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december 2008 ? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6849 rev. 1.6.1 sg6849 ?low-power, green-mode pwm flyback power controller without secondary feedback sg6849 low-power, green-mode pwm flyback power controller without secondary feedback 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: 5 a ? low operating current: 3.6ma ? leading-edge blanking (leb) ? 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 ? gate output maximum voltage clamped at 16.7v ? small ssot-6 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 proprieta ry 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 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. an advantage of the sg6849 is a typical startup current of only 5a, while the typical operating current can be as low as 3.6ma. a large startup resistance can 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 90v ac to 264v ac . the sg6849 provides many protection functions. pulse- by-pulse current limiting ensures a constant output current, even if a short circuit occurs. the internal protection circuit disables 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 shuts down 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, ssot-6 package. related resources ? an-6849 - low cost, green-mode pwm controller for flyback converters
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6849 rev. 1.6.1 2 sg6849 ?low-power, green-mode pwm flyback power controller without secondary feedback ordering information part number operating temperature range package eco status packing method SG684965TZ -40 c to +105 c small sot-26 package rohs tape & reel sg684965dz -40 c to +105 c 8-pin dual in-line package (dip) rohs tube sg684965dy -40 c to +105 c 8-pin dual in-line package (dip) green tube for fairchild?s definition of ?green? eco status, please visit: http://www.fairchildsemi.com/com pany/green/rohs_green.html . application diagram v in c in r in d 1 w aux c o d o q1 v o r s sens e gate v dd gnd figure 1. typical application internal block diagram 2(5) 8(1) 7(2) green mode controller internal supply uvlo gnd gate v dd 17v/8v 1(6) otp sense 4(4) sense blanking circuit driver v dd fb s q r osc 4.5v vdd vddz comp slope compensation pwm comp ocp v dd power limi ter figure 2. functional block diagram
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6849 rev. 1.6.1 3 sg6849 ?low-power, green-mode pwm flyback power controller without secondary feedback marking information *marking for SG684965TZ (pb-free) *marking for sg684965dz (pb-free) *marking for sg684965dy (green compound) figure 3. top mark xx: bb=sg6849-65t tt : die run code . . . : year code ---: week code f - fairchild logo z- plant code x- 1 digit year code y- 1 digit week code tt: 2 digits die run code t: package type (d=dip) p: z: pb-free, y: green package m: manufacture flow code dxytt dxytt zxytt 68 4 965 tpm t: d=dip p: z= lead free + rohs compatible null=regular package xxxxxxxx: wafer lot y: year ww: week v: assembly location
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6849 rev. 1.6.1 4 sg6849 ?low-power, green-mode pwm flyback power controller without secondary feedback pin configurations figure 4. ssot-6 pin configuration fi gure 5. dip-8 pin configuration pin definitions dip pin # ssot pin # name description 1 6 gate the totem-pole output driver for driving the power mosfet. 2 5 vdd power supply. 3 nc no connection. 4 4 sense current sense. it senses the voltage acro ss a sensed resistor. to provide over- current protection, pwm output is dis abled if the voltage exceeds an internal threshold. this pin provides current information for current-mode control. 5 3 nc no connection. 6 nc no connection. 7 2 fb feedback. the fb pin provides feedback information to the internal pwm comparator. this feedback is used to cont rol the duty cycle. when no feedback is provided, this pin is left open. 8 1 gnd ground.
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6849 rev. 1.6.1 5 sg6849 ?low-power, green-mode pwm flyback power controller without secondary feedback absolute maximum ratings stresses exceeding the absolute maximum ratings may dam age the device. the device may not function or be operable above the recommended operating conditions and stressing the parts to these levels is not recommended. in addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. the absolute maximum ratings are stress ratings only. symbol parameter min. max. unit v vdd dc supply voltage (1, 2) 25 v v fb input voltage to fb pin -0.3 7.0 v v sense input voltage to sense pin -0.3 7.0 v t j operating junction temperature -40 +125 c ssot 263.3 c/w ja thermal resistance (junction-to-air) dip 135.7 c/w t stg storage temperature range -55 +150 c t l lead temperature (wave soldering or ir, 10 seconds) +260 c human body model, jedec:jesd22-a114 3.0 kv esd machine model, jedec:jesd22-c101 300 v notes: 1. all voltage values, except differential vo ltages, are given with respect to gnd pin. 2. stresses beyond those listed under "absolute maximu m ratings" may cause permanent damage to the device.
