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aat1232 24v 100ma step-up converter 1232.2006.12.1.3 1 switchreg ? general description the aat1232 is a high frequency, high efficiency boost converter capable of 24v maximum output voltage. the internal power switch can deliver 100ma load current. it is the ideal power solution to power oled, lcd, and ccd applications operat- ing from a single cell lithium-ion battery. the high switching frequency (up to 2mhz) pro- vides fast response to load transients with small external components. the fully integrated control ic simplifies the design while reducing the total pcb footprint. the aat1232 offers a true load dis- connect feature which isolates the load from the power source when en/set is pulled low. this eliminates leakage current and maintains zero volt- age at the output while disabled. the output voltage can be dynamically set by acti- vating one of two reference levels (fb1 or fb2) through the sel logic pin. optionally, analogictech?s simple serial control? (s 2 cwire?) interface pro- vides dynamic programmability across a wide output voltage range through the en/set pin. the aat1232 is available in a pb-free, thermally- enhanced 16-pin 3x4mm tdfn low-profile pack- age or a pb-free 12-pin tsopjw package. features ?v in range: 2.7v to 5.5v ? maximum output: 24v @ 100ma ? true load disconnect ? dynamic voltage control options ? hysteretic control ? no external compensation components ? excellent load transient response ? high efficiency at light load ? up to 2mhz switching frequency ? ultra-small inductor and capacitors ? integrated low r ds(on) mosfet switches ? up to 85% efficiency ? <1a shutdown current ? integrated soft start ? cycle-by-cycle current limit ? short-circuit, over-temperature protection ? available in tsopjw-12 or tdfn34-16 package ? -40c to +85c temperature range applications ? ccd bias circuit ? digital still cameras ? lcd bias circuit ? mobile handsets ? mp3 players ? oled displays ? pdas and notebook pcs typical application lin en/set pgnd vp c 1 2.2f l 1 2.2h d 1 schottky r 1 576k r 2 10.0k c 2 2.2f, 25v r 3 20.0k input: 2.7v~5.5v aat1232 sw fb1 fb2 sel 24v @ 100ma vin gnd
pin descriptions pin configuration tsopjw-12 tdfn34-16 (top view) (top view) pin # tsopjw-12 tdfn34-16 symbol function 1 15, 16 vp input power pin; connected to the source of the p-channel mosfet. connect a 2.2f or larger capacitor from these pins to pgnd. 2 14 en/set ic active high enable pin. alternative input pin for s 2 cwire control uti- lizing fb2 reference. 3 13 sel logic high selects fb1 high output reference; logic low selects fb2 low output reference. pull low for s 2 cwire control. see tables 1 and 2. 4 12 vin input voltage for the converter. connect this pin directly to the vp pin. 5 11 n/c no connection. do not make any connection to this pin. 6, 7 9, 10 sw boost converter switching node. connect the power inductor between the sw pin and the lin pin. 8 6, 7, 8 pgnd power ground for the boost converter; connected to the source of the internal n-channel mosfet. connect input and output capacitor returns to pgnd. 9 5 gnd ground pin. 10 4 fb2 feedback pin for low output voltage set point. pin set to 0.6v when sel is low and disabled when sel is high. voltage is set from 0.6v to 1.2v using s 2 cwire control. 11 3 fb1 feedback pin for high output voltage set point. pin set to 1.2v when sel is high and disabled when sel is low. disabled with s 2 cwire control. 12 1, 2 lin switched power input. connected to the power inductor. n/a ep exposed paddle (bottom). internally connected to sw. may be exter- nally connected to sw pins or left floating. do not connect to gnd or pgnd. aat1232 24v 100ma step-up converter 2 1232.2006.12.1.3 fb1 fb2 gnd lin lin 3 pgnd pgnd pgnd en/set sel vin vp vp n/c sw sw 4 5 1 2 6 7 8 14 13 12 16 15 11 10 9 1 2 3 4 5 6 12 11 10 9 8 7 vp en/set sel vin n/c sw lin fb1 fb2 gnd pgnd sw
absolute maximum ratings 1 t a = 25c, unless otherwise noted. recommended operating conditions symbol description value units ja thermal resistance tdfn34-16 44 c/w tsopjw-12 160 p d maximum power dissipation (t a = 25oc) tdfn34-16 2270 mw tsopjw-12 625 t j operating temperature range -40 to 150 c symbol description value units v in , v p input voltage -0.3 to 6.0 v sw switching node 28 v l in , en/set, maximum rating v in + 0.3 v sel, fb1, fb2 t j operating temperature range -40 to 150 c t s storage temperature range -65 to 150 c t lead maximum soldering temperature (at leads, 10 sec) 300 c aat1232 24v 100ma step-up converter 1232.2006.12.1.3 3 1. stresses above those listed in absolute maximum ratings may cause permanent damage to the device. functional operation at c ondi- tions other than the operating conditions specified is not implied. only one absolute maximum rating should be applied at any one time.
