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product specification highly-integrated green-mode pwm controller sg6842j ? system general corp. - 1 - www.sg.com.tw version 1.4(iao33.0015.b4) feb. 13, 2006 features green-mode pwm controller low start-up current (8ua) low operating current (4ma) programmable pwm frequency with jittering peak-current-mode operation cycle-by-cycle current limiting synchronized slope compensation leading-edge blanking constant output power limit (full ac input range) vdd over voltage protection (ovp) programmable over temperature protection (otp) internal latch circuit (otp, ovp) options internal open-loop protection applications general-purpose switch mode power supplies and flyback power converters, including: notebook power adapters open-frame smps description the highly integrated sg6842j 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 at light-load conditions. to avoid acoustic-noise problem, the minimum pwm frequency set above 20khz. this green-mode function enables the power supply to easily meet international power conservation requirements. to further reduce power consumption, sg6842j is manufactured by using the bicmos process. this allows the lowest start-up current around 8ua, and the operating current is only 4ma. as a result, large start-up re sistance can be used. sg6842j integrates frequency jittering function internally. the frequency jittering function helps reduce emi emission of a power supply with minimum line filters. also, its built-in synchronized slope compensation achieves stable peak-current-mode control. the proprietary internal line co mpensation ensures constant output power limit over a wide ac input voltages, from 90vac to 264vac. sg6842j provides many protection functions. in addition to cycle-by-cycle current limiting, the internal open-loop protection circuit ensures safety should an open loop or output short-circuit failure occurs. pwm output is disabled till v dd drops below the uvlo lower limit. then, the controller starts up again. as long as v dd exceeds about 24v, the internal ovp circuit is triggered. an external ntc thermistor can be applied for over-temperature protection. for ovp and otp, the protection mode can be chosen to be latch off or auto recovery. sg6842j is available in an 8-pin dip or sop package. typical application
product specification highly-integrated green-mode pwm controller sg6842j ? system general corp. - 2 - www.sg.com.tw version 1.4(iao33.0015.b4) feb. 13, 2006 marking diagrams pin configuration ordering information part number otp latch package SG6842JLSZ yes 8-pin sop (lead free) sg6842jldz yes 8-pin dip (lead free) sg6842jcsz no 8-pin sop (lead free) sg6842jcdz no 8-pin dip (lead free) pin descriptions pin no. symbol function description 1 gnd ground ground. 2 fb feedback the signal from the external com pensation circuit is fed into th is pin. the pwm duty cycle is determined in response to the signal from this pi n and the current-sense signal from pin 6. if fb voltage exceeds a threshold, the internal prot ection circuit will di sable pwm output after a predetermined delay time. 3 vin start-up input for start-up, this pin is pulled high to the rect ified line input via a resistor. since the start-up current requirement of the sg6842j is very sm all, a large start-up resistance can be used to minimize power loss. under normal operation, this pin is also used to detect the line voltage. as a result, constant output power limit over a universal ac input range can be achieved. 4 ri reference setting a resistor connected from the ri pin to g nd pin will provide the sg6842j with a constant current source. this determines the center pwm frequency. increasing the resistance will reduce pwm frequency. using a 26k ? resistor r i results in a 65khz center pwm frequency. 5 rt temperature detection for over-temperature protection. an external nt c thermistor is connected from this pin to gnd pin. the impedance of the ntc will decrease at high temperatures. once the voltage of the rt pin drops below a fixed limit , pwm output will be disabled. 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. if vdd exceeds a threshold, the internal protection circuit will disable pwm output. 8 gate driver output the totem-pole output driver fo r the power mosfet. it is internally clamped below 18v sg6842j ftp xxxxxxxyywwv f: l = otp latch, c = otp auto-recovery t : d = dip, s = sop p : z =lead free + rohs compatible null=regular package xxxxxxx: wafer lot yy : year; ww : week v : assembly location ri vin gate vdd sense rt gnd fb
