View ZXSC44005_4885563.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

semiconductors description the zxsc440 is a dedicated photoflash charger, charging an 80 f photoflash capacitor to 300v in 3.5 seconds from a 3v supply. the flyback conversion efficiency is typically 75%, much higher than the commonly used discrete charging circuits. the charge pin enables the circuit to be initiated from the camera's microprocessor, using negligible current when flash is not being used. features ? charges a 80 f photoflash capacitor to 300v in 3.5 seconds from 3v ? charges various value photoflash capacitors ? over 75% flyback efficiency ? charge and ready pins ? consumes only 4.5 a when not charging ? small msop8 low profile package the ready pin signals the microprocessor when the flash is charged and ready to be fired. a small amount of hysteresis on the voltage feedback shuts down the device as long as the capacitor remains fully charged, again using negligible current. applications ? digital camera flash unit ? film camera flash unit zxsc440 issue 1 - january 2005 photoflash charger 1 pinout msop8 pin top view typical application circuit device device description temperature range part mark taping options zxsc440x8ta camera flash charger -40c to +85c zxsc440 ta, tc zxsc440x8tc ordering information ? ta reels hold 1000 devices ? tc reels hold 4000 devices
zxsc440 semiconductors issue 1 - january 2005 2 parameter limit unit v cc -0.3 to +10 v drive -0.3 to v cc + 0.3 v ready -0.3 to v cc + 0.3 v charge -0.3 to the lower of (+5.0) or (v cc +0.3) v v fb , sense -0.3 to the lower of (+5.0) or (v cc +0.3) v operating temperature -40 to +85 c storage temperature -55 to +150 c power dissipation at 25c 450 mw absolute maximum ratings symbol parameter conditions min. typ. max. unit v cc v cc range 1.8 8 v iq (1) quiescent current v cc =8v 220 a i stdn shutdown current 4.5 a eff (2) efficiency 85 % acc ref reference tolerance 1.8v < v cc < 8v -3.0 3.0 % tco ref reference temp co 0.005 %/c t drv discharge pulse width 1.8v < v cc < 8v 1.7 s f osc operating frequency 200 khz input parameters v sense sense voltage 22 28 34 mv i sense sense input current v fb =0v;v sense =0v -1 -7 -15 a v fb feedback voltage 291 300 309 mv i fb (2) feedback input current v fb =0v;v sense =0v -1.2 -4.5 a vih (3) shutdown threshold 1.5 v cc v vil shutdown threshold 0 0.55 v dv ln line voltage regulation 0.5 %/v output parameters i drive transistor drive current v drive = 0.7v 2 3.4 5 ma v drive transistor voltage drive 0 v cc -0.4 v c drive mosfet gate drive cpbty 300 pf voh ready ready flag output high i eor = -300na, t a =25c 2.5 v cc v vol ready ready flag output low i eor =1ma,t a =25c 0 1 v t ready t a =25c 195 s di ld load current regulation 0.01 %/ma electrical characteristics (test conditions v cc = 3v, t= 25c unless otherwise stated) notes (1) excluding gate/base drive current. (2) i fb is typically half of these at 3v. (3) shutdown pin voltage must not exceed (v cc +0.3v) or 5v, whichever is lower.
zxsc440 semiconductors issue 1 - january 2005 3 block diagram pin # name description 1 drive drive output for external switching transistor. connect to base or gate of external switching transistor 2v fb reference voltage. internal threshold set to 300mv. connect external resistor network to set output voltage 3 sense inductor current sense input. internal threshold voltage set to 28mv. connect external sense resistor 4 n/c 5 charge initiate photoflash capacitor charging 6 ready signal to microprocessor when photoflash capacitor charged 7 gnd ground 8v cc supply voltage, 1.8v to 8v absolute maximum ratings
device description bandgap reference all threshold voltages and internal currents are derived from a temperature compensated bandgap reference circuit with a reference voltage of 1.22v nominal. if the ref terminal is used as a reference for external devices, the maximum load should not exceed 2 a. dynamic drive output depending on the input signal, the output is either "low" or "high". in the high state a 3.4ma current source (max drive voltage = v cc -0.4v) drives the base or gate of the external transistor. in order to operate the external switching transistor at optimum efficiency, both output states are initiated with a short transient current in order to quickly discharge the base or the gate of the switching transistor. switching circuit the switching circuit consists of two comparators, comp1 and comp2, a gate u1, a monostable and the drive output. normally the drive output is "high"; the external switching transistor is turned on. current ramps up in the inductor, the switching transistor and external current sensing resistor. this voltage is sensed by comparator, comp2, at input sense. once the current sense voltage across the sensing resistor exceeds 28mv, comparator, comp2, through gate u1, triggers a re-triggerable monostable and turns off the output drive stage for 1.7 s. the inductor discharges into the reservoir capacitor. after 1.7 s a new charge cycle begins, thus ramping the output voltage. when the output voltage reaches the nominal value and v fb gets an input voltage of more than 300mv, the monostable is forced "on" from comp1 through gate u1, until the feedback voltage falls below 300mv. the above action continues to maintain regulation, with slight hysteresis on the feedback threshold. ready detector the ready circuit is a re-triggerable 195 s monostable, which is re-triggered by every down regulating action of comparator comp1. as long as regulation takes place, output ready is "high" (high impedance, 100k to v cc ). short dips of the output voltage of less than 195 s are ignored. if the output voltage falls below the nominal value for more than 195 s, output ready goes "low". this can be used to signal to the camera controller that the flash unit has charged fully and is ready to use. zxsc440 semiconductors issue 1 - january 2005 4
zxsc440 semiconductors issue 1 - january 2005 5 typical operating characteristics (for typical application circuit at v in =3v and t a =25 c unless otherwise stated)
applications switching transistor selection the choice of switching transistor has a major impact on the converter efficiency. for optimum performance, a bipolar transistor with low v ce(sat) and high gain is required. the v ceo of the switching transistor is also an important parameter as this sees typically three times the input voltage when the transistor is switched off. zetex supersot ? transistors are an ideal choice for this application. at input voltages above 4v, suitable zetex mosfet transistors will give almost the same performance with a simpler drive circuit, omitting the zxtd6717 pre-drive stage. using a mosfet, the schottky diode may be omitted, as the body diode of the mosfet will perform the same function, with just a small loss of efficiency. output rectifier diode selection the diode should have a fast recovery, as any time spent in reverse conduction removes energy from the reservoir capacitor and dumps it, via the transformer, into the protection diode across the output transistor. this seriously reduces efficiency. two bas21 diodes in series have been used, bearing in mind that the reverse voltage across the diode is the sum of the output voltage together with the input voltage multiplied by the step-up ratio of the transformer: v r(diode) = v out(max) + (v in x t urns r atio ) sense resistor a low value sense resistor is required to set the peak current. power in this resistor is negligible due to the low sense voltage threshold, v sense . below is a table of recommended sense resistors: using a 22m sense resistor results in a peak current of just over 1.2a. therefore, with a 300v output, a supply of 8 volts and a 1:12 step-up transformer, there will be a 396v across the diode. this occurs during the current ramp-up in the primary, as it transforms the input voltage up by the turns ratio and the polarity at the secondary is such as to add to the output voltage already being held off by the diode. peak current definition in general, the i pk value must be chosen to ensure that the switching transistor, q1, is in full saturation with maximum output power conditions, assuming worse-case input voltage and transistor gain under all operating temperature extremes. once i pk is decided the value of r sense can be determined by: r v i sense sense pk = zxsc440 semiconductors issue 1 - january 2005 6 manufacturer series r dc ( ) range size tolerance url cyntec rl1220 0.022 - 10 0805 5% http://www.cyntec.com irc lr1206 0.010 - 1.0 1206 5% http://www.irctt.com
