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aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 1 www.analogictech.com general description the aat2861 is a highly integrated charge pump-based lighting management unit (lmu) offering eight led channels with three linear regulators optimized for sin- gle-cell lithium-ion/polymer systems. the charge pump provides power for all led outputs; multiple backlight and flash led configurations are available. the backlight led outputs can be programmed up to 31ma each and the flash led output current can be programmed up to 600ma total. analogictech?s as 2 cwire? (advanced simple serial control?) single-wire interface is used to enable, disable, and set the current to one of 32 levels for the backlight and one of 16 levels for the flash. a programmable safety timer and separate flash control input are included for easy flash control. backlight cur- rent matching is better than 3% for uniform display brightness, and flash current matching is better than 5% for uniform power dissipation. the aat2861 also offers three high-performance low- noise micropower? ldo linear regulators. the regulators output voltages are set through the as 2 cwire serial interface. each ldo can supply up to 300ma load cur- rent and ground-pin current is only 80 a, making the aat2861 ideal for battery-operated applications. the aat2861 is available in a pb-free, space-saving tqfn34-24 package and operates over the -40c to +85c ambient temperature range. features ? input voltage range: 2.7v to 5.5v ? as 2 cwire serial interface ? tri-mode charge pump ? drives up to eight leds (backlight/flash) ? programmable backlight current settings ? 31ma maximum current per channel ? 32 linear current settings ? independent main/sub settings ? programmable fade-in and fade-out ? programmable flash current ? 600ma total flash current ? 16 linear current settings ? 1- or 2-channel configuration ? 1mhz switching frequency ? automatic soft-start ? three linear low dropout regulators ? 300ma output current ? 150mv dropout ? programmable output voltage from 1.2v to 3.3v ? output auto-discharge for fast shutdown ? built-in thermal protection ? automatic soft start ? -40c to +85c temperature range ? tqfn34-24 package applications ? camera enabled mobile devices ? digital still cameras ? multimedia mobile phones typical application cf1 1f cf2 1f c1+ c1- c2+ c2- in c out 2. 2f v out out bl1 bl2 bl3 bl4 bl7/fl2 v ldoa at 300ma ldoa c ldoa 2. 2f v bat 3.6v aat2861-x agnd bl5 bl6 en/set en/set fl_en fl_en c in 2.2f ldob c ldob 2. 2f ldoc c ldoc 2. 2f pgnd v ldob at 300ma v ldoc at 300ma en_ ldoa en_ ldoa en_ldob/c en_ ldob/c wleds osram lw m673 or equivalent in flash leds lumiled lxcl-pwf1 or equivalent fl1
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2 2861.2009.02.1.2 www.analogictech.com aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2 2861.2009.02.1.2 www.analogictech.com pin descriptions pin # symbol description 1 out charge pump output. out is the output of the charge pump and supplies current to the backlight and ash leds. connect the backlight and ash led anodes to out. bypass out to pgnd with a 2.2 f or larger ceramic capacitor as close to the aat2861 as possible. 2 c2+ positive terminal of charge pump capacitor 2. connect the 1 f charge pump capacitor 2 from c2+ to c2-. 3 en/set as 2 cwire serial input. en/set is the address and data input of the as 2 cwire serial interface. as 2 cwire is used to control backlight, ash and ldo functions. 4 fl_en flash enable. fl_en is the enable control for the flash leds. for the fl_en pin to enable the ash current, the en/set pin must also be pulled high. 5 en_ldoa ldo a enable pin. en_ldoa turns on or off ldo regulator a. the en/set pin must also be pulled high for ldo a to be enabled. the en_ldoa input can be overwritten via the as 2 cwire interface to disable ldo a. 6 en_ldob/c ldo b and ldo c enable pin. en_ldob/c enables both ldo regulators b and c. the en/set pin must also be pulled high for the ldo regulators to be enabled. the en_ldob/c input can be overwritten via the as 2 cwire interface to disable either ldo b or ldo c. 7 agnd analog ground. connect agnd to pgnd at a single point as close to the aat2861 as possible. 8 ldoc ldoc is the voltage output of ldo c. bypass ldoc to agnd with a 2.2 f or larger capacitor as close to the aat2861 as possible. 9 in input power pin for all three ldos. connect pin 9 to pin 23 with as short a pcb trace as practical. 10 ldob ldob is the voltage output of ldo b. bypass ldob to agnd with a 2.2 f or greater capacitor as close to the aat2861 as possible. 11 ldoa ldoa is the voltage output of ldo a. bypass ldoa to agnd with a 2.2 f or larger ceramic capacitor as close to the aat2861 as possible. 12 bl1 backlight led 1 current sink. bl1 controls the current through backlight led 1. connect the cathode of backlight led 1 to bl1. if not used, connect bl1 to out. 13 bl2 backlight led 2 current sink. bl2 controls the current through backlight led 2. connect the cathode of backlight led 2 to bl2. if not used, connect bl2 to out. 14 bl3 backlight led 3 current sink. bl3 controls the current through backlight led 3. connect the cathode of backlight led 3 to bl3. if not used, connect bl3 to out. 15 bl4 backlight led 4 current sink. bl4 controls the current through backlight led 4. connect the cathode of backlight led 4 to bl4. if not used, connect bl4 to out. 16 bl5 backlight led 5 current sink. bl5 controls the current through backlight led 5. connect the cathode of backlight led 5 to bl5. if not used, connect bl5 to out. 17 bl6 backlight led 6 current sink. bl6 controls the current through backlight led 6. connect the cathode of backlight led 6 to bl6. if not used, connect bl6 to out. 18 bl7 (fl2) aat2861-1/3: backlight led 7 current sink. bl7 controls the current through backlight led 7. connect the cathode of backlight led 7 to bl7. if not used, connect bl7 to out. aat2861-2: flash led 2 current sink. fl2 controls the current through flash led 2. connect the cathode of flash led 2 to fl2. if not used, connect fl2 to out. 19 fl1 flash led 1 current sink. fl1 controls the current through flash led 1. connect the cathode of flash led 1 to fl1. if not used, connect fl1 to out. 20 pgnd power ground. connect pgnd to agnd at a single point as close to the aat2861 as possible. 21 c2- negative terminal of charge pump capacitor 2. 22 c1- negative terminal of charge pump capacitor 1. 23 in power input. connect in to the input source voltage. bypass in to pgnd with a 2.2 f or larger ceramic capacitor as close to the aat2861 as possible. 24 c1+ positive terminal of charge pump capacitor 1. connect the 1 f charge pump capacitor 1 from c1+ to c1-. ep exposed paddle (bottom) connect to pgnd/agnd.
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 3 www.analogictech.com aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 3 www.analogictech.com pin configuration tqfn34-24 (top view) 1 2 3 4 5 6 7 8 9 24 23 22 21 20 10 11 12 19 18 17 16 15 14 13 out c2+ en/set fl _ en en _ ldoa en _ ldob/c agnd ldoc in ldob ldoa bl1 bl5 bl6 bl4 bl3 bl2 bl7 (fl2) fl1 pgnd c2- c1- in c1+ part number descriptions 1 part number backlight led outputs flash led outputs main sub aat2861imk-1-t1 4 3 1 aa t2861imk-2-t1 4 2 2 aat2861imk-3-t1 5 2 1 absolute maximum ratings 2 symbol description value units in, out, bl1, bl2, bl3, bl4, bl5, bl6, bl7/fl2, fl1 voltage to agnd -0.3 to 6.0 v c1+, c2+ voltage to agnd -0.3 to v out + 0.3 v c1-, c2-, ldoa, ldob, ldoc, en/set, fl_en, en_ldoa, en_ldob/c voltage to agnd -0.3 to v in + 0.3 v pgnd voltage to agnd -0.3 to 0.3 v t j operating junction temperature range -40 to 150 c t lead maximum soldering temperature (at leads, 10 sec) 300 c thermal information 3,4 symbol description value units p d maximum power dissipation 2.0 w ja maximum thermal resistance 50 c/w 1. backlight and flash configuration within a part number is configured though the as 2 cwire serial interface. for example, disabling the ?main equals sub? feature (address 8, data 5 - 8) in the aat2861-1 will configure bl1-bl4 led outputs as main and bl5-bl7 outputs as sub. 2. stresses above those listed in absolute maximum ratings may cause permanent damage to the device. functional operation at conditions other than the operating conditions specified is not implied. only one absolute maximum rating should be applied at any one time. 3. derate 20mw/c above 25c ambient temperature. 4. mounted on a fr4 circuit board.
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 4 2861.2009.02.1.2 www.analogictech.com aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 4 2861.2009.02.1.2 www.analogictech.com electrical characteristics 1 v in = 3.6v; c in = c out = 2.2 f; c 1 = c 2 = 1 f; t a = -40c to +85c, unless otherwise noted. typical values are t a = 25c. symbol description conditions min typ max units v in in operating voltage range 2.7 5.5 v i in in operating current (1x mode, main channels enabled, iblx not included) en/set = in, bl1-bl7 = in, fl_en = en_ldoa = en_ldob/c = agnd 600 a in operating current (2x mode, main channels enabled, iblx not included) 2x mode; en/set = in, fl_en = en_ldoa = en_ldob/c = agnd; bl1-bl7 = open 5.5 ma in operating current (ldoa, ldob and ldoc enabled) en/set = en_ldoa = en_ldob/c = in; fl_en = agnd; addr = 3; data = 1; no load 225 a in operating current (only ldoa enabled) en/set = en_ldoa = in; fl_en = en_ldob/c = agnd, addr = 3; data = 1; no load 80 a i in(shdn) in shutdown current en/set, fl_en, en_ldoa, en_ldob/c = agnd 1.0 a t sd over-temperature shutdown threshold 140 c t sd(hys) over-temperature shutdown hysteresis 15 c charge pump section v out out output voltage 5.2 v i out(max) out maximum output current v in = 3.0v, v out = 4.0 800 ma v in(th_h, bl) bl1-bl7 charge pump mode transition hysteresis en/set = in; v in ? v f = 1v; addr = 0, data = 16; addr = 3, data = 3; addr = 2, data = 12 0.3 v v in(th_h, fl) fl1-fl2 charge pump mode transition hysteresis en/set = fl_en = in; v in ? v f = 1v; addr = 10, data = 1 1v f osc charge pump oscillator frequency t a = 25c 1 mhz t cp(ss) charge pump soft-start time t a = 25c 100 s bl1-bl6, bl7/fl2, fl1 led drivers i blx bl1-bl7 current accuracy en/set = in; v in ? v f = 1v; addr = 0, data = 16; addr = 3, data = 3; addr = 2, data = 12 18 20 22 ma i bl_x bl1-bl7 current accuracy en/set = in; v in ? v f = 1v; addr = 0, data = 16; addr = 3, data = 4; addr = 2, data = 14 1.6 2 2.4 ma i (blx) / i bl(avg) bl1-bl7 current matching 2 en/set = in; v in ? v f = 1v; addr = 0, data = 16; addr = 3, data = 3; addr = 2, data = 12 3% v bl_(th) bl1-bl7 charge pump transition threshold en/set = in; v in ? v f = 1v; addr=0, data = 16; addr = 3, data = 3; addr = 2, data = 12 0.2 v t fade bl1-bl7 automatic fade-in/fade-out timer en/set = in; v in ? v f = 1v; addr = 0, data = 16; addr = 1, data = 1; addr = 2, data = 12; addr = 3, data = 3 0.75 1 1.25 s i fl[1] fl1 current accuracy en/set = fl_en = in; v in ? v f = 1v; addr = 10, data = 1 540 600 660 ma i fl[1](data13) fl1 current accuracy en/set = fl_en = in; v in ? v f = 1v; addr = 10, data = 13 108 120 132 ma i (flx) / i fl(avg) fl1-fl2 current matching (aat2861-2 only) en/set = fl_en = in; v in ? v f = 1v, addr = 10, data = 1 5% v fl[1/2](th) fl1 charge pump transition threshold en/set = fl_en = in; v in ? v f = 1v; addr = 10, data = 1 0.45 v t fl /t fl_set flash safety timer period en/set = fl_en = in; v in ? v f = 1v; addr = 11, data = 1 1.5 2 2.5 s 1. the aat2861 is guaranteed to meet performance specifications over the -40c to +85c operating temperature range and is assu red by design, characterization, and correla- tion with statistical process controls. 2. current matching is defined as the deviation of any sink current from the average of all active channels.
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 5 www.analogictech.com aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 5 www.analogictech.com electrical characteristics (continued) 1 v in = 3.6v; c in = c out = 2.2 f; c 1 = c 2 = 1 f; t a = -40c to +85c, unless otherwise noted. typical values are t a = 25c. symbol description conditions min typ max units linear regulators v ldo[a/b/c] / v ldo[a/b/c] ldoa, ldob, ldoc output voltage tolerance i ldo = 1ma to 200ma; t a = 25c -1.5 1.5 % i ldo = 1ma to 200ma; t a = -40c to +85c -3.0 3.0 % i ldo[a/b/c](max) ldoa, ldob, ldoc load current 200 ma v ldo[a/b/c](do) ldoa, ldob, ldoc dropout voltage 2 v ldo[a/b/c] 3.0v; i ldo = 150ma 75 150 mv 'v ldo / v ldo *'v in ldoa, ldob, ldoc line regulation v in = (v ldo[a/b/c] + 1v) to 5v 0.09 %/v psrr [a/b/c] ldoa, ldob, ldoc power supply rejection ratio i ldo[a/b/c] = 10ma, 1khz 50 db r out_(dchg) ldoa, ldob, ldoc auto-discharge resistance 20 en/set as 2 cwire and logic control v ih en/set, fl_en, en_ldoa, en_ldob/c input high threshold voltage 2.7v v in 5.5v 1.4 v v il en/set, fl_en, en_ldoa, en_ldob/c input low threshold voltage 2.7v v in 5.5v 0.4 v i in(lkg) en/set, fl_en, en_ldoa, en_ldob/c input leak- age current en/set = in = 5v -1 1 a t en/set(off) en/set input off timeout 500 s t en/set(lat) en/set input latch timeout 500 s t en/set(low) en/set input low time 0.3 75 s t enset(h-min) en/set minimum high time 50 ns t enset(h-max) en/set maximum high time 75 s 1. the aat2861 is guaranteed to meet performance specifications over the -40c to +85c operating temperature range and is assu red by design, characterization, and correla- tion with statistical process controls. 2. v do[a/b/c] is defined as v in ? ldo[a/b/c] when ldo[a/b/c] is 98% of nominal.
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 6 2861.2009.02.1.2 www.analogictech.com aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 6 2861.2009.02.1.2 www.analogictech.com typical characteristics backlight efficiency vs. input voltage input voltage (v) efficiency (%) 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 30 40 50 60 70 80 90 100 30ma/ch, v f = 3.95v 15ma/ch, v f = 3.5v 4.2ma/ch, v f = 3.4v flash efficiency vs. input voltage input voltage (v) efficiency (%) 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 30 40 50 60 70 80 90 100 320ma/ch, v f = 3.25v 160ma/ch, v f = 3.15v backlight current matching vs. temperature (v in = 3.6v; 20ma/ch) temperature (c) backlight output current (ma) -40 -15 10 35 60 85 16 17 18 19 20 21 22 channel 1 - channel 6/7 charge pump output turn on characteristic (v in = 3.6v; 0ma/ch; c out = 2.2f) time (50s/div) v en/set (top) (v) output voltage (bottom) (v) 0.0 2.0 4.0 0.0 1.0 2.0 3.0 4.0 turn on to 1x mode flash (v in = 4.2v; 300ma/ch) time (50s/div) v fl_en (2v/div) v out (2v/div) i in (200ma/div) v flx (2v/div) 0 2 4 0 200 400 600 0 2 4 turn on to 1.5x mode flash (v in = 3.6v; 300ma/ch) time (50s/div) v fl_en (2v/div) v out (2v/div) i in (200ma/div) v flx (2v/div) 0 2 4 0 200 400 600 0 2 4
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 7 www.analogictech.com aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 7 www.analogictech.com typical characteristics turn on to 2x mode flash (v in = 2.8v; 300ma/ch) time (50s/div) v fl_en (2v/div) v out (2v/div) i in (200ma/div) v flx (2v/div) 0 2 4 0 200 400 600 0 2 4 turn on to 1x mode backlight (v in = 3.6v; 20ma/ch) time (200s/div) v en/set (2v/div) v out (2v/div) i in (100ma/div) v sink (2v/div) 0v 0v 0a turn on to 1.5x mode backlight (v in = 3.2v; 20ma/ch) time (200s/div) v en/set (2v/div) v out (2v/div) i in (200ma/div) v sink (2v/div) 0v 0v 0 a turn on to 2x mode backlight (v in = 3.0v; 20ma/ch) time (200s/div) v en/set (2v/div) v out (2v/div) i in (200ma/div) v sink (2v/div) 0v 0v 0a turn off from 1.5x mode backlight (v in = 3.2v; 20ma/ch) time (200s/div) v en/set (2v/div) v diode (2v/div) i in (200ma/div) operating characteristic (v in = 3.2v; 20ma/ch backlight; 1.5x mode; c out = 2.2f) time (500ns/div) input voltage (ac coupled) (top) (mv) charge pump out put voltage (ac coupled) (bottom) (mv) 0 10 20 -50 0 50
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 8 2861.2009.02.1.2 www.analogictech.com aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 8 2861.2009.02.1.2 www.analogictech.com typical characteristics operating characteristic (v in = 3.0v; 20ma/ch backlight; 2x mode; c out = 2.2f) time (500ns/div) input voltage (ac coupled) (top) (mv) charge pump out put voltage (ac coupled) (bottom) (mv) 0 10 20 -20 -10 0 10 20 ldo a/b/c load regulation (v in = 3.6v) load current (ma) ldo output voltage deviatoin (%) 0.1 1 10 100 1000 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 v out = 1.8v v out = 3.0v ldo a/b/c output voltage vs. temperature (v in = 3.6v; i ldo = 0ma) temperature (c) ldo output voltage deviatoin (%) -40 -15 10 35 60 85 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 v out = 1.8v v out = 3.3v ldo a/b/c load transient response ( i ldo = 10ma to 200ma; v in = 3.6v; v ldo = 1.8v; c ldo = 2.2f) time (20s/div) ldo output current (top) (ma) ldo output voltage (bottom) (v) -500 -400 -300 -200 -100 0 100 200 1.60 1.70 1.80 1.90 2.00 ldo a/b/c line transient response (v in = 3.6v to 4.2v; i ldo = 10ma; v out = 1.8v; c ldo = 2.2f) time (1ms/div) input voltage (top) (v) ldo output voltage (bottom) (v) 3.6 4.0 4.4 1.78 1.79 1.80 1.81 1.82 ldo a/b/c turn on characteristic (v ldo = 1.8v; v in = 3.6v; c ldo = 2.2f) time (20s/div) v enldox (top) (v) ldo output (bottom) (v) 0.0 2.0 4.0 0.0 0.5 1.0 1.5
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 9 www.analogictech.com aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 9 www.analogictech.com typical characteristics en/set, fl_en, en_ldoa, en_ldob/c high threshold voltage vs. input voltage input voltage (v) v en/set(h) , v fl_en(h) , v en_ldoa(h) , v en_ldob/c(h) (v) 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 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 -40c 25c 85c en/set, fl_en, en_ldoa, en_ldob/c low threshold voltage vs. input voltage input voltage (v) v en/set(l) , v fl_en(l) , v en_ldoa(l) , v en_ldob/c(l) (v) 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 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 -40c 25c 85c en/set input latch timeout vs. input voltage input voltage (v) t lat (s) 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 100 150 200 250 300 350 400 -40c 25c 85c en/set input off timeout vs. input voltage input voltage (v) t off (s) 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 100 150 200 250 300 350 400 450 500 -40c 25c 85c
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 10 2861.2009.02.1.2 www.analogictech.com aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 10 2861.2009.02.1.2 www.analogictech.com functional block diagrams aat2861imk-1-t1 bl5 c1- c1+ c2- c2+ in ldoa out bl1 bl2 bl3 bl4 bl6 bl7 agnd en_ldoa ldob ldoc in en_ldob/c en/set fl_en pgnd ref 8 fl1 5 5 4 1x/1.5x/2x tri-mode charge pump control logic main backlight current control sub backlight current control flash control
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 11 www.analogictech.com aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 11 www.analogictech.com AAT2861IMK-2-T1 bl5 1x/1.5x/2x tri-mode charge pump c1- c1+ c2- c2+ in ldo a out bl1 bl2 bl3 bl4 bl6 control logic fl2 agnd en_ldoa ldob ldo c in en_ldob/c en/set fl_en pgnd ref 8 fl1 flash control sub backlight current control main backlight current control 5 5 4
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 12 2861.2009.02.1.2 www.analogictech.com aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 12 2861.2009.02.1.2 www.analogictech.com aat2861imk-3-t1 bl5 1x/1.5x/2x tri-mode charge pump c1- c1+ c2- c2+ in ldoa out bl1 bl2 bl3 bl4 bl6 control logic bl7 agnd en_ldoa ldob ldoc in en_ldob/c en/set fl_en pgnd ref 8 fl1 flash control sub backlight current control main backlight current control 5 5 4
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 13 www.analogictech.com functional description the aat2861 is a highly integrated backlight and photo- flash driver family with three ldo regulators. the charge pump led driver powers the backlight and flash leds from the 2.7v to 5.5v input voltage. the ldo regulators are powered from the same input and produce regulated output voltage between 1.2v and 3.3v. control of the leds and the ldo output voltage is through an as 2 cwire serial interface for easy programming. led drivers the aat2861 drives six or seven backlight leds up to 31ma each and a total of 600ma flash current through one or two channels. the leds are driven from a charge pump to insure that constant current is maintained over the entire battery voltage range. the charge pump auto- matically switches from 1x, to 1.5x, to 2x modes and back to maintain the led current while minimizing power loss for high efficiency. the charge pump operates at the high 1mhz switching frequency, allowing the use of small 1 f ceramic capacitors. each individual led is driven by a current sink to gnd, allowing individual current control with high accuracy over a wide range of input voltages and led forward voltages while maintaining high efficiency. the charge pump is controlled by the voltage across the led current sinks. when any one of the active backlight current sink/channel voltages drops below 200mv or the flash current sink/channel drops below 450mv, the charge pump goes to the next higher mode (from 1x to 1.5x or from 1.5x to 2x mode) to maintain sufficient led voltage for constant led current. the aat2861 con- tinuously monitors the led forward voltages and uses the input voltage to determine when to reduce the charge pump mode for better efficiency. there is also a 300mv mode-transition hysteresis that prevents the charge pump from oscillating between modes. led current control both the backlight and flash led currents are controlled through the as 2 cwire serial interface. the backlight led current can be set between 0.5ma and 31ma in approx- imately 1ma steps while the flash led current can be set between 0 and 600ma in 40ma steps or 0 to 300ma in 20ma steps for two channel flash version. the backlight led currents match to within 3% while the flash led currents match to within 5%. to eliminate the latency of the as 2 cwire serial interface, the flash led is enabled through a dedicated input, fl_en. the aat2861 also includes a safety timer that prevents thermal overstress of the flash led(s). this is important because many flash leds operate for a brief period beyond their steady-state operating limitations. if the flash driving hardware and/or software fail to turn the led off, the safety timer insures that the led or other circuitry is not damaged. both the backlight and flash led currents are pro- grammed through the as 2 cwire serial interface as are the backlight fade-in/fade-out timer and the flash safety timer. see the ?as 2 cwire serial interface programming? section of this datasheet for more information on setting the led currents. ldo regulators the aat2861 includes three low dropout (ldo) linear regulators. these regulators are powered from the bat- tery and produce a fixed output voltage set through the as 2 cwire serial interface. the output voltage can be set to one of 16 output voltages between 1.2v and 3.3v. the ldo regulators can be turned on/off with the external enable pins en_ldoa and en_ldob/c. additionally, the as 2 cwire interface allows the ldo regulators to be enabled independently when the en_ldoa and en_ ldob/c pins are pulled high. the ldo regulators require only a small 2.2 f ceramic output capacitor for stability. if improved load transient response is required, larger-valued capacitors can be used without stability degradation. as 2 cwire serial interface protocol the aat2861 is dynamically programmable by the as 2 cwire single-wire interface. as 2 cwire records rising edges detected at the en/set pin to address and load the data registers. the timing diagram in figure 1 shows the typical transmission protocol.
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 14 2861.2009.02.1.2 www.analogictech.com address data 1 en/set 2 17 18 address data reg 1 data reg 2 1 2 . . . n <= 16 0 1 0 0 n t hi t lo t lat t lat figure 1: as 2 cwire serial interface timing diagram. as 2 cwire latches data or address after the en/set input has been held high for time t lat (500 s). address or data is differentiated by the number of en/set rising edges. since the data registers are 4 bits each, the differentiating number of pulses is 2 4 or 16, so that address 0 is identi- fied by 17 rising edges, address 1 by 18 rising edges, address 2 by 19 rising edges, etc. data is set to any num- ber of rising edges between 1 and 16. a typical write protocol is a burst of en/set rising edges identifying a particular address, followed by a pause with en/set held high for the t lat timeout period, then a burst of rising edges signifying data, and another t lat timeout after the data has been sent. once an address is set, multiple writes to that address are allowed since the address is not reset after each write. address edges are needed when changing the address, or writing to an address other than the default after shutdown. address 0 is the default address after shutdown. if the part is enabled with only data edges and no address, then address 0 will be pro- grammed and led backlight channels bl1-bl7 will be enabled according to the number of data edges applied. when en/set is held low for a time longer than t off (500 s), the aat2861 enters shutdown mode and draws less than 1 a of current from in. at shutdown, the data and address registers are reset to 0. as 2 cwire serial interface programming the aat2861?s as 2 cwire programmable address regis- ters are listed in table 1. there are 14 address registers, four registers control the three ldos, six control the backlight led configuration, two control the flash/lamp led configuration and two are used to individually dis- able each backlight or flash channel. backlight current control (address 0) address 0 controls the enabling of the main and sub channels. table 2 shows the data codes used to control the main and sub channels independently. the default condition for all backlight outputs (bl1-bl7) is off after power-up. the aat2861 family of lmus also provides an internal led current fade-in, fade-out feature. this feature is useful in those applications where it is preferred to turn on and off the backlight current using a smooth transition versus an abrupt transition. during the fade-in cycle, the led cur- rent will be slowly increased to the programmed current level (set in addresses 2 to 5). during the fade-out cycle, the led current will be decreased linearly down to its programmed fade-out current threshold (set by address 1) at which point the bl channels will be turned off. the fade-in and fade-out current is a linear transition over a time period of approximately 1 second. the fade-in and fade-out function can be enabled and disabled independently for the main and sub groups by writing the desired data to address 0. table 2 also lists the data codes used to program enable and disable the fade functions for the main and sub channels. if the ?main equals sub? feature (address 3) is enabled (meqs=1), the fade-in and fade-out settings for the main and sub channels are controlled by the ?main fade? set- ting and the ?sub fade? bit in address 1 will be ignored. at startup when the en/set pin is first pulled high, address 0 is the default active register. the main and sub channels can be turned on by immediately writing data. for example, if data = 4 is written the main and sub channels will turn on to the default value of 19ma.
