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product specification high-integrated green-mode pwm controller sg6841 ?system general corp. - 1 - www.sg.com.tw version 2.1 (iro33.0001.b5) jun.15,2006 features ? green-mode pwm to support ?blue angel? norm ? low start up current 30ua ? low operation current 3ma ? leading-edge blanking ? built-in synchronized slope compensation ? constant output power limit for universal ac input ? current mode operation ? cycle-by-cycle current limiting ? under voltage lockout (uvlo) ? programmable pwm frequency ? gate output maximum voltage clamped at 18v ? totem pole output includes soft driving for better emi ? build-in limited-power-control to meet safety requirement ? programmable over-temperature protection ? few external components & low cost solution applications general-purpose switching mode power supplies and flyback power converters, and ? power adapter ? open-frame smps ? battery charger adapter description this highly integrated pwm controllers, sg6841 series, provides several features to enhance the performance of low power flyback converters. to minimize standby power consumption, the proprietary green-mode function provides off-time modulation to linearly decrease the switching frequency under light-load conditions. this green-mode function assists the power supply to easily meet the power conservation requirement. due to bicm os process, the start-up current and opera tion current is reduced to 30ua and 3ma, respectively, to improve power conversion efficiency. large start-up resistance can be used for further power saving. built-in synchronized slope compensation ensures the stability of peak current mode control. a proprietary inte rnal compensation ensures constant output power limit for universal ac input voltage from 90vac to 264vac. sg6841 provides many protection functions. pulse by pulse current limit ensures a constant output current under short circuit. if a short circuit failure or over load happens, the sg6841 will shut off after a continuous high voltage detection on fb pin. the gate output is clamped at 18v to protect the power mos from over voltage damage. an external ntc thermistor can be applied to sense the ambient temperature for over-temperature protection. the sg6841 series are available in 8-pin dip and so packages. typical application sg6842 from auxiliary winding fb gate sense gnd vin rin rg r s from bridge rectifier 127~ 373vdc c in ra ri rt q1 rt ri vdd d1
product specification high-integrated green-mode pwm controller sg6841 ?system general corp. - 2 - www.sg.com.tw version 2.1 (iro33.0001.b5) jun.15,2006 marking diagrams pin configuration ordering information part number package sg6841s 8-pin sop sg6841d 8-pin dip sg6841sz 8-pin sop(lead free) sg6841dz 8-pin dip(lead free) pin descriptions pin no. symbol function description 1 gnd ground ground. 2 fb feedback the signal from external compens ation circuit is feed into this pin. the pwm duty cycle is determined by this fb pin and curr ent sense signal from pin 6. 3 vin start-up input this pin is pulled high to the rectified line i nput through a resistor for start-up. since the start-up current requirement for sg6841 is very small, a large start-up resistance can be used to minimize power loss. under normal ope ration, this pin is also used to detect line voltage to compensate for constant output power limit for universal ac input. 4 ri reference setting a resistor from ri pin to ground will generate a constant current source forsg6841. this current is used to charge an internal c apacitor and hence the switching frequency are determined. increasing the resistance will dec rease the current source and reduce the switching frequency. a 26k ? resistor r i creates a 50ua constant current i i and generates 65khz switching frequency. 5 rt temperature protection for over-temperature protection. an external ntc thermistor is connected from this pin to ground. the impedance of the ntc will decrease under high temperature. once the voltage on rt pin drops below a fixed limit, the pwm output will be disabled. 6 sense current sense current sense. the sensed voltage is used for current mode control and pulse-by-pulse current limiting. 7 vdd power supply power supply. 8 gate driver output the totem-pole output driver for the power mosfet. a soft driving waveform is implemented to improve emi. t : d = dip, s = sop p : z = lead free null=regular package xxxxxxx : wafer lot yy : year; ww : week v : assembly location sg6841 tp xxxxxxxyywwv ri vin gate vdd sense rt gnd fb
product specification high-integrated green-mode pwm controller sg6841 ?system general corp. - 3 - www.sg.com.tw version 2.1 (iro33.0001.b5) jun.15,2006 block diagram slope compensation 1 gnd rt 5 0.65v + _ i rt vdd uvlo 7 16v/10v _ + comp internal bias qs r comp green mode controller osc 0.85v vin 3 + _ ri 4 on/off driver fb 2 6v sense 6 gate 8 vdd limited power controller 2r r 4.2v
