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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) & &r 9 2 ' 5fv 4 287 )% &6 *1' $31 1v 1 $8; 1s ,r 9v 9 $8; ,s v in / 0 &03 &
primary side control ic for off-line battery chargers ap3708n preliminary datasheet 9 bcd semiconductor manufacturing limited feb. 2009 rev. 2. 0 operation descrip tion (continued) where vd is the diode forward drop voltage. the output voltage is different from the secondary voltage in a diode forward drop voltage that depends on the current. if the secondary voltage is always detected at a fixed secondary current, the difference between the output voltage and the secondary voltage will be a fixed vd. the voltage detection point is at two-thirds of the d1 on-time. the cv loop control function of ap3708n then generates a d1 off-time to regulate the output voltage. constant current operation figure 13 shows the secondary current waveforms. in cc operation, the cc loop control function of ap3708n will keep a fixed proportion between d1 on-time tons and d1 off-time toffs by discharging or charging the capacitance connected in cmp pin. the fixed proportion is the relationship between the output constant-current and secondary peak current ipks is given by: at the instant of d1 turn -on, the primary current transfers to the secondar y at an amplitude of: thus the output constant-current is given by: leading edge blanking when the power switch is turned on, a turn-on spike will occur on the sense-resistor. to avoid false- termination of the switching pulse, a 430ns leading- edge blanking is built in. during this blanking period, the current sense comparator is disabled and the gate driver can not be switched off. ccm protection the ap3708n is designed to operate in discontinuous conduction mode (dcm) in both cv and cc modes. to avoid operating in continuous conduction mode (ccm), the ap3708n detects the falling edge of the fb input voltage on each cycle. if a 0.1v falling edge of fb is not detected, the ap3708n will stop switching. ovp & ockp the ap3708n includes output over-voltage protection (ovp) and open circuit protection (ockp) circuitry as shown in figure 14. if the voltage at fb pin exceeds 8v, 100% above the normal detection voltage, or the -0.7v falling edge of the fb input can not be monitored, the ap3708n will immediately shut off and enter hiccup mode. the ap3708n sends out a fault detection pulse every 32ms in hiccup mode until the fault has been removed. figure 12. auxiliary voltage waveform is 0a see equation 8 tons toffs iout figure 13. secondary current waveform 3 4 toffs tons ...... (6) toffs tons tons ipks iout u u 2 1 ...... (7) ipk n n ipks s p u ...... (8) ipk n n toffs tons tons ipk n n iout s p s p u u u u u 7 2 2 1 ...... (9) 0v see equation 5 tons 2/3 tons
primary side control ic for off-line battery chargers ap3708n preliminary datasheet 10 bcd semiconductor manufacturing limited feb. 2009 rev. 2. 0 operation descrip tion (continued) rq s comp comp 8v -0.7v timer_32ms uvlo fb pro figure 14. ovp and ockp function block cmp fb tons 3.65v ra rb vout1 v cmp figure 15. output cable compensation function block cmp out v r a rb v r a rb v ? + = 65 . 3 ) 1 ( 1 ...... (10) output cable compensation the ap3708n integrates the output cable compensation circuitry as shown in figure 15. tons shows the variation for fb flyback voltage. tons can be converted to a dc voltage by a low-pass filter. when system load curren t iout changed from open load to full load iload, the amplified voltage vout1 through a rail-to-rail operation amplifier is obtained: through the internal ra and rb, the fb voltage can be compensated by the vout1, the compensation voltage is 0.4v when full load switch frequency is 60khz.