electrical characteristics 1 t a = -40c to +85c, unless otherwise noted. typical values are t a = 25c, v in = 3.6v. symbol description conditions min typ max units power supply v in input voltage range 2.7 5.5 v v out(max) maximum output voltage 24 v v in rising 2.7 v v uvlo uvlo threshold hysteresis 150 mv v in falling 1.8 v sel = gnd, v out = 18v, 0.3 ma i q quiescent current i out = 0, r3 = 20k 2 , switching sel = gnd, fb2 = 1.5v, 40 70 a not switching i shdn v in pin shutdown current en/set = gnd 1.0 a i out output current 2.7v < v in < 5.5v, v out = 24v 100 ma fb1 fb1 reference voltage i out = 0 to 100ma, v in = 2.7v 1.164 1.2 1.236 v to 5.0v, sel = high fb2 fb2 reference voltage i out = 0 to 100ma, v in = 2.7v 0.582 0.6 0.618 v to 5.0v, sel = low v loadreg load regulation i out = 0 to 100ma, r3 = 20k 3 0.02 %/ma v linereg / v in line regulation v in = 2.7v to 5.5v, r3 = 20k 3 0.6 %/v r ds(on)l low side switch on resistance 0.08 r ds(on)in input disconnect switch 0.18 on resistance t ss soft-start time from enable to output 0.35 ms regulation; v out = 15v t sd over-temperature shutdown 140 c threshold t hys shutdown hysteresis 15 c i lim n-channel current limit v in = 3.6v 3.0 a sel, en/set v sel(l) sel threshold low v in = 2.7v 0.4 v v sel(h) sel threshold high v in = 5.5v 1.4 v v en/set(l) enable threshold low v in = 2.7v 0.4 v v en/set(h) enable threshold high v in = 5.5v 1.4 v t en/set lo en/set low time 0.3 75 s t en/set hi min minimum en/set high time 50 ns t en/set hi max maximum en/set high time 75 s t off en/set off timeout 500 s t lat en/set latch timeout 500 s i en/set en/set input leakage -1 1 a aat1232 24v 100ma step-up converter 4 1232.2006.12.1.3 1. the aat1232 is guaranteed to meet performance specifications over the -40c to +85c operating temperature range and is assu red by design, characterization, and correlation with statistical process controls. 2. switching input current will vary with r1, r2, r3 resistor values. 3. some improvement in line and load regulation is possible with smaller resistor values.
typical characteristics aat1232 24v 100ma step-up converter 1232.2006.12.1.3 5 output error vs. output current (v out = 24v; r3 = 20k ) output current (ma) output error (%) v in = 2.7v -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 0.1 1 10 100 v in = 5v v in = 3.6v v in = 4.2v efficiency vs. output current (v out = 24v; r3 = 20k ) output current (ma) efficiency (%) 20 30 40 50 60 70 80 90 0.1 1 10 100 v in = 5v v in = 4.2v v in = 3.6v output error vs. output current (v out = 20v; r3 = 20k ) output current (ma) output error (%) -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 0.1 1 10 100 v in = 5v v in = 4.2v v in = 3.6v v in = 2.7v efficiency vs. output current (v out = 20v; r3 = 20k ) output current (ma) efficiency (%) 20 30 40 50 60 70 80 90 0.1 1 10 100 v in = 5v v in = 4.2v v in = 3.6v output error vs. output current (v out = 18v; r3 = 20k ) output current (ma) output error (%) -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 0.1 1 10 100 v in = 5v v in = 4.2v v in = 3.6v v in = 2.7v efficiency vs. output current (v out = 18v; r3 = 20k ) output current (ma) efficiency (%) 20 30 40 50 60 70 80 90 0.1 1 10 100 v in = 5v v in = 4.2v v in = 3.6v
typical characteristics aat1232 24v 100ma step-up converter 6 1232.2006.12.1.3 output ripple (v in = 4.2v; v out = 18v; no load) output voltage (top) (v) inductor current (bottom) (a) time (100s/div) 17.0 17.2 17.4 17.6 17.8 18.0 18.2 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 output ripple (v in = 4.2v; v out = 18v; i out = 100ma) output voltage (top) (v) inductor current (bottom) (a) time (500ns/div) 17.0 17.2 17.4 17.6 17.8 18.0 18.2 -1.0 0.0 1.0 2.0 3.0 4.0 5.0 no load input current vs. temperature (v in = 3.6v; v out = 18v) temperature ( c) supply current (ma) 0.0 0.2 0.3 0.5 0.6 0.8 0.9 1.1 1.2 -40 -15 10 35 60 85 no load quiescent current vs. input voltage (v out = 18v; en_high) input voltage (v) supply current (ma) 0.08 0.12 0.16 0.2 0.24 0.28 0.32 0.36 0.4 2.5 3 3.5 4 4.5 5 5.5 output voltage error vs. temperature (v in = 5v; v out = 18v; i out = 100ma) temperature ( c) output error (%) -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 -40 -15 10 35 60 85 line regulation (v out = 18v; r3 = 20k ) input voltage (v) accuracy (%) -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 2.5 3 3.5 4 4.5 5 5.5 6
typical characteristics aat1232 24v 100ma step-up converter 1232.2006.12.1.3 7 load transient response (v in = 3.6v; i out = 20ma?60ma; v out = 12v) output voltage (v) (top) inductor current (a) (bottom) time (200s/div) 11.80 11.85 11.90 11.95 12.00 12.05 12.10 -0.30 0.00 0.30 0.60 0.90 1.20 1.50 load transient response (v in = 4.2v; i out = 20ma?60ma; v out = 18v) output voltage (v) (top) inductor current (a) (bottom) time (200s/div) 17.80 17.85 17.90 17.95 18.00 18.05 18.10 -0.3 0.0 0.3 0.6 0.9 1.2 1.5 soft start (v in = 3.6v; c in = 2.2f; i out = 100ma; v out = 12v) enable voltage (middle) (v) output voltage (top) (v) input current (bottom) (a) time (200s/div) -16 -12 -8 -4 0 4 8 12 16 -0.4 0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 n-channel r ds(on) vs. input voltage input voltage (v) r ds(on) (m ) 40 60 80 100 120 140 160 2.5 3 3.5 4 4.5 5 5.5 6 120 c 100 c 25 c 85 c p-channel r ds(on) vs. input voltage input voltage (v) r ds(on) (m ) 140 160 180 200 220 240 260 280 300 2.5 3 3.5 4 4.5 5 5.5 6 120 c 100 c 25 c 85 c
aat1232 24v 100ma step-up converter 8 1232.2006.12.1.3 functional block diagram functional description the aat1232 consists of a dc/dc boost controller, an integrated slew rate controlled input disconnect mosfet switch, and a mosfet power switch. a high voltage rectifier, power inductor, output capac- itor, and resistor divider network are required to implement a dc/dc boost converter. control loop the aat1232 provides the benefits of current mode control with a simple hysteretic feedback loop. the device maintains exceptional dc regulation, tran- sient response, and cycle-by-cycle current limit with- out additional compensation components. the aat1232 modulates the power mosfet switching current in response to changes in output voltage. this allows the voltage loop to directly program the required inductor current in response to changes in the output load. the switching cycle initiates when the n-channel mosfet is turned on and current ramps up in the inductor. the on interval is terminated when the inductor current reaches the programmed peak current level. during the off interval, the input current decays until the lower threshold, or zero inductor current, is reached. the lower current is equal to the peak current minus a preset hystere- sis threshold - which determines the inductor ripple current. the peak current is adjusted by the con- troller until the output current requirement is met. control v ref output output timer select fb1 fb2 sel en/set vp lin vin s w pgnd gnd 1.2v
