View AAT3194ITP-20-T1_2591418.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

aat3194 high efficiency 1.5x fractional charge pump for white led applications typical application 3194.2006.09.1.0 1 chargepump ? general description the aat3194 is a low noise, constant frequency charge pump dc/dc converters that use fractional (1.5x) conversion to increase efficiency in white led applications. the devices can be used to pro- duce current levels up to 20ma for each output from a 2.7v to 5.5v input. a low external parts count (two 1f flying capacitors and two small bypass capacitors at in and out) makes these devices ideally suited for small, battery-powered applications. analogictech?s simple serial control? (s 2 cwire?) interface is used to enable, disable, and set the led drive current for 32-level logarithmic scale led brightness control. the aat3194 has a thermal management system for protection in the event of a short-circuit condition on any of the output pins. built-in soft-start circuitry prevents excessive inrush current during start-up. a high switching frequency enables the use of small external capacitors. a low- current shutdown feature disconnects the load from v in and reduces quiescent current to less than 1a. the aat3194 is available in a pb-free 12-pin tsopjw package. features ?v in range: 2.7v to 5.5v ? 20ma full-scale current ? simple serial control (s 2 cwire) interface ? 32-position logarithmic scale with digital control ? low noise constant frequency operation ? 33% less input current than doubler charge pump ? high accuracy brightness matching ? small application circuit ? regulated output current ? automatic soft start ? no inductors ? 600khz switching frequency ?i q <1a in shutdown ? temperature range: -40c to 85c ? 12-pin tsopjw package applications ? programmable current source ? white led backlighting c in 1f v battery c out 1f en/set c1 1f c2 1f d4 d3 d2 d1 in out c1+ c1- c2+ c2- d1 d2 d3 d4 en/set gnd aat3194
pin descriptions pin configuration tsopjw-12 (top view) pin # symbol function 1 c2+ flying capacitor 2 positive terminal. connect a 1f ceramic capacitor between c2+ and c2-. 2 out charge pump output. requires 1f bypass capacitor to ground. 3 c1- flying capacitor 1 negative terminal. 4 c1+ flying capacitor 1 positive terminal. connect a 1f ceramic capacitor between c1+ and c1-. 5 d4 current source output 4. 6 d3 current source output 3. 7 d2 current source output 2. 8 d1 current source output 1. required reference current source. do not leave pin floating. 9 en/set control pin using s 2 cwire serial interface. 10 in input power supply. requires 1f or larger ceramic capacitor to ground. 11 gnd ground. 12 c2- flying capacitor 2 negative terminal. aat3194 high efficiency 1.5x fractional charge pump for white led applications 2 3194.2006.09.1.0 1 2 3 4 5 6 12 11 10 9 8 7 c2+ out c1- c1+ d4 d3 c2- gnd in en/set d1 d2
absolute maximum ratings t a = 25c, unless otherwise noted. thermal information 1 symbol description value units ja thermal resistance 160 c/w p d maximum power dissipation 2 625 mw symbol description value units v in input voltage -0.3 to 6 v v out charge pump output -0.3 to 6 v v en/set en/set to gnd voltage -0.3 to 6 v v en/set(max) maximum en/set to input voltage 0.3 v i out maximum dc output current (sum of i out and d currents) 120 ma t j operating junction temperature range -40 to 150 c aat3194 high efficiency 1.5x fractional charge pump for white led applications 3194.2006.09.1.0 3 1. mounted on an fr4 board. 2. derate 6.25mw/c above 25c
aat3194 high efficiency 1.5x fractional charge pump for white led applications 4 3194.2006.09.1.0 electrical characteristics v in = 3.5v, t a = -40c to +85c, unless otherwise noted. typical values are at t a = 25c. symbol description conditions min typ max units input power supply v in operation range 2.7 v i cc operating current active, no load current 3 ma i shdn shutdown current en = 0v 1 a i dx output current 3.0v v in 5.5v, t a = 25c, all outputs max current 16 20 24 ma i d / v in output current line 3.0v v in 5.5v -3 3 %/v regulation current matching i (d-match) between any vd1:dn = 3.6v, v in = 3.3v 0.3 % two outputs efficiency v in = 3.5v, i out(total) = 40ma 93 % charge pump t ss soft-start time 400 s f clk clock frequency 300 khz en/set v en(l) enable threshold low v in = 2.7v to 5.5v 0.5 v v en(h) enable threshold high v in = 2.7v to 5.5v 1.4 v t lo en/set low time 0.3 75 s t hi minimum en/set 50 ns high time t off en/set off timeout 500 s input en/set input leakage v in = 5.5v -1 1 a current
typical characteristics v in = 3.5v, c in = c out = c 1 = c 2 = 1f; t a = 25c, unless otherwise noted. aat3194 high efficiency 1.5x fractional charge pump for white led applications 3194.2006.09.1.0 5 oscillator frequency vs. temperature 610 620 630 640 650 660 670 680 690 700 710 -40 -20 0 20 40 60 80 100 temperature ( shutdown current vs. temperature 0.001 0.010 0.100 1.000 -40 -20 0 20 40 60 80 100 temperature ( efficiency vs. load current 80 82 84 86 88 90 92 94 96 020406080 load current (ma) efficiency (%) quiescent current vs. supply voltage 0.6 0.7 0.8 0.9 1.0 1.1 1.2 3.0 3.5 4.0 4.5 5.0 5.5 supply voltage (v) i q (ma) efficiency vs. supply voltage 60 65 70 75 80 85 90 95 100 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 supply voltage (v) efficiency (%) 80ma 60ma 40ma 30ma 20ma quiescent current vs. temperature 0.86 0.88 0.90 0.92 0.94 0.96 0.98 1.00 -40 -20 0 20 40 60 80 100 temperature (