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 15 www.analogictech.com data sub fade on main fade on sub channel main channel 1* no* no* off* off* 2 no no off on 3 no no on off 4n on oo no n 5 no yes off off 6 no yes off on 7 no yes on off 8 no yes on on 9 yes no off off 10 yes no off on 11 yes no on off 12 yes no on on 13 yes yes off off 14 yes yes off on 15 yes yes on off 16 yes yes on on table 2: backlight main/sub on/off and fade enable (address 0). backlight fade-in and fade-out control (address 1) during the fade-out cycle, the led current will be decreased linearly down to its programmed fade-out current threshold (set by address 1) at which point the bl channels will be turned off. the default fade-out cur- rent level is 500 a, but can be changed to 1ma, 2ma or 3ma using the data codes listed in table 3. data fade out current level (ma) 1* 0.50* 2 1.0 3 2.0 4 3.0 table 3: backlight fade-in and fade-out control (address 1). backlight current control (addresses 2 to 5) the aat2861?s as 2 cwire addresses 2, 3, 4, and 5 control the backlight led output current level in main and sub group of outputs. address 2 and address 3 control the main backlight channel current to one of 32 levels according to table 4 below. address 3 acts as the msb and address 2 acts as the lsb for the current level setup. address 4 and address 5 control the sub back- light channels current to one of 32 levels according to table 5 below. *denotes the default (power-on-reset) value address en/set rising edges function d3 d2 d1 d0 0 17 backlight main/sub on/off and fade enable fade_sub fade_main sub_on main_on 1 18 backlight fade control x x floor[1] floor[0] 2 19 backlight current main, lsb's blm[3] blm[2] blm[1] blm[0] 3 20 backlight current main, msb reserved x meqs blm[4] 4 21 backlight current sub, lsb's bls[3] bls[2] bls[1] bls[0] 5 22 backlight current sub, msb x x x bls[4] 6 23 ldo disable control x off_ldoc off_ldob off_ldoa 7 24 ldo a output voltage control ldoa[3] ldoa[2] ldoa[1] ldoa[0] 8 25 ldo b output voltage control ldob[3] ldob[2] ldob[1] ldob[0] 9 26 ldo c output voltage control ldoc[3] ldoc[2] ldoc[1] ldoc[0] 10 27 flash current f_hi[3] f_hi[2] f_hi[1] f_hi[0] 11 28 flash timer control x x f_time[1] f_time[0] 12 29 led channel disable control (bl1 ? bl4) off_bl4 off_ bl3 off_ bl2 off_ bl1 13 30 led channel disable control (bl5, bl6, bl7/fl2, fl1) off_fl1 off_bl7/fl2 off_bl6 off_bl5 table 1: aat2861- 1 configuration/control register allocation (* signifies that the data bit has a por default bit value = 1; x signifies ?don?t care?).
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 16 2861.2009.02.1.2 www.analogictech.com main equals sub off (meqs=0) main equals sub on (meqs=1) address data address data main current address data address data main current 3121 3 1 3321 3 1 3122 3 0 3322 3 0 3123 2 9 3323 2 9 3124 2 8 3324 2 8 3125 2 7 3325 2 7 3126 2 6 3326 2 6 3127 2 5 3327 2 5 3128 2 4 3328 2 4 3129 2 3 3329 2 3 3 1 2 10 22 3 3 2 10 22 3 1 2 11 21 3 3 2 11 21 3 1* 2 12* 20* 3 3 2 12 20 3 1 2 13 19 3 3 2 13 19 3 1 2 14 18 3 3 2 14 18 3 1 2 15 17 3 3 2 15 17 3 1 2 16 16 3 3 2 16 16 3221 1 5 3421 1 5 3222 1 4 3422 1 4 3223 1 3 3423 1 3 3224 1 2 3424 1 2 3225 1 1 3425 1 1 3226 1 0 3426 1 0 3227 9 3427 9 3228 8 3428 8 3229 7 3429 7 3221 0 6 3421 0 6 3221 1 5 3421 1 5 3221 2 4 3421 2 4 3221 3 3 3421 3 3 3221 4 2 3421 4 2 3221 5 1 3421 5 1 3 2 2 16 0.5 3 4 2 16 0.5 table 4: backlight main current control (addresses 2 and 3).
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 17 www.analogictech.com sub backlight address data address data sub current 5141 31 514 2 30 5143 29 5144 28 5145 27 5146 26 5147 25 5148 24 5149 23 51410 22 51411 21 5 1* 4 12* 20* 51413 19 51414 18 51415 17 51416 16 5241 15 5242 14 5243 13 5244 12 5245 11 5246 10 5247 9 5248 8 5249 7 52410 6 52411 5 52412 4 52413 3 52414 2 52415 1 5 2 4 16 0.5 table 5: backlight sub current control (addresses 4 and 5). the current settings for the main and sub channels are each divided into two addresses. any change in data to the ?backlight current main (or sub), lsb?s? address will result in an immediate change to the led current output level. programming new current settings that require a change to both ?backlight current main (or sub), msb? and ?backlight current main (or sub), lsb?s? addresses could result in an errant intermediate current setting. to avoid this problem when the data in ?backlight current main (or sub), msb? address is changed the new current setting will not take effect until ?backlight current main (or sub), lsb?s? address has been written to and latched. for example, a change from 28ma to 8ma in the main backlight channels should follow this procedure. first, 28ma is set by programming data = 3 to address 2 and data=1 to address 3. when changing to 8ma first write data=2 to address 3. the current level will not change after this step. then write data=7 to address 2. after address 2 has been latched the new 8ma current level will be set. address 3 also controls the ?main equals sub? feature in the aat2861 products. this feature allows all backlight channels to be controlled with only the main channel current settings. if the ?main equals sub? feature is turned on (data 3, or 4 in address 3) the current set- tings of the sub channel are ignored. all backlight chan- nels will be set to the same current levels as determined by the data programmed to ?backlight current main? in addresses 2 and 3. the main and sub channels are turned on and off by the ?main on? setting in address 0. the default condition is for the ?main equals sub? feature to be turned off (meqs=0) after power-up. table 6 shows the main and sub channel configurations for the three versions of the aat2861. the effect of the ?main equals sub? feature is clearly represented in this table. part number main equals sub (i main = i sub ) yes (default) no aat2861-1 7m+0s+1fl 4m+3s+1fl aa t2861-2 6m+0s+2fl 4m+2s+2fl aat2861-3 7m+0s+1fl 5m+2s+1fl table 6: main and sub channel configurations. ldo output voltage control (addresses 6 to 9) the aat2861?s three ldo regulators are configured by programming addresses 6, 7, 8, and 9 via the as 2 cwire interface. with the en/set pin pulled high and the aat2861 turned on, ldoa can be enabled using the en_ ldoa pin. ldob and ldoc can be enabled together using the en_ldob/c pin. additional ldo regulator control can be achieved using address 6 to override the enable com- mand of the en_ldoa and en_ldob/c pins. for example, with the en_ldoa and en_ldob/c pins enabled, writing data 5 to address 6 will disable ldob and leave ldoa and ldoc enabled. table 7 shows the ldo disable control. writing data to addresses 7, 8, and 9 set the output volt- ages for ldoa, ldob, and ldoc to one of 16 levels. the available ldo output voltages are shown in table 8.
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 18 2861.2009.02.1.2 www.analogictech.com data ldo c ldo b ldo a 1* controlled by en_ldob/c* controlled by en_ldob/c* controlled by en_ldoa* 2 controlled by en_ldob/c controlled by en_ldob/c off 3 controlled by en_ldob/c off controlled by en_ldoa 4 controlled by en_ldob/c off off 5 off controlled by en_ldob/c controlled by en_ldoa 6 off controlled by en_ldob/c off 7 off off controlled by en_ldoa 8 off off off table 7: ldo disable control (address 6). data v ldoa (v) v ldob (v) v ldoc (v) 1 1.2 1.2 1.2 2 1.3 1.3 1.3 3 1.5 1.5 1.5 4 1.6 1.6 1.6 5* 1.8* 1.8* 1.8* 6222 7 2.2 2.2 2.2 8 2.5 2.5 2.5 9 2.6 2.6 2.6 10 2.7 2.7 2.7 11 2.8 2.8 2.8 12 2.9 2.9 2.9 1 3333 14 3.1 3.1 3.1 15 3.2 3.2 3.2 16 3.3 3.3 3.3 table 8: ldo x output voltage (addresses 7, 8, and 9). fast turn-off response time is achieved by an active out- put pull-down circuit, which is enabled when the ldo regulator is disabled. flash driver control (address 10 and 11) the aat2861-1 and aat2861-3 are both configured with a single 600ma led flash channel, while the aat2861-2 is configured with two led flash channels each capable of driving 300ma per channel. address 10 programs the flash current level. table 9 lists the data codes for the programming address 10. upon startup, the power-on- reset value in address 10 is set to data code 13. data flash current (ma) per output aat2861-1 or -3 aat2861-2 1 600 300 2 560 280 3 520 260 4 480 240 5 440 220 6 400 200 7 360 180 8 320 160 9 280 140 10 240 120 11 200 100 12 160 80 13* 120* 60* 14 80 40 15 40 20 16 off off table 9: flash current level (address 10). once the en/set pin is pulled high and the aat2861 has turned on, the led flash channels can be enabled by pulling the fl_en to in. the current setting of the led flash channels can be changed prior to enabling the flash current, or while the flash current is on. the led flash controller also comes with a safety timer to prevent excessive heat generation and power loss from extended high current power dissipation. the led flash safety timer duration can be set to four values by writing to address 11. the default value at startup is 2 seconds. table 10 shows the data codes for the flash safety timer. *denotes default (power-on-reset) value.
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 19 www.analogictech.com torch/movie mode is automatically entered when the flash current setting is programmed to 120ma (60ma for channel for the aat2861-2) or lower with data = 13, 14, or 15. at these current levels the safety timer is auto- matically disabled and the flash channels will remain on as long as the fl_en pin remains active. extended dura- tion flash use can be achieved for higher current settings by writing data 4 to address 11 to disable the safety timer. though the aat2861 includes an internal thermal limit circuit, be careful to limit the current setting (address 10) to a value that will not generate excessive heat which may damage the flash leds or external circuitry. data flash time (sec) 1* 2* 21 3 0.5 4 always on table 10: flash safety timer (address 11). led channel disable control (address 12 and 13) addresses 12 and 13 allow for additional programming flexibility by allowing each led channel to be indepen- dently disabled. normally, the backlight channels are controlled by main_on and sub_on controls in address 0, while the fl_en pin turns on the flash channels. writing to addresses 12 and 13 can override these con- trols to allow for any combination of leds to be turned on. the default state is for all led channels to be ?conditionally on? to allow the normal enable control. in the following example we see how to turn on bl1, bl2, bl6, and bl7 in the aat2861-1 (4m+3s+1fl). first write address 12, data=13 and address 13, data=10 to disable bl3, bl4, bl5, fl1. then program the desired current setting using addresses 2 through 5. finally, write address 0, data=4. (note: ?conditionally on? state allows the led channel to be turned on but does not turn the channel on. for bl1 to be enabled data=2, 4, 6, 8? must be written to address 0, and data=1, 3, 5, 7? must be written to address 12.) *denotes default (power-on-reset) value. data bl4 bl3 bl2 bl1 1* conditionally on* conditionally on* conditionally on* conditionally on* 2 conditionally on conditionally on conditionally on off 3 conditionally on conditionally on off conditionally on 4 conditionally on conditionally on off off 5 conditionally on off conditionally on conditionally on 6 conditionally on off conditionally on off 7 conditionally on off off conditionally on 8 conditionally on off off off 9 off conditionally on conditionally on conditionally on 10 off conditionally on conditionally on off 11 off conditionally on off conditionally on 12 off conditionally on off off 13 off off conditionally on conditionally on 14 off off conditionally on off 15 off off off conditionally on 16 off off off off table 11: led channel individual disable control, bl1-bl4 (address 12).
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 20 2861.2009.02.1.2 www.analogictech.com applications information led selection the aat2861 is specifically intended for driving white leds. however, the device design will allow the aat2861 to drive most types of leds with forward voltage speci- fications ranging from 2.0v to 4.7v. led applications may include mixed arrangements for display backlight- ing, color (rgb) leds, infrared (ir) diodes and any other load needing a constant current source generated from a varying input voltage. since the bl1 to bl6, bl7/ fl2 and fl1 constant current sinks are matched with negligible voltage dependence, the constant current channels will be matched regardless of the specific led forward voltage (v f ) levels. the low-dropout current sinks in the aat2861 maximize performance and make it capable of driving leds with high forward voltages. multiple channels can be com- bined to obtain a higher led drive current without com- plication. device switching noise performance the aat2861 operates at a fixed frequency of approxi- mately 1mhz to control noise and limit harmonics that can interfere with the rf operation of cellular telephone handsets or other communication devices. back-injected noise appearing on the input pin of the charge pump is 20mv peak-to-peak, typically ten times less than induc- tor-based dc/dc boost converter white led backlight solutions. the aat2861 soft-start feature prevents noise transient effects associated with in-rush currents during the start up of the charge pump circuit. device power efficiency charge-pump efficiency discussion in the following sec- tions accounts only for the efficiency of the charge pump section itself. due to the unique circuit architecture and design of the aat2861, it is very difficult to measure efficiency in terms of a percent value comparing input power over output power. data fl1 bl7/fl2 bl6 bl5 1* conditionally on* conditionally on * conditionally on* conditionally on* 2 conditionally on conditionally on conditionally on off 3 conditionally on conditionally on off conditionally on 4 conditionally on conditionally on off off 5 conditionally on off conditionally on conditionally on 6 conditionally on off conditionally on off 7 conditionally on off off conditionally on 8 conditionally on off off off 9 off conditionally on conditionally on conditionally on 10 off conditionally on conditionally on off 11 off conditionally on off conditionally on 12 off conditionally on off off 13 off off conditionally on conditionally on 14 off off conditionally on off 15 off off off conditionally on 16 off off off off table 12: led channel individual disable control, bl5, bl6, bl7/fl2, fl1 (address 13). *denotes default (power-on-reset) value.
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 21 www.analogictech.com since the aat2861 outputs are pure constant current sinks and typically drive individual loads, it is difficult to measure the output voltage for a given output (bl1 to bl6, bl7/fl2, and fl1) to derive an overall output power measurement. for any given application, white led for- ward voltage levels can differ, yet the output drive cur- rent 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 better 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 component count, reliability, operating range and total energy usage... not just "% efficiency." the aat2861 efficiency may be quantified under very specific conditions and is dependant upon the input volt- age versus the output voltage seen across the loads applied to outputs bl1 through bl6, bl7/fl2 or fl1 for a given constant current setting. depending on the com- bination of in and voltages sensed at the current sinks, the device will operate in "load switch" (1x) mode. when any one of the voltages sensed at the current sinks nears dropout the device will operate in 1.5x or 2x charge pump mode. each of these modes will yield dif- ferent efficiency values. one should refer to the following two sections for explanations for each operational mode. aat2861 charge pump conversion efficiency is defined as the power delivered to the white led load divided by the input power: = = p leds p in v led1 i led1 + ... + v ledx i ledx v in i in v ledx = white led forward voltage (v f ) i ledx = white led bias current (i d ) x = number of white leds the expression to define the estimated ideal efficiency ( ) for the aat2861 in 1x mode is as follows: = = p leds p in x v ledx i ledx v in i in x = 1, 2, 3, ..., 6 or 7 and i in = x i ledx = v ledx v in the aat2861 charge pump is a fractional charge pump which will boost the input supply voltage in the event where in is less then the required output voltage across the backlight white led load. the efficiency can be sim- ply defined as a linear voltage regulator with an effective white led forward voltage that is equal to one and a half (1.5x mode) times the input voltage. with an ideal 1.5x charge pump, the input current is 1.5x of the output current. the expression to define the estimated ideal efficiency ( ) for the aat2861 in 1.5x mode is as follows: = = p leds p in v led1 i led1 + ... + v ledx i ledx v in i in = ; x = 1, 2, 3, ..., 6 or 7 and i in = 1.5(x i ledx ) = x v ledx i ledx v in i in v ledx 1.5v in the same calculations apply for the aat2861 in 2x mode where for an ideal 2x charge pump, the input current is 2x of the output current. the expression for the esti- mated ideal efficiency ( ) for the aat2861 in 2x mode is as follows: = = p leds p in v led1 i led1 + ... + v ledx i ledx v in i in = ; x = 1, 2, 3, ..., 6 or 7 and i in = 2(x i ledx ) = x v ledx i ledx v in i in v ledx 2v in in addition, with an ideal 1.5x charge pump, the output current may be expressed as 2/3 of the input current. for a charge pump with an output of 5v and a nominal input of 3.5v, the theoretical efficiency is 95%. due to internal switching losses and ic quiescent current con- sumption, the actual efficiency can be measured at 93%. efficiency will decrease substantially as load current drops below 1ma or when the level of in approaches out. the same calculations apply for 2x mode where the output current then becomes 1/2 of the input current. capacitor selection careful selection of all external capacitors c in , c 1 , c 2 , c ldo(a/b/c) , and c out is important because they will affect turn-on time, output ripple and transient performance. optimum performance will be obtained when low esr
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 22 2861.2009.02.1.2 www.analogictech.com aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 22 2861.2009.02.1.2 www.analogictech.com manufacturer part number value voltage temp. co. case avx 0603zd105k 1 f1 0 x5r 0603 0603zd225k 2.2 f1 0 tdk c1608x5r1e105k 1 f2 5 x5r 0603 c1608x5r1c225k 2.2 f1 6 c1608x5r1a475k 4.7 f1 0 murata grm188r61c105k 1 f1 6 x5r 0603 grm188r61a225k 2.2 f1 0 taiyo yuden lmk107bj475ka 4.7 f 10 x5r 0603 table 13: surface mount capacitors. ceramic capacitors are used. in general, low esr may be defined as less than 100m . ceramic composition capacitors are highly recommended over all other types of capacitors for use with the aat2861. ceramic capacitors offer many advantages over their tantalum and aluminum electrolytic counter- parts. a ceramic capacitor typically has very low esr, is lowest cost, has a smaller printed circuit board (pcb) footprint, and is non-polarized. since ceramic capacitors are non-polarized, they are not prone to incorrect con- nection damage. equivalent series resistance (esr) 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 connec- tions, size or area, material composition and ambient temperature. capacitor esr is typically measured in mil- liohms for ceramic capacitors and can range to more than several ohms for tantalum or aluminum electrolytic capacitors. ceramic capacitor materials ceramic capacitors less than 0.1 f are typically made from npo or cog materials. npo and c0g materials typically have tight tolerance and are stable over tem- perature. larger capacitor values are typically composed of x7r, x5r, z5u or y5v dielectric materials. large ceramic capacitors, typically greater than 2.2 f are often available in low cost y5v and z5u dielectrics, but capacitors greater than 1 f are typically not required for aat2861 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 size capacitors can improve circuit transient response when compared to an equal value capacitor in a smaller package size. pcb layout to achieve adequate electrical and thermal performance, 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. figures 2 and 3 illustrate an example pcb layout. the bottom of the package features an exposed metal pad- dle. the exposed paddle acts, thermally, to transfer heat from the chip and, electrically, as a ground connection. the junction-to-ambient thermal resistance ( ja ) for the connection can be significantly reduced by following 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. 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 to the agnd and pgnd pins. it is good prac- tice to connect the gnd pins to the exposed paddle area with traces as shown in the example. the flying capacitors c1 and c2 should be connected close to the ic. 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.
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 23 www.analogictech.com aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 23 www.analogictech.com button(s) pushed description sw1 [push/release once] ldoa, ldob and ldoc outputs are programmed to 1.2v. with every subsequent push/release ldoa, ldob and ldoc output voltages are incremented according to table 8. [push/hold more than 2 sec] ldoa, ldob and ldoc outputs will start to cycle through all programmable voltage settings according to table 8. sw2 [push/release once] all channels are turned on as main backlight with 31ma per channel. with every subsequent push/release the backlight current is decreased according to table 4. [push/hold more than 2 sec] all channels main and sub are turned on with 31ma per channel and fade out sequence is initiated. the cycle proceeds with fade in for main channels only, followed by fade in se- quence for sub channels. when these sequences are nished the program will restart fade out sequence for all main and sub channels. sw3 [push/release once] flash channels are programmed with maximum current and timer. with every sub- sequent push/release the ash current is decreased according to table 9. the flash button needs to be pressed down simultaneously. flash this button is connected directly to fl_en pin. press and hold for the ash to be enabled. table 14: aat2861 evaluation board user interface. evaluation board user interface the user interface for the aat2861 evaluation board is provided by four buttons and a number of connection terminals. the board is operated by supplying external power and pressing individual buttons or button combi- nations. table 14 indicates the function of each button or button combination. to power-on the evaluation board, connect a power sup- ply or battery to the dc- and dc+ terminals. a red led indicates that power is applied. the evaluation board is made flexible so that the user can disconnect the enable line from the microcontroller and apply external enable signal. external enable signal must be applied to the en/set pin. when applying external enable signal, consideration must be given to the voltage levels. the externally applied voltage should not exceed the supply voltage that is applied to the in pins of the device (dc+). the ldo loads can be connected directly to the evalua- tion board. for adequate performance, be sure to con- nect the load between ldoa/ldob/ldoc and dc- as opposed to some other gnd in the system.
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 24 2861.2009.02.1.2 www.analogictech.com aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 24 2861.2009.02.1.2 www.analogictech.com c3 2.2f c6 2.2f c5 4.7f c7 2.2f r1 1k r2 1k r3 1k d1 d2 d3 d4 out dc+ vdd 1 gp5 2 gp4 3 gp3 4 gp2 5 gp1 6 gp0 7 vss 8 pic12f675 u3 c9 1f r6 330 led7 red 1 4 2 3 5 sw2 1 4 2 3 5 sw3 1 4 2 3 5 flash dc+ dc+ df2 df1 1 4 2 3 5 sw1 out 1 c2+ 2 en/set 3 fl_en 4 en_ldoa 5 en_ldob/c 6 agnd 7 bl2 bl1 ldoa ldob in ldoc 13 12 11 10 89 bl3 14 bl4 15 bl5 16 bl6 17 bl7/fl2 18 fl1 19 20 21 22 23 24 u1 aat2861-x d5 d6 d7 dc+ in r5 0 r4 10k r7 10k c8 2.2f c2 1.0f c1 1.0f c4 4.7f c1+ in pgnd c1- c2- figure 2: aat2861 evaluation board schematic.
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 25 www.analogictech.com aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 25 www.analogictech.com figure 3: aat2861 evaluation board top side layout. figure 4: aat2861 evaluation board bottom side layout.
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 26 2861.2009.02.1.2 www.analogictech.com aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 26 2861.2009.02.1.2 www.analogictech.com component part# description manufacturer u1 aat2861imk-x-t1 high eff. 1x/1.5x/2x cp for white led, triple ldo analogictech u2 pic12f675 8-bit cmos, flash mcu; 8-pin pdip microchip d1-d7 lw m673 mini topled white led; smt osram df1, df2 lxcl pwf1 mini topled flash led; smt lumileds, philips c1, c2 grm18x 1.0 f, 10v, x5r, 0603, ceramic murata c3, c6, c7, c8 grm18x 2.2 f, 10v, x5r, 0603, ceramic murata c4, c5 grm18x 4.7 f, 10v, x5r, 0603, ceramic murata r1-r3 chip resistor 1k, 5%, 1/4w; 0603 vishay r4 chip resistor 10k, 5%, 1/4w; 0603 vishay r6 chip resistor 330, 5%, 1/4w; 1206 vishay r5 chip resistor 0, 5%, 1/4w; 1206 rohm led7 cmd15-21src/tr8 red led; 1206 chicago miniature lamp sw1-sw3, flash pts645tl50 switch tact, spst, 5mm itt industries table 15: aat2681 evaluation board bill of materials (bom),
aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 27 www.analogictech.com aat2861 backlight/flash led driver and multiple ldo lighting management unit chargepump tm product datasheet 2861.2009.02.1.2 27 www.analogictech.com advanced analogic technologies, inc. 3230 scott boulevard, santa clara, ca 95054 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 product. 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 speci cations or to discontinue any product or service without notice. except as provided in analogictech?s terms and conditions of sale, analogictech assumes no liability whatsoever, and analogictech disclaims any express or implied warranty relating to the sale and/or use of analogictech products including liability or warranties relating to tness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right . in order to minimize risks associated with the customer?s applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. testing and other quality control techniques are utilized to the extent analogictech deems necessary to support this warranty. speci c testing of all parameters of each device is not necessarily performed. analogictech and the analogictech logo are trademarks of advanced analogic technologies incorporated. all other brand and product names appearing in this document are registered trademarks or trademarks of their respective holders. ordering information package marking 1 part number (tape and reel) 2 tqfn34-24 4kxyy aat2861imk-1-t1 tqfn34-24 4lxyy AAT2861IMK-2-T1 tqfn34-24 4xxyy aat2861imk-3-t1 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/about/quality.aspx. package information tqfn34-24 3 3.000 0.050 4.000 0.050 top view bottom view side view detail ?a? 1.700 0.050 detail ?a? r(5x) index area 0.210 0.040 2.700 0.050 0 + 0.10 - 0.00 0.750 0.050 0.203 ref 0.400 bsc 0.400 0.050 all dimensions in millimeters. 1. xyy = assembly and date code. 2. sample stock is generally held on part numbers listed in bold. 3. the leadless package family, which includes qfn, tqfn, dfn, tdfn, and stdfn, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing process. a solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder c onnection.

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