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primary side control ic for off-line battery chargers ap3708n preliminary datasheet 1 bcd semiconductor manufacturing limited feb. 2009 rev. 2. 0 general description the ap3708n is a high performance ac/dc power supply controller for battery charger and adapter appli- cations. the device uses pulse frequency modulation (pfm) method to build discontinuous conduction mode (dcm) flyback power supplies. the ap3708n provides accurate constant voltage, con- stant current (cv/cc) regulation without requiring the opto-coupler and the second ary control circuitry. it also eliminates the need of loop compensation circuitry while maintaining stability. the ap3708n achieves excellent regulation and high power efficiency, the no-load power consumption is less than 150mw. the ap3708n is available in soic-8 package. features primary side control for rectangular constant current and constant voltage output eliminates opto-coupler and secondary cv/cc control circuitry eliminates control loop compensation circuitry output cable resistor compensation flyback topology in dcm operation random frequency modulation to reduce system emi valley turn on of external power npn transistor built-in soft start over voltage protection short circuit protection applications adapters/chargers for cell/cordless phones, pdas, mp3 and other portable apparatus standby and auxiliary power supplies figure 1. package type of ap3708n soic-8
primary side control ic for off-line battery chargers ap3708n preliminary datasheet 2 bcd semiconductor manufacturing limited feb. 2009 rev. 2. 0 1 2 3 4 8 7 6 5 pin configuration figure 2. pin configuration of ap3708n (top view) m package (soic-8) cs out vcc gnd bias vdd fb cmp pin description pin number pin name function 1 cs the primary current sense 2, vcc supply voltage 3 out this pin drives the base of external power npn switch 4 gnd ground 5 cmp this pin connects a capacito r for output cable compensation 6 fb the voltage feedback from the auxiliary winding 7 vdd the 5v output of the internal voltage regulator 8 bias this pin sets the bias current inside ap3708n with an external resistor to gnd primary side control ic for off-line battery chargers ap3708n preliminary datasheet 3 bcd semiconductor manufacturing limited feb. 2009 rev. 2. 0 regulator & bias ovp & ockp tonsec detector s&h 0.1v 4.0v pfm tons uvlo vea comp comp ea tons v+ pfm_d uvlo pro cv_ctrl comp comp leb delay 430ns pfm_d pfm pfm driver rq s rq s v dd i tons 0.5v 0.46v 0.75*i 3.75v cc_ctrl vea v+ u comp 3.65v fb 7 3 2 8 6 1 5 4 functional block diagram figure 3. functional block diagram of ap3708n vcc out gnd vdd bias fb cmp cs primary side control ic for off-line battery chargers ap3708n preliminary datasheet 4 bcd semiconductor manufacturing limited feb. 2009 rev. 2. 0 parameter value unit supply voltage vcc -0.3 to 30 v voltage at cs, bias, out, vdd, cmp to gnd -0.3 to 7 v fb input (pin 6) -40 to 10 v output current at out internally limited a power dissipation at t a =25 o c 0.657 w operating junction temperature 150 o c storage temperature -65 to 150 o c lead temperature (soldering, 10s) 300 o c thermal resistance junction-to-ambient 190 o c/w esd (machine model) 200 v note 1: stresses greater than those li sted under "absolute maximum ratings" may cause permanent damage to the device. these are stress ratings only, and functiona l operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not implied. ex posure to "absolute maximum ratings" for extended periods may affect device reliability. absolute maximum ratings (note 1) package temperature range part number marking id packing type soic-8 -40 to 85 o c AP3708NM-G1 3708nm-g1 tube ap3708nmtr-g1 3708nm-g1 tape & reel bcd semiconductor's pb-free products, as designated with "g1" suffix in the pa rt number, are rohs compliant and green. ordering information circuit type g1: green ap3708n - tr: tape and reel blank: tube package m: soic-8 primary side control ic for off-line battery chargers ap3708n preliminary datasheet 5 bcd semiconductor manufacturing limited feb. 2009 rev. 2. 