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6849 rev. 1.6.1 6 sg6849 ?low-power, green-mode pwm flyback power controller without secondary feedback electrical characteristics unless otherwise noted, v dd =15v and t a =25 c. symbol parameter conditions min. typ. max. units v dd section v dd-on turn-on threshold voltage 16 17 18 v v dd-off turn-off threshold voltage 7.5 8.0 8.5 v i dd-st startup current v dd =15v 5 20 a i dd-op operating supply current v dd =15v, c l =1nf 3.6 4.6 ma v dd-clamp zener diode breakdown voltage i dd =10ma 28 30 v 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 feedback input section i fb-zdc zero duty cycle fb input current 1.15 1.40 ma v fb-open open-loop voltage 4.5 v z fb input impedance i fb =0.1ma to 0.2ma 2.4 k ? fb is open 20.0 22.7 25.0 v v dd-fb v dd feedback threshold voltage* i fb =0.4ma 18 20 22 v current-sense section t pd delay to output 100 ns v dd =20v 0.84 0.89 0.94 v v dd =15v 0.72 0.77 0.82 v v sthva valley threshold voltage for current limit v dd =10v 0.58 0.63 0.68 v t leb leading-edge blanking time 310 ns figure 6. saw limit
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6849 rev. 1.6.1 7 sg6849 ?low-power, green-mode pwm flyback power controller without secondary feedback electrical characteristics (continued) unless otherwise noted, v dd =15v and t a =25 c. symbol parameter conditions min. typ. max. units oscillator section f osc frequency 60 65 70 khz f osc-g green-mode frequency 20 25 30 khz i fb-g green-mode ending fb current 0.90 1.15 1.40 ma f dv frequency variation vs. v dd deviation v dd =10 to 20v 2.00 % output section dcy max maximum duty cycle 70 75 80 % v gate-l output voltage low v dd =15v, i o =10ma 1.5 v v gate-h 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 gate- clamp output clamp voltage v dd =20v 16.7 18.0 v over-temperature protection (otp) t otp protection junction temperature +150 c t otp- restart restart junction temperature +130 c
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6849 rev. 1.6.1 8 sg6849 ?low-power, green-mode pwm flyback power controller without secondary feedback typical performance characteristics 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 v dd on (v) temperature (c) 7.00 7.50 8.00 8.50 9.00 -40 -25 -10 5 20 35 50 65 80 95 110 125 v dd off (v ) temperature (c) figure 7. turn-on threshold voltage (v dd-on ) vs. temperature figure 8. turn-off threshold voltage (v dd-off ) 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 (c) i dd st (a ) 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 i dd op (ma) temperature (c) figure 9. startup current (i dd-st ) vs. temperature figure 10. center 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 f osc (khz) temperature (c) 70.0 72.0 74.0 76.0 78.0 80.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 dc y max (%) temperature (c) figure 11. center frequency (f osc ) vs. temperature figure 12. maximum duty cycle (dcy max ) vs. temperature
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6849 rev. 1.6.1 9 sg6849 ?low-power, green-mode pwm flyback power controller without secondary feedback typical performance characteristics (continued) 4.0 4.2 4.4 4.6 4.8 5.0 -40 -30 -15 0 25 50 75 100 125 v fb (v) temperature (c) 0.70 0.72 0.74 0.76 0.78 0.80 -40 -25 -10 5 20 35 50 65 80 95 110 125 v th,va (v) temperature (c) figure 13. fb open-loop voltage (v fb ) vs. temperature figure 14. valley threshold voltage (v sthva ) vs. temperature 0.00 0.10 0.20 0.30 0.40 -40 -25 -10 5 20 35 50 65 80 95 110 125 v gate-l (v) temperature (c) 0.0 5.0 10.0 15.0 20.0 25.0 30.0 8 8.5 9 9.5 10 v dd (v) f osc (khz) f osc-g-bk f osc-g-off figure 15. output voltage low (v gate-l ) vs. temperature figure 16. green-mode burst back and green-mode off frequency vs. v dd 0.50 0.60 0.70 0.80 0.90 1.00 9 1011121314151617181920 v dd (v ) v th,va (v) 0.90 0.95 1.00 1.05 1.10 10 15 20 25 30 35 40 duty cycle (%) v limit (v) figure 17. valley threshold voltage (v sthva ) vs. v dd figure 18. v limit ramp vs. duty cycle 0 20 40 60 80 100 120 26.0 26.5 27.0 27.5 28.0 28.5 29.0 29.5 30.0 v dd zener clamp voltag e (v) v dd zener current (ma) figure 19. v dd zener current vs. zener clamp voltage
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6849 rev. 1.6.1 10 sg6849 ?low-power, green-mode pwm flyback power controller without secondary feedback 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 5 a. this allows a high-resistance, low-wattage startup resistor to be used to supply the controller?s startup power. a 1.5m /0.25w startup resistor can be used over a wide input range (90v ac -264v 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 10 f/25v v dd hold-up capacitor can be used over a wide input range (90v ac -264v ac ) with 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 dram atically reduces power consumption under light-load and zero-load conditions. power supplies using sg6849 can meet international restrictions regarding standby power-consumption. constant voltage (cv) and constant current (cc) without feedback the sg6849 tightly regulates 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 gradually drops to the uvlo voltage. some of the sg6849?s internal circuits are shut down and v dd gradually starts increasing again. when v dd reaches 17v, all the internal circuits, including the temperature sensing circuit, starts operating normally. if the junction temperature is still higher than 150 c, the pwm controller is shut down immediately. this situation continues until the temperature drops below 130 c. the pwm output then turns 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. leading-edge blanking (leb) each time the power mosfet is switched on, a turn-on spike occurs 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 necessary. 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 is turned off following a small propagation delay t pd . this propagation delay introduces an additional current proportional to t pd ?v in /l p . the propagation delay is nearly c onstant regardless of the input line voltage v in . higher input line voltages result in larger additional currents. under high input-line voltages, the output power limit is 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 (v limit - ramp ). this ramp signal varies from 0.77v to 1.05v for sg6849 and it flattens out at 1.05v. a smaller threshold voltage forces the output gate drive to terminate earlier, 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 (90v ac -264v ac ). 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 continues 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.
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6849 rev. 1.6.1 11 sg6849 ?low-power, green-mode pwm flyback power controller without secondary feedback gate output the sg6849 bicmos output stage is a fast totem-pole gate driver. cross-conduction is avoided to minimize heat dissipation, increase efficiency, and enhance reliability. the output driver is clamped by an internal 16.7v zener diode to protect the power mosfet transistors against 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 oscilla tions 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: duty(max.) duty 0.36 (1) 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. avoid long pcb traces and component leads. compensation and filter components should be located near the sg6849. increasing the power-mos gate resistance is advised.
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6849 rev. 1.6.1 12 sg6849 ?low-power, green-mode pwm flyback power controller without secondary feedback applications information 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 figure 20. reference circuit (without secondary-side feedback) bom reference component reference component bd1 bd di106 1a/600v f1 r 1 ? /0.5w cx1 (option) yc 472pf/400v (y1) l1 inductor 20mh 6*8mm cy1 (option) yc 102pf/400v (y1) l2 inductor 10 h 6mm c1 cc 0.01 f/500v q1 mosfet 1a/600v c2 ec 10 f/400v 105oc r1,r2 r 750k ? /1206 c3 cc 1000pf/500v r3,r4 r 47k ? /1206 c4 ec 10 f/50v r5 r 47 ? /1206 c7 (option) cc 102pf/100v 1206 r6 r 4.7 ? /0.5w c8 ec 470 f/10v 105oc r7 r 100 ? /0805 c9 ec 220 f/10v 105oc r8 r 10 ? /1206 d1 diode fri07 r10(option) r 10 ? /1206 d2 diode fr102 t1 transformer ee-16 d4 diode sb360 u4 ic sg6849 (green pwm ic) d5 (option) zd 6.8v/0.5w
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6849 rev. 1.6.1 13 sg6849 ?low-power, green-mode pwm flyback power controller without secondary feedback applications information (continued) 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 figure 21. reference circuit (with secondary-side feedback) bom reference component reference component bd1 bd di106 1a/600v l2 inductor 10 h 6mm cy1 (option) yc 102p/400v q1 mosfet 1a/600v c1 cc 0.01 f/500v r1,r2 r 750k ? /1206 c2 ec 10 f/400v 105oc r4,r3 r 47k ? /1206 c3 cc 1000p/500v r5 r 47 ? /1206 c4 ec 10 f50v r6 r 4.7 ? /0.5w c6 cc 472p/0805 r7 r 100 ? /0805 c7 cc 102p/100v 1206 r10 r 10 ? /1206 c8 ec 470 f10v 105oc r8 r 10 ? /1206 c9 ec 470 f10v 105oc r11 r 100 ? /1/8w c10 cc 222p/0805 r12 r 33k ? /0805 d1 diode fr107 r13 r 33k ? /1/8w d2 diode fr102 r14 r 4.7k ? /0805 d4 diode sb360 t1 transformer ee-16 d5 (option) zd 6.8v/0.5w u1 ic sg6849 (green pwm ic) f1 r 1 ? /0.5w resistor u2 ic pc817 l1 inductor 20mh 6*8mm u3 ic tl431
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6849 rev. 1.6.1 14 sg6849 ?low-power, green-mode pwm flyback power controller without secondary feedback physical dimensions 5.08 max 0.33 min 2.54 7.62 0.56 0.355 1.65 1.27 3.683 3.20 3.60 3.00 6.67 6.096 9.83 9.00 7.62 9.957 7.87 0.356 0.20 notes: unless otherwise specified a) this package conforms to jedec ms-001 variation ba b) all dimensions are in millimeters. c) dimensions are exclusive of burrs, mold flash, and tie bar extrusions. d) dimensions and toleranc es per asme y14.5m-1994 8.255 7.61 e) drawing filename and revsion: mkt-n08frev2. (0.56) figure 22. 8-pin dual inline (dip) package package drawings are provided as a service to customers considering fairchild components. drawings may change in any manner without notice. please note the revision and/or date on the drawing and contact a fairchild semiconductor representative to ver ify or obtain the most recent revision. package specifications do not expand the terms of fairchild?s worldwide terms and condition s, specifically the warranty therein, which covers fairchild products. always visit fairchild semiconductor?s online packaging area for the most recent package drawings: http://www.fairchildsemi.com/packaging/ .
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6849 rev. 1.6.1 15 sg6849 ?low-power, green-mode pwm flyback power controller without secondary feedback physical dimensions (continued) figure 23. 6-pin ssot-6 package package drawings are provided as a service to customers considering fairchild components. drawings may change in any manner without notice. please note the revision and/or date on the drawing and contact a fairchild semiconductor representative to ver ify or obtain the most recent revision. package specifications do not expand the terms of fairchild?s worldwide terms and condition s, specifically the warranty therein, which covers fairchild products. always visit fairchild semiconductor?s online packaging area for the most recent package drawings: http://www.fairchildsemi.com/packaging/ .
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6849 rev. 1.6.1 16 sg6849 ?low-power, green-mode pwm flyback power controller without secondary feedback

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