transformer parameters proprietary transformers are available, for example the pulse pao367, primary inductance: 24uh, core: pulse pao367, turns ratio: 1:12, see bill of materials below. if designing a transformer, bear in mind that the primary current may be over an amp and, if this flows through 10 turns, the primary flux will be 10 amp. turns and small cores will need an air gap to cope with this value without saturation. secondary winding capacitance should not be too high as this is working at 300v and could soon cause excessive losses. zxsc440 semiconductors issue 1 - january 2005 7 part no. size (wxlxh) mm l pri ( h) l pri -leak (nh) nr pri (m ) r sec ( ) manufacturer t-15-089 6.4x7.7x4 12 400 10:2 211 27 tokyo coil eng. www.tokyo-coil.co.jp t-15-083 8x8.9x2 20 500 10:2 675 35 sbl-5.6-1 5.6x8.5x4 10 200 10:2 103 26 kijima musen kijimahk@netvigator.com pao367 9.1x9.1x5.1 24 12:1 pulse www.pulseeng.com zxsc440 transformer specifications
output power calculation this is approximately the power stored in the coil times the frequency of operation times the efficiency. assuming a current of 1.2 amps in a 30h primary, the stored energy will be 21.6j. the frequency is set by the time it takes the primary to reach 1.2 amps plus the 1.7s time allowed to discharge the energy into the reservoir capacitor. using 3 volts, the ramp time is 12s, so the frequency will be 73khz, giving an input power of about 1.6 watts. with an efficiency of 75% the output power will be 1.2 watts. an 80f capacitor charged to 300 volts stores 3.6j, so 1.2 watts will take 3 seconds to charge it. higher input voltages reduce the ramp time, the frequency therefore goes up and the output power is increased, resulting in shorter charging times. output voltage adjustment the zxsc440 are adjustable output converters allowing the end user the maximum flexibility. for adjustable operation a potential divider network is connected as follows: the output voltage is determined by the equation: v out = v fb (1 + ra / rb), where v fb =300mv in a circuit giving 300 volts, the "1" in the above equation becomes negligible compared to the ratio which is around 1000. it will not be exactly 1000because of the negative input current in the feedback pin. the resistor values, ra and rb, should be maximized to improve efficiency and decrease battery drain. optimization can be achieved by providing a minimum current of i fb(max) =200na to the v fb pin. output is adjustable from v fb to the (br)v ceo of the switching transistor, q1. in practice, there will be some stray capacitance across ra and this will cause a lead in the feedback which can affect hysteresis (it makes the device shut down too early) and it is best to swamp this with a capacitor ca and then use a capacitor cb across rb where cb/ca = ra/rb. this is similar to the method used for compensating oscilloscope probes. zxsc440 semiconductors issue 1 - january 2005 8
layout issues layout is critical for the circuit to function in the most efficient manner in terms of electrical efficiency, thermal considerations and noise. for 'step-up converters' there are four main current loops, the input loop, power-switch loop, rectifier loop and output loop. the supply charging the input capacitor forms the input loop. the power-switch loop is defined when q1 is 'on', current flows from the input through the transformer primary, q1, r sense and to ground. when q1 is 'off', the energy stored in the transformer is transferred from the secondary to the output capacitor and load via d1, forming the rectifier loop. the output loop is formed by the output capacitor supplying the load when q1 is switched back off. to optimize for best performance each of these loops kept separate from each other and interconnected with short, thick traces thus minimizing parasitic inductance, capacitance and resistance. also the r sense resistor should be connected, with minimum trace length, between emitter lead of q1 and ground, again minimizing stray parasitics. zxsc440 semiconductors issue 1 - january 2005 9
reference designs general camera photoflash charger specification v in =5v v out = 275v efficiency = 71% charging time = 4 seconds zxsc440 semiconductors issue 1 - january 2005 10 circuit diagram ref value package part number manufacturer notes u1 msop8 zxsc440 zetex q1 sot23 zxmn6a07f zetex 60v n-channel mosfet d1 (2) 200v sot23 bas21 philips x2 200v fast rectifier diodes connected in series tx1 pulse see note (1) r1 22m 0805 rl1210 cyntec r2 10m /400v axial generic generic output voltage across resistor r3 10k 0805 generic generic r4 100k 0805 generic generic c1 100uf/10v 0805 generic murata c2 10pf/500v 1206 generic generic output voltage seen across capacitor c3 10nf/6v3 1206 generic generic c4 120uf/330v radial fw series rubycon photoflash capacitor bill of materials notes: (1) transformer specification: primary inductance: 24uh, core: pulse pao367, turns ratio: 1:12 (2) two bas21 200v rectifier diodes are connected in series and used in place of a 400v rectifier diode to provide faster switch ing speeds and higher efficiency.
high power digital camera photoflash charger specification v in =3v v out = 275v efficiency = 69% charging time = 5 seconds zxsc440 semiconductors issue 1 - january 2005 11 circuit diagram ref value package part number manufacturer notes u1 msop8 zxsc440 zetex u2 sot23-6 zxtd6717 zetex npn/pnp dual q1 sot23 fmmt619 zetex 50v npn low sat d1 200v sot23 bas21 philips 200v fast rectifier d2 200v sot23 bas21 philips 200v fast rectifier d3 2a sot23-6 zlls2000 zetex 2a schottky diode tx1 pao367 pulse see note (1) r1 22m 0805 rl1210 cyntec r2 130 0805 generic generic r3 2k2 0805 generic generic r4 10m /400v axial generic generic output voltage across resistor r5 10k 0805 generic generic c1 100uf/10v 0805 generic murata c2 220nf 0805 grm series murata c3 10pf/500v 1206 generic generic output voltage seen across capacitor c4 10nf/6v3 1206 generic generic c5 120uf/330v radial fw series rubycon photoflash capacitor bill of materials notes: (1) transformer specification: primary inductance: 24uh, core: pulse pao367, turns ratio: 1:12
low power digital camera photoflash charger specification v in =3v v out = 275v efficiency = 58% charging time = 6.8 seconds zxsc440 semiconductors issue 1 - january 2005 12 circuit diagram ref value package part number manufacturer notes u1 msop8 zxsc440 zetex u2 sot23-6 zxtd6717 zetex npn/pnp dual q1 sot23 fmmt619 zetex 50v npn low sat d1 200v sot23 bas21 philips 200v fast rectifier d2 200v sot23 bas21 philips 200v fast rectifier d3 2a sot23-6 zlls2000 zetex 2a schottky diode tx1 sumida see note (1) r1 33m 0805 rl1210 cyntec r2 200 0805 generic generic r3 2k2 0805 generic generic r4 10m /400v axial generic generic output voltage across resistor r5 10k 0805 generic generic c1 100uf/10v 0805 generic murata c2 220nf 0805 grm series murata c3 10pf/500v 1206 generic generic output voltage seen across capacitor c4 10nf/6v3 1206 generic generic c5 80uf/330v radial fw series rubycon photoflash capacitor bill of materials notes: (1) transformer specification: primary inductance: 32uh, core: sumida ceeh64, turns ratio: 1:10
notes: zxsc440 semiconductors issue 1 - january 2005 13
notes: zxsc440 semiconductors issue 1 - january 2005 14
notes: zxsc440 semiconductors issue 1 - january 2005 15
zxsc440 semiconductors 16 issue 1 - january 2005 europe zetex gmbh streitfeldstra?e 19 d-81673 mnchen germany telefon: (49) 89 45 49 49 0 fax: (49) 89 45 49 49 49 europe.sales@zetex.com americas zetex inc 700 veterans memorial hwy hauppauge, ny 11788 usa telephone: (1) 631 360 2222 fax: (1) 631 360 8222 usa.sales@zetex.com asia pacific zetex (asia) ltd 3701-04 metroplaza tower 1 hing fong road, kwai fong hong kong telephone: (852) 26100 611 fax: (852) 24250 494 asia.sales@zetex.com corporate headquaters zetex semiconductors plc zetex technology park chadderton, oldham, ol9 9ll united kingdom telephone (44) 161 622 4444 fax: (44) 161 622 4446 hq@zetex.com these offices are supported by agents and distributors in major countries world-wide. this publication is issued to provide outline information only which (unless agreed by the company in writing) may not be used, applied or reproduced for any purpose or form part of any order or contract or be regarded as a representation relating to the products or services concerned. the company reserves the right to alter without notice the specification, design, price or conditions of supply of any product or service. for the latest product information, log on to www.zetex.com ? zetex semiconductors plc 2005 dim millimeters inches dim millimeters inches min max min max min max min max a - 1.10 - 0.0433 e 4.90 bsc 0.025 bsc a1 0.05 0.15 0.002 0.006 e1 2.90 3.10 0.114 0.122 a2 0.75 0.95 0.0295 0.0374 e 0.65 bsc 0.193 bsc b 0.25 0.40 0.010 0.0157 l 0.40 0.70 0.0157 0.0192 c 0.13 0.23 0.005 0.009 r 0.07 - 0.0027 - d 2.90 3.10 0.114 0.122 r1 0.07 - 0.0027 - package dimensions controlling dimensions are in millimeters. approximate conversions are given in inches e e1 e d a a1 a2 l 0.25 15%%d max gage plane r1 r c indent area (d/2 x e1/2) b 0%%d-6%%d 1 8 package outline

▲Up To Search▲

Price & Availability of ZXSC44005

	To Download ZXSC44005 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .