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dec, 2006 v1.5 1/15 CR6850 novel low cost green-power pwm controller features z low cost, pwm&pfm&crm (cycle reset mode) z low start-up current (about 8a) z low operating current (about 2ma) z current mode operation z under voltage lockout (uvlo) z built-in synchronized slope compensation z programmable pwm frequency z audio noise free operation z leading edge blanking on sense input z constant output power limiting for universal ac input z cycle-by-cycle current limiting z soft clamped gate output voltage 16.8v z over voltage protect 25.5v z high-voltage cmos process with esd z sot-23-6l ? sop8 & dip-8 pb-free packaging z compatible with sg5701 & sg5848 & ld7535 & ob2262/63 applications z switching ac/dc adaptor z battery charger z open frame switching power supply z 384x replacement general description the CR6850 is a highly integrated low cost current mode pwm controller, which is ideal for small power current mode of offline ac-dc fly-back converter applications. making use of external resistors, the ic changes the operating frequency and automatically enters the pfm/crm (cycle reset mode) under light-load/zero-load conditions. this can minimize standby power consumption and achieve green-power functions. with a very low start-up current, the CR6850 could use a large value start-up resistor (2mohm). built-in synchronized slope compensation enhances the stability of the system and avoids sub-harmonic oscillation. dynamic peak limiting circuit minimizes output power change caused by delay time of the system over a universal ac input range. leading edge blanking circuit on current sense input could remove the signal glitch due to snubber circuit diode reverse recovery and thus greatly reduces the external component count and system cost in the design. pulse-by-pulse current limiting ensures safe operation even during short-circuit. the CR6850 offers more protection like ovp (over voltage protection) and ocp (over current protection). the CR6850?s output driver is soft clamped to maximum 16.8v to protect the power mosfet. excellent emi performance is achieved soft switching control at the totem pole gate driver output. CR6850 is offered in sot-23-6, sot-8 and dip-8 packages. tel:0755-25311262 fax:0755-25311968 web:www.kingkeyelec.com www..net www..net
CR6850 dec, 2006 v1.5 2/15 cr68xx series part number pwm frequency package description cr6848 external adjustable dip-8 ? sop8 sot-23-6l pwm&pf&crm ? current mode ? slope compensation leading-edge blanking ? gate clamped ? over-voltage protection ? over-current protection ? soft drive. CR6850 external adjustable dip-8 ? sop8 sot-23-6l with all functions of cr6848 ? gate soft clamped cr6851 external adjustable dip-8 ? sop8 sot-23-6l with all functions of CR6850 ? frequency jitter ? soft start ? sense fault protect ? olp ? scp ? otp typical application pin assignment pin descriptions name description gnd gnd pin fb analog input. voltage feedback pin (same as the comp pin in uc384x), ri this pin is to program the switching frequency. by connecting a resistor to ground to set the switching frequency. sen current sense pin, connect to sense the mosfet current. vdd supply voltage pin. gate totem output to drive the external power mosfet. tel:0755-25311262 fax:0755-25311968 web:www.kingkeyelec.com www..net www..net
CR6850 dec, 2006 v1.5 3/15 block diagram simplified internal circuit architecture absolute maximum ratings symbol parameter rating unit v dd supply voltage pin voltage 40 v i ovp vdd ovp maximal enter current 20 ma v fb input voltage to fb pin -0.3 to 6v v v sen input voltage to sen pin -0.3 to 6v v p d power dissipation 300 mw esd capability, hbm model 2500 v esd esd capability, machine model 250 v 20second sot-23-6l 220 ?? t l lead temperature (soldering) 10second dip-8 260 ?? t stg storage temperature range -55 to + 150 ?? recommended operation condition symbol parameter min ~ max unit vdd vdd supply voltage 11~20 v ri ri pin resistor value 65~130 k ohm t oa operation ambient temperature -20~85 ?? p o output power 0~60 w f pwm frequency of pwm 50~100 khz tel:0755-25311262 fax:0755-25311968 web:www.kingkeyelec.com www..net www..net