aat3194 high efficiency 1.5x fractional charge pump for white led applications 6 3194.2006.09.1.0 typical characteristics v in = 3.5v, c in = c out = c 1 = c 2 = 1f; t a = 25c, unless otherwise noted. 0.750 0.775 0.800 0.825 0.850 0.875 0.900 0.925 0.950 0.975 1.000 2.5 3.0 3.5 4.0 4.5 5.0 5.5 v in (v) v ih and v il (v) v ih v il v ih and v il vs. v in i diode vs. v diode 0 20 40 60 80 100 3.0 3.2 3.4 3.6 3.8 4.0 v diode (v) i diode (ma) i diode response (-9db to -10db) time (10s/div) enset (2v/div) i diode -9db 0db -10db -31db i diode vs. v in 0 20 40 60 80 100 3.0 3.5 4.0 4.5 v in (v) i diode (ma) i diode response (-31db to 0db) time (10s/div) enset (2v/div) i diode -31db 0db normalized i diode vs. temperature 0.95 0.96 0.97 0.98 0.99 1.00 1.01 1.02 -40 -20 0 20 40 60 80 100 temperature (
typical characteristics v in = 3.5v, c in = c out = c 1 = c 2 = 1f; t a = 25c, unless otherwise noted. aat3194 high efficiency 1.5x fractional charge pump for white led applications 3194.2006.09.1.0 7 turn-on time (100s/div) enset (2v/div) out (5v/div) v diode (2v/div) i in (50ma/div) 80ma load characteristics time (1s/div) 20mv/div in out v diode 60ma load characteristics time (1s/div) 20mv/div in out v diode 40ma load characteristics time (1s/div) 10mv/div in out v diode turn-off time (200s/div) enset (2v/div) out (5v/div) v diode (5v/div) i in (50ma/div)
aat3194 high efficiency 1.5x fractional charge pump for white led applications 8 3194.2006.09.1.0 functional block diagram functional description the aat3194 is a high efficiency 1.5x fractional charge pumps intended for white led backlight applications. the fractional charge pump consists of a linear regulator followed by a 1.5x charge pump. the aat3194 requires only four external components: two 1f ceramic capacitors for the charge pump flying capacitors (c1 and c2), one 1f ceramic capacitor for c in , and one 0.33f to 1f ceramic capacitor for c out . the charge pump output is converted into four constant current out- puts (d1 to d4) to drive four individual leds with a maximum of 20ma each. the current source out- put magnitude is controlled by the en/set serial data s 2 cwire interface. the interface records rising edges of the en/set pin and decodes them into 32 individual current level settings each 1db apart (see table 1, current level settings). code 32 is full scale, and code 1 is full scale attenuated by 31db. the modulo 32 interface wraps states back to state 1 after the 32nd clock. with each en/set pulse, the output current increases by 1db. to decrease the output current by 1db, 31 en/set clock pulses are required. the counter can be clocked at speeds up to 1mhz, so intermediate states are not visible. the first rising edge of en/set enables the ic and initially sets the output led current to -31db, the lowest setting equal to 525a. once the final clock cycle is input for the desired brightness level, the en/set pin is held high to maintain the device output current at the programmed level. the device is disabled 500s after the en/set pin transitions to a logic low state. voltage reference soft start 600khz oscillator 1.5x charge pump s 2 cwire interface 32x8 bit rom current mode dac 8 5 in c1+ c1- c2+ c2- out d1 d2 d3 d4 gnd en/set
aat3194 high efficiency 1.5x fractional charge pump for white led applications 3194.2006.09.1.0 9 applications information current level settings led current level is set via the serial interface according to a logarithmic scale where each code is 1db greater than the previous code. in this man- ner, the led brightness appears linear with each increasing code. table 1: current level settings. code 20ma max code 20ma max 1 0.549 17 3.529 2 0.627 18 4.000 3 0.706 19 4.471 4 0.784 20 5.020 5 0.863 21 5.647 6 1.020 22 6.353 7 1.098 23 7.059 8 1.255 24 7.922 9 1.412 25 8.941 10 1.569 26 10.039 11 1.804 27 11.216 12 1.961 28 12.627 13 2.275 29 14.118 14 2.510 30 15.843 15 2.824 31 17.804 16 3.137 32 20.000 normalized current level settings 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1 2 3 4 5 6 7 8 9 1011121314151617181920212223242526272829303132 code normalized current to full scale
aat3194 high efficiency 1.5x fractional charge pump for white led applications 10 3194.2006.09.1.0 en/set serial interface the current source output magnitude is controlled by the en/set pin using analogictech?s simple serial control (s 2 cwire) interface. the interface records rising edges of the en/set pin and decodes them into 32 individual current level set- tings each 1db apart. code 32 is full scale, and code 1 is full scale attenuated by 31db. the mod- ulo 32 interface wraps states back to state 1 after the 32nd clock, so 1db of attenuation is achieved by clocking the en/set pin 31 times (see graph titled, ?i diode response -9db to -10db?). the counter can be clocked at speeds up to 1mhz, so intermediate states are not visible. the first rising edge of en/set enables the ic and initially sets the output led current to -31db, the lowest setting equal to 525a. once the final clock cycle is input for the desired brightness level, the en/set pin is held high to maintain the device output current at the programmed level. the device is disabled 500s after the en/set pin transitions to a logic low state. 