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product specification highly integrated green-mode pwm controller sg6846a ? system general corp. - 1 - www.sg.com.tw ? www.fairchildsemi.com version 1.1.1 (iao33.0059.b1) september 26, 2007 features ? two-level ocp with 1700ms delay time ? output short-circuited delay time: 100ms ? low start-up current (8a) ? low operating current (3.7ma) ? peak-current mode operation with cycle-by-cycle current limiting ? programmable pwm frequency with frequency hopping ? pwm frequency continuously decreasing with burst mode at light loads ? v dd over-voltage protection (ovp) ? ac input brownout protection with hysteresis and constant output power limit ? constant output power limit (full ac input range) ? internal latch circuit for ovp, otp, and ocp ? built-in soft-start ? open-loop protection with 1700ms delay time applications general-purpose switch-mode power supplies and flyback power converters, including: ? power adapters ? open-frame smps ? specifically fit for smps with surge-current output (such as for printers, scanners, motor drivers, etc.) description the highly integrated sg6846a series of pwm controllers provides 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. the sg6846a is especially designed for smps with surge-current output, incorporated with a two-level ocp function. besides the cycle-by-cycle current limiting, if the switching current is higher than two thirds the peak-current threshold for 1700ms, over-current protection is activated and the sg6846a latches off. if the switching current is higher than two thirds the peak-current threshold for 100ms and the voltage on the vdd pin is higher than v dd-off + 1v, the pwm pulses are latched off immediately once v dd voltage is lower than v dd-off + 1v; useful if an output short-circuit occurs. sg6846a also integrates a frequency hopping function that reduces emi emission of a power supply with minimum line filters. its built-in synchronized slope compensation provides proprietary internal compensation for constant output power limit over a universal ac input range. also, the gate output is clamped at 18v to protect the external mosfet from over-voltage damage. internal soft-start is built-in to reduce stress on the mosfet and start-up current during power-on period. other protection functions include: ac input brownout protection with hysteresis, v dd over-voltage protection, and over-temperature protection. for over-temperature protection, an external ntc thermistor can be applied to sense the ambient temperature. when ocp, v dd ovp, or otp are activated, an internal latch circuit is used to latch-off the controller. the pwm pulses stay latched off until the power supply is unplugged from the main outlet. sg6846a is available in an 8-pin sop package. typical application
product specification highly integrated green-mode pwm controller sg6846a ? system general corp. - 2 - www.sg.com.tw ? www.fairchildsemi.com version 1.1.1 (iao33.0059.b1) september 26, 2007 marking diagrams pin configuration ordering information part number ocp latch pb-free package sg6846alsz yes 8-pin sop SG6846ACSZ (preliminary) no 8-pin sop 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 from this pin and the current-sense signal from pin 6. 3 vin line-voltage detection line-voltage detection. the line-voltage detection is used for brownout protection with hysteresis. constant output power limit over a universal ac input range is also achieved using this vin pin. consider adding a low-pass filter to filter out line ripple on the bulk capacitor. 4 ri reference setting a resistor from the ri pin to ground generates a reference current source that determines the switching frequency. increasing the resistance reduces the switching frequency. using a 26k ? resistor results in a 65khz switching frequency. 5 rt temperature detection for over-temperature protection, an external 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 for peak-current-mode control and cycle-by-cycle current limiting. if the switching current is higher than two thirds of the peak-current threshold for longer than 100ms and v dd is higher than 12v and lasts for 1700ms, over-current protection is activated. if an output short over-current also occurs and lasts for 100ms and v aux is lower than 12v, sg6846a turns off immediately. this two-level ocp feature is especially suitable for smps with surge current output. it also has built-in 5ms soft-start time as switching frequency operates at 65khz. 7 vdd power supply power supply. if an open-circuit failure occurs in the feedback loop, the internal protection circuit disables pwm output as long as v dd exceeds the threshold. 8 gate driver output the totem-pole output driver for the power mosfet, internally clamped below 18v. f: l=ocp latch, c=ocp auto-recovery t : s=sop p : z=lead free null=regular package xxxxxxxx : wafer lot y : year; ww : week v : assembly location gate vdd gnd fb sg6846aftp xxxxxxxxywwv vin sense ri rt
product specification highly integrated green-mode pwm controller sg6846a ? system general corp. - 3 - www.sg.com.tw ? www.fairchildsemi.com version 1.1.1 (iao33.0059.b1) september 26, 2007 block diagram
product specification highly integrated green-mode pwm controller sg6846a ? system general corp. - 4 - www.sg.com.tw ? www.fairchildsemi.com version 1.1.1 (iao33.0059.b1) september 26, 2007 absolute maximum ratings symbol parameter value unit v vdd supply voltage 25 v v l input voltage to vin, fb, sense pins -0.3 to 7.0 v p d power dissipation 400 mw r jc thermal resistance (junction-to-case) 54.4 c/w t j operating junction temperature -40 to +125 c t stg storage temperature range -65 to +150 c t l lead temperature (wave soldering or infrared, 10 seconds) 260 c electrostatic discharge capability, human body model 5.0 kv esd electrostatic discharge capability, machine model 200 v * all voltage values, except differential voltages, are given with respect to gnd pin. * stresses beyond those listed under "absolute maximu m ratings" may cause permanent damage to the device. recommended operating junction temperature symbol parameter value unit t a operating ambient temperature -20c ~ 85c v *for proper operation electrical characteristics v dd =15v, t a =25c, unless otherwise noted. v dd section symbol parameter test condition min. typ. max. unit 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 i dd-st start-up current v dd-on ? 0.16v 30 a i dd-op operating supply current gate open 5 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-ovp v dd ovp latch-up holding current v dd =5v 70 a v dd-scp threshold voltage on v dd for short-circuit protection v cs >v sth lasts for t delay-short v dd-off + 0.5v v dd-off + 1v v dd-off + 1.5v v v in section symbol parameter min. typ. max. unit v in-off pwm turn-off threshold voltage 0.65 0.70 0.75 v v in-on pwm turn-on threshold voltage v in-off +0.18 v in-off +0.2 v in-off +0.22 v
product specification highly integrated green-mode pwm controller sg6846a ? system general corp. - 5 - www.sg.com.tw ? www.fairchildsemi.com version 1.1.1 (iao33.0059.b1) september 26, 2007 feedback input section symbol parameter test condition min. typ. max. unit a v input voltage to current-sense attenuation at green mode 1/4 v/v z fb input impedance 5.5 k v fb-open fb pin open voltage 5.6 6.2 6.6 v v fb-olp fb open-loop trigger level 4.7 5.2 5.7 v t d-olp delay time of fb pin open-loop protection r i =26k ? 1600 1700 1800 ms current-sense section symbol parameter test condition min. typ. max. unit z sense input impedance 12 k t pd delay to output 250 ns t leb leading-edge blanking time 270 360 ns v sth1v threshold voltage for current limit v in =1v 0.83 v v sth3v threshold voltage for current limit v in =3v 0.70 v v sth1v-2/3 2/3 threshold voltage for current limit v in =1v 0.58 0.61 0.64 v v sth3v-2/3 2/3 threshold voltage for current limit v in =3v 0.48 0.51 0.54 v t d-ocp *delay time for over-current protection r i =26k ? 1500 1600 1700 ms v slope slope compensation duty=dcy max 0.33 v t d-short *output short delay time v cs > v sth , r i =26k ? 92 100 108 ms t ss-65khz soft-start time r i =26k ? 5 ms t ss-130khz soft-start time r i =13k ? 2.5 ms oscillator section symbol parameter test condition min. typ. max. unit center frequency 62 65 68 f osc normal pwm frequency jitter range r i =26k ? , v fb >v n 4.2 khz center frequency 124 130 136 f osc,max maximum pwm frequency jitter range r i =13k ? , v fb >v n 8.4 khz center frequency 44.8 47.0 49.2 f osc,min minimum pwm frequency jitter range r i =36k ? , v fb >v n 2.9 khz t hop-1 jitter period r i =26k ? , v fb >v n 4.4 ms f osc-g green-mode minimum frequency r i =26k ? 18.0 22.5 25.0 khz pin, fb voltage 2.1 v v fb-n fb pin frequency reduction threshold jitter range r i =26k ? , v fb =v n 4.2 khz pin, fb voltage 1.6 v v fb-g fb voltage at f osc-green jitter range r i =26k ? , v fb =v g 1.45 khz 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 85 c 1.5 5.0 %
product specification highly integrated green-mode pwm controller sg6846a ? system general corp. - 6 - www.sg.com.tw ? www.fairchildsemi.com version 1.1.1 (iao33.0059.b1) september 26, 2007 65khz 22.5khz v v fb-n fb-g fb v frequency pwm frequency +4.2khz -4.2khz +1.45khz -1.45khz pwm output section symbol parameter test condition min. typ. max. unit dcy max maximum duty cycle 90 % v gate-l output voltage low v dd =15v, i o =50ma 1.5 v v gate-h output voltage high v dd =12v, i o =50ma 8 v t r rising time gate=1nf 350 ns t f falling time gate=1nf 50 ns v gate-clamp gate output clamping voltage v dd =20v 18 v over-temperature protection section symbol parameter test condition min. typ. max. unit i rt output current of rt pin r i =26k ? 64 70 76 a v rtth threshold voltage for over-temperature protection 1.015 1.065 1.115 v t d-otp over-temperature latch-off debounce r i =26k ? 100 ms ri section symbol parameter test condition min. typ. max. unit ri nor ri operating range 13 36 k
product specification highly integrated green-mode pwm controller sg6846a ? system general corp. - 7 - www.sg.com.tw ? www.fairchildsemi.com version 1.1.1 (iao33.0059.b1) september 26, 2007 typical characteristics t urn-on threshold voltage (v dd-on ) vs temperature 10 12 14 16 18 20 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) v dd-on (v ) t urn-off v oltage (v dd-off ) vs t emperature 9.5 9.9 10.3 10.7 11.1 11.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) v dd-off (v ) start-up current (i dd-s t ) vs t emperature 14.0 17.2 20.4 23.6 26.8 30.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) i dd-st (ua ) pwm turn-off threshold voltage (v in-off ) vs temperature 0.0 0.5 1.0 1.5 2.0 2.5 -40 -24 -7 10 26 43 59 76 92 109 125 temperature ( ) v in-off (v ) p wm turn-on t hreshold voltage (v in -o n ) vs temperature 0.90 0.92 0.94 0.96 0.98 1.00 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) v in-on (v ) start-up current vs vdd voltage 0 2 4 6 8 10 10 11 12 13 14 15 16 vdd (v) i dd-st (ua )
product specification highly integrated green-mode pwm controller sg6846a ? system general corp. - 8 - www.sg.com.tw ? www.fairchildsemi.com version 1.1.1 (iao33.0059.b1) september 26, 2007 normal pwm f requency (f osc ) vs t emperature 62 63 64 66 67 68 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) f osc (khz ) pwm frequency vs fb voltage 0 14 28 42 56 70 1.61.71.81.92.02.12.22.32.4 vfb (v) pwm frequency (kh z c urrent - limit threshold vs vin voltage 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3 2.5 2.7 2.9 3.1 3.3 v in ( v ) v th-p (v ) 2/ 3 c urrent - limit t hres hold vs v in v oltage 0.50 0.58 0.66 0.74 0.82 0.90 0.70.91.11.31.51.71.92.12.32.52.72.93.13.3 v in (v) v th-o (v ) output current of rt pin (i rt ) vs t emperature 68.5 69.0 69.5 70.0 70.5 71.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) i rt (ua ) fb output high voltage (v rtth ) vs t emperature 0.4 0.6 0.8 1.0 1.2 1.4 -40 -25 -10 5 20 35 50 65 80 95 110 125 temperature ( ) v rtth (v )
product specification highly integrated green-mode pwm controller sg6846a ? system general corp. - 9 - www.sg.com.tw ? www.fairchildsemi.com version 1.1.1 (iao33.0059.b1) september 26, 2007 operation description start-up operation the turn-on/turn-off thresholds are fixed internally at 16.5v/10.5v. to enable the sg6846a during start-up, the hold-up capacitor must first be charged to 16.5v through the start-up 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 start-up process. this uvlo hysteresis window ensures that the hold-up capacitor can adequately supply v dd during start-up. the typical start-up current is only 8a, which allows a high-resistance, low-wattage start-up resistor to minimize power loss. a 1.5m /0.25w start-up resistor and a 10f/25v v dd hold-up capacitor are sufficient for a universal input range. the required operating current has been reduced to 3.7ma, which enables higher efficiency and reduces the v dd hold-up capacitance requirement. green-mode operation 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. this green-mode function dramatically reduces power consumption under light-load and zero-load conditions. power supplies using the sg6846a can meet even the most restrictive international regulations regarding standby power consumption. oscillator operation a resistor connected from the ri pin to gnd generates a reference current source 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 results in a corresponding 65khz switching frequency. the relationship between r i and the switching frequency is: ) (k i r 1690 (khz) pwm 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 the 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 two thirds the peak-current threshold, the internal counter counts down. when the total accumulated counting time is more than around 1600ms (r i =26k ? ), the controller is latched off the internal counter counting up. when the switching current is lower than two thirds of the peak current threshold, the internal counter counts down. when the total accumulated counting time is more than about 1700ms (r i =26k ? ), the controller is latched off. this two-level ocp protection and up/down counter are especially designed for smps with surge current for printers, scanners, motor drivers, etc. constant output power limit for constant output power limit over a 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.
product specification highly integrated green-mode pwm controller sg6846a ? system general corp. - 10 - www.sg.com.tw ? www.fairchildsemi.com version 1.1.1 (iao33.0059.b1) september 26, 2007 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 0.7v, the pwm output shuts off. if the v in voltage is over 0.9v, the pwm output turns on again. the hysteresis window for on/off is around 0.2v. v dd over-voltage protection v dd over-voltage protection is built-in to prevent the controller from over-voltage destruction. when v dd voltage is over 23.6v, the sg6846a is latched off. over-temperature protection 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 1.065v, the sg6846a is turned off. for the protection modes options, please see order information. noise immunity noise from the current sense or the control signal may cause significant pulse 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 sg6846a. usually an rc network is put on between sensing resistor and the cs pin to filter high-frequency switching noise, as shown figure 1. fig-1 current sense rc filter
product specification highly integrated green-mode pwm controller sg6846a ? system general corp. - 11 - www.sg.com.tw ? www.fairchildsemi.com version 1.1.1 (iao33.0059.b1) september 26, 2007 reference circuit 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 47 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 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
product specification highly integrated green-mode pwm controller sg6846a ? system general corp. - 12 - www.sg.com.tw ? www.fairchildsemi.com version 1.1.1 (iao33.0059.b1) september 26, 2007 package information8pins-sop(s) 1 4 8 5 h e e b a a1 d c f l dimensions millimete r 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 sg6846a ? system general corp. - 13 - www.sg.com.tw ? www.fairchildsemi.com version 1.1.1 (iao33.0059.b1) september 26, 2007

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