aat1232 24v 100ma step-up converter 1232.2006.12.1.3 9 the magnitude of the feedback error signal deter- mines the average input current. therefore, the aat1232 controller implements a programmed current source connected to the output capacitor and load resistor. there is no right-half plane zero, and loop stability is easily achieved with no addi- tional compensation components. increased load current results in a drop in the out- put feedback voltage (fb1 or fb2) sensed through the feedback resistors (r1, r2, r3). the controller responds by increasing the peak inductor current, resulting in higher average current in the inductor. alternatively, decreased output load results in an increase in the output feedback voltage (fb1 or fb2 pin). the controller responds by decreasing the peak inductor current, resulting in lower aver- age current in the inductor. at light load, the inductor off interval current goes below zero and the boost converter enters discon- tinuous mode operation. further reduction in the load results in a corresponding reduction in the switching frequency. aat1232 pulsed frequency operation reduces switching losses and maintains high efficiency at light loads. operating frequency varies with changes in the input voltage, output voltage, and inductor size. once the boost converter has reached continuous mode, further increases in the output load will not significantly increase the operating frequency. a small 2.2h (20%) inductor is selected to maintain high frequency switching (up to 2mhz) and high efficiency operation for outputs from 10v to 24v. output voltage programming the output voltage may be programmed through a resistor divider network located from output capaci- tor to fb1/fb2 pins to ground. pulling the sel pin high activates the fb1 pin which maintains a 1.2v reference voltage, while the fb2 reference is dis- abled. pulling the sel pin low activates the fb2 pin which maintains a 0.6v reference, while the fb1 reference is disabled. this function allows dynam- ic selection between two distinct output voltages across a 2x range (maximum). an additional resis- tor between fb1 and fb2 allows the designer to program the outputs across a reduced <2x range. alternatively, the output voltage may be pro- grammed to any of 16 voltage levels using the s 2 cwire serial digital input. the single wire s 2 cwire interface provides high-speed output volt- age programmability across a 2x output voltage range. s 2 cwire functionality is enabled by pulling the sel pin low and providing s 2 cwire input to the en/set pin. table 2 details the fb2 reference voltage versus s 2 cwire rising edges. soft start / enable the input disconnect switch is activated when a valid input voltage is present and the en/set pin is pulled high. the slew rate control on the p-chan- nel mosfet ensures minimal inrush current as the output voltage is charged to the input voltage, prior to switching of the n-channel power mos- fet. monotonic turn-on is guaranteed by the built- in soft-start circuitry. soft-start eliminates output voltage overshoot across the full input voltage range and all loading conditions. current limit and over-temperature protection the switching of the n-channel mosfet termi- nates when current limit of 3.0a (typical) is exceed- ed. this minimizes power dissipation and compo- nent stresses under overload and short-circuit con- ditions. switching resumes when the current decays below the current limit. thermal protection disables the aat1232 when internal dissipation becomes excessive. thermal protection disables both mosfets. the junction over-temperature threshold is 140c with 15c of temperature hysteresis. once an over-temperature or over-current fault condition is removed, the output voltage automatically recovers. under-voltage lockout internal bias of all circuits is controlled via the v in input. under-voltage lockout (uvlo) guarantees sufficient v in bias and proper operation of all inter- nal circuitry prior to activation.
aat1232 24v 100ma step-up converter 10 1232.2006.12.1.3 application information selecting dc/dc boost capacitors the high output ripple inherent in the boost con- verter necessitates low impedance output filtering. multi-layer ceramic (mlc) capacitors provide small size and adequate capacitance, low parasitic equivalent series resistance (esr) and equivalent series inductance (esl), and are well suited for use with the aat1232 boost regulator. mlc capac- itors of type x7r or x5r are recommended to ensure good capacitance stability over the full operating temperature range. the output capacitor is sized to maintain the output load without significant voltage droop during the power switch on interval, when the output diode is not conducting. a ceramic output capacitor from 2.2f to 4.7f is recommended. typically, 25v rated ceramic capacitors are required for the 24v boost output. ceramic capacitors sized as small as 0805 are available which meet these requirements. mlc capacitors exhibit significant capacitance reduction with applied voltage. output ripple measurements should confirm that output voltage droop is acceptable. the boost converter input current flows during both on and off switching intervals. the input ripple current is less than the output ripple and, as a result, less input capacitance is required. a ceramic output capacitor from 1f to 3.3f is recommended. minimum 6.3v rated ceramic capacitors are required at the input. ceramic capacitors sized as small as 0603 are available which meet these requirements. large capacitance tantalum or solid-electrolytic capacitors may be necessary to meet stringent out- put ripple and transient load requirements. these can replace (or be used in parallel with) ceramic capacitors. both tantalum and oscon-type capac- itors are suitable due to their low esr and excellent temperature stability (although they exhibit much higher esr than mlc capacitors). aluminum-elec- trolytic types are less suitable due to their high esr characteristics and temperature drift. unlike mlc capacitors, these types are polarized and proper orientation on input and output pins is required. 30% to 70% voltage derating is recommended for tantalum capacitors. selecting the output diode to ensure minimum forward voltage drop and no recovery, high voltage schottky diodes are consid- ered the best choice for the aat1232 boost convert- er. the aat1232 output diode is sized to maintain acceptable efficiency and reasonable operating junction temperature under full load operating condi- tions. forward voltage (v f ) and package thermal resistance ( ja ) are the dominant factors to consider in selecting a diode. the diode's published current rating may not reflect actual operating conditions and should be used only as a comparative measure between similarly rated devices. 20v rated schottky figure 1: aat1232 demo board schematic. lin 12 fb1 11 fb2 10 gnd 9 pgnd 8 sw 7 sw 6 n/c 5 vin 4 sel 3 en/set 2 vp 1 u1 1 2 3 jp1 1 2 3 jp2 r3 20k vout vin r4 10k u1 aat1232 tsopjw12 c1 10v 0805 2.2f c2 25v 0805 2.2f d1 30v 0.5a mbr0530t sod-123 l1 2.2h nr4018t2r2 r1 576k 0603 r2, r4 10k 0603 r3 20k 0603 c2 2.2 f c1 2.2f d1 schottky l1 2.2h r1 576k r2 10k enable select
aat1232 24v 100ma step-up converter 1232.2006.12.1.3 11 diodes are recommended for outputs less than 15v, while 30v rated schottky diodes are recommended for outputs greater than 15v. the average diode current is equal to the output current. the average output current multiplied by the for- ward diode voltage determines the loss of the out- put diode. diode junction temperature can be estimated. the junction temperature should be maintained below 110oc, but may vary depending on applica- tion and/or system guidelines. the diode ja can be minimized with additional pcb area on the cathode. pcb heatsinking the anode may degrade emi performance. the reverse leakage current of the rectifier must be considered to maintain low quiescent (input) cur- rent and high efficiency under light load. the recti- fier reverse current increases dramatically at high temperatures. selecting the boost inductor the aat1232 controller utilizes hysteretic control and the switching frequency varies with output load and input voltage. the value of the inductor deter- mines the maximum switching frequency of the aat1232 boost converter. increased output induc- tance decreases the switching frequency, resulting in higher peak currents and increased output volt- age ripple. to maintain 2mhz maximum switching frequency, an output inductor sized from 1.5h to 2.7h is recommended. the switching period is divided between on and off time intervals. the on time is the period which the n-channel power mosfet is conducting and storing energy in the boost inductor. duty cycle is defined as the on time divided by the total switching interval. the maximum duty cycle can be estimated from the relationship for a continuous mode boost con- verter. maximum duty cycle (d max ) is the duty cycle at minimum input voltage (v in(min) ). where v f is the schottky diode forward voltage and can be estimated at 0.5v. manufacturer?s specifications list both the inductor dc current rat- ing, which is a thermal limitation, and peak inductor current rating, which is determined by the satura- tion characteristics. measurements at full load and high ambient temperature should be completed to ensure that the inductor does not saturate or exhib- it excessive temperature rise. the output inductor (l) is selected to avoid satura- tion at minimum input voltage, maximum output load conditions. peak current may be calculated from the following equation, again assuming continuous con- duction mode. worst-case peak current occurs at minimum input voltage (maximum duty cycle) and maximum load. switching frequency can be estimat- ed at 500khz with a 2.2h inductor. the rms current flowing through the boost induc- tor is equal to the dc plus ac ripple components. under worst-case rms conditions, the current waveform is critically continuous. the resulting i out (1 - d max ) d max v in(min) (2 f s l) i peak = + (v out + v f - v in(min) ) (v out + v f ) d max = t on t on + t off d = = t on ? f s = t on + t off 1 f s t j = t amb + ja p loss_diode p loss_diode = i avg v f = i out v f i avg = i out
aat1232 24v 100ma step-up converter 12 1232.2006.12.1.3 rms calculation yields worst-case inductor loss. the rms value should be compared against the manufacturer's temperature rise, or thermal derat- ing, guidelines. for a given inductor type, smaller inductor size leads to an increase in dcr winding resistance and, in most cases, increased thermal impedance. winding resistance degrades boost converter efficiency and increases the inductor operating temperature. to ensure high reliability, the inductor temperature should not exceed 100oc. manufacturer's recom- mendations should be consulted. in some cases, pcb heatsinking applied to the aat1232 l in node (non-switching) can improve the inductor's thermal capability. pcb heatsinking may degrade emi per- formance when applied to the sw node (switching) of the aat1232. shielded inductors provide decreased emi and may be required in noise sensitive applications. unshielded chip inductors provide significant space savings at a reduced cost compared to shielded (wound and gapped) inductors. chip-type induc- tors have increased winding resistance when com- pared to shielded, wound varieties. setting the output voltage the output voltage may be programmed through a resistor divider network located from the output to fb1 and fb2 pins to ground. pulling the sel pin high activates the fb1 pin which maintains a 1.2v reference voltage, while the fb2 reference is dis- abled. pulling the sel pin low activates the fb2 pin which maintains a 0.6v reference, while the fb1 reference is disabled. the aat1232 output voltage can be programmed by one of three methods. first, the output voltage can be static by pulling the sel logic pin either high or low. second, the output voltage can be dynam- ically adjusted between two pre-set levels within a 2x operating range by toggling the sel logic pin. third, the output can be dynamically adjusted to any of 16 preset levels within a 2x operating range using the integrated s 2 cwire single wire interface via the en/set pin. option 1: static output voltage a static output voltage can be configured by pulling the sel either high or low. sel pin high activates the fb1 reference pin to 1.2v (nominal). alternatively, the sel pin is pulled low to activate the fb2 refer- ence at 0.6v (nominal). table 1 provides details of resistor values for common output voltages from 10v to 24v for sel = high and sel = low options. in the static configuration, the fb1 pin should be directly connected to fb2. the resistor between fb1 and fb2 pins is not required. option 2: dynamic voltage control using sel pin the output may be dynamically adjusted between two output voltages by toggling the sel logic pin. output voltages v out(1) and v out(2) correspond to the two output references, fb1 and fb2. pulling the sel logic pin high activates v out(1) , while pulling the sel logic pin low activates v out(2) . the minimum output voltage must be greater than the specified maximum input voltage plus margin to maintain proper operation of the aat1232 boost converter. in addition, the ratio of output voltages v out(2) /v out(1) is always less than 2.0, correspon- ding to a 2x (maximum) programmable range. table 1 is provided to allow programming of com- mon output voltages using option 1 or 2. the feed- back references fb1 and fb2 are enabled or dis- abled using the sel logic pin, corresponding to v out(1) and v out(2) . option 3: dynamic voltage control using s 2 cwire interface the output can be dynamically adjusted by the host controller to any of 16 pre-set output voltage levels using the integrated s 2 cwire interface. the en/set pin serves as the s 2 cwire interface input. the sel pin must be pulled low when using the s 2 cwire interface. p loss_inductor = i rms 2 dcr i peak i rms = 3
aat1232 24v 100ma step-up converter 1232.2006.12.1.3 13 s 2 cwire serial interface analogictech's s 2 cwire serial interface is a propri- etary high-speed single-wire interface available only from analogictech. the s 2 cwire interface records rising edges of the en/set input and decodes into 16 different states. each state corre- sponds to a voltage setting on the fb2 pin. s 2 cwire serial interface timing the s 2 cwire serial interface has flexible timing. data can be clocked-in at speeds up to 1mhz. after data has been submitted, en/set is held high to latch the data for a period t lat . the output is sub- sequently changed to the predetermined voltage. when en/set is set low for a time greater than t off , the aat1232 is disabled. when disabled, the register is reset to the default value, which sets the fb2 pin to 0.6v if en is subsequently pulled high. table 2: s 2 cwire voltage control settings (sel = low). en/set fb2 en/set fb2 rising reference rising reference edges voltage (v) edges voltage (v) 1 0.60 (default) 9 0.92 2 0.64 10 0.96 3 0.68 11 1.00 4 0.72 12 1.04 5 0.76 13 1.08 6 0.80 14 1.12 7 0.84 15 1.16 8 0.88 16 1.20 table 1: sel pin voltage control resistor values (1% resistor tolerance). v out v out r3 = 4.99k r3 = 20.0k (sel = high) (sel = low) r1 (k ) r2 (k ) r1 (k ) r2 (k ) 10.0 - 36.5 0 147 0 12.0 - 44.2 0 182 0 15.0 - 57.6 0 232 0 16.0 - 61.9 0 249 0 18.0 - 69.8 0 280 0 20.0 - 78.7 0 316 0 24.0 - 95.3 0 383 0 - 10.0 78.7 0 316 0 - 12.0 95.3 0 383 0 - 15.0 121 0 487 0 - 16.0 127 0 511 0 - 18.0 143 0 590 0 - 20.0 162 0 649 0 - 24.0 196 0 787 0 12.0 10.0 75.0 3.32 301 13.0 15.0 10.0 76.8 1.65 309 6.65 16.0 10.0 76.8 1.24 309 4.99 18.0 10.0 78.7 0.562 316 2.21 15.0 12.0 90.9 3.01 374 12.1 16.0 12.0 93.1 2.49 374 10.0 18.0 12.0 93.1 1.65 374 6.65 18.0 15.0 115 3.32 464 13.3 20.0 15.0 118 2.49 475 10.0 24.0 15.0 118 1.24 475 4.99 24.0 18.0 143 2.49 576 10.0
aat1232 24v 100ma step-up converter 14 1232.2006.12.1.3 s 2 cwire output voltage programming the aat1232 is programmed through the s 2 cwire interface according to table 2. the rising clock edges received through the en/set pin determine the feedback reference and output voltage set- point. upon power up with the sel pin low and prior to s 2 cwire programming, the default feed- back reference voltage is set to 0.6v. pcb layout guidelines boost converter performance can be adversely affected by poor layout. possible impact includes high input and output voltage ripple, poor emi per- formance, and reduced operating efficiency. every attempt should be made to optimize the layout in order to minimize parasitic pcb effects (stray resistance, capacitance, inductance) and emi cou- pling from the high frequency sw node. a suggested pcb layout for the aat1232 boost converter is shown in figures 4 and 5. the follow- ing pcb layout guidelines should be considered: 1. minimize the distance from capacitor c1 and c2 negative terminal to the pgnd pins. this is especially true with output capacitor c2, which conducts high ripple current from the output diode back to the pgnd pins. 2. place the feedback resistors close to the output terminals. route the output pin directly to resis- tor r1 to maintain good output regulation. r3 should be routed close to the output gnd pin. 3. minimize the distance between l1 to d1 and switching pin sw; minimize the size of the pcb area connected to the sw pin. 4. maintain a ground plane and connect to the ic rtn pin(s) as well as the gnd terminals of c1 and c2. 5. consider additional pcb area on d1 cathode to maximize heatsinking capability. this may be necessary when using a diode with a high thermal resistance. 6. when using the tdfn34-16 package, connect paddle to sw pin or leave floating. do not con- nect to rtn/gnd conductors. figure 4: aat1232 evaluation board figure 5: aat1232 evaluation board top side. bottom side. figure 3: s 2 cwire timing diagram to program the output voltage. 1 en/set 2 n-1 n 16 data reg 0n-1 0 t hi t lo t lat t off
