View AAT3174IWP-T1_2715857.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

general description the aat3174 is a high output current, high effi- ciency, low noise, low profile charge pump dc/dc converter. the device is ideal for multi-functional led photo-flash applications where solution cost, size, and efficiency are critical. the aat3174 is capable of driving a regulated out- put current up to 800ma. output current levels can be easily programmed in 16 steps through analogictech's simple serial control? (s 2 cwire?) interface controlled by a single microcontroller gpio line. this allows smooth transitions and flexi- ble adjustment of brightness in flash or other light- ing modes. the maximum output current can also be set with an external r set resistor. the tri-mode (1x/1.5x/2x) operation of the internal charge pump offers excellent power efficiency throughout the output current range for both flash and movie modes. combined with a low external parts count (two 1f flying capacitors and two small bypass capacitors at v in and out), the aat3174 is ideally suited for small battery-pow- ered applications. the aat3174 has a thermal management system to protect the device in the event of a short-circuit con- dition at the output pin. built-in soft-start circuitry pre- vents excessive inrush current during start-up. the shutdown feature disconnects the load from v in and reduces quiescent current to less than 1a. the aat3174 is available in a pb-free, thermally- enhanced 12-pin 3x3mm tdfn package and is spec- ified over the -40c to +85c temperature range. features ? up to 800ma output current ? tri-mode 1x/1.5x/2x in current mode ? 16 current steps set by s 2 cwire ? external r set to set maximum current ? <1a of shutdown ? small application circuit ? no inductors ? automatic soft start ? 12-pin tdfn 3x3mm package ? -40c to +85c temperature range applications ? camcorders ? camera phones ? digital still cameras ? pdas and notebook pcs ? smart phones aat3174 high current, high efficiency charge pump typical application 3174.2006.05.1.2 1 chargepump ? aat3174 c1 1f c2 1f c out 2.2f c in 4.7f en/set vin c1+ c1- c2+ c2- out fl v in (2.7v to 5.5v) enable or s 2 cwire flash led gnd rset
pin descriptions pin configuration tdfn33-12 (top view) pin # symbol function 1 vin input power supply pin. requires 4.7f bypass capacitor to ground. 2 c1+ flying capacitor c1 positive terminal. connect a 1f capacitor between c1+ and c1-. 3 c1- flying capacitor c1 negative terminal. 4 gnd ground connection. 5 fl controlled current sink. connect the flash led cathode to this pin. 6 rset connect resistor here to set maximum output current. 7 en/set charge pump enable / set input control pin. when in the low state, the aat3174 is powered down and consumes less than 1a. when connected to logic high level, the aat3174 charge pump is active. this pin should not be left floating. 8 n/c not connected. 9 c2- flying capacitor c2 negative terminal. 10 c2+ flying capacitor c2 positive terminal. connect a 1f capacitor between c2+ and c2-. 11 out charge pump output. requires 2.2f bypass capacitor to ground. connect to flash led anode to drive the led. 12 vin input power supply pin. requires 4.7f bypass capacitor to ground. ep exposed paddle (bottom). connect to gnd directly beneath package. aat3174 high current, high efficiency charge pump 2 3174.2006.05.1.2 vin c1+ c1- 1 gnd fl rset vin out c2+ c2- n/c en/se t 2 3 4 5 6 12 11 10 9 8 7
absolute maximum ratings 1 t a = 25c, unless otherwise noted. thermal information 2 symbol description value units ja thermal resistance 50 c/w p d maximum power dissipation 2.0 mw symbol description value units v in input voltage -0.3 to 6.0 v v en en to gnd voltage -0.3 to 6.0 v v en(max) maximum en to input voltage v in + 0.3 v i out maximum output current 1000 ma t j operating temperature range -40 to 150 c t s storage temperature range -65 to 150 c t lead maximum soldering temperature (at leads, 10 sec) 300 c aat3174 high current, high efficiency charge pump 3174.2006.05.1.2 3 1. stresses above those listed in absolute maximum ratings may cause permanent damage to the device. functional operation at c ondi- tions other than the operating conditions specified is not implied. only one absolute maximum rating should be applied at any one time. 2. mounted on an fr4 board.
electrical characteristics 1 c in = 4.7f, c out = 2.2f, 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 power supply v in input voltage range 2.7 5.5 v 1x, no load current 300 a 3.0 v in 5.5, 1.5x mode, 2.0 4.0 i cc operating current no load current ma 3.0 v in 5.5, 2x mode, 3.0 6.0 no load current i shdn(max) v in pin shutdown current en = 0 1.0 a i out(max) 2 maximum output current v f = 3.6v 800 ma i dx output current accuracy programmed for 600ma; 540 660 ma r set = 187k t ss soft-start time 200 s v rset r set pin voltage 0.7 v 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 60 s t en/set hi minimum en/set high time 50 ns t en/set hi max maximum en/set high time 60 s t off en/set off timeout 500 s t lat en/set latch timeout 500 s input current en/set input leakage -1 1 a aat3174 high current, high efficiency charge pump 4 3174.2006.05.1.2 1. the aat3174 is guaranteed to meet performance specifications from 0c to 70c. specification over the -40c to +85c operati ng temperature range is assured by design, characterization, and correlation with statistical process controls. 2. mounted on an fr4 board.
typical characteristics v in = 3.6v, c in = 4.7f, c out = 2.2f, c 1 = c 2 = 1f, t a = 25c, unless otherwise noted. aat3174 high current, high efficiency charge pump 3174.2006.05.1.2 5 turn-off from 1.5x mode (v in = 3.2v; i led = 150ma) time (200s/div) en (2v/div) i in (200ma/div) v f (1v/div) turn-on to 2x mode (v in = 3.2v; i led = 600ma) time (200s/div) en (2v/div) v out (2v/div) i in (500ma/div) v sink (1v/div) turn-on to 1x mode (v in = 4.2v; i led = 600ma) time (200s/div) en (2v/div) v out (2v/div) i in (500ma/div) v sink (1v/div) turn-on to 1.5x mode (v in = 3.2v; i led = 150ma) time (200s/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; i led = 150ma) time (200s/div) en (2v/div) v out (2v/div) i in (200ma/div) v sink (1v/div) efficiency vs. supply voltage supply voltage (v) efficiency (%) 0 10 20 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 i led = 300ma i led = 150ma
typical characteristics v in = 3.6v, c in = 4.7f, c out = 2.2f, c 1 = c 2 = 1f, t a = 25c, unless otherwise noted. aat3174 high current, high efficiency charge pump 6 3174.2006.05.1.2 t off vs. v in input voltage (v) t off (s) 0 20 40 60 80 100 120 140 160 180 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 5.1 5.3 5. 5 4.7 4.9 2.7 2.9 -40 c 25 c 85 c t lat vs. v in input voltage (v) t lat (s) 0 20 40 60 80 100 120 140 160 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 5.1 5.3 5.5 4.7 4.9 -40 c 25 c 85 c led current vs. r set (data = 1) r set (k ) i led (ma) 0 100 200 300 400 500 600 700 800 900 1000 100 200 300 400 500 600 700 800 900 1000 operating characteristic (v in = 2.9v; 2x mode; i led = 300ma) time (2s/div) v in (100mv/div) v sink (200mv/div) v out (200mv/div) operating characteristic (v in = 3.3v; 1.5x mode; i led = 300ma) time (2s/div) v in (100mv/div) v sink (200mv/div) v out (200mv/div)
typical characteristics v in = 3.6v, c in = 4.7f, c out = 2.2f, c 1 = c 2 = 1f, t a = 25c, unless otherwise noted. aat3174 high current, high efficiency charge pump 3174.2006.05.1.2 7 v il vs. v in over temperature input voltage (v) v il (v) 0.4 0.5 0.6 0.7 0.8 0.9 1.0 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 5.1 5.3 5.5 4.7 4.9 2.7 2.9 -40 c 25 c 85 c v ih vs. v in over temperature input voltage (v) v ih (v) 0.4 0.5 0.6 0.7 0.8 0.9 1.0 3.1 3.3 3.5 3.7 3.9 2.7 2.9 4.1 4.3 4.5 5.1 5.3 5.5 4.7 4.9 -40 c 25 c 85 c
aat3174 high current, high efficiency charge pump 8 3174.2006.05.1.2 functional block diagram functional description the aat3174 is a high efficiency, low noise, dual stage tri-mode 1x/1.5x/2x charge pump device intended for photo-flash led applications. the device requires only four external components: two ceramic capacitors for the charge pump flying capacitors, one ceramic capacitor for c in , and one ceramic capacitor for c out . the charge pump is designed to deliver regulated load currents up to 800ma. the dual stage charge pump section contains soft-start circuitry to pro- hibit excessive inrush current during start-up. system efficiency is maximized with a tri-mode, dual stage charge pump topology. the internal clock oscillator at 1mhz allows the use of small external components. the tri-mode charge pump operation further opti- mizes power conversion efficiency. depending upon the variance of load current (at different modes), input voltage, and nominal led forward voltage, the charge pump will operate in a 1x, 1.5x, or 2x mode to generate the output voltage required to power the load for a given controlled constant current. this results in significant power savings over voltage doubling architectures, especially when the leds are also operated at lower current levels in movie, viewing, or flashlight modes. s 2 cwire serial interface the aat3174 utilizes analogic tech's single wire s 2 cwire interface to enable/disable the charge pump and adjust the output current at 16 current levels. each code defines the output current to be a percentage of the maximum current set by the resistor at the r set pin (see table 1). charge pump section 1 charge pump section 2 1mhz oscillator soft-start control c1+ c1- c2+ c2- out fl rset gnd en/set vin system control; s 2 cwire; timing
aat3174 high current, high efficiency charge pump 3174.2006.05.1.2 9 table 1: current level settings. the s 2 cwire interface records rising edges of the en/set pin and decodes them into 16 individual current level settings with code 1 reserved for maximum 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 subse- quent 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 aat3174 enters into shut- down mode and draws less than 1a from v in . data and address registers are reset to 0 during shutdown. total output data (% of i max ) 1 100.0 2 89.1 3 79.4 4 70.8 5 63.1 6 56.2 7 50.1 8 44.7 9 39.8 10 35.5 11 31.6 12 28.2 13 25.1 14 22.4 15 20.0 16 0.0 s 2 cwire serial interface timing 1 en/set 2 n-1 n 16 data reg 0n 0 t hi t lo t lat t off
application information flash/torch control using the rset pin an alternative method can be used for flash/torch control that eliminates the need to use the s 2 cwire single-wire interface. by using any typical digital i/o port, an additional enable can be created (see figure 1). the i/o port output configuration can be any one of open-drain nmos, open-drain pmos, or push-pull type. the control will always act as an active-low flash enable or, equivalently, an active-high torch enable (see table 2). table 2: flash/torch control modes. according to i/o port type, the following equations can be used to calculate appropriate resistor values. for an open-drain nmos i/o port output configu- ration, the line is pulled low to gnd or left floating, according to state. to calculate the appropriate r 1 and r 2 resistor values, first calculate the r 1 resis- tor value needed for the desired torch level led current: next, choose r 2 based on the desired flash level led current: the current and resistance values used in the equa- tions come from the conditions placed on the i dx parameter of the electrical characteristics table. en enfl mode 0 0 off 0 1 off 1 0 flash 1 1 torch aat3174 high current, high efficiency charge pump 10 3174.2006.05.1.2 figure 1: flash/torch control using the rset pin. r 1 600ma 187k r 1 i led (flash) - 600ma 187k r 2 = 600ma 187k i led (torch) r 1 = aat 3174 en/set vin c1+c1-c2+c2- vout f1 2.7v to 5.5v en flash led gnd c in 4.7f c 1 1f c 2 1f c out 2.2f r1 r2 rset enfl
for examples of standard 1% values where the led flash current level is targeted for 700ma, see table 3. table 3: open-drain i/o example resistor values. if the i/o port must be configured as an open-drain pmos type output, the appropriate equations can be generated from these same concepts. as done in the previous example, the necessary values can then be calculated. as a reference, the equations applicable to the pmos case are: the value to use for v io must come from the i/o supply voltage used in the system. 0.7v is the typ- ical value of the v rset parameter found in the electrical characteristics. for a push-pull i/o port output configuration, first calculate the overall r set value needed for the desired flash level led current: next, choose a reasonable value for r 1 . a value that is slightly larger than r set , calculated from above, is appropriate. calculate r 2 and then calcu- late the torch mode current level that results: once again, the current and resistance values used in the equations come from the conditions placed on the i dx parameter of the electrical characteristics table. 0.7v is the typical value for the v rset param- eter. the value to use for v io must come from the i/o supply voltage used in the system. example standard 1% values are provided in table 4. table 4: push-pull i/o example resistor values. in all of the approaches mentioned, the open-drain nmos or pmos type configurations offer the most flexibility for current level selection. when configured as an output, if the i/o port is only push-pull type, then the equivalent open-drain nmos can also be realized. to realize this, acti- vate the port as output only when driving the line low. otherwise, to release the line, set the port to be tri-stated. r1 r2 i led i led (k )(k ) torch (ma) flash (ma) 169 1000 95 776 165 1000 111 792 162 1000 124 805 160 1000 132 813 r1 r2 i led i led (k )(k ) torch (ma) flash (ma) 920 193 122 703 732 205 153 701 649 210 173 707 562 223 200 703 aat3174 high current, high efficiency charge pump 3174.2006.05.1.2 11 i led (torch) = 600ma 187k - r 2 - r 1 r 1 r 2 v io 0.7v r 2 ? ? ? ? r set r 1 r 1 - r se t r 2 = 600ma 187k i led (flash) r set = v io 0.7 1 r 1 i led (torch) 600ma 187k r 2 = - 1 - 600ma 187k i led (flash) r 1 =
aat3174 high current, high efficiency charge pump 12 3174.2006.05.1.2 device power efficiency the aat3174 power conversion efficiency depends on the charge pump mode. by definition, device efficiency is expressed as the output power delivered to the led divided by the total input power consumed. when the input voltage is sufficiently greater than the led forward voltage, the device optimizes effi- ciency by operating in 1x mode. in 1x mode, the device is working as a bypass switch and passing the input supply directly to the output. the power conversion efficiency can be approximated by, due to the very low 1x mode quiescent current, the input current nearly equals the current delivered to the led. further, the low-impedance bypass switch introduces negligible voltage drop from input to output. the aat3174 further maintains optimized perform- ance and efficiency by detecting when the input voltage is not sufficient to sustain led current. the device automatically switches to 1.5x mode when the input voltage drops too low in relation to the led forward voltage. 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 current, 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 doubling of the input current. for ideal conversion, the 2x mode effi- ciency is given by: led selection the aat3174 is designed to drive high-intensity white leds. it is particularly suitable for leds with an oper- ating forward voltage in the range of 4.2v to 1.5v. the charge pump device can also drive other loads that have similar characteristics to white leds. for various load types, the aat3174 provides a high-cur- rent, programmable ideal constant current source. 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 the flying capacitors is a good starting point when choosing capacitors. if the led current sinks are only programmed for light current levels, then the capacitor size may be decreased. ceramic composition capacitors are highly recom- mended over all other types of capacitors for use with the aat3174. 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 compo- sition, and ambient temperature. capacitor esr is typically measured in milliohms for ceramic capac- = = 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
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 val- ues are usually composed of x7r, x5r, z5u, or y5v dielectric materials. large ceramic capacitors are often available in lower-cost dielectrics, but capacitors greater than 4.7f are not typically required for aat3174 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 aat3174 has a thermal protection circuit that will shut down the charge pump if the die tempera- ture rises above the thermal limit, as is the case during a short-circuit of the out pin. pcb layout to achieve adequate electrical and thermal per- formance, careful attention must be given to the pcb layout. in the worst-case operating condition, the chip must dissipate considerable power at full load. adequate heat-sinking must be achieved to ensure intended operation. figure 2 illustrates an example of an adequate pcb layout. the bottom of the package features an exposed metal paddle. the exposed paddle acts, thermally, to transfer heat from the chip and, elec- trically, as a ground connection. the junction-to-ambient thermal resistance ( ja ) for the package can be significantly reduced by follow- ing a couple of important pcb design guidelines. the pcb area directly underneath the package should be plated so that the exposed paddle can be mated to the top layer pcb copper during the re-flow process. this area should also be connect- ed to the top layer ground pour when available. further, multiple copper plated thru-holes should be used to electrically and thermally connect the top surface paddle area to additional ground plane(s) and/or the bottom layer ground pour. the chip ground is internally connected to both the paddle and the gnd pin. the gnd pin conducts large currents and it is important to minimize any differences in potential that can result between the gnd pin and exposed paddle. it is good practice to connect the gnd pin to the exposed paddle area using a trace as shown in figure 2. figure 2: example pcb layout. the flying capacitors c1 and c2 should be con- nected close to the chip. trace length should be kept short to minimize path resistance and potential coupling. the input and output capacitors should also be placed as close to the chip as possible. aat3174 high current, high efficiency charge pump 3174.2006.05.1.2 13
aat3174 high current, high efficiency charge pump 14 3174.2006.05.1.2 advanced analogic technologies, inc. 830 e. arques avenue, sunnyvale, ca 94085 phone (408) 737-4600 fax (408) 737-4611 ordering information package information tdfn33-12 all dimensions in millimeters. package marking 1 part number (tape and reel) 2 tdfn33-12 rsxyy AAT3174IWP-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. top view bottom view detail "b" detail "a" side view 3.00 2.40 + 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.

▲Up To Search▲

Price & Availability of AAT3174IWP-T1

	To Download AAT3174IWP-T1 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .