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product specification highly-integrated green-mode pwm controller sg6741 ? system general corp. - 1 - www.sg.com.tw ? www.fairchildsemi.com version 1.2.1 (iao33.0047.b2) september 19, 2007 features ? high-voltage start-up ? low operating current (4ma) ? linearly decreasing pwm frequency to 22khz ? frequency hopping to reduce emi emission ? peak-current-mode control ? cycle-by-cycle current limiting ? leading-edge blanking ? synchronized slope compensation ? gate output maximum voltage clamp (18v) ? v dd over-voltage protection (auto restart) ? v dd under-voltage lockout (uvlo) ? internal open-loop protection ? constant power limit (full ac input range) applications general-purpose switch-mode power supplies and flyback power converters, including: ? power adapters ? open-frame smps description the highly integrated sg6741 series of pwm controllers provides several features to enhance the performance of flyback converters. to minimize standby power consumption, a proprietary green-mode function provides off-time modulation to linearly decrease the switching frequency at light-load conditions. to avoid acoustic-noise problems, the minimum pwm frequency is set above 22khz. this green-mode function enables the power supply to meet international power conservation requirements. with the internal high-voltage start-up circuitry, the power loss due to bleeding resistors is also eliminated. to further reduce power consumption, sg6741 is manufactured using the bicmos process, which allows operating current as low as 4ma. sg6741 integrates a frequency-hopping function that helps reduce emi emission of a power supply with minimum line filters. its built-in synchronized slope compensation achieves stable peak-current-mode control. the proprietary internal line compensation ensures constant output power limit over a wide range of ac input voltages, from 90vac to 264vac. sg6741 provides many protection functions. in addition to cycle-by-cycle current limiting, the internal open-loop protection circuit ensures safety when an open-loop or output short-circuit failure occurs. pwm output is disabled until v dd drops below the uvlo lower limit; then the controller starts again. as long as v dd exceeds about 26v, the internal ovp circuit is triggered. sg6741 is available in an 8-pin dip or sop package. typical application
product specification highly-integrated green-mode pwm controller sg6741 ? system general corp. - 2 - www.sg.com.tw ? www.fairchildsemi.com version 1.2.1 (iao33.0047.b2) september 19, 2007 marking information pin configuration ordering information part number pb-free package SG6741SZ sop-8 pin descriptions pin no. symbol function description 1 gnd ground ground. 2 fb feedback the signal from the external compensation circuit is fed into this pin. the pwm duty cycle is determined in response to the signal on this pin and the current-sense signal on the sense pin. 3 nc na nc pin. 4 hv start-up input for start-up, this pin is pulled high to the line input or bulk capacitor via resistors. 5 ri reference setting a resistor connected from the ri pin to gnd pin provides the sg6741 with a constant current source. this determines the center pwm frequency. increasing the resistance reduces pwm frequency. using a 26k ? resistor (r i ) results in a 65khz center pwm frequency. 6 sense current sense current sense. the sensed voltage is used for peak-current-mode control and cycle-by-cycle current limiting. 7 vdd power supply power supply. the internal protection circuit disables pwm output as long as v dd exceeds the ovp trigger point. 8 gate driver output the totem-pole output driver. soft driving waveform is implemented for improved emi. hv n c gate vdd sense ri gnd fb t : s = sop p: z =lead free null=regular package xxxxxxxx: wafer lot y : year; ww : week v : assembly location sg6741 tp xxxxxxxxywwv
product specification highly-integrated green-mode pwm controller sg6741 ? system general corp. - 3 - www.sg.com.tw ? www.fairchildsemi.com version 1.2.1 (iao33.0047.b2) september 19, 2007 block diagram
product specification highly-integrated green-mode pwm controller sg6741 ? system general corp. - 4 - www.sg.com.tw ? www.fairchildsemi.com version 1.2.1 (iao33.0047.b2) september 19, 2007 absolute maximum ratings symbol parameter value unit v dd supply voltage 30 v v hv input voltage to hv pin 500 v v l input voltage to fb, sense, pin -0.3 to 7 v dip 800 mw p d power dissipation, t a < 50c sop 400 mw dip 82.5 c/w r ja thermal resistance, junction-to-air sop 141 c/w t j operating junction temperature -40 to +125 c t stg storage temperature range -55 to +150 c t l lead temperature (wave soldering or ir, 10 seconds) 260 c electrostatic discharge capability, human body model (all pins except hv pin) 3 kv esd electrostatic discharge capability, machine model (all pins except hv pin) 250 v *all voltage values, except differential voltages, are given with respect to the gnd pin. *stresses above those listed may cause permanent damage to the device. recommended operating conditions symbol parameter value unit t a operating ambient temperature -20 to +85 c *for proper operation electrical characteristics 12v v dd 25v; -20c t a 85c, unless otherwise noted. v dd section symbol parameter test condition min. typ. max. unit v dd-op continuously operating voltage 22 v v dd-on start threshold voltage 15.5 16.5 17.5 v v dd-off minimum operating voltage 9.5 10.5 11.5 v i dd-st start-up current v dd-on ? 0.16v 30 a i dd-op operating supply current v dd = 15v, gate open 4 5 ma i dd-olp internal sink current v dd-olp +0.1v 50 70 90 a v dd-olp i dd-olp off voltage 6.5 7.5 8.0 v v dd-ovp v dd over-voltage protection (auto restart) 25 26 27 v t d-vddovp v dd over-voltage-protection debounce time (auto restart) 100 180 260 s hv section symbol parameter test condition min. typ. max. unit i hv supply current drawn from pin hv v ac =90v(v dc =120v) v dd =0v 2 ma i hv-lc leakage current after start-up with auxiliary supply hv = 500v, v dd = 15v 1 20 a
product specification highly-integrated green-mode pwm controller sg6741 ? system general corp. - 5 - www.sg.com.tw ? www.fairchildsemi.com version 1.2.1 (iao33.0047.b2) september 19, 2007 oscillator section symbol parameter test condition min. typ. max. unit center frequency 62 65 68 f osc frequency in nominal mode hopping range 3.7 4.2 4.7 khz t hop hopping period 4.4 ms f osc-g green-mode frequency 18 22 25 khz f dv frequency variation vs. v dd deviation v dd =11v to 22v 5 % f dt frequency variation vs. temp. deviation t a =-20 to 85 5 % feedback input section symbol parameter test condition min. typ. max. unit a v input voltage to current-sense attenuation 1/3.75 1/3.20 1/2.75 v/v z fb input impedance 4 7 k ? v fb-open fb output high voltage fb pin open 5.5 v v fb-olp fb open-loop trigger level 3.7 4.0 4.3 v t d-olp delay time, fb pin open-loop protection r i =26k ? 50 56 62 ms v fb-n green-mode entry fb voltage 1.9 2.1 2.3 v v fb-g green-mode ending fb voltage v fb-n -0.5 v current-sense section symbol parameter test condition min. typ. max. unit z sense input impedance 12 k ? v sthfl current limit flatten threshold voltage 0.87 0.90 0.93 v v sthva current limit valley threshold voltage v sthfl ?v sthva 0.18 0.22 0.26 v t pd delay to output 100 200 ns t leb leading-edge blanking time 275 350 425 ns v s-scp threshold voltage for sense short-circuit protection 0.15 v t d-sscp delay time for sense short-circuit protection v sense <0.15v, r i =26k ? 180 s pwm frequency f osc f osc-g v fb v fb-n v fb-g
product specification highly-integrated green-mode pwm controller sg6741 ? system general corp. - 6 - www.sg.com.tw ? www.fairchildsemi.com version 1.2.1 (iao33.0047.b2) september 19, 2007 gate section symbol parameter test condition min. typ. max. unit dcy max maximum duty cycle 60 65 70 % v gate-l gate low voltage v dd =15v, i o =50ma 1.5 v v gate-h gate high voltage v dd =12.5v, i o =50ma 8 v tr gate rising time v dd =15v, c l =1nf 150 250 350 ns tf gate falling time v dd =15v, c l =1nf 30 50 90 ns i gate-source gate source current v dd =15v, gate=6v 250 ma v gate-clamp gate output clamping voltage v dd =22v 18 v
product specification highly-integrated green-mode pwm controller sg6741 ? system general corp. - 7 - www.sg.com.tw ? www.fairchildsemi.com version 1.2.1 (iao33.0047.b2) september 19, 2007 typical characteristic start-up current (i dd-st ) vs temperature 0 5 10 15 20 25 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) i dd-st (ua) operating supply current (i dd-op ) vs temperature 0.0 1.0 2.0 3.0 4.0 5.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) i dd-op (ma) start threshold voltage (v dd-on ) vs temperature 15.0 16.0 17.0 18.0 19.0 20.0 -40-25-105203550658095110125 temperature ( ) v dd-on (v) minimum operating voltage (v dd-off ) vs temperature 8.0 9.0 10.0 11.0 12.0 13.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) v dd-off (v) supply current drawn from pin hv (i hv ) vs temperature 0.0 1.0 2.0 3.0 4.0 5.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) i hv (ma) hv pin leakage current after start-up (i hv-lc ) vs temperature 0 2 4 6 8 10 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) i hv-lc (ua)
product specification highly-integrated green-mode pwm controller sg6741 ? system general corp. - 8 - www.sg.com.tw ? www.fairchildsemi.com version 1.2.1 (iao33.0047.b2) september 19, 2007 frequency in nominal mode (f osc ) vs temperature 60 62 64 66 68 70 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) f osc (khz) maximum duty cycle (dcy max ) vs temperature 60.0 62.0 64.0 66.0 68.0 70.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) dcy max (%) .
product specification highly-integrated green-mode pwm controller sg6741 ? system general corp. - 9 - www.sg.com.tw ? www.fairchildsemi.com version 1.2.1 (iao33.0047.b2) september 19, 2007 operation description start-up current for start-up, the hv pin is connected to the line input or bulk capacitor through an external resistor, r hv , which is recommended as 100k ? . typical start-up current drawn from pin hv is 2ma and it charges the hold-up capacitor through the resistor r hv . when the v dd capacitor level reaches v dd-on , the start-up current switches off. at that moment, the v dd capacitor only supplies the sg6741 to maintain the v dd before the auxiliary winding of the main transformer to carry on provide the operating current. operating current operating current is around 4ma. the low operating current enables better efficiency and reduces the requirement of v dd hold-up capacitance. green-mode operation the patented green-mode function provides an off-time modulation to reduce switching frequency in light-load and no-load conditions. the on time is limited for better abnormal or brownout protection. vfb, which is derived from the voltage feedback loop, is used as the reference. once vfb is lower than the threshold voltage, switching frequency is continuously decreased to the minimum green-mode frequency, around 22khz (r i =26k ? ). oscillator operation a resistor connected from the ri pin to gnd generates a constant current source for the sg6741 controller. this current is used to determine the center pwm frequency. increasing the resistance reduces pwm frequency. using a 26k ? resistor, r i , results in a corresponding 65khz pwm frequency. the relationship between r i and the switching frequency is: (khz) 1690 ) (k r i = pwm f --------------------- (1) the range of the pwm osci llation frequency is designed as 47khz ~ 109khz. current sensing / pwm current limiting peak-current-mode control is utilized in sg6741 to regulate output voltage and provide pulse-by-pulse current limiting. the switch current is detected by a sense resistor into the sense pin. the pwm duty cycle is determined by this current-sense signal and v fb , the feedback voltage. when the voltage on the sense pin reaches around v comp = (v fb ?1.2)/3.2, the switch cycle is terminated immediately. v comp is internally clamped to a variable voltage around 0.85v for output power limit. leading-edge blanking each time the power mosfet is switched on, a turn-on spike occurs on the sense-resistor. to avoid premature termination of the switching pulse, a leading-edge blanking time is built in. during this blanking period, the current-limit comparator is disabled and cannot switch off the gate driver. under-voltage lockout (uvlo) the turn-on and turn-off thresholds are fixed internally at 16.5v/10.5v. during start-up, the hold-up capacitor must be charged to 16.5v through the start-up resistor so that ic is enabled. the hold-up capacitor continues to supply v dd before the energy can be delivered from auxiliary winding of the main transformer. v dd must not drop below 10.5v during this start-up process. this uvlo hysteresis window ensures that hold-up capacitor is adequate to supply v dd during start-up. gate output / soft driving the sg6741 bicmos output stage is a fast totem pole gate driver. cross conduction has been avoided to minimize heat dissipation, increase efficiency, and enhance reliability. the output driver is clamped by an internal 18v zener diode to protect power mosfet transistors against undesirabl e gate over-voltage. a soft driving waveform is implemented to minimize emi.
product specification highly-integrated green-mode pwm controller sg6741 ? system general corp. - 10 - www.sg.com.tw ? www.fairchildsemi.com version 1.2.1 (iao33.0047.b2) september 19, 2007 built-in slope compensation the sensed voltage across the current-sense resistor is used for peak-current-mode control and pulse-by-pulse current limiting. built-in slope compensation improves stability and prevents sub-harmonic oscillation. sg6741 inserts a synchronized positive-going ramp at every switching cycle. constant output power limit when the sense voltage, across the sense resistor r s , reaches the threshold voltage around 0.9v, the output gate drive is turned off after a small delay, t pd . this delay introduces an additional current, proportional to t pd ? v in / l p . the delay is nearly constant, regardless of the input voltage v in. higher input voltage results in a larger additional current and the output power limit is also higher than that under low input line voltage. to compensate this variation for wide ac input range, a sawtooth power-limiter is designed to solve the unequal power-limit problem. the power limiter is designed as a positive ramp signal and is fed to the inverting input of the ocp comparator. this results in a lower current limit at high-line inputs than at low-line inputs. v dd over-voltage protection v dd over-voltage protection has been built in to prevent damage due to abnormal conditions. once the v dd voltage is over the v dd over-voltage protection voltage (v dd-ovp ), and lasts for t d-vddovp , the pwm pulses is disabled until the v dd voltage drops below the uvlo, then starts up again. over-voltage conditions are usually caused by open feedback loops. limited power control the fb voltage increases every time the output of the power supply is shorted or overloaded. if the fb voltage remains higher than a built-in threshold for longer than t d-olp , pwm output is turned off. as pwm output is turned off, the supply voltage v dd begins decreasing. when v dd goes below the turn-off threshold (eg, 10.5v) the controller totally shuts down. v dd is charged up to the turn-on threshold voltage of 16v through the start-up resistor until pwm output is re started. this protection is activated as long as the over loading condition persists. this prevents the power supply from overheating. noise immunity noise on the current sense 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 sg6741, and increasing the power mo gate resistance improves performance.
product specification highly-integrated green-mode pwm controller sg6741 ? system general corp. - 11 - www.sg.com.tw ? www.fairchildsemi.com version 1.2.1 (iao33.0047.b2) september 19, 2007 reference circuit circuit (12v/5a) 1 2 3 cn1 cn1 c2 2 1 + c4 2 1 3 4 bd1 2 1 d2 1 2 3 q2 r7 gnd 1 fb 2 nc 3 hv 4 ri 5 sense 6 vdd 7 gate 8 u1 sg6741 r4 1 2 4 3 u2 c6 r2 1 3 2 q1 2 1 + c7 2 1 d3 r9 r11 r10 r8 c11 2 1 + c9 vz1 c1 1 2 3 4 t1 4 2 3 7 8 6 5 t2 vo+ vo- c3 1 2 3 4 l1 2 1 + c8 1 2 3 4 l2 2 1 d1 a k r u3 vo+ 1 2 l4 r3 vo+ r1 c5 r6 c10 r5 c12 bom reference component reference component bd1 bd 4a/600v q2 mos 7a/600v c1 xc 0.68f/300v r1 r 100kohm 1/2w c2 xc 0.1f/300v r2 r 47ohm 1/4w c3 yc 222pf/y1 r3 r 100kohm 1/2w c4 ec 120f/400v r4 r 20ohm 1/8w c5 cc 0.01f/500v r5 r 100ohm 1/8w c6 cc 102pf/100v r6 r 33kohm 1/8w c7 ec 1000f/25v r7 r 0.3ohm 2w c8 ec 470f/25v r8 r 680ohm 1/8w c9 ec 22f/50v r9 r 4.7kohm 1/8w c10 cc 470pf/50v r10 r 150kohm 1/8w c11 cc 222pf/50v r11 r 39kohm 1/8w c12 cc 103pf/50v t1 10mh d1 zener diode 15v 1/2w (option) t2 600h(pq2620) d2 byv95c u1 ic sg6741 d3 fr103 u2 ic pc817 f1 fuse 4a/250v u3 ic tl431 l1 900h vz1 vz 9g q1 stp20-100ct
product specification highly-integrated green-mode pwm controller sg6741 ? system general corp. - 12 - www.sg.com.tw ? www.fairchildsemi.com version 1.2.1 (iao33.0047.b2) september 19, 2007 package information 8pins-sop(s) 1 4 8 5 h e e b a a1 d c f l dimensions millimeter inch symbol min. t yp .max.min.t yp .max. a 1.346 1.752 0.053 0.069 a 1 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 3.810 3.987 0.150 0.157 e 1.016 1.270 1.524 0.040 0.050 0.060 f 0.381x45 0.015x45 h 5.791 6.197 0.228 0.244 l 0.406 1.270 0.016 0.050 ? 0 8 0 8
product specification highly-integrated green-mode pwm controller sg6741 ? system general corp. - 13 - www.sg.com.tw ? www.fairchildsemi.com version 1.2.1 (iao33.0047.b2) september 19, 2007

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