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product specification low-power green-mode pwm flyback power controller without secondary feedback sg6849 ? system general corp. - 1 - www.sg.com.tw version 1.0(iro33.0002.b3) dec.29, 2003 v in c in r in d 1 w aux c o d o q1 v o r s sense gate vdd gnd features linearly decreasing pwm frequency green-mode under light-load and zero-load conditions constant voltage (cv) and constant current (cc) no secondary feedback low startup current (5ua) low operating current (3.6ma) leading-edge blanking constant power limit universal ac input range synchronized slope compensation 150 c otp sensor with hysteresis v dd over voltage clamping cycle-by-cycle current limiting under voltage lockout (uvlo) fixed pwm frequency (65khz/100khz) gate output maximum voltage clamped at 16.7v small sot-26 package applications low-power flyback power converters, such as battery chargers for cellular phones, cordless phones, pdas, digital cameras, and power tools. power adapters for ink jet printers, video game consoles, and portable audio players. open-frame smps for tv/dvd standby and other auxiliary supplies, home appliances, consumer electronics, and pc 5v standby-power. replacements for linear transformers and rcc smps. description this highly integrated pwm controller 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 and zero-load conditions. this green-mode function enables the power supply to easily meet international power conservation requirements. the supply voltage v dd is also used for feedback compensation, to regulate the output voltage without requiring a conventional tl431 and a photo-coupler. another advantage of the sg6849 is that the typical startup current is only 5ua, while the typical operating current can be as low as 3.6ma. a large startup resistance could be used to achieve even higher power conversion efficiency. built-in synchronized slope compensation maintains the stability of peak current-mode control. proprietary internal compensation ensures constant output power limiting over a universal range of ac input voltages, from 90vac to 264vac.the sg6849 provides many protection functions. pulse-by-pulse current limiting ensures a constant output current, even if a short circuit occurs. also, the internal protection circuit will disable pwm output, if v dd exceeds 22.7v. the gate output is clamped at 16.7v to protect the power mos from over-voltage damage. the built-in over temperature protection (otp) function will shutdown the controller at 150 c with a 20 c hysteresis. the sg6849 is designed to provide a low-cost total solution for flyback converters. it is available in a small footprint, 6-pin, sot-26 package. typical ic application
product specification low-power green-mode pwm flyback power controller without secondary feedback sg6849 ? system general corp. - 2 - www.sg.com.tw version 1.0(iro33.0002.b3) dec.29, 2003 marking information pin configuration ordering information part number pwm frequency package sg6849-65t 65khz 6-pin sot-26 SG6849-100T 100khz 6-pin sot-26 sg6849-65d 65khz 8-pin dip-8 sg6849-100d 100khz 8-pin dip-8 pin descriptions pin no. name dip-8 sot-26 type function gate 1 6 driver output the totem-pole output driver to drive the power mosfet. vdd 2 5 supply power supply. nc 3 na nc pin. sense 4 4 analog input current sense. it senses the voltage across a sensed resistor. to provide over-current protection, pwm output is disabled if the voltage exceeds an internal threshold. this pin also provides current information for current-mode control. nc 5 3 nc pin. nc 6 na nc pin. fb 7 2 analog input feedback. the fb pin provides feedback information to the internal pwm comparator. this feedback is used to control the duty cycle. when no feedback is provided, this pin is left open. gnd 8 1 supply ground. m : mask version x: b= sg6849-65t c= SG6849-100T y : year w w : work wee k 1 2 3 4 5 6 sot-26 gn d fb nc gate vdd sense 1 mxyww zzz: 65 or 100 xxxxxxx : wafer lot yy : year ww : week v : assembly location 8 1 sg6849- zzzd xxxxxxxyy wwv nc sense n c gnd fb nc gate vdd 3 1 2 4 5 6 8 7 dip-8
product specification low-power green-mode pwm flyback power controller without secondary feedback sg6849 ? system general corp. - 3 - www.sg.com.tw version 1.0(iro33.0002.b3) dec.29, 2003 block diagram 2(5) 8(1) 7(2) green mode controller internal supply uvlo gnd gate vdd 17v/8v 1(6) otp sense 4(4) sense blanking circuit driver v dd fb s q r osc 4.5v vdd vddz comp slo p e com p ensation pwm comp ocp v dd powe r limiter dip-8(sot-26)
product specification low-power green-mode pwm flyback power controller without secondary feedback sg6849 ? system general corp. - 4 - www.sg.com.tw version 1.0(iro33.0002.b3) dec.29, 2003 absolute maximum ratings symbol parameter value unit v dd dc supply voltage* zener clamp zener current 25 30 10 v v ma v fb fb pin input voltage -0.3 to 7 v v sense sense pin input voltage -0.3 to 7 v p d power dissipation 300 mw r ja thermal resistance (junction to air) sot-26 dip-8 243.3 113.0 c/w r jc thermal resistance (junction to case) sot-26 dip-8 115 67.1 c/w t j operating junction temperature 150 c t stg storage temperature range -55 to +150 c t l lead temperature (soldering) 20 sec sot-26 10 sec dip-8 220 260 c esd capability, human body model 3.0 kv esd capability, machine model 300 v *all voltage values, except differential voltages, are given with respect to the network ground terminal. operating conditions symbol parameter value unit v dd dc supply voltage < 22.7 v t a operating ambient temperature -30 to +85 c electrical characteristics (v dd =15v, t a =25c) feedback input section symbol parameter test condition min. typ. max. unit i oz zero duty-cycle fb input current 1.15 1.4 ma v fb open loop voltage 4.5 v r fb input impedance fb input current = 0.1ma 2.4 k ? fb input current = 0ma 20 22.7 25 v v ddz v dd feedback threshold voltage* fb input current = 0.8ma 18 20 22 v *the feedback input is pulled by a transistor that is controlled by the v dd signal while v dd v R ddz .
product specification low-power green-mode pwm flyback power controller without secondary feedback sg6849 ? system general corp. - 5 - www.sg.com.tw version 1.0(iro33.0002.b3) dec.29, 2003 current sense section symbol parameter test condition min. typ. max. unit tpd propagation delay 100 ns vdd = 20v 0.84 0.89 0.94 v vdd = 15v 0.72 0.77 0.82 v current limiting valley threshold voltage for 65khz vdd = 10v 0.58 0.63 0.68 v vdd = 20v 0.76 0.81 0.86 v vdd = 15v 0.65 0.70 0.75 v vth,va current limiting valley threshold voltage for 100khz vdd = 10v 0.52 0.57 0.62 v oscillator section symbol parameter test condition min. typ. max. unit f osc sg6849?65 frequency 60 65 70 khz f osc sg6849?100 frequency 92 100 108 khz f osc-g-bk green-mode burst back frequency* 20 25 30 khz f osc-g-off green-mode off frequency* 0 khz i fb-g-off green-mode off fb input current 0.9 1.15 1.4 ma f dv frequency variation versus v dd deviation v dd = 10 to 20v 2 % v dd-th-g v dd -low threshold voltage for exiting green-mode off v dd off +1.0 v dd off +1.5 v dd off +2.0 v *please see the ?green-mode burst back (f osc-g-bk ) and green-mode off frequency (f osc-g-off ) vs. v dd ? curves. 0.77v v limit ramp t off t on low-line sense voltage high-line sense voltage 0v t 1 t 2 v th,va v th,ft
product specification low-power green-mode pwm flyback power controller without secondary feedback sg6849 ? system general corp. - 6 - www.sg.com.tw version 1.0(iro33.0002.b3) dec.29, 2003 output section symbol parameter test condition min. typ. max. unit dcy max maximum duty cycle 70 75 80 % bnk leading edge blanking time 310 ns v ol output voltage low v dd = 15v, i o = 10ma 1.5 v v oh output voltage high v dd = 15v, i o = 10ma 8 v t r rising time v dd = 15v, c l = 1nf 200 ns t f falling time v dd = 15v, c l = 1nf 80 ns v clamp output clamp voltage v dd = 20v 16.7 18 v over temperature protection (otp) symbol parameter test condition min. typ. max. unit temp-off protection junction temperature *1 150 c temp-restart restart junction temperature *2 130 c *1 when activated, the output is disabled and the latch is turned off. *2 this is the threshold temperature for enabling the output again and resetting the latch, after over temperature protection has been activated. vdd section symbol parameter test condition min. typ. max. unit v dd on turn-on threshold voltage 16 17 18 v v dd off turn-off threshold voltage 7.5 8 8.5 v i dd st startup current v dd = 15v 5 30 ua i dd op operating supply current v dd = 15v gate is open 3.6 6 ma v dd clamp zener diode breakdown voltage i dd = 10ma 28 30 v
product specification low-power green-mode pwm flyback power controller without secondary feedback sg6849 ? system general corp. - 7 - www.sg.com.tw version 1.0(iro33.0002.b3) dec.29, 2003 typical characteristics sg6849-65 start-up current (i dd st ) vs. temperature 3.0 4.0 5.0 6.0 7.0 8.0 9.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) i dd st (ua ) v dd =15.0v operating supply current (i dd op ) vs. temperature 3.0 3.3 3.5 3.8 4.0 4.3 4.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) i dd op (ma ) v dd =15.0v vfb open loop voltage (v fb ) vs. temperature 4. 0 4. 2 4. 4 4. 6 4. 8 5. 0 -40 -30 -15 0 25 50 75 100 125 t emperature ( ) v fb (v ) v dd =15.0v maximum duty cycle (dcy max ) vs. temperature 70.0 72.0 74.0 76.0 78.0 80.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) dcy max (%) v dd =15.0v oscillator frequency (f osc ) vs. temperature 50.0 55.0 60.0 65.0 70.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) f osc (khz ) v dd =15.0v valley threshold voltage (v th,va ) vs. temperature 0.70 0.72 0.74 0.76 0.78 0.80 -40 -25 -10 5 20 35 50 65 80 95 110 125 t emperat ure ( ) v th ,va (v ) v dd =15.0v
product specification low-power green-mode pwm flyback power controller without secondary feedback sg6849 ? system general corp. - 8 - www.sg.com.tw version 1.0(iro33.0002.b3) dec.29, 2003 turn-on threshold voltage (v dd o n ) vs. temperature 15.0 15.5 16.0 16.5 17.0 17.5 18.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 t emperat ure ( ) v dd on (v) turn-off threshold voltage (v dd of f ) vs. temperature 7.00 7.50 8.00 8.50 9.00 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) v dd off (v ) output voltage low (v ol ) vs. temperature 0.00 0.10 0.20 0.30 0.40 -40-25-10 5 203550658095110125 temperature ( ) v ol (v ) green-mode burst back(f osc-g-bk ) and green-mode off frequency(f osc-g-off ) vs. v dd 0.0 5.0 10.0 15.0 20.0 25.0 30.0 88.599.510 v dd (v) f osc (k hz ) f osc-g-bk f osc- g-off valley threshold voltage(v th,va ) vs. v dd 0.50 0.60 0.70 0.80 0.90 1.00 9 1011121314151617181920 v dd (v) v th,va (v) v limit ramp vs. duty cycle 0.90 0.95 1.00 1.05 1.10 10 15 20 25 30 35 40 duty cycle (%) vlimit (v) v dd =15.0v
product specification low-power green-mode pwm flyback power controller without secondary feedback sg6849 ? system general corp. - 9 - www.sg.com.tw version 1.0(iro33.0002.b3) dec.29, 2003 operation description sg6849 devices integrate many useful functions for low power switch mode power supplies. the following descriptions highlight the key features of the sg6849. startup current the required startup current is only 5ua. this allows a high-resistance, low-wattage startup resistor to be used to supply the controller?s startup power. a 1.5 m ? /0.25w startup resistor can be used over a wide input range (100v-240v ac) with very little power loss. operating current the operating current is normally 3.6ma. the low operating current results in higher efficiency and reduces the required v dd hold-up capacitance. a 10uf/25v v dd hold-up capacitor can be used over a wide input range (100v-240v ac) with very little power loss. green mode operation the proprietary green-mode function provides off-time modulation to linearly decrease the switching frequency under light-load and zero-load conditions. the on-time is limited to provide better protection against brownouts and other abnormal conditions. this green-mode function dramatically reduces power consumption under light-load and zero-load conditions. power supplies using the sg6849 can easily meet international restrictions regarding standby power-consumption. constant voltage (cv) and constant current (cc) without feedback the sg6849 can tightly regulate the output voltage and provide over current protection without requiring secondary-side feedback signals. for improved cv and cc accuracy, the transformer leakage inductance should be reduced as much as possible. over temperature protection (otp) the sg6849 has a built-in temperature sensing circuit to shut down pwm output once the junction temperature exceeds 150 c. while pwm output is shut down, the v dd voltage will gradually drop to the uvlo voltage. some of the sg6849?s internal