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at1454/at1454a/at1454b preliminary product information photoflash capacitor charger for dsc 7f, no.9,park avenue. ii, science-based indu strial park, hsinchu 300,taiwan, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 3/24/2006 rev:1.2 email: service@aimtron.com.tw 1 feature ? 2.5v to 5.5v supply voltage operating range. ? low current consumption:1ma in operation. ? adjustable output voltage. ? adjustable switch on-time. ? charge complete indicator. ? built-in igbt driver. ? soft-start circuitry. ? thermal protection ? charges any size phot oflash capacitor. ? at1454 with auto-refresh function. ? at1454a/b without auto-refresh function. ? small 10-lead msop package. application ? digital / film camera flash ? pda / cell phone flash. description the at1454 series is a charger ic for photoflash capacitor with soft-start function, an igbt driver for igniting flash tube, adjustable output voltage and adjustable switch on-time to perform energy transition on each charge cycle. the output voltage can be adjusted by simply changing the turn ratio of transformer. at1454b is sensed by voltage divider connecting to the anode of the rectifying diode. the voltage sensing path is cut off when charging function to be completed to maintain minimum output voltage decay. the device allows user to control automatic refresh rate on charge pin. while the ready pin signals that the capacitor is fully charged. at1454/at1454a/at1454b is available in msop-10 package. block diagram aimtron reserves the right without notice to change this circuitry and specifications.
at1454/at1454a/at1454b preliminary product information photoflash capacitor charger for dsc 7f, no.9,park avenue. ii, science-based indu strial park, hsinchu 300,taiwan, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 3/24/2006 rev:1.2 email: service@aimtron.com.tw 2 pin configuration 1454 12 34 5 6 7 8 9 1 0 ordering information part number package marking at1454m_gre msop-10 , green at1454, date code with one bottom line at1454am_gre msop-10 , green at1454a, date code with one bottom line at1454bm_gre msop-10 , green at1454b, date code with one bottom line * for more marking information, contact our sales representative directly pin description pin n0. symbol i / o description 1 charge i charge enable input 2 fb i comparator input 3 trigger i igbt trigger signal input. 4 i sec i detecting transformer secondary current. take care to use the correct phasing of the transformer. 5 gnd p ground 6 lx i power mosfet n-channel drain. connect primary transformer. take care to use the correct phasing of the transformer. 7 driver o igbt driver output. 8 vcc p power supply. 9 ready o charge ready open drain output. 10 rsense i a resistor from rsense to vcc or v bat sets the constant on-time.
at1454/at1454a/at1454b preliminary product information photoflash capacitor charger for dsc 7f, no.9,park avenue. ii, science-based indu strial park, hsinchu 300,taiwan, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 3/24/2006 rev:1.2 email: service@aimtron.com.tw 3 absolute maximum ratings *1 parameter rated value unit vcc , trigger , driver , charge , fb and ready voltage -0.3 to +6.0 v lx voltage +30 v sec current 300 ma continuous power dissipation (msop-10,ta=+25 o c) 555 mw junction temperature 125 lead temperature (sol dering 10 sec) 260 storage temperature -40~125 hbm 2 kv esd susceptibility*2 mm 200 v 1. stresses beyond those listed under ?absolute maxi mum ratings? may cause permanent damage to the device. these are stress ratings only , and functional operation of th e device at these or any other conditions beyond those indicated in th e operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability . 2. device are esd sensitive. handling precautio n recommended. the human body model is a 100pf capacitor discharged through a 1.5k ? resistor into each pin. recommended operation conditions values parameter symbol min. typ. max. unit power supply voltage vcc 2.5 D +5.5 v operating temperature top -30 +25 +85 lx voltage v lx vcc D 28 v
at1454/at1454a/at1454b preliminary product information photoflash capacitor charger for dsc 7f, no.9,park avenue. ii, science-based indu strial park, hsinchu 300,taiwan, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 3/24/2006 rev:1.2 email: service@aimtron.com.tw 4 electrical characteristics (vcc=3.3v, ta=+25 , unless otherwise noted) parameter symbol test condition min. typ. max. units input operating voltage vcc 2.5 D 5.5 v input under-voltage threshold v uvlo vcc falling D 2.1 D v vcc uvlo hysteresis D 100 D mv feedback voltage v fb ta=+25 1.08 1.10 1.12 v shutdown current i off charge pin=gnd D 0.01 1 a quiescent current icc no switching , fb=1.2v D 40 60 a primary side current limit i lx(max) D 2.5 D a secondary side transit current isec D 5 D ma lx switch on-resistance r lx(on) i lx =2a D 0.17 D ? lx leakage current i lc v lx =28v D 0.01 6 a vcc=3.3v, c l =3900pf D 55 D ns igbt driver rising time tr vcc=3.3v, c l =8200pf D 90 D ns vcc=3.3v, c l =3900pf D 55 D ns igbt driver falling time tf vcc=3.3v, c l =8200pf D 90 D ns igbt trigger signal high 0.45vc c D D v igbt trigger signal low D D 0.3vcc v charge input voltage high v on 0.1v hysteresis 0.9 D D v charge input voltage low v off D D 0.8 v charge pin bias current v charge =3.3v D 3 D a ready output signal high 100k ? from vcc to ready pin D 3.27 D v ready output signal low 33 a into ready pin D 1.0 0 mv thermal shutdown D 140 D
at1454/at1454a/at1454b preliminary product information photoflash capacitor charger for dsc 7f, no.9,park avenue. ii, science-based indu strial park, hsinchu 300,taiwan, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 3/24/2006 rev:1.2 email: service@aimtron.com.tw 5 timing chart ready shutdown charging auto charge to refresh vout charge storbe trige vcc charge on timing power off timing at1454 auto-refresh mode ready shutdown charging toggling charge to refresh 1.up detected ready pin low ->high(charge complete) -->allow enter refresh mode or strobe tube 2.use up to delay photoflash capacitor self-discharge time ts 3.toggling charge pin high->low->high, force the ic into refresh charging mode. vout charge storbe trige vcc charge on timing power off timing at1454a/b charge toggle-refresh (soft-ware control)mode
at1454/at1454a/at1454b preliminary product information photoflash capacitor charger for dsc 7f, no.9,park avenue. ii, science-based indu strial park, hsinchu 300,taiwan, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 3/24/2006 rev:1.2 email: service@aimtron.com.tw 6 typical operating characteristics v lx & primary current time(1us/div) [ch2:v lx ; ch4:i pri ] v lx & primary current time(1us/div) [ch2:v lx ; ch4:i pri ] vout=100 vout=100v v lx (5v/div) i pri (1a/div) v lx (10v/div) i pri (1a/div) vout=300v
at1454/at1454a/at1454b preliminary product information photoflash capacitor charger for dsc 7f, no.9,park avenue. ii, science-based indu strial park, hsinchu 300,taiwan, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 3/24/2006 rev:1.2 email: service@aimtron.com.tw 7 v lx & secondary current time(1us/div) [ch2:v lx ; ch4:i sec ] charging waveform without auto-refresh function , time(1 s/div) vcc=3.3v, v bat =4.2v, c=120uf ch1:ready ch2:charge ch3:output voltage ch4:input current v lx (5v/div) i sec (50ma/div vout=100v
at1454/at1454a/at1454b preliminary product information photoflash capacitor charger for dsc 7f, no.9,park avenue. ii, science-based indu strial park, hsinchu 300,taiwan, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 3/24/2006 rev:1.2 email: service@aimtron.com.tw 8 charging waveform with auto-refresh function , time(1 s/div) vcc=3.3v, v bat =3.0v, c=47uf ch1:ready ch2:charge ch3:out put voltage ch4:input current
at1454/at1454a/at1454b preliminary product information photoflash capacitor charger for dsc 7f, no.9,park avenue. ii, science-based indu strial park, hsinchu 300,taiwan, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 3/24/2006 rev:1.2 email: service@aimtron.com.tw 9 application circuit
at1454/at1454a/at1454b preliminary product information photoflash capacitor charger for dsc 7f, no.9,park avenue. ii, science-based indu strial park, hsinchu 300,taiwan, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 3/24/2006 rev:1.2 email: service@aimtron.com.tw 10
at1454/at1454a/at1454b preliminary product information photoflash capacitor charger for dsc 7f, no.9,park avenue. ii, science-based indu strial park, hsinchu 300,taiwan, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 3/24/2006 rev:1.2 email: service@aimtron.com.tw 11
at1454/at1454a/at1454b preliminary product information photoflash capacitor charger for dsc 7f, no.9,park avenue. ii, science-based indu strial park, hsinchu 300,taiwan, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 3/24/2006 rev:1.2 email: service@aimtron.com.tw 12 application information at1454 series is designed to precise control of switching current to charge photoflash capacitors quickly and efficiently. when the ch arge pin is first driven high, a one shot set sr latches in the correct state. th e built-in power mosfet turns on and primary current ramps up linearly according to v bat and primary inductance. comparator monitors the switch on-time and when the switch on-time reaches limit value, mosfet is turned off. during this phase, stored energy of primary transformer is delivered to the photoflash capacitor vi a the secondary and diode. the secondary current is decreased linearly at a rate de termined by the secondary inductance. the secondary current is monitored by the is ec pin. when the secondary current drops below 10ma, the fires a one shot will turn on mosfet. the charging cycle repeats to deliver power to the output. at1454 series can adjust external resistance r sense to set n-mos switch on-time, but switch on-time value must match with electri cal characteristic of transformer. it is usually equal to or less than saturation cu rrent of transformer otherwise transformer will be saturated. therefore, efficiency will be reduced. the output voltage is detected by a voltage divider connecting to output capacitor. when the output voltage reaches the desired voltage set by resistive voltage-divider, comparator output goes high which resets th e master latch and disable the charging block. the n-channel mosfet is turned off pulling the ready pin high, indicating that the part has finished charging. powe r delivery can be restarted automatically when feedback voltage is less than 90% of reference voltage. power delivery can only be restarted by toggling the charge pin. the charge pin gives full control of the part to the user. the igbt buffer will provide a su fficient current to drive igbt to ignite flash tube. transformer design the fly-back transformer is a key element for at1454 series. it must be designed carefully and checked that it does not cause excessive current or voltage on any pin of the part. the first transformer parameter that needs to be set is the turns ratio n, should be high enough so that the absolute maximum voltage rating for the nmos drain to source voltage is not exceeded. choose the minimum turns ratio according to following formula: bat max ds out min v v v n ? ) (
at1454/at1454a/at1454b preliminary product information photoflash capacitor charger for dsc 7f, no.9,park avenue. ii, science-based indu strial park, hsinchu 300,taiwan, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 3/24/2006 rev:1.2 email: service@aimtron.com.tw 13 vout: target output voltage v ds(max) :maximum drain to source voltage of nmos. adjustable output voltage the at1454/1454a/b senses output voltage by a voltage divider connecting to output terminal. r7 to (r8+r9) ratio determin es the output voltage as shown in the application circuit figure 1. the feedback reference voltage is 1.1v. calculate the remaining resistors with following equations: ) 1 ( 7 9 8 r r r v v fb out + + = r8and r9 must be greater than 0805 si ze resistor for endur ing secondary hv. rectifying diode the rectifying diode should be low capac itance type with sufficient reverse recovery-voltage and forward current ratings . the peak reverse r ecovery-voltage that diode is approximately: v pk-r ? v out + (n x v cc ) the peak current of the diode is simply: i pk-sec = i pk-pri / n primary inductance a fly-back transformer needs to store substa ntial amounts of energy in the core during each switching cycle. the transformer will gene rally require an air gap. the use of an air gap in the core makes the energy storage. while the power switch is off, energy transferred to the output capacitor is proportional to the primary inductance for a constant primary current. the primary inducta nce needs to be equal or larger than a certain minimum value to ensure that at1454 series has adequate time to respond to the fly-back waveform. the switch off time should be 500ns or larger for the at1454 series. the minimum inductance can be calculated with the following formula: pri pk out pri i n v l ? ? 9 10 500 vout: target output voltage n: transformer turns ratio i pk-pri : primary peak current
at1454/at1454a/at1454b preliminary product information photoflash capacitor charger for dsc 7f, no.9,park avenue. ii, science-based indu strial park, hsinchu 300,taiwan, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 3/24/2006 rev:1.2 email: service@aimtron.com.tw 14 leakage inductance and parasitic capacitance the leakage inductance on the primary of th e transformer results in the first spike voltage when nmos turns off. the spike voltage is proportional to the leakage inductance. the spike voltage must not ex ceed the dynamic rating of the nmos drain to source voltage. it is important not to minimize the leakage inductance to a very low level. although this woul d result in a very low leak age spike, the parasitic capacitance of the transformer will be high be tween windings. this will result in the initial spike of current in the primary becoming excessively high while the nmos turns on. therefore, trade of f is necessary between leak age inductance and parasitic capacitance. spike voltage @switching time(1us/div) swing current @switching time(1us/div) v lx (5v/div) , i pri (1a/div) v lx (10v/div) , i pri (1a/div) ch1:v lx ; ch2:input current transformer secondary capacitance the total capacitance on the secondary of the transformer will severely affect the efficiency of the circuit. any sec ondary capacitance is multiplied by n 2 when reflected to the primary. since this capac itance forms a resonant circuit with the primary leakage inductance of the transfor mer. as such, both the primary leakage inductance and secondary side capacitance should be minimized. spike voltage swing current ch2 ch1
at1454/at1454a/at1454b preliminary product information photoflash capacitor charger for dsc 7f, no.9,park avenue. ii, science-based indu strial park, hsinchu 300,taiwan, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 3/24/2006 rev:1.2 email: service@aimtron.com.tw 15 adjustable input current the at1454/1454a/b can adjust n-mos switc h on-time by a resist or connecting to rsense pin. this resistor determines the primary peak current and on-time of primary n-mos as the following equation: bat pri pri pk on cc bat rsense pri rsense bat pri pk v l i t k r k v or v v l v v i = ? + ? = = ? ? ? 25 25 ) , ( , 10 2 4 6 where l pri : primary inductance ( h) i pk-pri : peak primary current (a) r4: it is recommended several k grade if setting constant on-time by a resistor r 10 is connected to vcc, then r4 resistor need to remove from application circuitry. in this case, on-tim e is a constant. at another topology, if r4 connect to vbat to set constant on-time, then r10 need to remove from application circuitry. howe ver, on-time can change dependent on vbat because battery voltage level is differen t from full energy to low power. external capacitor css is connected to vcc and rsense to perform soft-start function to reduce inrush current on vbat i nput current and avoid the internal switching noise. lx vcc vbat rsense l1 33uh /option c1 22u/6v3 t1 st-982610a 1:25 10uh/6.1mh at1454/at1454a/at1454b vcc isec r4 css 0.1uf r10
at1454/at1454a/at1454b preliminary product information photoflash capacitor charger for dsc 7f, no.9,park avenue. ii, science-based indu strial park, hsinchu 300,taiwan, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 3/24/2006 rev:1.2 email: service@aimtron.com.tw 16 auto-refresh at1454 supports auto-refresh function require d in some dcs application. when the output capacitor is charged complete, the ready pin will goes high and vout will decrease slightly due to leakage current . the refresh block trip point is v fb x90%. while the vout is decreased to the refresh trip point, it enables the charge block, disable the refresh block and pull low th e ready pin. this cycle of recharge operation will repeat again until charge pin is pulled low. thermal-overload protection thermal-overload protection limits total power dissipation in the at1454 series. when the junction temperature exceeds tj=140 , a thermal sensor activates the thermal protection, which shuts down the ic, allowing the ic to cool. once the device cools down by 15 , ic will automatically recover normal operation. for continuous operation , do not exceed the absolute maximum junction-temperature rating of tj=130 . prevent the leakage of ready pin charge ready vcc ready if pull-high resistor of ready signal connect to charge pi n, then it can reduce power consumption on pull-high resistor of re ady during charge pin goes low. board layout the high voltage operation of the at1454/at1454a/at1454b demands careful attention to board layout. you will not get a dvertised performance with careless layout. keep the area for the high voltage end of th e secondary as small as possible. also note the larger than minimum spacing for a ll high voltage nodes in order to meet breakdown voltage requirements for the circ uit board. remember that lethal voltages are present in this circuit. use caution when working with the circuit.
at1454/at1454a/at1454b preliminary product information photoflash capacitor charger for dsc 7f, no.9,park avenue. ii, science-based indu strial park, hsinchu 300,taiwan, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 3/24/2006 rev:1.2 email: service@aimtron.com.tw 17 outline 10-pin msop
at1454/at1454a/at1454b preliminary product information photoflash capacitor charger for dsc 7f, no.9,park avenue. ii, science-based indu strial park, hsinchu 300,taiwan, r.o.c. tel: 886-3-563-0878 fax: 886-3-563-0879 www: http://www.aimtron.com.tw 3/24/2006 rev:1.2 email: service@aimtron.com.tw 18 reflow profiles sn-pb eutectic assembly pb-free assembly profile feature large body pkg. thickness 2.5mm or pkg. volume 350mm 3 small body pkg. thickness <2.5mm or pkg. volume <350mm 3 large body pkg. thickness 2.5mm or pkg. volume 350mm 3 small body pkg. thickness 2.5mm or pkg. volume 350mm 3 average ramp-up rate (t l to t p ) 3 c/second max. 3 c/second max. preheat -temperature min(tsmin) -temperature max (tsmax) -time (min to max)(ts) 100 c 150 c 60-120 seconds 150 c 200 c 60-180 seconds ts m a x t o t l -ramp-up rate 3 c/second max. time maintained above: -temperature (t l ) -time (t l ) 183 c 60-150 seconds 217 c 60-150 seconds peak temperature(t p ) 225+0/-5 c 240+0/-5 c 245+0/-5 c 250+0/-5 c time within 5 c of actual peak temperature (t p ) 10-30 seconds 10-30 seconds 10-30 seconds 20-40 seconds ramp-down rate 6 c/second max. 3 c/second max. time 25 c to peak temperature 6 minutes max. 8 minutes max. * all temperatures refer to topside of the package, measured on the package body surface.

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