product specification highly-integrated green-mode pwm controller sg6842j ? system general corp. - 3 - www.sg.com.tw version 1.4(iao33.0015.b4) feb. 13, 2006 block diagram
product specification highly-integrated green-mode pwm controller sg6842j ? system general corp. - 4 - www.sg.com.tw version 1.4(iao33.0015.b4) feb. 13, 2006 absolute maximum ratings symbol parameter test condition value unit v dd supply voltage 25 v v in input terminal 30 v v fb input voltage to fb pin -0.3 to 7v v v sense input voltage to sense pin -0.3 to 7v v v rt input voltage to rt pin -0.3 to 7v v v ri input voltage to ri pin -0.3 to 7v v p d power dissipation at t a < 50c dip sop 800 400 mw r j-a thermal resistance junction-air dip sop 82.5 141 c/w t j operating junction temperature -40 to +125 c t stg storage temperature range -55 to +150 c t l lead temperature (soldering) 10 sec dip 10 sec sop 260 230 c *all voltage values, except differential volt ages, are given with respect to gnd pin. * stresses beyond those listed under "absolute maxi mum ratings" may cause permanent damage to the device. recommended operating junction temperature: -30c ~ 85c* *for proper operation electrical characteristics (vdd = 15v, t a = 25c, unless noted) vdd section symbol parameter test condition min. typ. max. unit v op continuously operating voltage 22 v v th-on turn-on threshold voltage 15.5 16.5 17.5 v v th-off turn-off voltage 9.5 10.5 11.5 v i dd-st start-up current v dd = 15v, r i = 26 k gate with 1nf to gnd 30 ua i dd-op operating supply current gate open 4 5 ma v dd-ovp v dd over voltage protection 23.2 24.2 25.2 v t vdd-ovp v dd ovp debounce time ri = 26k 100 usec ri section symbol parameter test condition min. typ. max. unit ri nor r i operating range 15.5 36 k ? ri max max. r i value for protection 230 k ? ri min min. r i value for protection 10 k ?
product specification highly-integrated green-mode pwm controller sg6842j ? system general corp. - 5 - www.sg.com.tw version 1.4(iao33.0015.b4) feb. 13, 2006 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 3.7 4.2 4.7 khz t jtr jittering period r i = 26k 3.9 4.4 4.9 ms f osc-g-min green-mode min. frequency r i = 26k 18 22 25 khz f dv frequency variation versus v dd deviation vdd = 11.5v to 20v 5 % f dt frequency variation versus temp. deviation t a = -30 to 85 5 % feedback input section symbol parameter test condition min. typ. max. unit a v fb input to current comparator attenuation @green mode 1/4.5 1/4 1/3.5 v/v z fb input impedance 4 7 k ? v hgh output high voltage fb pin open 5.5 v v fb-ol fb open-loop trigger level 5 5.4 v t lps fb open-loop protection delay r i = 26k 50 56 62 ms v n green-mode entry fb voltage 1.9 2.1 2.3 v v g green-mode ending fb voltage v n -0.6 v n -0.5 v n -0.4 v f g-test burst-mode test frequency v g +20mv f osc-g-min +0.5 khz i zero pwm off fb voltage 1.5 ma current sense section symbol parameter test condition min. typ. max. unit z cs input impedance 12 k ? v th80 threshold voltage for current limit i vin = 80ua, r i = 26k 0.81 0.84 0.87 v v th160 threshold voltage for current limit i vin = 160ua, r i = 26k v th80 -0.085 v th80 -0.07 v th80 -0.055 v t pd propagation delay to gate output 100 200 ns t leb leading edge blanking time 260 360 460 ns v slope slope compensation sense=2k ? , duty = dcy max 0.34 0.37 0.41 v
product specification highly-integrated green-mode pwm controller sg6842j ? system general corp. - 6 - www.sg.com.tw version 1.4(iao33.0015.b4) feb. 13, 2006 gate section symbol parameter test condition min. typ. max. unit dcy max maximum duty cycle 80 85 90 % v ol output voltage low v dd =15v, i o = 50ma 1.5 v v oh output voltage high v dd =12v, i o = 50ma 8v v t r rising time v dd =15v, c l = 1nf 150 250 350 ns t f falling time v dd =15v, c l = 1nf 30 50 90 ns i o peak output current v dd =15v, gate=6v 230 ma v clamp gate output clamping voltage vdd = 22v 18 19 v rt section symbol parameter test condition min. typ. max. unit i rt output current of rt pin r i = 26k 67 70 73 ua v otp-stop trigger voltage for over-temperature protection 1.015 1.05 1.085 v t otp-latch over-temperature latch-off debounce. r i = 26k ,v rt <0.7v 60 100 140 us