circuits will be shut down, and v dd will gradually start increasing again. when v dd reaches 17v, all the internal circuits, including the temperature sensing circuit, will start operating normally. if the junction temperature is still higher than 150 c, the pwm controller will be shut down immediately. this situation will continue until the temperature drops below 130 c. the pwm output will then be turned back on. the temperature hysteresis window for the otp circuit is 20 c. v dd over voltage clamping v dd over voltage clamping is built in to prevent damage from over-voltage conditions. when v dd exceeds 22.7v, pwm output is shut down. over-voltage conditions may be caused by an open photo-coupler loop or a short circuit in the output. oscillator operation the oscillation frequency is fixed at 65khz for the sg6849-65, and at 100khz for the sg6849-100. leading edge blanking each time the power mosfet is switched on, a turn-on spike will inevitably occur at the sense-resistor. to avoid premature termination of the switching pulse, a 310ns leading-edge blanking time is built in. conventional rc filtering is not n ecessary. during this blanking period, the current-limit comparator is disabled, and it cannot switch off the gate drive. constant output power limit when the sense voltage across the sense resistor r s reaches the threshold voltage (around 1.0v), the output gate drive will be turned off following a small
product specification low-power green-mode pwm flyback power controller without secondary feedback sg6849 ? system general corp. - 10 - www.sg.com.tw version 1.0(iro33.0002.b3) dec.29, 2003 propagation delay t pd . this propagation delay will introduce an additional current proportional to t pd *v in /l p . the propagation delay is nearly constant regardless of the input line voltage v in . higher input line voltages will result in larger additional currents. thus, under high input-line voltages the output power limit will be higher than under low input-line voltages. over a wide range of ac input voltages, the variation can be significant. to compensate for this, the threshold voltage is adjusted by adding a positive ramp. this ramp signal can vary from 0.77v to 1.05v for sg6849-65 and 0.70 to 1.03v for sg6849-100, and it flattens out at 1.05v and 1.03v respectively. a smaller threshold voltage forces the output gate drive to terminate earlier, thus reducing total pwm turn-on time and making the output power equal to that of the low line input. this proprietary internal compensation feature ensures a constant output power limit over a wide range of ac input voltages (90vac to 264vac). under voltage lockout (uvlo) the turn-on/turn-off thresholds of the sg6849 are fixed internally at 17v/8v. to enable the sg6849 during startup, the hold-up capacitor must first be charged to 17v through the startup resistor. the hold-up capacitor will continue to supply v dd before energy can be delivered from the auxiliary winding of the main transformer. v dd must not drop below 8v during this startup process. this uvlo hysteresis window ensures that the hold-up capacitor can adequately supply v dd during startup. gate output the sg6849 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 16.7v zener diode in order to protect the power mosfet transistors against any harmful over-voltage gate signals. slope compensation the sensed voltage across the current sense resistor is used for current mode control and pulse-by-pulse current limiting. the built-in slope compensation function improves power supply stability. furthermore, it prevents sub-harmonic oscillations that normally would occur because of peak current mode control. a positively sloped, synchronized ramp is activated by the sg6849 with every switching cycle. the slope of the ramp is (max) 33 . 0 duty duty . noise immunity noise from the current sense or the control signal may cause significant pulse width jitter, particularly in continuous-conduction mode. slope compensation helps alleviate this problem. good placement and layout practices should be followed. the designer should avoid long pcb traces and component leads. compensation and filter components should be located near the sg6849. finally, increasing the power-mos gate resistance is advised.
product specification low-power green-mode pwm flyback power controller without secondary feedback sg6849 ? system general corp. - 11 - www.sg.com.tw version 1.0(iro33.0002.b3) dec.29, 2003 reference circuit 3w flyback 5v/0.6a circuit, without secondary-side feedback c7 cx1 d5 2 1 r2 r5 r8 cy1 r1 + c8 n l vo r3 d4 2 1 c1 d2 2 1 t1 8 5 7 3,4 1,2 10 9 d1 2 1 u4 sg6849 1 2 3 4 6 5 gnd fb nc sense gate vdd r6 r7 l2 1 2 q1 1 2 3 + c4 l1 1 2 r4 + c9 gnd + c2 r10 -+ bd1 1 4 3 2 c3 f1 bom symbol component symbol component bd1 bd 1a/500v l1 20mh 6*8mm cx1 (option) yc 472pf/400v (y1) l2 10uh 6mm cy1 (option) yc 102pf/400v (y1) q1 mosfet 1a/600v c2 ec 10uf/400v 105 r1,r2 r 750k ? 1206 c1 cc 103pf/500v r3,r4 r 47k ? 1206 c3 cc 1000pf/500v r5 r 47 ? 1206 c4 ec 10uf/50v r6 r 4.7 ? 1206 c7 (option) cc 102pf/100v 1206 r7 r 100 ? 0805 c8 ec 470uf/10v 105 r8 r 10 ? 1206 c9 ec 220uf/10v 105 r10 (option) r 10 ? 1206 d1 diode fri07 t1 ee-16 d2 diode fr102 u4 ic sg6849 (green pwm ic) d4 diode sb360 d5 (option) zd 6.8v 0.5w f1 r 1 ? /0.5w
product specification low-power green-mode pwm flyback power controller without secondary feedback sg6849 ? system general corp. - 12 - www.sg.com.tw version 1.0(iro33.0002.b3) dec.29, 2003 3w flyback 5v/0.6a circuit, with secondary-side feedback vo gnd r12 r14 c10 r13 u3 3 1 2 + c9 d5 2 1 r1 r8 d1 2 1 c3 q1 1 2 3 u1 sg6849 1 2 3 4 5 6 gnd fb nc sense vdd gate + c2 f1 l1 1 2 d4 2 1 r11 r4 r2 u2 1 2 4 3 r7 -+ bd1 1 4 3 2 r5 t1 8 5 7 3,4 1,2 10 9 l2 1 2 c6 + c4 r10 + c1 d2 2 1 r3 r6 c7 cy1 + c8 l n bom symbol component symbol component bd1 (reference only) di106 1a/600v l2 10uh 6mm cy1 (option) yc 102p/400v q1 mosfet 1a/600v c2 10uf/400v 10 *16mm 105 r1,r2 750k 1206 c1 103p/500v (0.01uf/500v) r4,r3 47k/1206 c3 1000p/500v cer r5 47 1206 c4 10u/50v 5mm r6 3.7 1206 c6 472p 0805 r7 100 0805 c7 102p/100v 1206 r10 10 1206 c8 470u/10v 8 *11.5mm 105 r8 5 1206 c9 470u/10v 8 *11.5mm 105 r11 100 1/8w c10 222p 0805 r12 33k 0805 d1 fr107 r13 33k 1/8w d2 fr102 r14 4.7k 0805 d4 sb360 (3a/60v; schottky) t1 ee-16 d5 (option) zd/6.8v 0.5w u1 sg6849 (green pwm ic) f1 1 ? 1/2w resistor u2 pc817 l1 20mh 6*8mm u3 tl431 bd1 (reference only) di106 1a/600v l2 10uh 6mm
product specification low-power green-mode pwm flyback power controller without secondary feedback sg6849 ? system general corp. - 13 - www.sg.com.tw version 1.0(iro33.0002.b3) dec.29, 2003 package information the sot-26 package 1 3 64 e e1 e1 e d b a2 a1 a r 1 r l2 l1 l detail a detail a c 1 1 dimensions: millimeters inches symbol min. typ. max. min. typ. max. a 1.45 0.057 a 1 0.15 0.006 a 2 0.90 1.15 1.30 0.036 0.045 0.051 b 0.30 0.50 0.011 0.020 c 0.08 0.22 0.003 0.009 d 2.90 0.114 e 2.80 0.110 e1 1.60 0.063 e 0.95 0.037 e1 1.90 0.075 l 0.30 0.45 0.60 0.020 0.018 0.24 l1 0.60 0.024 l2 0.25 0.010 r 0.10 0.004 r1 0.10 0.25 0.004 0.25 ? 0 ? 4 ? 8 ? 0 ? 4 ? 8 ? 1 ? 5 ? 10 ? 15 ? 5 ? 10 ? 15 ?
product specification low-power green-mode pwm flyback power controller without secondary feedback sg6849 ? system general corp. - 14 - www.sg.com.tw version 1.0(iro33.0002.b3) dec.29, 2003 the dip-8 package 4 1 85 d e1 e e b a1 a2 a b b1 l e dimensions: millimeter inch symbol min. typ. max. min. typ. max. a 5.334 0.210 a 1 0.381 0.015 a 2 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 low-power green-mode pwm flyback power controller without secondary feedback sg6849 ? system general corp. - 15 - www.sg.com.tw version 1.0(iro33.0002.b3) dec.29, 2003 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 components intended for surgical implant into the body, or other applications in which the failure of system general?s products could create a situation where personal death or injury may occur, is not authorized without the express written approval 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 military applications. use of system general?s products in military applications is not authorized without the express written approval 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 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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