aat1232 24v 100ma step-up converter 1232.2006.12.1.3 15 table 3: typical surface mount schottky rectifiers for various output loads. (select t j < 110 c in application circuit). table 4: typical surface mount inductors for various output loads (select i peak < i sat ). table 5: typical surface mount capacitors for various output loads. value voltage footprint manufacturer part number type (f) (v) temp. co. lxwxh (mm) murata grm188r60j475ke19d ceramic 2.2 6.3 x5r 0603 murata grm188r61a225ke34d ceramic 2.2 10 x5r 0603 murata grm188r61c225ka88 ceramic 2.2 16 x5r 0805 murata grm21br61e225ka12l ceramic 2.2 25 x5r 0805 murata grm188r61e105ka12d ceramic 1.0 25 x5r 0603 inductance max dc i sat dcr size (mm) manufacturer part number (h) current (a) ( ) lxwxh type sumida cdrh4d22/hp-2r2 2.2 2.50 35 5.0x5.0x2.4 shielded sumida cdr4d11/hp-2r4 2.4 1.70 105 4.8x4.8x1.2 shielded sumida cdrh4d18-2r2 2.2 1.32 75 5.0x5.0x2.0 shielded murata lqh662n2r2m03 2.2 3.30 19 6.3x6.3x4.7 shielded murata lqh55dn2r2m03 2.2 3.20 29 5.0x5.7x4.7 non-shielded taiyo yuden nr4018t2r2 2.2 2.70 60 4.0x4.0x1.8 shielded taiyo yuden nr3015t2r2 2.2 1.48 60 3.0x3.0x1.5 shielded coiltronics sd3814-2r2 2.2 1.90 77 3.8x3.8x1.4 shielded coiltronics sd3114-2r2 2.2 1.48 86 3.1x3.1x1.4 shielded coiltronics sd3112-2r2 2.2 1.12 140 3.1x3.1x1.2 shielded thermal rated i f(av) rated resistance manufacturer part number current (a) 1 voltage (v) ( ja , c/w) 1 case diodes, inc. b340la 3.00 40 25 sma diodes, inc. sd103aws 0.35 30 625 sod-323 diodes, inc. bat42ws 0.20 30 625 sod-323 diodes, inc. b0520ws 0.50 20 426 sod-323 on semi mbr130lsft 1.00 30 325 sod-123 on semi mbr0530t 0.50 30 206 sod-123 zetex zhcs350 0.35 40 330 sod-523 zetex bat54 0.20 30 330 sot-23 1. results may vary depending on test method used and specific manufacturer.
aat1232 24v 100ma step-up converter 16 1232.2006.12.1.3 ordering information package information tsopjw-12 all dimensions in millimeters. package marking 1 part number (tape and reel) 2 tsopjw-12 sxxyy AAT1232ITP-T1 tdfn34-16 sxxyy aat1232irn-t1 1. xyy = assembly and date code. 2. sample stock is generally held on part numbers listed in bold . 0.20 + 0.10 - 0.05 0.055 0.045 0.45 0.15 7 nom 4 4 3.00 0.10 2.40 0.10 2.85 0.20 0.50 bsc 0.50 bsc 0.50 bsc 0.50 bsc 0.50 bsc 0.15 0.05 0.9625 0.0375 1.00 + 0.10 - 0.065 0.04 ref 0.010 2.75 0.25 all analogictech products are offered in pb-free packaging. the term ?pb-free? means semiconductor products that are in compliance with current rohs standards, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. for more information, please visit our website at http://www.analogictech.com/pbfree.
aat1232 24v 100ma step-up converter 1232.2006.12.1.3 17 advanced analogic technologies, inc. 830 e. arques avenue, sunnyvale, ca 94085 phone (408) 737-4600 fax (408) 737-4611 tdfn34-16 all dimensions in millimeters. ? advanced analogic technologies, inc. analogictech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an analogictech pr oduct. no circuit patent licenses, copyrights, mask work rights, or other intellectual property rights are implied. analogictech reserves the right to make changes to their products or specifi cations or to discontinue any product or service without notice. customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information b eing relied on is current and complete. all products are sold sub- ject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. analogictech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with anal ogictech?s standard warranty. testing and other quality con- trol techniques are utilized to the extent analogictech deems necessary to support this warranty. specific testing of all param eters of each device is not necessarily performed. analogictech and the analogictech logo are trademarks of advanced analogic technologies incorporated. all other brand and produ ct names appearing in this document are regis- tered trademarks or trademarks of their respective holders. 3.00

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