product specification highly-integrated green-mode pwm controller sg6842j ? system general corp. - 7 - www.sg.com.tw version 1.4(iao33.0015.b4) feb. 13, 2006 typical characteristics start-up current (iddst) vs temperature 10.000 12.000 14.000 16.000 18.000 20.000 -40 -25 -10 5 20 35 50 65 80 95 110 125 t emper at ur e ( ) iddst (ua) operation current (iddop) vs temperature 2.500 3.000 3.500 4.000 4.500 5.000 -40 -25 -10 5 20 35 50 65 80 95 110 125 t emper at ur e ( ) i ddop ( ma) on threshol d vol tage (vthon) vs temperature 16.0 16.2 16.4 16.6 16.8 17.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 t emper at ur e ( ) vthon (v) pwm frequency (fosc) vs temperature 64.000 64.400 64.800 65.200 65.600 66.000 -40 -25 -10 5 20 35 50 65 80 95 110 125 t emper at ur e ( ) fosc ( khz) vdd vs i dd 0 5 10 15 20 25 0 2 4 6 8 10 12 14 16 vdd (v) i dd (ua) ri voltage (vri) vs temperature 1.200 1.250 1.300 1.350 1.400 -40 -25 -10 5 20 35 50 65 80 95 110 125 t emper at ur e ( ) vri (v)
product specification highly-integrated green-mode pwm controller sg6842j ? system general corp. - 8 - www.sg.com.tw version 1.4(iao33.0015.b4) feb. 13, 2006 max. duty (dcy) vs temperature 70.000 74.000 78.000 82.000 86.000 90.000 -40 -25 -10 5 20 35 50 65 80 95 110 125 t emper at ur e ( ) dcy (%) votp,stop vs temperature 1.000 1.020 1.040 1.060 1.080 1.100 -40 -25 -10 5 20 35 50 65 80 95 110 125 t emper at ur e ( ) votp-latch-off (v) output current of pin rt (irt) vs temperature 60.000 64.000 68.000 72.000 76.000 80.000 -40 -25 -10 5 20 35 50 65 80 95 110 125 t emper at ur e ( ) irt (ua) green-mode min. frequency vs temperature 0.000 5.000 10.000 15.000 20.000 25.000 -40 -25 -10 5 20 35 50 65 80 95 110 125 t emper at ur e ( ) fose- green ( khz) of f t hr eshol d v ol t age ( v t h of f ) v s t emper at ur e 9.6 9.8 10.0 10.2 10.4 10.6 10.8 11.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 t emper at ur e ( ) vthoff (v) vsense vs ivin 0.44 0.49 0.54 0.59 0.64 0.69 0.74 0.79 0.84 0.89 0 40 80 120 160 200 240 280 320 360 ivin (ua) vsense (v)
product specification highly-integrated green-mode pwm controller sg6842j ? system general corp. - 9 - www.sg.com.tw version 1.4(iao33.0015.b4) feb. 13, 2006 operation description start-up current the typical start-up current is only 8ua. this allows a high resistance, low-wattage st art-up resistor to be used, to minimize power loss. a 1.5 m , 0.25w, start-up resistor and a 10uf/25v vdd hold-up capacitor would be sufficient for an ac/dc adapter with a universal input range. operating current the required operating current has been reduced to 4ma. this results in higher efficiency and reduces the vdd hold-up capacitance requirement. green-mode operation the proprietary green-mode function provides off-time modulation to continuously decrease the pwm frequency under light-load conditions. to avoid acoustic-noise problem, th e minimum pwm frequency set above 20khz. this green-mode function dramatically reduces power consumption under light-load and zero-load conditions. power supplies using a sg6842j controller can easily meet even the most restrictive international regulations regarding standby power consumption. oscillator operation a resistor connected from the ri pin to gnd pin generates a constant current source for the sg6842j controller. this current is used to determine the center pwm frequency. increasing the resistance will reduce 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) ) (k r i ? = 1690 pwm f ---------------------------- (1) sg6842j also integrates frequency jittering function internally. the frequency variation ranges from around 61khz to 69khz fo r a center frequency 65khz. the frequency jittering function helps reduce emi emission of a power supply with minimum line filters. 26 70 ? ? = ) (k r i ua rt i -------------------------------(2) 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 leading-edge blanking time is built in. during this blanking period, the current-limit comparator is disabled, and it cannot switch off the gate drive. under-voltage lockout (uvlo) the turn-on/turn-off thresholds are fixed internally at 10.5v/16.5v. to enable a sg6842j controller during start-up, the hold-up capacitor must first be charged to 16.5v through the start-up resistor. the hold-up capacitor will continue to supply vdd before energy can be delivered from the auxiliary winding of the main transformer. vdd must not drop below 10.5v during this start-up proces s. this uvlo hysteresis window ensures that the hold-up capacitor can adequately supply vdd during start-up. gate output / soft driving the sg6842j 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 in order to protect the power mosfet transistors from any harmful over-voltage gate signals. a soft driving waveform is implemented to minimize emi. slope compensation the sensed voltage across th e current sense resistor is used for peak-current-mode control and cycle-by-cycle current limiting. the built-in slope compensation
product specification highly-integrated green-mode pwm controller sg6842j ? system general corp. - 10 - www.sg.com.tw version 1.4(iao33.0015.b4) feb. 13, 2006 function improves power supply stability and prevents peak-current-mode control from causing sub-harmonic oscillations. within every switching cycle, the sg6842j controller produces a positively sloped, synchronized ramp signal. constant output power limit when the sense voltage across the sense resistor r s reaches the threshold voltage, the output gate drive will be turned off following a small propagation delay t pd . this propagation delay will result in 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. the output power limit variation can be significant over a wide range of ac input voltages. to compensate for this, the threshold voltage is adjusted by the current i in . since the pin vin is connected to the rectified input line voltage through the start-up resistor, a higher line voltage will result in a higher current i in through the pin vin. the threshold voltage decreases if the current i in increases. a small threshold voltage will force 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). vdd over-voltage protection vdd over-voltage protection has been built in to prevent damage due to over voltage conditions. when the voltage vdd exceeds the internal threshold due to abnormal conditions, pwm output will be turned off. over-voltage conditions are usually caused by open feedback loops. limited power control the fb voltage will increase every time the output of the power supply is shorted or over-loaded. if the fb voltage remains higher than a built-in threshold for longer than t lps , pwm output will then be turned off. as pwm output is turned off, the supply voltage vdd will also begin decreasing. when vdd goes below the turn-off threshold (eg, 10.5v) the controller will be totally shut down. vdd will be charged up to the turn-on threshold voltage of 16.5v through the start-up resistor until pwm output is restarted. this protection feature will continue to be activated as long as the over-loading condition persists. this will prevent the power supply from overheating due to over loading conditions. protection latch circuit for the sg6842j family, the built-in latch function provides a versatile protection feature that does not require external components. see ordering information for a detailed description. to reset the latch circuit, it is necessary to disconnect the ac line voltage of the power supply. thermal protection an external ntc thermistor can be connected from the rt pin to ground. a fixed current i rt is sourced from the rt pin. because the impedance of the ntc will decrease at high temperatures, when the voltage of the rt pin drops below 1.065v, pwm output will be disabled. the rt pin output current is related to the pwm frequency programming resistor r i noise immunity noise from the current sense or the control signal may cause significant pulse wi dth jitter, particularly in continuous-conduction mode. slope compensation helps alleviate this problem. good placement and layout practices should be followed. the designer should avoiding long pcb traces and component leads. compensation and filter components should be located near the sg6842j. finally, increasing the power-mos gate resistance is advised.
product specification highly-integrated green-mode pwm controller sg6842j ? system general corp. - 11 - www.sg.com.tw version 1.4(iao33.0015.b4) feb. 13, 2006 package information 8pins-dip(d) 4 1 8 5 d e1 e e b a1 a2 a b b1 l e dimensions millimeters inches symbol min. typ. max. min. typ. max. a 5.334 0.210 a1 0.381 0.015 a2 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 eb 8.509 9.017 9.525 0.335 0.355 0.375 ? 0 ? 7 ? 15 ? 0 ? 7 ? 15 ?
product specification highly-integrated green-mode pwm controller sg6842j ? system general corp. - 12 - www.sg.com.tw version 1.4(iao33.0015.b4) feb. 13, 2006 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 a1 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 sg6842j ? system general corp. - 13 - www.sg.com.tw version 1.4(iao33.0015.b4) feb. 13, 2006 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 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 ge neral?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 m ilitary applications. use of system general?s products in military applications is not authorized without the expre ss 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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