aat3152 high efficiency 1x/1.5x/2x charge pump for white led applications preliminary information 3152.2004.12.0.9 1 chargepump ? general description the aat3152 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 applications. the aat3152 is capable of driving four-channel leds from a 2.7v to 5.5v input. the current sinks may be operated individually or in par- allel for driving higher-current leds. low external parts count (two 1f flying capacitors and two small 1f capacitors at v in and v out ) makes this part ide- ally 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 eight settings (20ma down to 50a) including main/sub-display group control. the aat3152 consumes extremely low cur- rent internally (80a typical) at light load for opti- mized efficiency. each output of the aat3152 is equipped with built- in protection for v out short circuit and auto-disable for load short-circuit condition. built-in soft-start cir- cuitry prevents excessive inrush current during start-up. a low current shutdown feature discon- nects the load from v in and reduces quiescent cur- rent to less than 1a. the aat3152 is available in a space-saving, ther- mal-enhanced 12-pin 3x3mm dfn package. features ?v in range: 2.7v to 5.5v ? fully programmable current with single wire ? eight-step current: 20ma to 50a ? individual main-sub group control ? low i q (80a) at light load ? tri-mode 1x, 1.5x, and 2x charge pump for maximum efficiency and v f coverage ? drives 1-4 channels of leds ? no inductors, low noise operation ? 1mhz constant switching frequency ? small application circuit ? built-in thermal protection ? built-in auto-disable for short-circuit ? automatic soft-start ?i q <1a in shutdown ? thermal-enhanced 3x3mm12-pin dfn package applications ? color (rgb) lighting ? programmable current sinks ? white led backlighting ? white photo flash for dscs typical application c1 1 f c2 1 f d1 d2 d3 d4 c ou t 1 f c in 1 f 2.7v to 5.5v en/set v in en/set c1+ c1- c2+ c2- v out d1 d2 d3 d4 gnd aat3152
pin descriptions pin configuration dfn33-12 (topview) 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. 2 en/set s 2 cwire serial interface control pin. 3 c1+ flying capacitor 1 + terminal. connect a 1f capacitor between c1+ and c1-. 4 c1- flying capacitor 1 - terminal. 5 outcp charge pump output to drive load circuit. requires 1f capacitor connected between this pin and ground. 6 c2+ flying capacitor 2 + terminal. connect a 1f capacitor between c2+ and c2-. 7 c2- flying capacitor 2 - terminal. 8 in input power supply. requires 1f capacitor connected between this pin and ground. 9 gnd ground. 10 d1 current sink input #1. 11 d2 current sink input #2. 12 d3 current sink input #3. ep exposed paddle (bottom); connect to gnd directly beneath package. aat3152 high efficiency 1x/1.5x/2x charge pump for white led applications 2 3152.2004.12.0.9
absolute maximum ratings 1 notes: 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. thermal information notes: 1. mounted on an fr4 board. 2. derate 20mw/c above 25c. symbol description value units p d maximum power dissipation 1, 2 2.0 w ja maximum thermal resistance 1 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 150 ma t j operating junction temperature range -40 to 150 c t lead maximum soldering temperature (at leads, 10 sec) 300 c aat3152 high efficiency 1x/1.5x/2x charge pump for white led applications 3152.2004.12.0.9 3
electrical characteristics1 c in = c out = c1 = c2 = 1.0f; t a = -40c - 85c, unless otherwise noted. typical values are at t a = 25c, v in = 3.6v. notes: 1. the aat3152 is guaranteed to meet performance specifications over the -40c to 85c operating temperature range and is assur ed 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. 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, 1.5 3 no load current 50a setting, 1x mode 80 a i shdn shutdown current en/set = 0 1 a i dx i sink average current accuracy i set = 20ma, t a = 25c -10 10 % i (d-match) current matching (note 2) v f :d1:d4 = 3.6v 12 % v th 1x to 1.5x or 1.5x to 2x transition 150 mv threshold at any current 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 0.4 v v en(h) enable threshold high 1.4 v t en/set lo en/set low time v en/set <0.6v 0.3 75 s t en/set hi minimum en/set high time v en/set >1.4v 50 ns t off en/set off timeout v en/set <0.6v 500 s t lat en/set latch timeout v en/set >1.4v 500 s i en/set en/set input leakage -1 1 a aat3152 high efficiency 1x/1.5x/2x charge pump for white led applications 4 3152.2004.12.0.9
typical characteristics turn off from 1.5x mode (v in = 3.5v; 20ma load) 200 s/div en (2v/div) i in (100ma/div) v f (1v/div) turn on to 2x mode (v in = 2.8v; 20ma load) 200 s/div en (2v/div) cp (2v/div) i in (200ma/div) v sink (500mv/div) turn on to 1.5x mode (v in = 3.5v; 20ma load) 200 s/div en (2v/div) cp (2v/div) i in (200ma/div) v sink (500mv/div) turn on to 1x mode (v in = 4.2v; 20ma load) 200 s/div en (2v/div) cp (2v/div) i in (200ma/div) v sink (500mv/div) efficiency vs. supply voltage supply voltage (v) efficiency (%) 50 60 70 80 90 100 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 10ma 20ma aat3152 high efficiency 1x/1.5x/2x charge pump for white led applications 3152.2004.12.0.9 5
aat3152 high efficiency 1x/1.5x/2x charge pump for white led applications 6 3152.2004.12.0.9 functional block diagram 1x, 1.5x and 2x charge pump d/a d/a d/a d/a 6 x 16 bit rom 6 x 16 bit rom s 2 c interface soft-start control 1mhz oscillator voltage reference vin en/set gnd d4 d3 d2 d1 vout c1+ c1- c2+ c2- functional description the aat3152 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 aat3152 charge pump is enabled when any of the four cur- rent sink inputs near dropout. the charge pump ini- tially starts in 1.5x mode. if the charge pump out- put drops enough for any current source output to become close to dropout, the charge pump will automatically transition to 2x mode. the aat3152 requires only four external components: two 1f ceramic capacitors for the charge pump flying capacitors (c1 and c2), 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 v out , otherwise the part will operate only in 2x charge pump mode. the s 2 cwire serial interface enables the aat3152 and sets the cur- rent sink magnitudes. s 2 cwire addressing allows independent control of two groups of current sink input: d1-d3 and d4.
constant current output level settings the constant current sink levels for d1 to d4 are set via the serial interface. 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 (up to 1mhz data rate), the input sink current of the aat3152 can be changed suc- cessively to brighten or dim leds, giving the users real-time control of led brightness. because the inputs d1 to d4 are true independent constant cur- rent sinks, the voltage observed on any single given input will be determined by the actual forward voltage (v f ) for the led being driven. s 2 cwire serial interface the current sink input magnitude on the aat3152 is controlled by analogictech's s 2 cwire serial digi- tal input. it relies on the number of rising edges of the en/set pin to address and load the registers. s 2 cwire latches data or address after the en/set pin has been held high for time t lat . the interface records rising edges of the en/set pin and decodes them into 16 different states, as indicated in the current setting table. there are four bright- ness levels for main or sub-display group with the possibility of individually turning on or off each group. to further optimize power efficiency, the aat3152 also offers four low-current levels for dim led operation (data 13-16). during this low current mode, the internal supply current reduces to only 80a typical. the counter can be clocked at speeds up to 1mhz, such that intermediate states are not visible. the first rising edge of en/set enables the ic and ini- tially sets the output led current to 20ma. once the final clock cycle is input for the desired bright- ness level, the en/set pin is held high to maintain the device output current at the programmed level. the device is disabled 500s (t off ) after the en/set pin transitions to a logic low state. aat3152 current setting the en/set timing is designed to accommodate a wide range of data rates. after the first rising edge of en/set, the charge pump is enabled and reach- es full capacity after the soft-start time (t ss ). during the soft-start time, multiple clock pulses may be entered on the en/set pin to set the final output current level with a single burst of clocks. alternatively, the en/set clock pulses may be entered one at a time to gradually increase the led brightness over any desired time period. the current outputs remain constant as long as en/set remains in a logic high state. the current outputs are switched off after en/set has remained in a low state for at least the t off timeout period; then, the aat3152 enters shutdown mode and draws less than 1a from v in . data are reset to 0 during shutdown. data main group sub group (d1-d3) (d4) i out (ma) i out (ma) 120 20 214 14 310 10 47 7 520 0 614 0 710 0 87 0 90 20 10 0 14 11 0 10 12 0 7 13 0.05 0.05 14 0.5 0.5 15 1 1 16 2 2 aat3152 high efficiency 1x/1.5x/2x charge pump for white led applications 3152.2004.12.0.9 7