0 parameter symbol conditions min typ max unit uvlo section start-up threshold v th (st) 16.5 17.5 18.5 v minimal operating voltage v opr (min) after turn on 6.3 6.7 7.1 v reference voltage section bias pin voltage v bias r bias =200k ? , before turn on 1.073 1.10 1.127 v vdd pin voltage v dd 4.82 5.00 5.18 v standby current section start-up current i st v cc = v th (st) -0.5v, r bias =200k ? , before turn on 44 52 a operating current i cc(opr) r bias =200k ? 635 700 a drive output section out maximum current sink i out r bias =200k ? 50 ma source 24 30 current sense section current sense threshold v cs 486 508 530 mv pre-current sense v cs(pre) 388 410 432 mv leading edge blanking 430 ns feedback input section feedback pin input leakage current i fb v fb =4v 1.82.252.7 a feedback threshold voltage v fb 3.99 4.03 4.07 v enable turn-on voltage v fb(en) -0.9 -0.7 -0.5 v cable compensation voltage f sw =60khz 0.40 v protection section over voltage protection v fb(ovp) 789v (v cc =15v, t a =25 o c, unless otherwise specified.) electrical characteristics primary side control ic for off-line battery chargers ap3708n preliminary datasheet 6 bcd semiconductor manufacturing limited feb. 2009 rev. 2. 0 typical performance characteristics figure 6. operating curren t vs. ambient temperature figure 4. start-up voltage vs. am bient temperature figure 5. start-up current vs. ambient temperature figure 7. v dd vs. ambient temperature -40-20 0 20406080100120 15.0 15.5 16.0 16.5 17.0 17.5 18.0 18.5 19.0 19.5 20.0 start-up voltage (v) ambient temperature ( o c) -40 -20 0 20 40 60 80 100 120 20 30 40 50 60 70 80 start-up current ( a) ambient temperature ( o c) -40 -20 0 20 40 60 80 100 120 200 300 400 500 600 700 800 900 1000 operating current ( a) ambient temperature ( o c) -40-20 0 20406080100120 4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.6 v dd (v) ambient temperature ( o c) primary side control ic for off-line battery chargers ap3708n preliminary datasheet 7 bcd semiconductor manufacturing limited feb. 2009 rev. 2. 0 typical performance ch aracteristics (continued) figure 8. start-up current vs. bias resistor figure 9. out source current vs. bias resistor 100 150 200 250 300 350 400 20 30 40 50 60 70 80 90 100 start-up current ( a) bias resistor (ko) t a =25 o c 100 150 200 250 300 350 400 0 10 20 30 40 50 60 70 80 out source current (ma) bias resistor (ko) t a =25 o c primary side control ic for off-line battery chargers ap3708n preliminary datasheet 8 bcd semiconductor manufacturing limited feb. 2009 rev. 2. 0 operation description figure 10 illustrates a si mplified flyback converter controlled by ap3708n. constant primary peak current the primary current ip(t) is sensed by a current sense resistor r cs as shown in figure 10. the current rises up linearly at a rate of: as illustrated in figure 11, when the current ip(t) rises up to ipk, the switch q1 turns off. the constant peak current is given by: the energy stored in the magnetizing inductance l m each cycle is therefore: so the power transferring fr om the input to the output is given by: where f sw is the switching frequency. when the peak current ipk is constant, the output power depends on the switching frequency f sw . constant voltage operation the ap3708n captures the auxiliary winding feedback voltage at fb pin and operates in constant- voltage (cv) mode to regulate the output voltage. assuming the secondary winding is master, the auxiliary winding is slave during the d1 on-time. the auxiliary voltage is given by: figure 10. simplified flyback converter controlled by ap3708n m l t vg dt t dip ) ( ) ( = ...... (1) ip 0a see equation 2 figure 11. primary current waveform r cs vcs ipk = ...... (2) 2 2 1 ipk l eg m = sw m f ipk l p = 2 2 1 ...... (4) () vd vo n n v s aux aux + = ...... (5) ...... (3) & |