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. a constant current is sourced as long as en/set remains in a logic high state. the current source outputs are switched off after en/set has remained in a low state for at least the t off timeout period (see figure 1). led selection the aat3194 is designed to drive white leds with forward voltages to 4.2v. since the d1:d4 output current sources are matched with negligible voltage dependence, the led brightness will be matched regardless of their forward voltage matching. charge pump efficiency the aat3194 uses a fractional charge pump. the efficiency ( ) can be simply defined as a linear volt- age regulator with an effective output voltage that is equal to one and one half 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: 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 5 volts and a nominal input of 3.5 volts, the theoretical efficiency is 95%. due to internal switching losses and ic quiescent current consumption, the actual efficien- cy can be measured at 93%. these figures are in close agreement for output load conditions from 1ma to 100ma. efficiency will decrease as load figure 1: en/set timing diagram. (%) = 100 v out 1.5v in ?? ?? = p out = v out i out = v out p in v in 1.5i out 1.5v in = p ou t p in en/set code 1 2 3 off off t hi t lo t off
aat3194 high efficiency 1.5x fractional charge pump for white led applications 3194.2006.09.1.0 11 current drops below 0.05ma or when the level of the power supply of in approaches out. refer to the typical characteristics section of this datasheet for measured plots of efficiency versus input volt- age and output load current for the given charge pump output voltage options. power efficiency and device evaluation the charge pump efficiency discussion in the previ- ous section only accounts for efficiency of the charge pump section itself. due to the unique cir- cuit architecture and design of the aat3194, it is very difficult to measure efficiency in terms of a per- cent value comparing input power over output power. since the device outputs are pure constant current sources, it is difficult to measure the output voltage for a given output (d1 to d4) to derive an output power measurement. for any given appli- cation, white led forward voltage levels can differ, yet the output 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 bet- ter 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 application should be based on trade-offs of size, external components count, relia- bility, operating range, and total energy usage... not just "% efficiency." 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 minimal 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 aat3194. 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 impor- tant characteristic to consider when selecting a capacitor. esr is a resistance internal to a capac- itor that is caused by the leads, internal connec- tions, size or area, material composition, and ambi- ent temperature. capacitor esr is typically meas- ured 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 generally have tight tolerance and are very stable over tem- perature. larger capacitor values are usually com- posed of x7r, x5r, z5u, or y5v dielectric materi- als. 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 aa t3194 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. aat3194 input power vs. led current 0 100 200 300 400 500 600 700 0 20 40 60 80 100 output (led) current (ma) input power (mw) v in = 3.6v
aat3194 high efficiency 1.5x fractional charge pump for white led applications 12 3194.2006.09.1.0 application circuits typical aat3194 application circuit: test current/channel disable each channel of the output is equipped with a test current function. the aat3194 uses a small (~2a) current source injected into each output pin to detect the presence of an led. unused channels that are tied to ground or led load fail short will be automatically diasbled instead of wasting the pro- grammed output current. thermal protection the aat3194 has a thermal protection circuit that will shut down the charge pump and current out- puts if the die temperature rises above the thermal limit. c in 1 f v battery c out 1 f en/set c1 1 f c2 1 f d4 d3 d2 d1 in out c1+ c1- c2+ c2- d1 d2 d3 d4 en/set gnd aat3194 on/1 t hi > 50ns 50ns minimum to enable 300ns < t lo < 75 s 23456 n (n < =32) off enable / disable / led brightness level set data input
aat3194 high efficiency 1.5x fractional charge pump for white led applications 3194.2006.09.1.0 13 ordering information package information tsopjw-12 all dimensions in millimeters. package marking 1 part number (tape and reel) 2 tsopjw-12 uuxyy AAT3194ITP-20-T1 1. xyy = assembly and date code. 2. sample stock is generally held on part numbers listed in bold . 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.
aat3194 high efficiency 1.5x fractional charge pump for white led applications 14 3194.2006.09.1.0 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.

▲Up To Search▲

Price & Availability of AAT3194ITP-20-T1

	To Download AAT3194ITP-20-T1 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .