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aat2833/34 240ma total display solution for portable devices 2833.2007.09.1.0 1 chargepump ? general description the aat2833/34 is a total solution ic for portable display applications. based on a tri-mode charge pump power engine, it is capable of delivering 240ma of output current for white led (wled) backlight and rgb applications. the high conver- sion efficiency and high level of integration make the aat2833/34 an optimal solution for battery life and size-critical applications. analogictech's as 2 cwire? (advanced simple serial control?) serial digital interface is used to enable, disable, and set current levels for all of the light emitting diodes (leds). each backlight chan- nel can be programmed to 16 levels of current, from a recommended maximum of 30ma programmed by the r bset resistor. the rgb module can be adjust- ed to 8 levels of current, up to a recommended max- imum of 60ma. the rgb module is programmable with up to 4096 (aat2833) or 64 (aat2834) color/intensity (brightness) combinations. the aat2833/34 is offered in a pb-free, thermally enhanced 24-pin 4x4x0.75mm tqfn package. applications ? digital still cameras ? lcd display modules ? mp3 players ? white led drivers ? wireless handsets features ? input supply voltage range: 2.7v to 5.5v ? tri-mode (1x/1.5x/2x) charge pump: delivers up to 240ma of output current switching frequency: up to 2mhz ? total display solution for rgb and backlight applications 6-channel backlight wled backlight ? user-programmable full-scale current, up to 30ma 3-channel rgb ? user-programmable full-scale output current/duty cycle ? aat2833: 4096 color/intensity combinations ? aat2834: 64 color/intensity combinations ? single-wire as 2 cwire serial interface for configuration/control eleven addressable registers fast, 1mhz serial interface ? true load disconnect in shutdown, i in < 1a ? built-in thermal protection ? built-in auto-disable for open led condition ? automatic soft-start minimizes inrush current ? available in 4x4x0.75mm tqfn44-24 package typical application c in 2.2f c out 2.2f c1 1f c2 1f in aat2833/34 pgnd en/set out as 2 cwire serial control v battery single-cell li+ c1+ c1- c2+ c2- bl1 rgb led rgb agnd r bset 280k bset bl3 bl4 bl2 bl5 bl 6
pin description pin configuration tqfn44-24 (top view) 1 3 2 5 4 6 18 16 17 14 15 13 10 11 12 8 9 7 19 21 20 23 22 24 bl3 bl2 bl1 agnd n/c en/set r g b c2+ c2- ou t c1- pgnd c1+ in n/c n/c n/c n/c bset bl6 bl5 bl4 pin # symbol function 1 bl3 power return (cathode) for backlight channel 3. if not used, connect to the out pin. 2 bl2 power return (cathode) for backlight channel 2. if not used, connect to the out pin. 3 bl1 power return (cathode) for backlight channel 1. if not used, connect to the out pin. 4 agnd signal ground. 5, 17, 18, 19, 20 n/c not connected. 6 en/set enable and as 2 cwire serial interface control input. 7 r power return (cathode) for red led of the rgb module. 8 g power return (cathode) for green led of the rgb module. 9 b power return (cathode) for blue led of the rgb module. 10 c2+ positive node of flying capacitor 2. 11 c2- negative node of flying capacitor 2. 12 out output voltage pin. connect to anode of all leds. 13 in input voltage pin. 14 c1+ positive node of flying capacitor 1. 15 c1- negative node of flying capacitor 1. 16 pgnd power ground. 21 bset maximum backlight current programming resistor input. ground this pin to use default values. 22 bl6 power return (cathode) for backlight channel 6. if not used, connect to the out pin. 23 bl5 power return (cathode) for backlight channel 5. if not used, connect to the out pin. 24 bl4 power return (cathode) for backlight channel 4. if not used, connect to the out pin. ep exposed pad (bottom); connect to gnd directly beneath the package. 2 2833.2007.09.1.0 aat2833/34 240ma total display solution for portable devices
aat2833/34 240ma total display solution for portable devices 2833.2007.09.1.0 3 1. stresses above those listed in absolute maximum ratings may cause damage to the device. functional operation at conditions o ther than the operating conditions specified is not implied. only one absolute maximum rating should be applied at any one time. 2. mounted on a demo board (fr4, in still air). absolute maximum ratings 1 t a = 25c, unless otherwise noted. thermal characteristics 2 recommended operating conditions symbol description value units t ambient temperature range -40 to +85 c symbol description value units ja maximum thermal resistance 50 c/w p d maximum power dissipation 2.0 w symbol description value units v n [out, in, bl1, bl2, bl3, bl4, bl5, bl6, r, g, b] to gnd -0.3 to 6.0 v v n [c1+, c2+] to gnd -0.3 to v out + 0.3 v v n [en/set, bset, c1-, c2-] to gnd -0.3 to v in + 0.3 v t j operating junction temperature range -40 to +150 c t lead maximum soldering temperature (at leads, 10 sec) 300 c
electrical characteristics 1 v in = 3.6v; c in = 4.7f; c1 = c2 = 1f; c out = 2.2f; t a = -40c to +85c, unless otherwise noted. typical values are t a = 25c. symbol description conditions min typ max units charge pump section v in in operating supply voltage range 2.7 5.5 v 1x mode, address = 0, data = 1, v en/set = v in 0.6 1.5x mode, address = 0, data = 1, i in in operating supply current v en/set = v in 4 ma 2x mode, address = 0, data = 1, v en/set = v in 5 1x ll mode, address = 3, data = 1, v en/set = v in 0.3 i shdn in shutdown current v en/set = 0v, t a = 25c 1 a i out out maximum output current 240 ma v th(hys) bl1-bl6, rgb charge pump 500 mv mode transition hysteresis v bset bset pin voltage 0.7 v f osc charge pump oscillator frequency 2 mhz t ss charge pump soft-start delay 200 s t sd over-temperature shutdown threshold 140 c t sd(hys) over-temperature shutdown hysteresis 15 c bl1-bl6 backlight led outputs i bl_(max) bl1-bl6 maximum current address = 0, data = 1, v in - v f = 1.5v 27 30 33 ma i bl bl1-bl6 current matching 2 address = 0, data = 1, v in - v f = 1.5v 1% v bl_(th) bl1-bl6 charge pump mode 100 mv transition threshold rgb led outputs i rgb_(max) r-g-b maximum current address = 12, data = 7, v in - v f = 1.5v 51 60 69 ma v rgb_(th) rgb charge pump mode 100 mv transition threshold 1. the aat2833/34 is guaranteed to meet performance specifications over the -40c to +85c operating temperature range and is assured by design, characterization, and correlation with statistical process controls. 2. current matching is defined as the deviation of any sink current from the average of all active channels. 4 2833.2007.09.1.0 aat2833/34 240ma total display solution for portable devices
aat2833/34 240ma total display solution for portable devices 2833.2007.09.1.0 5 electrical characteristics 1 v in = 3.6v; c in = 4.7f; c1 = c2 = 1f; c out = 2.2f; t a = -40c to +85c, unless otherwise noted. typical values are t a = 25c. symbol description conditions min typ max units en/set logic control v ens(l) en/set input low threshold voltage 0.4 v v ens(h) en/set input high threshold voltage 1.4 v i en/set en/set input leakage current -1 1 a t en/set _ lo en/set low time 0.3 75 s t en/set _ hi _ min minimum en/set high time 50 ns t en/set _ hi _ max maximum en/set high time 75 s t off en/set off timeout 500 s t lat en/set latch timeout 500 s
typical characteristics en/set high threshold voltage vs. input voltage input voltage (v) en/set high threshold (v) 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 -40c 25c 85c en/set low threshold voltage vs. input voltage input voltage (v) en/set low threshold (v) 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 -40c 25c 85c 1x mode hysteresis vs. current settings current setting (address 0, data #) hysteresis (mv) 0 50 100 150 200 250 300 350 400 450 500 2 4 6 8 10 12 14 16 bl1-bl6 mode transition threshold vs. current setting current setting (address 0, data #) threshold (mv) 0 20 40 60 80 100 120 140 2 4 6 8 10 12 14 1 6 aat2833 backlight section efficiency input voltage (v) efficiency (%) 30 40 50 60 70 80 90 100 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 30ma/channel 19ma/channel 2.1ma/channel backlight current matching vs. temperature temperature (c) led current (ma) 28 28.5 29 29.5 30 30.5 31 31.5 32 -40 -15 10 35 60 85 channel 4 channel 5 channel 6 channel 3 channel 2 channel 1 aat2833/34 240ma total display solution for portable devices 6 2833.2007.09.1.0
typical characteristics turn on to 2x mode backlight (30ma/channel; address 0, data 16; v in = 2.7v) time (200s/div) v blx (0.5v/div) v out (2v/div) v en/set (2v/div) i in (0.2a/div) turn off from 1.5x mode backlight (30ma/channel; address 0, data 16) time (100s/div) v diode (2v/div) v en/set (2v/div) i led (0.02a/div) turn on to 1x mode backlight (30ma/channel; address 0, data 16; v in = 4.4v) time (200s/div) v blx (0.5v/div) v out (2v/div) v en/set (2v/div) i in (0.1a/div) turn on to 1.5x mode backlight (30ma/channel; address 0, data 16; v in = 3.5v) time (200s/div) v blx (0.5v/div) v out (2v/div) v en/set (2v/div) i in (0.2a/div) en/set latch timeout vs. input voltage input voltage (v) t lat (s) 150 200 250 300 350 400 450 500 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5. 5 85c 25c -40c en/set off timeout vs. input voltage input voltage (v) t off (s) 150 200 250 300 350 400 450 500 550 600 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5. 5 -40c 25c 85c aat2833/34 240ma total display solution for portable devices 2833.2007.09.1.0 7
