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november 2008 ? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6846 ? rev. 1.3.1 sg6846 ? highly integrated green-mode pwm controller sg6846 highly integrated green-mode pwm controller features ? low startup current: 8a ? low operating current: 3.7ma ? peak-current mode of operation with cycle-by- cycle current limiting ? pwm frequency continuously decreasing with burst mode at light loads ? v dd over-voltage protection (ovp) ? ac input brownout protection with hysteresis ? constant output-power limit (full ac input range) ? internal latch circuit for ovp, otp, and ocp ? two-level over-current protection (ocp) with 96ms delay time ? very few external components ? programmable over-temperature protection (otp) applications general-purpose switch-mode power supplies and flyback power converters, including: ? power adapters ? open-frame smps ? smps with surge-current output, such as for printers, scanners, motor drivers description the highly integrated sg6846 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 continuously decrease the switching frequency under light-load conditions. under zero-load conditions, the power supply enters burst-mode. this completely shuts off pwm output. the output restarts just before the supply voltage drops below the under-voltage lockout (uvlo) lower limit. this green-mode function enables power supplies to meet international power conservation requirements easily. the sg6846 is designed especially for switch-mode power supply (smps) with surge-current output. it is incorporated with a two-level ocp function. besides the cycle-by-cycle current limiting, if the switching current is higher than 2/3 of the peak-current threshold for a delay time, ocp is activated such that the sg6846 is totally shut down. other protection functions include: ac-input brownout protection with hysteresis and v dd ovp. for otp, an external ntc thermistor can be applied to sense the ambient temperature. when ocp, v dd ovp, or otp are activated, an inter nal latch circuit is used to latch off the controller. the latch resets when the v dd supply is removed. other features of this controller include built-in synchronized slope compensation and proprietary internal compensation for constant output-power limit over universal-ac-input range. also, the gate output is clamped at 18v to protect the external mosfet from over-voltage damage. the sg6846 series controllers are available in both 8- pin dual in-line (dip) and small outline (sop) packages. ordering information part number operating temperature range otp latch eco status package packing method sg6846lsz -20 to +85c yes rohs 8-pin sop tape & reel SG6846LSY -20 to +85c yes green 8-pin sop tape & reel sg6846ldz -20 to +85c yes rohs 8-pin dip tube sg6846ldy -20 to +85c yes green 8-pin dip tube for fairchild?s definition of ?green? eco status, please visit: http://www.fairchildsemi.com/company/green/rohs_green.html .
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6846 ? rev. 1.3.1 2 sg6846 ? highly integrated green-mode pwm controller typical application figure 1. typical application block diagram figure 2. block diagram
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6846 ? rev. 1.3.1 3 sg6846 ? highly integrated green-mode pwm controller marking information sg6846ftp xxxxxxxxywwv marking for sg6846lsz (pb-free) sg6846ldz (pb-free) figure 3. top mark 1 marking for SG6846LSY (green-compound) sg6846ldy (green-compound) figure 4. top mark 2 : fairchild logo z: plant code x: year code y: week code tt: die run code f: l = ocp latch t : package type (d = dip, s = sop) p: y = green package m: manufacturing flow code f: l = otp latch t : d = dip, s = sop 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 sg6846 ? rev. 1.3.1 4 sg6846 ? highly integrated green-mode pwm controller pin configuration figure 5. pin configuration pin definitions pin # name function description 1 gnd ground ground. 2 fb feedback the signal from the external compensation circuit is fed into this pin. the fb pin and the current-sense signal from pin 6 determine the pwm duty cycle. 3 vin line-voltage detection line-voltage detection. the line-voltage detection is used for brownout protection with hysteresis. constant-out put-power limit over universal-ac-input range is also achieved using the v in signal. it is suggested to add low-pass filter to filter out line ripple on bulk capacitor. 4 ri reference setting a resistor from the ri pin to ground generates a reference current source inside sg6846. this determines the switching frequency. increasing the resistance reduces the switching frequency. using a 26k ? resistor ri results in a 65khz switching frequency. 5 rt temperature detection for otp. an external negative temperature coefficient (ntc) thermistor is connected from this pin to the gnd pin. the impedance of the ntc decreases at high temperatures. once the voltage of the rt pin drops below a threshold, pwm output is disabled. 6 sense current sense current sense. the sensed voltage is used fo r peak-current-mode control and cycle-by-cycle current limiting. if the swit ching current is higher than 2/3 of the peak-current threshold for longer than 96ms, otp is activated. this two-level ocp feature is especially suitable for smps with surge current output. 7 vdd power supply power supply. the internal protection circuit disables pwm output in response to v dd over voltage. 8 gate driver output the totem-pole output driver for the power mosfet. a soft driving waveform is implemented for improved electr omagnetic interference (emi).
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6846 ? rev. 1.3.1 5 sg6846 ? highly integrated green-mode pwm controller 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. all voltage values, except differential voltages, are given with respect to gnd pin. symbol parameter min. max. unit v dd supply voltage 25 v v l input voltage to fb, sense, vin, rt, ri pins -0.3 7.0 v sop 400 p d power dissipation dip 800 mw sop 41.2 r jc thermal resistancejunction-to-case) dip 67.1 c/w t j operating junction temperature -40 +125 c t stg storage temperature range -65 +150 c t l lead temperature, wave soldering, 10 second +260 c human body model, jesd22-a114 2.0 kv esd machine model, jesd22-a115a 200 v recommended operating conditions the recommended operating conditions table defines the conditions for actual device operation. recommended operating conditions are specified to ens ure optimal performance to the datasheet specifications. fairchild does not recommend exceeding them or designing to absolute maximum ratings. symbol parameter min. max. unit t a operating ambient temperature -20 +85 c
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6846 ? rev. 1.3.1 6 sg6846 ? highly integrated green-mode pwm controller electrical characteristics v dd = 15v and t a = 25c unless otherwise noted. symbol parameter conditions min. typ. max. unit v dd section v dd-op continuously operating voltage 20 v v dd-on turn-on threshold voltage 15.5 16.5 17.5 v v dd-off turn-off voltage 9.5 10.5 11.5 v v dd-th-g low-threshold voltage for v dd to exit green-off mode v dd-off +1.25v v v dd-lh threshold voltage for latch-off release 3 4 5 v i dd-st startup current v dd-on ? 0.16v 8 30 a i dd-op operating supply current gate open 3.7 5.0 ma v dd-ovp v dd over-voltage protection (latch off) 22.6 23.6 24.6 v t d-vddovp v dd ovp debounce time r i = 26k ? 100 s i dd-h v dd ovp latch-off holding current v dd = 5v, t a =27 o c 45 a v in section v in-off pwm turn-off threshold voltage 0.67 0.72 0.77 v v in-on pwm turn-on threshold voltage v in-off +0.20 v feedback input section a v input-voltage to current-sense attenuation 1/4.2 v/v z fb input impedance 4.0 5.5 7.0 k ? v fbo fb-pin open voltage 6.2 v current sense section z sense input impedance 12 k ? t pd delay to output 100 200 ns t leb leading-edge blanking time 360 ns v sth1v threshold voltage for current limit v in = 1v, r i = 26k ? 0.78 0.83 0.88 v v sth3v threshold voltage for current limit v in = 3v, r i = 26k ? 0.65 0.70 0.75 v v sth1v-2/3 ocp threshold voltage for current limit v in = 1v, r i = 26k ? 0.56 0.61 0.66 v v sth3v-2/3 ocp threshold voltage for current limit v in = 3v, r i = 26k ? 0.46 0.51 0.56 v t d-ocp delay time for otp r i = 26k ? 82 96 110 ms continued on following page?
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6846 ? rev. 1.3.1 7 sg6846 ? highly integrated green-mode pwm controller electrical characteristics (continued) v dd = 15v and t a = 25c unless otherwise noted. symbol parameter conditions min. typ. max. unit oscillator section f osc normal pwm frequency r i = 26k ? 60 65 70 khz f osc-g green-mode minimum frequency r i = 26k ? 18.0 22.5 25.0 khz v fb-n fb-pin threshold for the beginning of green mode 2.1 v v fb-g green-off-mode voltage at fb pin 1.6 v s g slope for green-mode modulation r i = 26k ? 85 hz/mv f dv frequency variation vs. v dd deviation v dd = 11.5v to 20v 5 % f dt frequency variation vs. temperature deviation t a = -20 to 85c 1.5 5.0 % continued on following page? f osc :65khz f osc -green :22.5khz v v fb -n fb -g fb v f r equen cy pw m f r equen cy f osc -off :0hz figure 6. pwm frequency
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6846 ? rev. 1.3.1 8 sg6846 ? highly integrated green-mode pwm controller electrical characteristics (continued) v dd = 15v and t a = 25c unless otherwise noted. symbol parameter conditions min. typ. max. unit pwm output section dcy max maximum duty cycle 80 85 90 % v ol output voltage low v dd = 15v, i out = 50ma 1.5 v v oh output voltage high v dd = 12v, i out = 50ma 8 v t r rising time v dd = 15v, gate = 1nf 350 ns t f falling time v dd = 15v, gate = 1nf 50 ns v clamp gate output clamping voltage v dd = 20v 18 v otp section i rt output current of rt pin r i = 26k ? 64 70 76 a v rtth threshold voltage for otp 1.015 1.065 1.115 v t dotp-latch over-temperature latch-off debounce r i = 26k ? 100 s v rt-rls otp release voltage (for non-latch-off version) v rtth + 0.1 v r i section ri nor r i operating range 15.5 36.0 k ? ri max maximum r i value for protection 216 k ? ri min minimum r i value for protection 6 k ?
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6846 ? rev. 1.3.1 9 sg6846 ? highly integrated green-mode pwm controller typical performance characteristics 15.5 16.0 16.5 17.0 17.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature (c) ) v th -on (v) 9.5 9.7 9.9 10.1 10.3 10.5 10.7 10.9 11.1 11.3 11.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature (c) v th -off (v) figure 7. startup thres hold vs. temperature figure 8. minimum operating voltage vs. temperature 13.500 14.000 14.500 15.000 15.500 16.000 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature (c) i dd-st (a) 0 4 8 12 16 20 5 7 9 1113151719 v dd (v) i dd-st (a) figure 9. startup current vs. temperat ure figure 10. startup current vs. v dd voltage 0. 400 0. 500 0. 600 0. 700 0. 800 0. 900 1. 000 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature (c) ) v in-off (v) 0.400 0.500 0.600 0.700 0.800 0.900 1.000 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature (c ) v in-on (v) figure 11. pwm turn-off threshold voltage vs. temperature figure 12. pwm turn-on threshold voltage vs. temperature
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6846 ? rev. 1.3.1 10 sg6846 ? highly integrated green-mode pwm controller typical performance characteristics (continued) 64.600 64.700 64.800 64.900 65.000 65.100 65.200 65.300 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature (c) f osc (khz) 0 20 40 60 1.5 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3 v fb (v) pwm frequency (khz) figure 13. pwm frequency vs. temperature figure 14. pwm fr equency vs. fb voltage (r i =26k ? ) 0 0.2 0.4 0.6 0.8 1 11.522.53 v in (v) v th -p (v) 0 0.2 0.4 0.6 0.8 1 11.522.53 v in (v) v th -o (v) figure 15. current-limit threshold vs. v in voltage figure 16. 2/3 current-limit threshold vs. v in voltage 70.000 71.000 72.000 73.000 74.000 75.000 76.000 77.000 78.000 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature (c) i rt (a) 1.015 1.035 1.055 1.075 1.095 1.115 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature (c) v otp-off (v) figure 17. output current of rt pin (i rt ) vs. temperature figure 18. otp threshold vo ltage vs. temperature
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6846 ? rev. 1.3.1 11 sg6846 ? highly integrated green-mode pwm controller operation description startup operation the turn-on/turn-off thresholds are fixed internally at 16.5v/10.5v. to enable the sg6846 during startup, the hold-up capacitor must first be charged to 16.5v 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. the v dd must not drop below 10.5v during this startup proc ess. this uvlo hysteresis window ensures that the hold-up capacitor can adequately supply v dd during startup. the typical startup current is only 8 a. this allows a high resistance, low-wattage startup resistor to be used to minimize power loss. a 1.5m ? /0.25w, startup resistor and a 10f/25v v dd hold-up capacitor is sufficient for a universal input range. the required operating current has been reduced to 3.7ma. this enables higher efficiency and reduces the v dd hold-up capacitance requirement. green-mode operation power supplies using the sg6846 can easily meet even the most restrictive inter national regulations regarding standby power consumption. the proprietary green-mode function provides off-time modulation to continuously decrease the switching frequency under light-load conditions. maximum on time is limited to provide protection against abnormal conditions. to further reduce power consumption under zero-load condition, the pwm oscillator is completely turned off and the power supply enters burst-mode. after the pwm oscillator is turned off, the ic?s supply voltage v dd drops gradually. before the v dd voltage drops below the uvlo threshold, the pwm oscillator is turned on again. this green-mode function dramatically reduces power consumption under light-load and zero-load conditions. oscillator operation a resistor connected from the ri pin to gnd generates a reference-current source inside the sg6846. this current is used to determine the pwm frequency. increasing the resistance decreases the amplitude of the current source and reduces the pwm frequency. using a 26k ? resistor ri results in a corresponding 65khz switching frequency. the relationship between ri and the switching frequency is: ) (k 1690 (khz) = i pwm r f (1) if an open circuit or short circuit to ground occurs at the ri pin, the internal protection circuit immediately shuts down the controller. two-level over-current protection (ocp) cycle-by-cycle current limiting shuts down the pwm immediately when the switching current is over the peak-current threshold. additionally, when the switching current is higher than 2/3 of the peak-current threshold, the internal counter starts counting up. when the switching current is lower than 2/3 of the peak current threshold, the internal counter counts down. when the total accumulated counting time is more than about 96ms (r i = 26k ? ), the controller is latched off. the two-level ocp protection and up/down counter are especially designed for smps with surge current output such as those for printers, scanners, and motor drivers. constant-output-power limit for constant-output-power lim it over universal input- voltage range, the peak-current threshold is adjusted by the voltage of the vin pin. since the vin pin is connected to the rectified ac-input line voltage through the resistive divider, a higher line voltage generates a higher v in voltage. the threshold voltage decreases as the v in voltage increases, making the maximum output power at high-line input voltage equal to that at low-line input. brownout protection since the vin pin is connected through a resistive divider to the rectified ac input line voltage, it can also be used for brownout protection. if the v in voltage is less than 0.72v, the pwm output is shut off. if the v in voltage is over 0.92v, the pwm output is turned on again. the hysteresis window for on/off is around 0.2v. v dd over-voltage protection (ovp) v dd ovp is built in to prevent damage. if v dd is over 23.6v, sg6846 is latched off. over-temperature protection (otp) an external ntc thermistor can be connected from the rt pin to gnd. the impedance of the ntc decreases at high temperatures. when the voltage of the rt pin drops below 1.05v, the sg6846 is turned off. for protection-mode options, see ordering information.
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6846 ? rev. 1.3.1 12 sg6846 ? highly integrated green-mode pwm controller operation description (continued) 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 sg6846. figure 19. current sense r-c filter
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6846 ? rev. 1.3.1 13 sg6846 ? highly integrated green-mode pwm controller reference circuit f1 2 1 + c2 r16 2 1 + c12 2 1 + c13 fb p16v p32v p16v cx1 32v ri 4 vin 3 fb 2 gnd 1 rt 5 sense 6 vdd 7 gate 8 u1 1 2 3 4 lf2 2 1 + c3 2 1 + c5 1 2 3 4 lf1 vz1 t rt1 r1 r2 r3 r4 r12 c4 2 1 d2 c6 2 1 d1 1 2 4 3 u2 r18 r15 r20 a k r u3 r21 r19 c9 1 3 2 d4 r7 r13 r14 1 2 3 q1 l1 c7 2 1 3 4 bd1 5 1 7 9 11 13 3 6 10 tx1 r17 2 1 + c14 2 1 + c15 16v c11 1 3 2 d5 l2 p32v p16v 2 1 d3 1 2 l4 r8 r9 r5 2 1 + c1 r6 r10 ntc1 cx2 p1 p2 fb 1 2 l3 2 1 + c16 2 1 + c17 cy1 cy2 p7 r11 fb 16v 32v p32v p16v p32v p16v p16v figure 20. application circuit for 32v / 16v output bom part no. value part no . value part no. value r1, r2, r3, r4 470k ? +/-5% c4 103 p 630v d3 fr103 1.0a 200v r8, r9 s1m ? +/-1% c10,c11 102 p 1kv bd1 dbl406g r5 16k2 ? +/-1% c6,c7 102 p 50v d4 byt28-300 r15 1k5 ? +/-5% c9 222 p 50v d5 byv32-150 r13 10 ? +/-5% c14,c17 470 25v f1 250v4a quick r18 4k7 ? +/-5% c15 220 25v l1,l2 1.8h r21 15k ? +/-1% c13,c16 220 50v l4 10h r7 27k ? +/-5% c2 150 400v u3 tl431 +/-1% r6 330 ? +/-1% c1 4.7 50v u1 sg 6846 r19 102k ? +/-1% c3 10 50v u2 pc817 r14 0 ? 22 +/-5% cx1 x1 0.47 275v q1 7nb60 r16, r17 1w 20 ? +/-5% c8 y2 222p 250v tx1 ei-33 r11 20k ? +/-5% c5 100 50v rt1 sck053 r12 100k ? +/-5% cx2 x2 0.1f 275v vz1 14 470v r20 887k ? +/-1% d1 1n4148 r22 10k ? +/-1% d2 byv95c
? 2008 fairchild semiconductor corporation www.fairchildsemi.com sg6846 ? rev. 1.3.1 14 sg6846 ? highly integrated green-mode pwm controller 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 21. 8-pin dual in-line package (dip) 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 sg6846 ? rev. 1.3.1 15 sg6846 ? highly integrated green-mode pwm controller physical dimensions 8 0 see detail a notes: unless otherwise specified a) this package conforms to jedec ms-012, variation aa, issue c, b) all dimensions are in millimeters. c) dimensions do not include mold flash or burrs. d) landpattern standard: soic127p600x175-8m. e) drawing filename: m08arev13 land pattern recommendation seating plane 0.10 c c gage plane x 45 detail a scale: 2:1 pin one indicator 4 8 1 c m ba 0.25 b 5 a 5.60 0.65 1.75 1.27 6.20 5.80 3.81 4.00 3.80 5.00 4.80 (0.33) 1.27 0.51 0.33 0.25 0.10 1.75 max 0.25 0.19 0.36 0.50 0.25 r0.10 r0.10 0.90 0.406 (1.04) option a - bevel edge option b - no bevel edge figure 22. 8-pin small outline package (sop) 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 sg6846 ? rev. 1.3.1 16 sg6846 ? highly integrated green-mode pwm controller

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