primary side control ic for off-line battery chargers ap3708n preliminary datasheet 11 bcd semiconductor manufacturing limited feb. 2009 rev. 2. 0 typical application figure 16. 5v/1a output for battery charger of mobile phone + j1 ac 85-264v bridge c1 5.1v/0.75a + c6 v o + v o - d2 + r1 r3 r2 r4 r5 rbias c3 c4 r6 rs q1 r7 r8 r9 c5 t1 d1 z1 c2 vcc out fb vdd cmp cs bias gnd ap3708n na ns nfb np
primary side control ic for off-line battery chargers ap3708n preliminary datasheet 12 bcd semiconductor manufacturing limited feb. 2009 rev. 2. 0 mechanical dimensions mechanical dimensions unit: mm(inch) soic-8 0 8 1 5 r 0 . 1 5 0 ( 0 . 0 0 6 ) r0.150(0.006) 1.000(0.039) 0.330(0.013) 0.510(0.020) 1.350(0.053) 1.750(0.069) 0.100(0.004) 0.300(0.012) 0.900(0.035) 0.800(0.031) 0.200(0.008) 3.800(0.150) 4.000(0.157) 7 7 2 0 : 1 d 1.270(0.050) typ 0.190(0.007) 0.250(0.010) 8 d 5.800(0.228) 6.200(0.244) 0.675(0.027) 0.725(0.029) 0.320(0.013) 8 0.450(0.017) 0.800(0.031) 4.700(0.185) note: eject hole, oriented hole and mold mark is optional.
important notice bcd semiconductor manufacturing limited reserves the right to make changes without further not ice to any products or specifi- cations herein. bcd semiconductor manufacturing limited does not as sume any responsibility for us e of any its products for any particular purpose, nor does bcd semiconductor manufacturi ng limited assume any liability aris ing out of the application or use of any its products or circui ts. bcd semiconductor manufacturing limited does not convey any license under its patent rights or other rights nor the rights of others. - wafer fab shanghai sim-bcd semiconductor manufacturing co., ltd. 800 yi shan road, shanghai 200233, china tel: +86-21-6485 1491, fax: +86-21-5450 0008 main site regional sales office shenzhen office shanghai sim-bcd semiconductor manuf acturing co., ltd., shenzhen office room e, 5f, noble center, no.1006, 3rd fuzhong road, futian district, shenzhen, 518026, china tel: +86-755-8826 7951 fax: +86-755-8826 7865 taiwan office bcd semiconductor (taiwan) company limited 4f, 298-1, rui guang road, nei-hu district, taipei, taiwan tel: +886-2-2656 2808 fax: +886-2-2656 2806 usa office bcd semiconductor corp. 30920 huntwood ave. hayward, ca 94544, usa tel : +1-510-324-2988 fax: +1-510-324-2788 - headquarters bcd semiconductor manufacturing limited no. 1600, zi xing road, shanghai zizhu sc ience-based industrial park, 200241, china tel: +86-21-24162266, fax: +86-21-24162277 bcd semiconductor manufacturing limited important notice bcd semiconductor manufacturing limited reserves the right to make changes without further not ice to any products or specifi- cations herein. bcd semiconductor manufacturing limited does not as sume any responsibility for us e of any its products for any particular purpose, nor does bcd semiconductor manufacturi ng limited assume any liability aris ing out of the application or use of any its products or circui ts. bcd semiconductor manufacturing limited does not convey any license under its patent rights or other rights nor the rights of others. - wafer fab shanghai sim-bcd semiconductor manufacturing limited 800, yi shan road, shanghai 200233, china tel: +86-21-6485 1491, fax: +86-21-5450 0008 bcd semiconductor manufacturing limited main site regional sales office shenzhen office shanghai sim-bcd semiconductor manuf acturing co., ltd. shenzhen office advanced analog circuits (shanghai) corporation shenzhen office room e, 5f, noble center, no.1006, 3rd fuzhong road, futian district, shenzhen 518026, china tel: +86-755-8826 7951 fax: +86-755-8826 7865 taiwan office bcd semiconductor (taiwan) company limited 4f, 298-1, rui guang road, nei-hu district, taipei, taiwan tel: +886-2-2656 2808 fax: +886-2-2656 2806 usa office bcd semiconductor corporation 30920 huntwood ave. hayward, ca 94544, u.s.a tel : +1-510-324-2988 fax: +1-510-324-2788 - ic design group advanced analog circuits (shanghai) corporation 8f, zone b, 900, yi shan road, shanghai 200233, china tel: +86-21-6495 9539, fax: +86-21-6485 9673 bcd semiconductor manufacturing limited http://www.bcdsemi.com bcd semiconductor manufacturing limited

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