typical characteristics operating characteristics (v in = 3.4v; 1.5x mode; 30ma/channel; ac coupled) time (500ns/div) v out (100mv/div) i in (20ma/div) v in (100mv/div) operating characteristics (v in = 2.7v; 2x mode; 30ma/channel; ac coupled) time (500s/div) v out (100mv/div) i in (20ma/div) v in (100mv/div) aat2833/34 240ma total display solution for portable devices 8 2833.2007.09.1.0
aat2833/34 240ma total display solution for portable devices 2833.2007.09.1.0 9 functional description the aat2833/34 is a multi-functional power solu- tion for display systems in portable devices. it includes six individual channels for backlight white leds, and three individual channels for rgb leds. all of these functionalities are powered by a highly efficient tri-mode charge pump power engine that is capable of delivering 240ma of output current. the six backlight channels can be turned on or off all together, in two groups, or individually. the two- group operation allows leds to be turned on and off in for dual display applications: the main display (bl1-bl4) and sub-display (b5-b6). the individual on/off feature supports applications other than main/sub-display backlighting, such as keypad lighting. the maximum backlight current is pro- grammable with an external resistor, r bset . the rgb channels can be programmed with up to 4096 or 64 different combinations of colors and light- ing intensities (brightness). r, g, and b channels are individually controlled and can be used for alter- native functions, such as keyboard lighting, "fun" lighting, etc. as 2 cwire serial interface each current channel input on the aat2833/34 is controlled by analogictech's as 2 cwire serial digital interface. the as 2 cwire interface uses the number of rising edges on the en/set pin to address and load the led configuration registers. as 2 cwire latches data or addresses after the en/set pin has been held logic high for longer than t lat (500s). addresses and data are differentiated by the num- ber 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 signified by 17 rising edges, address 1 by 18 rising edges, address 2 by 19 rising edges, and so on. data is set to any num- ber of rising edges between 1 and including 16. a typical write protocol consist of the following: first a burst of en/set rising edges that identify/target a particular address followed by en/set being held logic high for the t lat timeout period to latch the address value in the registers, then another burst of rising edges that signify data with the accompanying t lat timeout period to latch the data value in the reg- isters. once an address is set, then multiple writes to the corresponding data register are allowed with- out having to write to the address for every change functional block diagram en/set bset bl6 c1C c1+ c2C c2+ out pgnd agnd in bl5 bl4 bl3 bl2 bl1 r g b as 2 cwire control dac rgb ref sub ref main ref tri-mode charge pump control v f monitoring 36
aat2833/34 240ma total display solution for portable devices 10 2833.2007.09.1.0 in data values. when en/set is held low longer than t off (500s), the aat2833/34 enters shutdown mode operation and draws less than 1a from the input supply voltage. data and address registers are cleared (reset to 0) in shutdown mode operation. table 1a contains the as 2 cwire serial interface address functionality when independent channel control is disabled (independent channel control is disabled by default) and conversely table 1b con- tains the as 2 cwire serial interface address function- ality when independent channel control is enabled. table 1a: as 2 cwire serial interface addressing with independent channel control disabled. table 1b: as 2 cwire serial interface addressing with independent channel control enabled. backlight current control (addresses 0-2) the six channel backlight inputs, bl1-bl6, can drive six individual leds to a maximum current of 30ma per channel. the en/set as 2 cwire serial interface enables all channels and sets the current magnitude as a percentage of the maximum cur- rent, programmed by an external resistor at bset (see figure 4). to set the backlight current (mini- mum to maximum current) of the main display leds (bl1-bl4), the user would write data to address 1. to set the backlight current for the sub display leds (bl5-bl6), the user would write data to address 2. to write to both main display and sub display leds (bl1-bl6) at the same time, the user would write to address 0. table 2a: addresses 0-2 with independent channel control disabled, backlight current level. table 2b: address 1 with independent channel control enabled, backlight current level. data bl % of bset data bl % of bset 10944 2211051 3221156 4251263 5291371 6321479 7351589 8 40 16 100 data bl % of bset data bl % of bset 10944 2211051 3221156 4251263 5291371 6321479 7351589 8 40 16 100 en/set rising address edges function 0 17 not applicable 1 18 backlight current bl1-bl6 2 19 bl1-bl4 on/off control 3 20 bl5-bl6 on/off control 7 24 red color 8 25 green color 9 26 blue color 10 27 rgb intensity 11 28 rgb mode 12 29 rgb current 15 32 not applicable en/set rising address edges function 0 17 backlight current bl1-bl6 1 18 main backlight current bl1-bl4 2 19 sub backlight current bl5-bl6 3 20 low backlight current 7 24 red color 8 25 green color 9 26 blue color 10 27 rgb intensity 11 28 rgb mode 12 29 rgb current 15 32 backlight independent channel control
figure 1: addresses 0-2 backlight current level. low backlight current (address 3) in addition to the current levels set by addresses 0, 1, and 2 (shown in table 2a and figure 1), there is also a low backlight current level that can be set. to set the low backlight current level, the user would write data to address 3, as shown in table 3. for example, to toggle between 1.7% and 25% of the maximum backlight current on all leds, write data = 14 to address 3 and data 4 to address 0. to set bl1- bl4 to 25% and bl5-bl6 to 0.2%, write data = 5 to address 3, and data = 4 to address 2. table 3: address 3 with independent channel control disabled, low-backlight current levels (r bset = 280k ). backlight independent channel control (address 15) the aat2833/34 can also individually control each backlight channel. this mode allows the user to turn on some or all of the channels in any desired com- bination. this control is achieved by changing the functionality of the as 2 cwire registers. to enable individual led control mode, a user would write data 8 to address 15. all channels that are enabled must carry the same current, which is set using the new functionality of address 1 (see table 2b). table 4: address 15, backlight independent channel control table 5: address 2 with independent channel control enabled, bl3-bl6 on/off control. data bl6 bl5 bl4 bl3 1 off off off off 2 off off off on 3 off off on off 4 off off on on 5 off on off off 6 off on off on 7 off on on off 8 off on on on 9 on off off off 10 on off off on 11 on off on off 12 on off on on 13 on on off off 14 on on off on 15 on on on off 16 on on on on data individual bl control 8on bl1-bl4 bl5-bl6 bl % data current on current on of bset 1no no 0 2no no 0 3no no 0 4no no 0 5 no yes 0.2 6 no yes 1.7 7 no yes 3.5 8 no yes 7.0 9 yes no 0.2 10 yes no 1.7 11 yes no 3.5 12 yes no 7.0 13 yes yes 0.2 14 yes yes 1.7 15 yes yes 3.5 16 yes yes 7.0 i bled (% of bset) data code 0 20 40 60 80 100 120 12345678910111213141516 2833.2007.09.1.0 11 aat2833/34 240ma total display solution for portable devices
aat2833/34 240ma total display solution for portable devices 12 2833.2007.09.1.0 table 6: address 3 with independent channel control enabled, bl1-bl2 on/off control. with independent channel control enabled, the functionality of addresses 1, 2, and 3 will conform to what is described in tables 2b, 5, and 6. also, addresses 0 and 15 are no longer applicable after independent channel control has been enabled. as indicated by the possible settings listed in the tables, any combination of backlight channels can be enabled and disabled. the original functionali- ties (sub backlight current bl5-bl6 and low backlight current) of addresses 2 and 3 are no longer available unless the internal state machine has been reset to default mode operation (when en/set is logic low for >500s). the functionality of addresses 7-12 are unmodified by the enabling of independent channel control. data bl2 bl1 1 off off 2 off off 3 off off 4 off off 5offon 6offon 7offon 8offon 9onoff 10 on off 11 on off 12 on off 13 on on 14 on on 15 on on 16 on on figure 2: as 2 cwire serial interface timing details. data 1 data 0 a ddress address t hi t lo t lat 1 2 17 18 1 2 . . . n 16 data 1 n 01 1 en/set
rgb control the red, green, and blue led pwm timing, along with the overall period, is controlled by five registers. the current level for the rgb leds is controlled by another register (address 12) which makes it possi- ble to change the peak currents from 33% up to 200% of the backlight maximum current set by r bset . a mode register (address 11) sets the method of update for the color and intensity regis- ters. all registers are updated simultaneously or indi- vidually, depending on how the mode register is set. if updated simultaneously, the color registers are updated when the period register is updated. up to 4096 different color/brightness combinations are pro- grammable in the aat2833 and 64 color/brightness combinations are programmable in the aat2834. address 7, 8, 9: rgb color registers the aat2833's rgb color registers store up to 16 levels of lighting intensity for a given color channel. the first level (data = 1) is reserved for the off-state. every setting thereafter increases the on-time of the respective led by 128s. the settings can be cal- culated as follows: where r, g, and b are the on-times of the respec- tive leds and data 7 , data 8 , and data 9 are the data inputs into registers 7, 8, and 9, respectively. data n can be set to a value from 1 to 16 with the default data n value equal to 1. since the aat2834 supports 64 color/brightness combinations, data n can be set from 1 to 4. address 10: rgb timebase register - t the overall period is set by the aat 2833/34's t reg- ister. adjusting this register allows a user to adjust how often the rgb led sequence is repeated. the longer the period, the smaller the effective duty cycle, and thus rgb light intensity (brightness) is reduced. the rgb period can be calculated using the follow- ing equation: where t is the period of repetition and data 10 is the data input into register 10. in the aat2833, data 10 can be set to a value from 1 to 16, with the default data 10 value equal to 1. in the aat2834, data 10 can be set from 1 to 4, with the default data 10 value equal to 1. please note that if the user sets the period to be smaller than the combined on-times (r+g+b), then the rgb sequence will automatically begin again once time t has been reached, whether or not all on-times have been completed. address 11: rgb mode register the aat2833/34 's rgb mode register can have one of two data 11 values. if data 11 is set to 1 (the default), then each rgb led on-time will be updat- ed immediately after their respective register is set. if data 11 is set to 2, then as the user sets the red, green, and blue on-time registers, none of the leds will be updated until the timebase register is set. for example, if the user wants to set a certain red-green-blue combinations, the red on-time can be programmed first, followed by the green on- time, followed by the blue on-time, and then the rgb period t last. if data 11 is set to 1, then after the red on-time is programmed the user will see the red led turn on immediately. after the green on-time is programmed, the red-green color com- binations will appear, etc. if data 11 is set to 2, then none of those intermediate colors will appear until the rgb period register t has been set and loaded. address 12: rgb current level register, i sink the i sink current level in the rgb led can be adjusted by writing data to register 12. the maxi- mum current is two times (200%) the maximum backlight current set by r bset (see table 7). by increasing or decreasing the current, the brightness level can easily be changed for any particular color combination. t = [(data 10 - 1) 3 + 15] 128s r = (data 7 - 1) 128s g = (data 8 - 1) 128s b = (data 9 - 1) 128s 2833.2007.09.1.0 13 aat2833/34 240ma total display solution for portable devices
aat2833/34 240ma total display solution for portable devices 14 2833.2007.09.1.0 figure 3: rgb diode current timing. i sink i sink red green blue r g i sink i sink b t table 7: address 12, rgb current level register (i sink ). rgb led current calculation the average current in a particular color channel is a function of the values in the r, g, b, t, and i sink registers, as follows: shutdown since the channel backlight power returns are the only power returns for all the leds, there is no leakage current if all channels are disabled. applying a high-to-low transition on the en/set pin and holding low for at least t off (500s) will activate the aat2833/34's shutdown mode. data and address registers are cleared (reset to 0) dur- ing shutdown. i r = i sink r t i g = i sink g t i b = i sink b t data rgb current as % of bset 10 233 366 4 100 5 133 6 167 7 200
applications information adjusting the maximum backlight led current level the value of r bset determines the maximum led current level for the backlight section. in the typical application, selecting r bset = 280k results in a maximum 30ma/channel led current level. the relationship between r bset and the maximum backlight current is illustrated graphically in figure 4. the aat 2833/34's led current control circuits have been optimized for full-scale current settings higher than 15ma, r bset > 550k . figure 4: maximum backlight led current vs r bset . device power efficiency the aat2833/34's power conversion efficiency depends on the charge pump mode of operation. by definition, device efficiency is expressed as the output power delivered to the leds divided by the total input power consumed. when the input voltage is sufficiently greater than the led forward voltages, the device optimizes efficiency by operating in 1x