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general description the aat3164 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 is capable of driving up to six channels of leds at up to 30ma 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 out) makes this part ideally suited for small, battery-powered applications. analogictech's patented single-wire simple serial control? (s 2 cwire?) serial digital input is used to enable, disable, and set current for each led with 16 levels from a maximum of 40ma down to 50a. the maximum current level is programmed via an external resistor. to save power, the low-current mode supply current can be programmed as low as 70a. each output of the aat3164 is equipped with built- in protection for v out short-circuit and auto-disable for led short-circuit conditions. built-in soft-start circuitry 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 aat3164 is available in a pb-free, space-saving, ultra-thin (3x4x0.75mm), thermally-enhanced 16-pin tdfn package. features ?v in range: 2.7v to 5.5v ? tri-mode (1x/1.5x/2x) charge pump operation ? maximizes efficiency and led v f coverage ? 1mhz constant switching frequency ? no inductors, low noise operation ? drives six channels of leds up to 30ma/ channel ? user-programmable r set sets maximum led current ? excellent led channel-to-channel current match ? digitally programmable led current with single-wire s 2 cwire interface ? 16 current levels from i led_max to 50a ? low i q (70a) for low current mode operation ? true load disconnect in shutdown; i q < 1a ? built-in thermal protection ? built-in auto-disable for open led circuit ? automatic soft-start minimizes inrush startup current ? small 3x4mm tdfn34-16 package applications ? color (rgb) lighting ? programmable current sinks ? white led backlighting ? white photo flash for digital still cameras aat3164 high efficiency 1x/1.5x/2x charge pump for six-channel white led applications typical application 3164.2006.07.1.0 1 chargepump ? c out 1 f c in 1 f en/set in en/set c1+ c1- c2+ c2- out d1 d1 d2 d3 d4 d5 d6 d2 d3 d4 d5 d6 gnd aat3164 rset 1f 1f 26.1k 1% li-ion battery v nom = 3.6v osram lw m67 c
pin descriptions pin configuration tdfn34-16 (top view) pin # symbol function 1 d5 current sink input #5. 2 d6 current sink input #6. 3 rset connect resistor here to set maximum output current level. 1% resistor is recommended. 4 en/set enable input or s 2 cwire serial interface control. 5 c1+ flying capacitor 1 positive terminal. connect a 1f ceramic capacitor between c1+ and c1-. 6 c1- flying capacitor 1 negative terminal. 7 out charge pump output to drive load circuit. requires 1f ceramic capacitor connected between this pin and ground. 8 c2+ flying capacitor 2 positive terminal. connect a 1f ceramic capacitor between c2+ and c2-. 9 c2- flying capacitor 2 negative terminal. 10, 12 gnd ground. 11 in input power supply. requires 1f ceramic capacitor connected between this pin and ground. 13 d1 current sink input #1. 14 d2 current sink input #2. 15 d3 current sink input #3. 16 d4 current sink input #4. ep exposed paddle; connect to gnd directly beneath the package. aat3164 high efficiency 1x/1.5x/2x charge pump for six-channel white led applications 2 3164.2006.07.1.0 rset en/set c1+ d5 d6 3 c1- out c2+ d2 d1 gnd d4 d3 in gnd c2- 4 5 1 2 6 7 8 14 13 12 16 15 11 10 9
absolute maximum ratings 1 thermal information 3 symbol description value units p d maximum power dissipation 4 2w 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 aat3164 high efficiency 1x/1.5x/2x charge pump for six-channel white led applications 3164.2006.07.1.0 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 = 1f; 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, 3.0v v in 5.5v, 0.3 1 active, no load current 1.5x mode, 3.0v v in 5.5v, 13 i cc operating current active, no load current ma 2x mode, 3.0v v in 5.5v, 13 active, no load current 50a led current setting, 1x mode 70 a i shdn shutdown current en/set = 0 1 a t a = -20c to +85c, r set = 26.1k , -7 2 7 data = 1 (100%) i dx i sink average current t a = -40c to +85c, r set = 26.1k , accuracy data = 1 (100%) -8 2 8 % t a = -40c to +85c, r set = 26.1k , -20 20 data = 12 (14%) t a = 25c, data = 14 (1ma) -10 10 i (d-match) current matching 2 0.5 1 % v th 1x to 1.5x or 1.5x to 2x 150 mv transition threshold at any i sink pin i set current set ratio i sink /i rset 870 a/a v rset rset pin voltage 0.6 v charge pump section t ss soft-start time output ramp up 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 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 = 5v -1 1 a aat3164 high efficiency 1x/1.5x/2x charge pump for six-channel white led applications 4 3164.2006.07.1.0 1. the aat3164 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.
typical characteristics c in = c out = c 1 = c 2 = 1.0f; t a = 25c, r set = 26.1k , v in = 3.6v, unless otherwise noted. aat3164 high efficiency 1x/1.5x/2x charge pump for six-channel white led applications 3164.2006.07.1.0 5 current matching vs. temperature temperature ( c) current (ma) 19.2 19.4 19.6 19.8 20.0 20.2 -40 -20 0 20 40 60 80 channel 2 channel 1 channel 5 channel 3 channel 4 channel 6 turn-off from 1.5x mode (v in = 3.5v; 20ma/channel; data 1) time (100s/div) en (2v/div) i in (100ma/div) v f (1v/div) turn-on to 2x mode (v in = 2.8v; 20ma/channel; data 1) time (100s/div) en (2v/div) cp (2v/div) i in (200ma/div) v sink (500mv/div) turn-on to 1.5x mode (v in = 3.8v; 20ma/channel; data 1) time (100s/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/channel; data 1) time (100s/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 5.0ma/ch v f = 2.9v 20ma/ch v f = 3.4v 10.2ma/ch v f = 3.1v
typical characteristics c in = c out = c 1 = c 2 = 1.0f; t a = 25c, r set = 26.1k , v in = 3.6v, unless otherwise noted. aat3164 high efficiency 1x/1.5x/2x charge pump for six-channel white led applications 6 3164.2006.07.1.0 t off vs. v in v in (v) t off ( 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 t lat vs. v in v in (v) t lat ( 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 load characteristics (v in = 3.1v; 2x mode; 20ma/channel; data 1) time (500ns/div) v in (40mv/div) v sink (40mv/div) cp (40mv/div) load characteristics (v in = 4.0v; 1.5x mode; 20ma/channel; data 1) time (500ns/div) v in (40mv/div) v sink (40mv/div) cp (40mv/div) load characteristics (v in = 2.9v; 2x mode; 14.2ma/channel; data 3) time (500ns/div) v in (40mv/div) v sink (40mv/div) cp (40mv/div) load characteristics (v in = 3.8v; 1.5x mode; 14.2ma/channel; data 3 ) time (500ns/div) v in (40mv/div) v sink (40mv/div) cp (40mv/div)
typical characteristics c in = c out = c 1 = c 2 = 1.0f; t a = 25c, r set = 26.1k , v in = 3.6v, unless otherwise noted. aat3164 high efficiency 1x/1.5x/2x charge pump for six-channel white led applications 3164.2006.07.1.0 7 input ripple vs. v in v in (v) amplitude (mv) 0 2 4 6 8 10 12 14 16 18 20 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 20ma/ch 10.2ma/ch v il vs. v in v in (v) v il (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 v ih vs. v in v in (v) v ih (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 maximum led current vs. r set r set (k ) i d (ma) 0 5 10 15 20 25 30 35 40 45 10 15 20 25 30 35 40 45 50 55 60 65 70 7 5
aat3164 high efficiency 1x/1.5x/2x charge pump for six-channel white led applications 8 3164.2006.07.1.0 functional block diagram functional description the aat3164 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 aat3164 charge pump is enabled when any of the six cur- rent sink inputs near dropout. the charge pump initially starts in 1.5x mode. if the charge pump output droops enough for any current sink input to become close to dropout, the charge pump will automatically transition to 2x mode. the aat3164 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 s 2 cwire serial interface enables the aat3164 and sets the current sink magnitudes. since all cur- rent sinks are truly independent constant current sinks, the voltage observed on any single given input will be determined by the actual forward volt- age (v f ) for the led being driven. unused sink inputs must be connected to out, otherwise the part will operate in 2x charge pump mode only. constant current output level settings the current sink magnitude is controlled by analogictech's s 2 cwire serial digital input. the maximum current is programmed by an external resistor at the rset pin. since each current sink is 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 man- age led or display brightness, allowing the user to "set it and forget it." with its high-speed serial inter- face (1mhz data rate), the input sink current can be changed quickly and easily. the code settings for the aat3164 are listed in table 1. 1x, 1.5x and 2x charge pump d/a d/a d/a s 2 cwire interface soft-start control 1mhz oscillator voltage reference in en/set gnd d4 d3 d2 d1 out c1+ c1- c2+ c2- d/a d5 d/a 6 x 16 bit rom d6 d/a maximum current adjustment rset
table 1: current level settings as a percentage of the maximum level set by r set . the built-in s 2 cwire interface records rising edges of the en/set pin and decodes them into these cur- rent level settings. s 2 cwire latches data after the en/set pin has been held high for time t lat . a sep- arate mode is available for ultra-low led current operation. this mode is enabled by setting data 13 to 16. while the aat3164 is operating in low current and 1x mode, the total quiescent current is reduced to typically 70a. when en/set is held low for an amount of time longer than t off (500s), the aat3164 enters shutdown mode and draws less than 1a from in. data register is reset to 0 during shutdown. auto-disable feature the aat3164 is equipped with an auto-disable fea- ture for each led channel. after the ic is enabled, a test current of 150a (typical) is forced through each sink channel. the led must develop a for- ward voltage of 0.8v for the channel to turn on. this allows individual channels to be disabled by connecting the respective sink pin to out. this feature is convenient for disabling an unused chan- nel or protecting against an led fail short event. thermal protection the aat3164 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 out pin. data all outputs d1~d6 1 100% 2 84% 3 71% 4 60% 5 51% 6 43% 7 35% 8 30% 9 25% 10 21% 11 17% 12 14% 13 1.8ma 14 1ma 15 530a 16 50a aat3164 high efficiency 1x/1.5x/2x charge pump for six-channel white led applications 3164.2006.07.1.0 9 figure 1: s 2 cwire serial interface timing diagram. 1 en/set 2 n - 1 n 16 data reg 1n 0 t hi t lo t lat t off
aat3164 high efficiency 1x/1.5x/2x charge pump for six-channel white led applications 10 3164.2006.07.1.0 applications information led selection although the aat3164 is specifically designed to drive 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 lcd display backlight- ing, 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 d6 input current sinks are matched with negligible voltage dependence, the led bright- ness will be matched regardless of the specific 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 (~0.1v @ 20ma i led ) current sinks in the aat3164 make it capable of driving leds with forward voltages as high as 4.7v from an input supply as low as 3.0v. outputs can be paralleled to drive high-cur- rent leds without complication. determining the maximum led current level the value of r set determines the maximum led current level. in the typical application, selecting r set = 26.1k results in 20ma/channel led cur- rent. from this reference point, the r set value required for other current levels can be calculated as: a visual representation of the maximum led cur- rent per channel versus r set value is shown in figure 2. figure 2: maximum led current vs. r set . brightness control using the rset pin additional methods of brightness control can be achieved with the rset pin. for example, using an additional resistor to connect the rset pin with a digital output provides a hi/lo control. figure 3 illustrates a configuration of the rset pin utilizing two resistors. figure 3: rset configuration using two resistors. when the digital output is asserted high, the result- ing brightness level is lo and the individual led currents are: when the digital output is asserted low, the result- ing brightness level is hi and the individual led currents are: i led(hi) = 870 ?? ?? 0.6 r 1 // r 2 i led(lo) = 870 - ?? ?? 0.6 r 1 // r 2 v io r 2 aat3164 rset r 1 r 2 hi/lo or v dac r set (k ) i d (ma) 0 5 10 15 20 25 30 35 40 45 10 15 20 25 30 35 40 45 50 55 60 65 70 75 r set = 20ma 26.1k i led(max)
additionally, a digital-to-analog converter can be used with the rset pin to control the brightness level. the result is like the equation above, where v io is replaced with v dac : for cases where pwm dimming is preferred, the pwm signal can be applied directly to the rset resis- tor, as shown in figure 4. in order for the led current to go to zero, the voltage level of the pwm signal must exceed the rset pin voltage level of 0.6v. figure 4: rset configuration for pwm dimming control. device power efficiency the aat3164 power conversion efficiency depends on the charge pump mode. by definition, device efficiency is expressed as the output power delivered to the leds divided by the total input power consumed. when the input voltage is sufficiently greater than the led forward voltages, the device optimizes efficiency by operating in 1x mode. in 1x mode, the device is working as a bypass switch and pass- ing the input supply directly to the output. by sim- plifying the conditions such that the leds have uni- form v f , the power conversion efficiency can be approximated by: due to the very low 1x mode quiescent current, the input current nearly equals the total output current delivered to the leds. further, the low resistance bypass switch introduces negligible voltage drop from input to output. the aat3164 further maintains optimized perform- ance and efficiency by detecting when the input voltage is not sufficient to sustain led drive cur- rent. the device automatically switches to 1.5x mode when the input voltage drops too low in rela- tion to the led forward voltages. in 1.5x mode, the output voltage can be boosted to 3/2 the input voltage. the 3/2 conversion ratio introduces a corresponding 1/2 increase in input current. for ideal conversion, the 1.5x mode effi- ciency is given by: similarly, when the input falls further, such that 1.5x mode can no longer sustain led drive cur- rent, the device will automatically switch to 2x mode. in 2x mode, the output voltage can be boosted to twice the input voltage. the doubling conversion ratio introduces a corresponding dou- bling of the input current. for ideal conversion, the 2x mode efficiency is given by: additional applications the current sinks of the aat3164 can be combined to drive higher current levels through a single led. as an example, each led of a three-die arrange- ment can be driven at 80ma each, or 240ma total (see figure 5). other applications that require constant current can also be accommodated by combining constant current channels to achieve the necessary current levels. aat3164 high efficiency 1x/1.5x/2x charge pump for six-channel white led applications 3164.2006.07.1.0 11 = v f i led v in 2i in v f 2 v in = v f i led v in 1.5i in v f 1.5 v in = v f i led v in i in v f v in = p ou t p in aat3164 rset r 1 pwm i led(lo) = 870 - ?? ?? 0.6 r 1 // r 2 v dac r 2
device switching noise performance the aat3164 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 aat3164 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 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 value may be decreased. capacitor characteristics ceramic composition capacitors are highly recom- mended over all other types of capacitors for use with the aat3164. ceramic capacitors offer many advan- tages over their tantalum and aluminum electrolytic 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 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 connections, size or area, material compo- sition, and ambient temperature. capacitor esr is typically measured in milliohms for ceramic capac- itors 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 generally have tight tolerance and are very stable over temperature. larger capacitor values are usually composed of x7r, x5r, z5u, or y5v dielec- tric 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 aat3164 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. aat3164 high efficiency 1x/1.5x/2x charge pump for six-channel white led applications 12 3164.2006.07.1.0 figure 5: configuration for a typical three-led application. c out 1f c in 1f en/set in en/set c1+ c1- c2+ c2- out d1 d2 d3 d4 d5 d6 gnd aat3164 rset 1f 1f 26.1k 3 led pac k v bat 80ma each
aat3164 high efficiency 1x/1.5x/2x charge pump for six-channel white led applications 3164.2006.07.1.0 13 ordering information package information tdfn34-16 all dimensions in millimeters. package marking 1 part number (tape and reel) 2 tdfn34-16 qbxyy AAT3164IRN-T1 1. xyy = assembly and date code. 2. sample stock is generally held on part numbers listed in bold . 3.00 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.
aat3164 high efficiency 1x/1.5x/2x charge pump for six-channel white led applications 14 3164.2006.07.1.0 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 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.

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