product specification high-integrated green-mode pwm controller sg6841 ?system general corp. - 4 - www.sg.com.tw version 2.1 (iro33.0001.b5) jun.15,2006 absolute maximum ratings symbol parameter value unit v dd dc supply voltage zener clamp zener current 30 32 10 v v ma i out gate output current 500 ma v fb input voltage to fb pin -0.3 to 7v v v sense input voltage to sense pin -0.3 to 7v v v rt input voltage to rt pin -0.3 to 7v v v ri input voltage to ri pin -0.3 to 7v v p d power dissipation 1 w r j-a thermal resistance junction-air dip sop 82.5 141 c /w t j operating junction temperature 150 c t a operating ambient temperature -30 to 85 c tstg storage temperature range -55 to +150 c t l lead temperature (wave soldering or ir, 10 seconds) 260 c esd capability, hbm model 3.0 kv esd capability, machine model 250 v recommended operating conditions symbol parameter value unit v dd dc supply voltage <20 v t a operating ambient temperature -20 to +85 r i current source setting 26 k ? electrical characteristics feedback input section symbol parameter test condition min. typ. max. unit a v input-voltage to current-sense attenuation 1/3.25 1/3 1/2.75 v/v z fb input impedance 2 4.5 8 k ? i fb bias current 2 ma v oz input voltage for zero duty cycle 1.2 v
product specification high-integrated green-mode pwm controller sg6841 ?system general corp. - 5 - www.sg.com.tw version 2.1 (iro33.0001.b5) jun.15,2006 current sense section symbol parameter test condition min. typ. max. unit z cs input impedance 8 12 16 k ? t pd delay to output 150 200 ns v th threshold voltage for current limit i vin = 0 ua 0.8 0.85 0.9 v v th @ i vin the change of threshold voltage versus the input current of the vin i vin = 220 ua -0.09 -0.15 -0.21 v v sense0 threshold voltage for i vin = 80ua i vin = 80 ua 0.73 0.81 0.89 v tdelay-lps the delay time of limited-power-control r i =26kohms 31 ms oscillator section symbol parameter test condition min. typ. max. unit f osc frequency in nominal mode r i =26kohms 60 65 70 khz fosc-green frequency in green mode r i =26kohms 10 16 khz v g end of green mode voltage at fb pin 1.4 v v n beginning of frequency reducing at fb pin 2.1 v s g slope for green mode modulation r i =26kohms 50 80 120 hz/mv f dv frequency variation versus v dd deviation v dd =10 to 20v 5 % f dt frequency variation versus temp. deviation t a =-30 to 85 5 % pwm section symbol parameter test condition min. typ. max. unit dc (max) maximum duty cycle 75 80 90 % dc (min) minimum duty cycle - - 0 % bnk leading edge blanking time 200 270 350 ns output section symbol parameter test condition min. typ. max. unit v ol output voltage low v dd = 12v, io = 150ma 1.5 v v oh output voltage high v dd = 12v, io = 50ma 8v v tr rising time v dd =13v, cl=1nf 150 250 350 ns tf falling time v dd =13v, cl=1nf 30 50 90 ns under-voltage lockout section symbol parameter test condition min. typ. max. unit v th(on) start threshold voltage 15 16 17 v v dd(min) min. operating voltage 9 10 11 v
product specification high-integrated green-mode pwm controller sg6841 ?system general corp. - 6 - www.sg.com.tw version 2.1 (iro33.0001.b5) jun.15,2006 over-temperature protection section symbol parameter test condition min. typ. max. unit i rt output current of pin rt r i =26kohms 92 100 108 ua v otp,stop threshold voltage for over-temperature protection. turn-off point. duty cycle is reduced to 0%. 0.585 0.62 0.655 v v otp,start threshold voltage for over-temperature protection. starting point. duty cycle starts to decrease. 0.65 v total standby cu rrent section symbol parameter test condition min. typ. max. unit i dd st start-up current vdd=14.5v 30 40 ua i dd op operating supply current fb=sense=0v gate=1000pf vdd=15.5v 3 5 ma
product specification high-integrated green-mode pwm controller sg6841 ?system general corp. - 7 - www.sg.com.tw version 2.1 (iro33.0001.b5) jun.15,2006 typical characteristics start-up current (i dd st ) vs tem perature 22.0 22.5 23.0 23.5 24.0 24.5 25.0 25.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) start-up current (ua) start-up current (i dd st ) vs vdd voltage 0 5 10 15 20 25 30 35 0 2 4 6 8 10 12 14 16 vdd voltage (v) start-up current (ua) frequency vs. fb voltage 0 10 20 30 40 50 60 70 1.1 1.4 1.7 2 2.3 2.6 2.9 fb voltage (v) frequency (khz) frequency in green mode (fosc-green) vs temperature 10.34 10.36 10.38 10.40 10.42 10.44 10.46 10.48 10.50 10.52 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) fosc-green (khz) pwm oscillator frequency (fosc) vs temperature 63.7 63.8 63.9 64.0 64.1 64.2 64.3 64.4 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) fosc (khz) maximum duty cycle dc( max. )vs temperature 84.20 84.25 84.30 84.35 84.40 84.45 84.50 84.55 84.60 84.65 84.70 84.75 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) max. duty cycle (%)
product specification high-integrated green-mode pwm controller sg6841 ?system general corp. - 8 - www.sg.com.tw version 2.1 (iro33.0001.b5) jun.15,2006 v sense vs i vin 0.44 0.49 0.54 0.59 0.64 0.69 0.74 0.79 0.84 0 40 80 120 160 200 240 280 320 360 i vin (ua) v sense min. operating voltage (v dd(min) ) vs temperature 9.70 9.75 9.80 9.85 9.90 9.95 10.00 10.05 10.10 10.15 10.20 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) v dd(min) (v) start threshold voltage (v th(on) ) vs temperature 16.20 16.25 16.30 16.35 16.40 16.45 16.50 16.55 16.60 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) v th(on) (v) rt voltage vs ton -2 0 2 4 6 8 10 12 14 0.620 0.628 0.636 0.644 0.652 0.660 rt voltage (v) ton (us) output current of pin rt (i rt ) vs temperature 98.5 99.0 99.5 100.0 100.5 101.0 101.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) i rt (ua) v otp, s top vs tem perature 0.60 0.60 0.61 0.61 0.62 0.62 0.63 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) v otp, stop (v)
product specification high-integrated green-mod e pwm controller sg6841 ?system general corp. - 9 - www.sg.com.tw version 2.1 (iro33.0001.b5) jun.15,2006 operation description start-up current typical start-up current is only 30ua so that a high resistance, and low-wattage, star t-up resistor can be used to minimize power loss. fo r an ac/dc adapter with universal input range, a 1.5 m ? , 0.25w, start-up resistor and a 10uf/25v vdd hold-up capacitor are enough for this application. operating current operating current has been reduced to 3ma. the low operating current enables a better efficiency and reduces the requirement of vdd hold-up capacitance. green mode operation the patented green-mode function provides an off-time modulation to reduce the switching frequency in the light load and no load conditions. the on time is limited for better abnormal or brownout protection. v fb , which is derived from the voltage feedback loop, is taken as the reference. once v fb is lower than the threshold voltage, switching frequency w ill be linearly decreased to the minimum green mode frequency around 10khz (r i =26k ? ). oscillator operation a resistor from ri pin to ground will generate a constant current source for sg6841. this current is used to charge an internal capac itor and hence the internal clock and switching frequency are determined. increase the resistance will decrease the current source and reduce the switching frequency. a 26k ? resistor r i creates a 50ua constant current i i and generates 65khz switching frequency. the relation between ri and switching freauency is: ) ( khz ) (k r 1690 i pwm f = ---------------------------- (1) the range of the pwm os cillation frequency is designed as 50khz ~ 90khz. current sensing and pwm current limiting peak current mode control is utilized in sg6841 to regulate output voltage and provide pulse by pulse current limiting. the switch current is detected by a sense resistor into the sense pin of sg6841. the pwm duty cycle is determined by this current sense signal and v fb , the feedback voltage. when the vo ltage on sense pin reaches v comp = (v fb ?1.0)/3, a switch cycle will be terminated immediately. v comp is internally clamped to a variable voltage around 0.85v for output power limit. leading edge blanking each time when the powe r mosfet is switched on, a turn-on spike will inevitably occur on the sense-resistor. to avoid premature terminati on of the switching pulse, a 270 nsec leading-edge blanking time is built in. conventional rc filtering can therefore be omitted. during this blanking period, the current-limit comparator is disabled and it cannot switch off the gate driver. under-voltage lockout (uvlo) the turn-on and turn-off threshold of sg6841 are fixed internally at 16v/10v. during start-up, the hold-up capacitor must be charged to 16v through the start-up resistor so that sg6841 will be enabled. the hold-up capacitor will continue to supply v dd before the energy can be delivered from auxiliary winding of the main transformer. v dd must not drop below 10v during this start-up process. this uvlo hysteresis window insures that hold-up capacitor is adequate to supply v dd during start-up. gate output / soft driving the sg6841 bicmos output stage is a fast totem pole gate driver. cross conduction has been avoided to minimize heat dissipation, increases efficiency and enhances reliability. the output driver is clamped by an internal 18v zener diode in order to protect power mosfet transistors against undesirable gate over voltage. a soft driving waveform is implemented to minimize emi.
product specification high-integrated green-mod e pwm controller sg6841 ?system general corp. - 10 - www.sg.com.tw version 2.1 (iro33.0001.b5) jun.15,2006 built-in slope compensation the sensed voltage across the current sense resistor is used for current mode control and pulse-by-pulse current limiting. built-in slope compensation will improve stability or prevent sub-harmonic oscillation of peak current mode control. sg6841 inserts a synchronized positive-goi ng ramp at every switching cycle. vs-comp = 0.33v. constant output power limit when the sense voltage, across the sense resistor rs, reaches the threshold vo ltage, around 1.0v, the output gate drive will be turned off after a small propagation delay t d . this propagation delay will introduce an additional current proportional to t d *vin/lp. since the propagation delay is nearly constant regardless of the input line voltage v in. higher input line voltage will result in a larger additional current and hence the output power limit is also higher than that under low input line voltage. to compensate this variation for wide ac input range, the threshold voltage is adjusted by the v in current. since vin pin is connected to the rectified input line voltage through the start-up resistor, a higher line voltage will generate higher v in current into the vin pin. the threshold voltage is decreased if the v in current is increased. smaller threshold voltage, forces the output gate drive to terminate earlier, thus reduce the total pwm turn-on time and make the output power equal to that of low line input. this proprietary internal compensation ensures a constant output power limit for wide ac input voltage from 90vac to 264vac. ? thermal protection an ntc thermistor rntc in series with a resistor ra can be connected from pin rt to ground. a constant current i rt is output from pin rt. the voltage on rt pin can be expressed as v rt = i rt (rntc + ra) in which i rt = 2 x (1.3v / ri). at high ambient temperature, rntc will be smaller such that v rt will decrease. when v rt is less than 0.65v (v otp,start ), the pwm duty cycle will be decreased to lower the internal temperatur e of power supply. if the over heating situation still exists such that v rt decreases further to 0.62v (v otp,stop ), the pwm will be completely turned off. limited power control every time when the output of power supply is shorted or over loaded, the fb voltage will increase. if the fb voltage is higher than a designed threshold, 4.2v, for longer than 31msec, the pwm output will then be turned off eternally. v dd , the supply voltage for sg6841, will decrease due to the supply current for sg6841. when v dd is lower than the turn-off threshold such as 10v, sg6841 will be totally shut down. due to the start up resistor, v dd will be charged up to the turn-on threshold voltage 16v until sg6841 is enabled again. if the over loading condition still exists , above protection will take place repeatedly. this will prevent the power supply from being overheated under over loading condition. noise immunity noise on the current sens e or control signal may cause significant pulse width jitter, particularly in the continuous conduction mode. slope compensation helps alleviate this problem. good placement and layout practices should be followed. avoiding long pcb traces and component leads, locating compensation and filter components near to the sg6841, and increasing the power mos gate resistance will always help.
product specification high-integrated green-mod e pwm controller sg6841 ?system general corp. - 11 - www.sg.com.tw version 2.1 (iro33.0001.b5) jun.15,2006 reference circuit circuit bom reference component reference component bd1 bd 4a/600v r1,r2 r 1mohm 1/4w c1 xc 0.1uf/275v r3 r 100kohm 1/2w c2 xc 0.22uf/275v r4 r 47ohm 1/4w c3 cc 0.01uf/500v r5,r7 r 750kohm 1/4w c4 ec 120u/400v r6 r 20kohm 1/8w c5 yc 222p/y1 r8 r 0.3ohm 2w c6 cc 1000pf/100v r9 r 33kohm 1/8w c7 cc 1000pf/50v r9 r 20kohm 1/8w 1% c8 ec 1000uf/35v r11 r 220ohm 1/8w c9 ec 220uf/35v r12 r 4.7ohm 1/8w d1 led r13 r 6.8kohm 1/8w d2 diode fr157 r14 r 154kohm 1/8w d3 zd 18v r15 r 390kohm 1/8w d4 diode fr102 ther1 thermistor sck054 f1 fuse 4a/250v t1 transformer l1 900uh u1 ic sg6841 l2 15mh u2 ic pc817 q1 diode 20a100v u3 ic tl431 q2 mos 7a/600v vz1 vz 9g vo+ vo+ r7 r1 1,2 3 4 5 6,7 8,9 1,2 3 4 5 6,7 8,9 c1 vz1 1 2 f1 r11 u1 sg6841 1 2 3 4 5 6 7 8 gnd fb vin ri rt sense vdd gate + c9 bd1 2 1 3 4 r4 u2 1 2 3 4 + c4 r3 d4 2 1 r10 r8 cn1 1 2 3 c5 r9 + c7 c6 l3 1 2 l1 1 2 3 4 r14 r15 r2 c10 r13 u3 3 1 2 + c8 c2 q1 1 3 2 r5 d3 2 1 d1 2 1 r12 d2 2 1 l2 1 2 3 4 q2 1 2 3 r6 ther1 1 2 c3 ther2 1 2
product specification high-integrated green-mod e pwm controller sg6841 ?system general corp. - 12 - www.sg.com.tw version 2.1 (iro33.0001.b5) jun.15,2006 package information 8 pins? dip (d) 4 1 8 5 d e1 e e b a1 a2 a b b1 l e dimension millimete r inch symbol min. typ. max. min. typ. max. a 5.334 0.210 a1 0.381 0.015 a2 3.175 3.302 3.429 0.125 0.130 0.135 b 1.524 0.060 b1 0.457 0.018 d 9.017 9.271 10.160 0.355 0.365 0.400 e 7.620 0.300 e1 6.223 6.350 6.477 0.245 0.250 0.255 e 2.540 0.100 l 2.921 3.302 3.810 0.115 0.130 0.150 e b 8.509 9.017 9.525 0.335 0.355 0.375 0 7 15 0 7 15
product specification high-integrated green-mod e pwm controller sg6841 ?system general corp. - 13 - www.sg.com.tw version 2.1 (iro33.0001.b5) jun.15,2006 8 pins? sop (s) 1 4 8 5 h e e b a a1 d c f l dimension millimete r inch symbol min. typ. max. min. typ. max. a 1.346 1.752 0.053 0.069 a1 0.101 0.254 0.004 0.010 b 0.406 0.016 c 0.203 0.008 d 4.648 4.978 0.183 0.196 e 0.381 3.987 0.150 0.157 e 1.270 0.050 f 0 . 38 1x4 5 0 . 0 1 5 x4 5 h 5.791 6.197 0.228 0.244 l 0.406 1.270 0.016 0.050 0 8 0 8
product specification high-integrated green-mod e pwm controller sg6841 ?system general corp. - 14 - www.sg.com.tw version 2.1 (iro33.0001.b5) jun.15,2006 disclaimers life support system general?s products are not designed to be used as components in devices intended to support or sustain human life. use of system general?s products in componen ts intended for surgical implant into the body, or other applications in which failure of the system general?s produc ts could create a situation where personal death or injury may occur, is not authorized without the express written appr oval of system general?s chief executive officer. system general will not be held liable for any damages or claims resulting from the use of its products in medical applications. military system general's products are not designed for use in mi litary applications. use of system general?s products in military applications is not authorized without the express written approval of system gene ral?s chief executive officer. system general will not be held liable for any damages or claims resulting from the use of its products in military applications. right to make changes system general reserves the right to change this document and/or this product without notice. customers are advised to consult their system general sales representative before ordering.

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