive inrush current during start-up. a low-current shut- down feature disconnects the load from v in and reduces quiescent current to less than 1a. the aat3175 is available in a pb-free, space-saving, thermally-enhanced 12-pin 3x3mm tdfn package. features ?v in range: 2.7v to 5.5v ? up to 300ma total flash current ? fully programmable current with single wire ? 16 logarithmic current levels ? tri-mode 1x, 1.5x, and 2x charge pump for maximum efficiency and v f coverage ? drives 3-in-1 or 2-in-1 flash leds ? 0.5% current matching ? no inductors, low noise operation ? 1mhz constant switching frequency ? small application circuit ? built-in thermal protection ? automatic soft-start ?i q <1a in shutdown ? tdfn33-12 package applications ? programmable current sinks ? white led backlighting ? white photo flash for mobile phones aat3175 high efficiency 1x/1.5x/2x charge pump for white led flash applications typical application c2+ c2- vout c1+ c1- vin gnd en/set en/set 2.7v to 5.5v d1 d2 d3 aat3175 d1 d2 d3 d4 c in 1 f c1 1 f c out 1 f 3175.2006.01.1.2 1 chargepump ?
pin descriptions pin configuration tdfn33-12 (top view) d4 en/set c1+ 1 c1- vout c2+ d3 d2 d1 gnd vin c2- 2 3 4 5 6 12 11 10 9 8 7 pin # symbol function 1 d4 current sink input #4; 100ma max. 2 en/set s 2 cwire serial interface control pin. 3 c1+ flying capacitor 1 positive terminal. connect a 1f capacitor between c1+ and c1-. 4 c1- flying capacitor 1 negative terminal. 5 vout charge pump output to drive load circuit. requires 1f capacitor connected between this pin and ground. 6 c2+ flying capacitor 2 positive terminal. connect a 1f capacitor between c2+ and c2-. 7 c2- flying capacitor 2 negative terminal. 8 vin input power supply. requires 1f capacitor connected between this pin and ground. 9 gnd ground. 10 d1 current sink input #1; 100ma max. 11 d2 current sink input #2; 50ma max. 12 d3 current sink input #3; 50ma max. ep exposed paddle (bottom). connect to gnd directly beneath package. aat3175 high efficiency 1x/1.5x/2x charge pump for white led flash applications 2 3175.2006.01.1.2
absolute maximum ratings 1 thermal information 3 symbol description value units p d maximum power dissipation 4 2.0 w ja maximum thermal resistance 50 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 300 ma t j operating junction temperature range -40 to 150 c t lead maximum soldering temperature (at leads, 10 sec) 300 c aat3175 high efficiency 1x/1.5x/2x charge pump for white led flash applications 3175.2006.01.1.2 3 1. stresses above those listed in absolute maximum ratings may cause permanent damage to the device. functional operation at co nditions 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 20mw/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 = 3.5v. 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, 0.3 1.0 active, no load current i cc operating current 1.5x mode, 3.0 v in 5.5, 1.0 3.0 active, no load current ma 2x mode, 3.0 v in 5.5, 2.0 3.7 active, no load current i shdn shutdown current en/set = 0 1.0 a i dx i sink average current accuracy d1, d4 max setting 90 100 110 ma d2, d3 max setting 45 50 55 i (d-match) current matching 2 v f :d1:d4 = 3.6v, d2 and d3 0.5 5.0 % in parallel v th 1x to 1.5x or 1.5x to 2x transition 250 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 aat3175 high efficiency 1x/1.5x/2x charge pump for white led flash applications 4 3175.2006.01.1.2 1. the aat3175 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.
aat3175 high efficiency 1x/1.5x/2x charge pump for white led flash applications 3175.2006.01.1.2 5 typical characteristics c in = c out = c 1 = c 2 = 1f, t a = 25c, v in = 3.5v, unless otherwise noted. turn-off from 1.5x mode (v in = 4.0v; 300ma load) time (200 s/div) i in (200ma/div) en (2v/div) v f (1v/div) turn-on to 2x mode (v in = 3.8v; 300ma load) time (200 s/div) v out (2v/div) i in (400ma/div) en (2v/div) v sink (1v/div) turn-on to 1.5x mode (v in = 4.0v; 300ma load) time (200 s/div) v out (2v/div) i in (400ma/div) en (2v/div) v sink (1v/div) turn-on to 1x mode (v in = 4.2v; 300ma load) time (200 s/div) v out (2v/div) i in (400ma/div) en (2v/div) v sink (1v/div) 300ma led pulse (v in = 3.8v) time (100ms/div) v out (2v/div) i out (200ma/div) efficiency vs. supply voltage supply 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 60ma v f = 3.0v 150ma v f = 3.2v
typical characteristics c in = c out = c 1 = c 2 = 1f, t a = 25c, v in = 3.5v, unless otherwise noted. en/set off timeout vs. input voltage input voltage (v) en/set off timeout ( s) 0 50 100 150 200 250 300 350 400 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 -40 c 25 c 85 c 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 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5. 5 -40 c 25 c 85 c input ripple vs. input voltage (150ma load) input voltage (v) input ripple (mv) 0 5 10 15 20 25 30 2.5 2.8 3.0 3.3 3.5 3.8 4.0 4.3 4.5 load characteristics (v in = 3.0v; 2x mode; 150ma load) time (500ns/div) v sink (100mv/div) v out (100mv/div) v in (100mv/div) load characteristics (v in = 3.5v; 1.5x mode; 150ma load) time (500ns/div) v sink (100mv/div) v out (100mv/div) v in (100mv/div) line response (1.5x mode; 150ma load) time (1ms/div) v out (500mv/div) i led (10ma/div) v in (500mv/div) v sink (500mv/div) 3.7v 3.6v 4.2v aat3175 high efficiency 1x/1.5x/2x charge pump for white led flash applications 6 3175.2006.01.1.2
typical characteristics c in = c out = c 1 = c 2 = 1f, t a = 25c, v in = 3.5v, unless otherwise noted. enable threshold low vs. input voltage input voltage (v) enable threshold low (v) 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 -40 c 25 c 85 c enable threshold high vs. input voltage input voltage (v) enable threshold high (v) 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 -40 c 25 c 85 c aat3175 high efficiency 1x/1.5x/2x charge pump for white led flash applications 3175.2006.01.1.2 7 3175.2006.01.1.2 7
aat3175 high efficiency 1x/1.5x/2x charge pump for white led flash applications 8 3175.2006.01.1.2 functional block diagram 1x, 1.5x, 2x charge pump d/a d/a d/a 6 x 16 bit rom s 2 cwire interface soft start control 1mhz oscillator voltage reference vin en/set gnd d4 d3 d2 d1 vout c1+ c1- c2+ c2- d/a d/a d/a functional description the aat3175 is a tri-mode load switch (1x) and high efficiency (1.5x or 2x) charge pump device intended for white led flash applications. to max- imize 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 aat3175 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 aat3175 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 out ). the four constant current sink inputs (d1 to d4) can drive four individual leds with a maximum current of 50ma each for d2 and d3. d1 and d4 are driven by two parallel current sources, resulting in a maxi- mum of 100ma each. unused sink inputs are con- nected to v out ; otherwise, the part will operate only in 2x charge pump mode. the s 2 cwire serial inter- face enables the aat3175 and sets the current sink magnitudes. the d1~d4 current configuration is optimized to drive either 2-in-1 leds by combining d1/d2, d3/d4, or 3-in-1 leds by combining d2/d3. 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 where each code is 1db lower than the previ- ous 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 aat3175 are programmable, no pwm (pulse width modulation) or 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 aat3175 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 s 2 cwire serial interface. the inter- face records rising edges of the en/set pin and decodes them into 16 different states. the 16 cur- rent 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 aat3175 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 aat3175 is equipped with an auto-disable fea- ture for each led channel. after the ic is enabled and started up, a test current of 150a (typical) is forced through each sink channel. the channel will be disabled if the voltage of that particular dx pin does not fall below a certain threshold. this feature is very convenient for disabling an unused channel or during an led fail-short event. thermal protection the aat3175 has a built-in thermal protection circuit that will shut down the charge pump if the die tem- perature rises above the thermal limit, as is general- ly the case during a short-circuit of the v out pin. d2, d3 d1, d4 data i out (ma) i out (ma) 1 50 100 24488 34080 43672 53264 62856 72550 82244 92040 10 17 34 11 16 32 12 14 28 13 13 26 14 11 22 15 10 20 16 0 0 aat3175 high efficiency 1x/1.5x/2x charge pump for white led flash applications 3175.2006.01.1.2 9 s 2 cwire serial interface timing 1 en/set 2 n-1 n 16 data reg 0n-1 0 t hi t lo t lat t off
aat3175 high efficiency 1x/1.5x/2x charge pump for white led flash applications 10 3175.2006.01.1.2 applications information led selection although the aat3175 is specifically intended for driving white leds, the device can also be used to drive most types of leds with forward voltage specifications ranging from 2.0v to 4.1v. led applications may include display backlighting, cam- era photo-flash applications, color (rgb) leds, infrared (ir) diodes for remotes, and other loads benefiting from a controlled output current generat- ed from a varying input voltage. since the d1 to d4 input current sinks are matched with negligible volt- age 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 aat3175 make it capable of driving leds with forward volt- ages as high as 4.1v at full current from an input supply as low as 3.5v. outputs can be paralleled to drive high-current leds without complication. device switching noise performance the aat3175 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 aat3175 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; generally, 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 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 aat3175. 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 aat3175 applications. capacitor area is another contributor to esr. capacitors that are physically large will have a lower esr when compared to an smaller capacitor made of equivalent material. these larger devices can improve circuit transient response when com- pared to an equal value capacitor in a smaller package size.
aat3175 high efficiency 1x/1.5x/2x charge pump for white led flash applications 3175.2006.01.1.2 11 ordering information package information tdfn33-12 all dimensions in millimeters. top view bottom view detail "b" detail "a" side view 3.00 0.05 index area (d/2 x e/2) detail "a" detail "b" 1.70 0.05 3.00 0.05 0.05 0.05 0.229 0.051 7.5 7.5 2.40 0.05 0.16 pin 1 indicator (optional) 0.375 0.125 0.3 0.10 0.45 0.05 0.23 0.05 0.075 0.075 0.1 ref 0.8 + 0.05 -0.20 option a: c0.30 (4x) max chamfered corner option b: r0.30 (4x) max round corner 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 tdfn33-12 qaxyy AAT3175IWP-T1 1. xyy = assembly and date code. 2. sample stock is generally held on part numbers listed in bold .
aat3175 high efficiency 1x/1.5x/2x charge pump for white led flash applications 12 3175.2006.01.1.2 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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