aat3152 high efficiency 1x/1.5x/2x charge pump for white led applications 8 3152.2004.12.0.9 auto-disable feature the aat3152 is equipped with an "auto-disable" feature 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 par- ticular current sink pin does not drop to a certain threshold. this feature is very convenient for dis- abling an unused channel (by tying the dx pin to v out ) or during an led fail short event. thermal protection the aat3152 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 v out pin. applications information led selection although the aat3152 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 4.7v. led applications may include main and sub-lcd dis- play 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 negligible voltage dependence, the led brightness will be matched regardless of the spe- cific led forward voltage (v f ) levels. in some instances (e.g., in high-luminous-output applica- tions such as photo-flash), it may be necessary to drive high-v f type leds. the low-dropout current sinks in the aat3152 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. device switching noise performance the aat3152 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 aat3152 soft-start feature prevents noise transient effects associated with in-rush cur- rents during start up of the charge pump circuit. capacitor selection careful selection of the four external capacitors c in , c1, c2, and c out is important because they will affect turn-on time, output ripple, and transient 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
aat3152 high efficiency 1x/1.5x/2x charge pump for white led applications 3152.2004.12.0.9 9 performance. optimum performance will be obtained when low equivalent series resistance (esr) (<100m ? ) ceramic capacitors are used. in general, low esr may be defined as less than 100m ? . a capacitor value of 1f for all four capac- itors is a good starting point when choosing capac- itors. if the led current sources are only pro- grammed 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 aat3152. 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 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, which is caused by the leads, internal connections, size or area, material composition, and ambient temperature. capacitor esr is typical- ly 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 cog materials. npo and cog materials typically have tight tolerance and are sta- ble over temperature. larger capacitor values are typically composed of x7r, x5r, z5u, or y5v dielectric materials. large ceramic capacitors, typ- ically greater than 2.2f, are often available in low- cost y5v and z5u dielectrics, but capacitors greater than 1f are typically not required for aat3152 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 aat3152 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 v out pin.
aat3152 high efficiency 1x/1.5x/2x charge pump for white led applications 10 3152.2004.12.0.9 advanced analogic technologies, inc. 830 e. arques avenue, sunnyvale, ca 94085 phone (408) 737-4600 fax (408) 737-4611 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 specifications or to discontinue any product or service wi thout notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being 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 warranty, patent infringement, and limitation of l iability. analogictech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accorda nce with analogictech?s standard warranty. testing and other quality control techniques are utilized to the extent analogictech deems necessary to support this warranty. specific tes ting of all parameters of each device is not necessarily performed. ordering information note 1: xyy = assembly and date code. package information 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" 3.00 0.05 0.05 0.05 0.229 0.051 7.5 7.5 0.16 pin 1 indicator (optional) 0.375 0.125 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 package marking 1 part number (tape and reel) dfn33-12 nqxyy AAT3152IWP-T1
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