CR6850 dec, 2006 v1.5 4/15 electrical characteristics ( ta=25c unless otherwise noted, v dd = 15v. ) symbol parameter conditions min. typ. max. unit supply voltage (v dd pin) i st startup current 8 a v fb =0v 2.9 ma v fb =3v 1.9 ma i ss operating current v fb =open 1.44 ma vdd on turn-on threshold voltage 15.3 v vdd off turn-off threshold voltage 9.8 v vd clamp vdd clamp voltage i vdd =20ma 25.5 v voltage feedback (fb pin) i fb short circuit current v fb =0v 1.68 ma v fb open loop voltage v fb =open 4.7 v i pfm enter pfm&pwm, fb current 1.2 ma i crm enter crm, fb current 1.5 ma v pfm pfm threshold v fb 1.15 v current sensing (sen pin) v th_l minimum voltage lever 0.55 0.65 0.75 v v th_h maximum voltage lever 0.75 0.85 0.95 v t pd delay to output 300 ns r cs input impedance 50 k oscillator (ri pin) f osc normal frequency ri=100kohm 60 65 70 khz f pfm pfm frequency ri=100kohm 20.6 khz dc max maximum duty cycle ri=100kohm 77 % | f temp frequency temp. stability -30-85 ?? 5 % t blank leading-edge blanking time 300 ns gate drive output (gate pin) v ol output low level v dd =15v, i o =20ma 1 v v oh output high level v dd =15v, i o =20ma 8 v t r rising time c l =1000pf 420 ns t f falling time c l =1000pf 120 ns vg clamp output clamp voltage vdd=20v 16.8 17.8 v tel:0755-25311262 fax:0755-25311968 web:www.kingkeyelec.com www..net www..net
CR6850 dec, 2006 v1.5 5/15 typical characteristics vdd startup current vs temperature vdd operation current vs temperature vdd (on) vs temperature vdd (off) vs temperature pwm frequency vs temperature duty cycle vs temperature tel:0755-25311262 fax:0755-25311968 web:www.kingkeyelec.com www..net www..net
CR6850 dec, 2006 v1.5 6/15 f osc vs ri resistor ovp vs temperature f osc vs fb current tel:0755-25311262 fax:0755-25311968 web:www.kingkeyelec.com www..net www..net
CR6850 dec, 2006 v1.5 7/15 operation description current model compared to voltage model control, current model control has a current feedback loop. when the voltage of the sense resistor peak current of the primary winding reaches the internal setting value v th , comparator reverse, register reset and power mosfet cut-off. so that to detect and modulate the peak current cycle by cycle could control the output of the power supply. the current feedback has a good linear modulation rate and a fast input and output dynamic impact avoid the pole that the output filter inductance brings and the second class system descends to first class and so it widens the frequency range and optimizes overload protection and short circuit protection. startup current and under voltage lockout the startup current of CR6850 is set to be very low so that a large value startup resistor can therefore be used to minimize the power loss. for ac to dc adaptor with universal input range design, a 2 m , 1/8 w startup resistor and a 10uf/25v vdd hold capacitor could be used . the turn-on and turn-off threshold of the CR6850 is designed to 15.3v/9.8v. during startup, the hold-up capacitor must be charge to 15.3v through the startup resistor. the hysteresis is implemented to prevent the shutdown from the voltage dip during startup. internal bias and osc operation a resistor connected between ri pin and gnd pin set the internal constant current source to charge or discharge the internal fixed cap. the charge time and discharge time determine the internal clock speed and the switching frequency. increasing the resistance will reduce the value of the input current and reduce the switching frequency. the relationship between ri pin and pwm switching frequency follows the below equation within the ri allowed range. ) ( ) ( 6500 khz k ri f osc ? = for example, a 100k resistor ri could generate a 50ua constant current and a 65khz pwm switching frequency. the suggested operating frequency range of CR6850 is within 50khz to 100khz. green power operation the power dissipation of switching mode power supply is very important in zero load or light load condition. the major dissipation result from conduction loss ? switching loss and consume of the control circuit. however, all of them related to the