mode. in 1x mode, the device is working as a bypass switch and pass- ing the input supply directly to the output. by sim- plifying the conditions such that the leds have uni- form v f , the power conversion efficiency can be approximated by: due to the very low 1x mode quiescent current, the input current nearly equals the total output current delivered to the leds. further, the low resistance bypass switch introduces a negligible voltage drop from input to output. the aat2833/34 further maintains optimized per- formance and efficiency by detecting when the input voltage is not sufficient to sustain the led bias current. the device automatically switches to 1.5x mode when the input voltage drops too low in relation to the led forward voltages. in 1.5x mode, the output voltage can be boosted to 1.5x the input voltage. the 1.5x conversion ratio introduces a corresponding 0.5x 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 the led bias cur- rents, the aat2833/34 will automatically switch to 2x mode. in 2x mode, the output voltage can be boosted to 2x the input voltage. the 2x conversion ratio introduces a corresponding 1x increase in input current. for ideal conversion, the 2x mode efficiency is given by: = ; x = 1, 2, 3 or 4 and i in = 2(4 i ledx ) = 4 v ledx i ledx v in i in v ledx 2v in = = p leds p in v led1 i led1 + ... + v led4 i led4 v in i in = = p leds p in v led1 i led1 + ... + v led4 i led4 v in i in = = p leds p in v led1 i led1 + ... + v led4 i led4 v in i in = ; x = 1, 2, 3 or 4 and i in = 1.5(4 i ledx ) = 4 v ledx i ledx v in i in v ledx 1.5v in = ; x = 1, 2, 3 or 4 and i in = 4 i ledx = 4 v ledx i ledx v in i in v ledx v in = = p leds p in v led1 i led1 + ... + v led4 i led4 v in i in i bled (ma) r bset (k ) 0 5 10 15 20 25 30 35 40 45 100 200 300 400 500 600 700 800 900 1000 2833.2007.09.1.0 15 aat2833/34 240ma total display solution for portable devices
aat2833/34 240ma total display solution for portable devices 16 2833.2007.09.1.0 led selection the aat2833/34 is designed to drive high-intensity white leds. it is particularly suitable for leds with an operating forward voltage in the range of 4.2v to 1.5v. the aat2833/34 can also drive other loads that have similar characteristics to white leds. for var- ious load types, the aa t2833/34 provides a high current, programmable, ideal constant current channel/sink. capacitor selection careful selection of the four external capacitors c in , c1, c2, and c out are important because they will affect turn-on time, output ripple, and transient performance. optimum performance will be obtained when low equivalent series resistance (esr) ceramic capacitors are used. in general, low esr is defined as a resistance that is less than 100m . x7r and x5r ceramic capacitors are highly rec- ommended over all other types of capacitors for use with the aat2833/34. for the input (c in ) and output (c out ) capacitors, a 2.2f or greater value is recommended, and a 1f or greater value is rec- ommended for the flying (c1/c2) capacitors. 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 pcb footprint, and is non-polarized. low esr ceramic capacitors help maximize charge pump transient response. pcb layout to achieve adequate electrical and thermal per- formance, careful attention must be given to the printed circuit board (pcb) layout. in the worst-case operating condition, the chip must dissipate consid- erable power at full load. adequate heat-sinking must be achieved to ensure intended operation. figures 6 and 7 illustrate an example pcb layout. the bottom of the package features an exposed metal pad. the exposed pad acts, thermally, to transfer heat from the chip and, electrically, as a ground connection. the junction-to-ambient thermal resistance ( ja ) for the aat2833/34 package can be significantly reduced by following a couple of important pcb design guidelines. the pcb area directly under- neath the package should be plated so that the exposed pad can be mated to the top layer pcb copper during the reflow process. multiple copper plated thru-holes should be used to electrically and thermally connect the aat2833/34s exposed pad area to additional ground plane(s). the chip ground is internally connected to both the paddle and to the agnd and pgnd pins. it is good practice to connect the gnd pins to the exposed pad area with traces as shown in figure 5. the flying capacitors (c1 and c2), input capacitor (c4), and output capacitor (c3) should be connect- ed as close as possible to the ic. in addition to the external passive components being placed as close as possible to the ic, all traces connecting the aat2833/34 should be as short and wide as possible to minimize path resistance and potential coupling.
aat2833/34 240ma total display solution for portable devices 2833.2007.09.1.0 17 figure 5: aat2833/34 package pcb layout. evaluation board layout figure 6: aat2833/34 evaluation board figure 7: aat2833/34 evaluation board component side layout. solder side layout. pin #1
aat2833/34 240ma total display solution for portable devices 18 2833.2007.09.1.0 evaluation board schematic figure 8: aat2833/34 evaluation board schematic. figure 9: aat2833/34 microcontroller section schematic. vdd 1 gp5 2 gp4 3 gp3 4 gp2 5 gp1 6 gp0 7 vss 8 pic12f675 u2 c6 1f r6 330 led7 red j2 100k r8 220 r7 sw1 sw2 sw3 sw4 sw5 1k r1 vin en vin 1k r2 1k r3 1k r4 1k r5 1.0f c1 1.0f c2 2.2f c3 c4 4.7f d1 d2 d3 d4 d5 d6 vout 280k r9 bl3 1 bl4 24 bl2 2 bl1 3 agnd 4 n/c 5 en/set 6 r 7 g 8 b 9 c2+ 10 c2- 11 out 12 vin 13 c1+ 14 c1- 15 pgnd 16 n/c 17 n/c 18 n/c 19 n/c 20 bset 21 bl6 22 bl5 23 aa t2833 u1 3 4 rgb en dc+ j1 r9 = 280k for 30ma/chnl backlight. b g r optional footprints for auxiliary lighting leds . c7 optional 100f lab supply bypass vin
aat2833/34 240ma total display solution for portable devices 2833.2007.09.1.0 19 options ordering information 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. package marking 1 part number (tape and reel) 2 tqfn44-24 svxyy AAT2833IBK-T1 tqfn44-24 aat2834ibk-t1 3 option flash backlight rgb package function aat2833 n y y tqfn44-24 backlight plus 4096-combination rgb aat2834 3 n y y tqfn44-24 backlight plus 64-combination rgb 1. xyy = assembly and date code. 2. sample stock is generally held on part numbers listed in bold . 3. contact factory for aat2834 availability.
package information tqfn44-24 all dimensions in millimeters. 4.000 0.050 2.700 0.050 pin 1 dot by marking 4.000 0.050 2.700 0.050 0.214 0.036 0.500 bsc 0.400 0.050 0.750 0.050 0.255 0.025 pin 1 identification chamfer 0.300 45 1 top view bottom view side view 0.000 ? 0.050 ? 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 specifications or to discontinue any product or service with- out notice. except as provided in analogictechs terms and conditions of sale, analogictech assumes no liability whatsoever, an d analogictech disclaims any express or implied war- ranty relating to the sale and/or use of analogictech products including liability or warranties relating to fitness for a part icular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. in order to minimize risks associated with the customers applications, adequa te 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 an alogictech deems necessary to support this warranty. specific testing of all parameters of each device is not necessarily performed. analogictech and the analogictech logo are trad emarks of advanced analogic technologies incorporated. all other brand and product names appearing in this document are registered trademarks or trademarks of their respective holder s. advanced analogic technologies, inc. 3230 scott boulevard, santa clara, ca 95054 phone (408) 737- 4600 fax (408) 737- 4611 20 2833.2007.09.1.0 aat2833/34 240ma total display solution for portable devices

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