switching frequency. there are many difference topologies has been implemented in different chip. the basic operation theory of all these approaches intended to reduce the switching frequency under light-load or no-load condition. CR6850`s green power function adapts pwm ? pfm and crm combining modulation. when ri resistor is 100k, the pwm frequency is 65khz in medium or heavy load operation. through modifying the pulse width, CR6850 could control output voltage. the current of fb pin increases when the load is in light condition and the internal mode controller enters pfm&pwm when the feedback current is over 1.2ma. the operation frequency of oscillator is to descend gradually. the invariable frequency of oscillator is 21khz when the feedback current is over 1.35ma. to decrease the standby consumption of the power supply , chip-rail introduces the cycle reset mode technology ? if the feedback current were over 1.5ma, mode controller of CR6850 would reset internal register all the time and cut off the gate pin, while the output voltage is lower than the set value, it would set register, gate pin operating again. although the frequency of the internal osc is invariable, the register would reset some pulses so that the practical frequency is decreased at the gate pin. CR6850 green-power function tel:0755-25311262 fax:0755-25311968 web:www.kingkeyelec.com www..net www..net
CR6850 dec, 2006 v1.5 8/15 internal synchronized slop compensation although there are more advantages of the current mode control than conventional voltage mode control, there are still several drawbacks of peak-sensing current-mode converter. especially the open loop instability when it operates in higher than 50% of the duty-cycle. CR6850 is introduced an internal slope compensation adding voltage ramp to the current sense input voltage for pwm generation to solve this problem. it improves the close loop stability greatly at ccm, prevents the sub-harmonic oscillation and thus reduces the output ripple voltage. duty duty duty v max slop = = 4389 . 0 33 . 0 current sensing & dynamic peak limiting the current flowing by the power mosfet comes in to being a voltage v sense on the sense pin cycle by cycle, which compares to the internal reference voltage, controls the reverse of the internal register, limits the peak current imax of the primary of the transformer. the energy 2 2 1 max i l e = deposited by the transformer. so adjusting the r sense can set the max output power of the power supple mode. the current flowing by the power mosfet has an extra value d p in t l v i = ? due to the system delay t that the current detected from the sense pin to power mosfet cut off in the CR6850 (among these, v in is the primary winding voltage of the transformer and l p is the primary wind inductance. in v ranges from 85vac to 264vac. to guarantee the output power is a constant for universal input ac voltage, there is a dynamic peak limit circuit to compensate the system delay t that the system delay brings on. leading-edge blanking (leb) each time the power mosfet is switched on, a turn-on spike will inevitably occur at the sense pin, which would disturb the internal signal from the sampling of the r sense . there is a 300n sec leading edge blanking time built in to avoid the effect of the turn-on spike and the power mosfet cannot be switched off during this time. so that the conventional external rc filtering on sense input is no longer required. over voltage protection (ovp) there is a 25.5v over-voltage protection circuit in the CR6850 to improve the credibility and extend the life of the chip. the gate is to shutdown immediately when the voltage of the vdd is over 25.5v and the voltage of vdd is to descend rapidly. gate driver & soft clamped CR6850? output designs a totem pole to drive a periphery power mosfet. the dead time is introduced to minimize the transfixion current when the output is drove. the nmos is shut off when the other nmos is turned on. the novel soft clamp technology is introduced to protect the periphery power mosfet from breaking down and current saturation of the zener. tel:0755-25311262 fax:0755-25311968 web:www.kingkeyelec.com www..net www..net
CR6850 dec, 2006 v1.5 9/15 package demensions dip-8l 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 ? tel:0755-25311262 fax:0755-25311968 web:www.kingkeyelec.com www..net www..net
CR6850 dec, 2006 v1.5 10/15 sot-23-6l dimensions in millimeters dimensions in inches symbol min max min max a 0.700 1.000 0.028 0.039 a1 0.000 0.100 0.000 0.004 b 1.397 1.803 0.055 0.071 b 0.300 0.559 0.012 0.022 c 2.591 3.000 0.102 0.118 d 2.692 3.099 0.106 0.122 e 0.838 1.041 0.033 0.041 h 0.080 0.254 0.003 0.010 l 0.300 0.610 0.012 0.024 sop-8l tel:0755-25311262 fax:0755-25311968 web:www.kingkeyelec.com www..net www..net
CR6850 dec, 2006 v1.5 11/15 dimensions disclaimers millimeter inch symbol min. typ. max. min. typ. 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 ?? tel:0755-25311262 fax:0755-25311968 web:www.kingkeyelec.com www..net www..net
CR6850 dec, 2006 v1.5 12/15 reference circuit 1 CR6850 drives a periphery power mosfet. 5v/6a 30w power supply quantity part number description quantity part number description 1 c1 102/1000v 1 f1 0.25a 1 c2 103/1000v 1 l1 10uh 1 c3 104 1 r1 20r 1 c4 33uf/400v 2 r2 ? r3 1k 1 c5 223/1000v 1 r4 100k 1 c7 103/1000v 1 r5 100k/0.5w 1 c8 102/100v 1 r6 47r 2 c6 ? c7 1000 uf/25v 1 r7 1.5m 1 c8 104 1 r8 0r51 1 bd1 kbl406 1 r9 20r 1 d1 fr107 2 r11 ? r12 3.3k 1 d2 1n4007 1 u1 CR6850 1 d3 y2010d 1 u2 pc817 1 d4 led 1 u3 tl431 1 t1 20mh 1 q1 2n60 1 t2 ei-22 notice: q1 is a power mosfet tel:0755-25311262 fax:0755-25311968 web:www.kingkeyelec.com www..net www..net
CR6850 dec, 2006 v1.5 13/15 reference circuit 2 CR6850 drives a periphery power mosfet 12v/1a& 5v/3a 27w dual power supply r1 c2 q1 d8 c5 2 c6 c15 + c13 + c4 + c8 + c9 d5 d6 a 1 k 2 c 4 e 3 u2 r9 r12 r6 r5 r8 r4 gate 1 vdd 2 nc 3 sense 4 ri 5 nc 6 fb 7 gnd 8 u1 2 3 1 u3 1 2 l1 r2 r3 1 2 3 4 t1 c1 c14 d2 d3 d4 c3 r11 input:ac 100v-240v f1 l n 6 7 8 t2 d7 c7 + c10 + c11 r7 1 2 l2 +12v +5v r10 +5v +12v +5v quantity part number description quantity part number description 1 f1 f2a/250v ac 1 r1 1.5m 3 c1 ? c2 ? c3 104/400v 1 r2 100k/0.5w 1 c4 100uf/400v 1 r3 100k 1 c5 103/1000v 1 r4 47 2 c6 ? c7 102/100v 1 r5 10 4 c8 ? c9 ? c10 ? c11 1000uf/25v 2 r6 ? r7 20 1 c12 472 1 r8 0.51 /1w 1 c13 22uf/50v 1 r9 510 1 c14 223/1000v 1 r10 2.8k 1 c15 104 1 r11 39k 1 u1 cr6848 1 r12 2.2k 1 u2 pc817 1 q1 4n60 1 u3 tl431 2 l1 ? l2 10uh 5 d1 ? d2 ? d3 ? d4 ? d5 1n4007 1 t1 20mh 1 d6 fr107 1 t2 pq20-20 2 d7 ? d8 1n5822 tel:0755-25311262 fax:0755-25311968 web:www.kingkeyelec.com www..net www..net
CR6850 dec, 2006 v1.5 14/15 reference circuit 3 CR6850 drives a periphery power bjt ? 5v/3a 15w power supply ? notice: q1 is a power bjt quantity part number description quantity part number description 2 c1 ? c2 104/400v 1 r2 100k 1 c3 472 1 r3 100k/0.5w 1 c4 102 1 r4 1k 1 c5 33uf/400v 1 r5 1.5m 1 c6 10uf/50v 2 r6 ? r7 220r/1w 1 c7 103/1000v 1 r8 220r 1 c8 102/100v 1 r9 20k 1 c9 223/1000v 2 r10 ? r11 20r 2 c10 ? c11 220uf/16v 1 r12 1r2/1w 1 c12 1.0uf/16v 1 r13 20k 5 d1 ? d2 ? d3 ? d4 ? d5 1n4007 1 r14 2k2 2 d6 ? d7 1n4148 1 u1 CR6850 1 d8 18v 1 u2 pc817 1 d9 sb560 1 u3 tl431 2 d10 ? d11 fr107 1 u4 lm358 1 t1 20mh 1 q1 13003 1 t2 ei-22 1 q2 9013 1 f1 0.25a tel:0755-25311262 fax:0755-25311968 web:www.kingkeyelec.com www..net www..net
CR6850 dec, 2006 v1.5 15/15 reference circuit 4 the power supply consisted of CR6850 is used to drive 2 leds of 1 watt. quantity part number description quantity part number description 2 c1 ? c2 104/400v 1 r2 100k 1 c3 472 1 r3 100k/0.5w 1 c4 102 2 r4 ? r9 1k 1 c5 33uf/400v 1 r5 1.5m 1 c6 10uf/50v 1 r6 220r/1w 1 c7 103/1000v 1 r7 510r/1w 1 c8 102/100v 1 r8 220r 1 c9 223/1000v 2 r10 ? r11 20r 1 c10 220uf/16v 1 r12 1r2/1w 3 c11 ? c12 ? c14 1.0uf/16v 2 r13 ? r14 2k2 2 c13 ? c15 104 2 r15 ? r16 100r 5 d1 ? d2 ? d3 ? d4 ? d5 1n4007 1 r17 1r/1w 4 d6 ? d7 ? d12 ? d13 1n4148 1 r18 18k 1 d8 18v 1 r19 10k 1 d9 sb560 1 rp1 2k 2 d10 ? d11 fr107 1 u1 CR6850 2 d14 ? d15 led/1w 1 u2 pc817 1 d16 1n60 1 u3 tl431 1 t1 20mh 1 u4 lm358 1 t2 ei-22 1 q1 13003 1 f1 0.25a 1 q2 9013 tel:0755-25311262 fax:0755-25311968 web:www.kingkeyelec.com www..net www..net

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