View LD7536GL_9085404.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

ld7536 12/15/2011 1 leadtrend technology corporation www.leadtrend.com.tw ld7536-ds-02a december 2011 green-mode pwm controller with frequency swapping and integrated protections rev. 02a general description the ld7536 is built-in with several functions, protection and emi-improved solution in a tiny package. it takes less components counts or circuit space, especially ideal for those total solutions of low cost. the implemented functions in clude low startup current, green-mode power-saving operation, leading-edge blanking of the current sensing and internal slope compensation. it also features more protections like olp (over load protection) and ovp (over voltage protection) to prevent circuit damage occurred under abnormal conditions. furthermore, the frequency swapping function is to reduce the noise level and thus helps the power circuit designers to easily deal with the emi filter design by spending minimum amount of component cost and developing time. features z high-voltage cmos process with excellent esd protection z very low startup current (<20 a) z current mode control z green mode control z uvlo (under voltage lockout) z leb (leading-edge blanking) on cs pin z internal frequency swapping z internal slope compensation z ovp (over voltage protection) on vcc pin z otp (over temperature protection) through a ntc z olp (over load protection) z 300ma driving capability applications z switching ac/dc adaptor and battery charger z open frame switching power supply typical application
ld7536 2 leadtrend technology corporation www.leadtrend.com.tw ld7536-ds-02a december 2011 pin configuration dip-8 (top view) sot-26 (top view) yy, y : year code (d : 2004, e: 2005?..) ww, w : week code pp : production code p36 : ld7536 123 4 5 6 gnd comp otp out vcc cs yw p 1 8 2 3 4 7 6 5 to p m ark yywwpp out vcc nc cs gn d comp nc otp 36 pp ordering information part number package top mark shipping ld7536 gl sot-26 green package ywp/36 3000 /tape & reel ld7536 gn dip-8 green package ld7536 gn 3600 /tube /carton protection mode switching freq. vcc ovp olp otp pin 65khz latch auto recovery/ 65ms latch pin descriptions pin sot-26 pin dip-8 name function 1 8 gnd ground 2 7 comp voltage feedback pin (same as the comp pin in uc384x). connect a photo-coupler to close the control loop and achieve the regulation. 3 5 otp pull this pin below 0.95v to shutdown the controller into latch mode until the ac resume power-on. connecting this pin to ground with ntc will achieve otp protection. keep this pin float to disable the latch protection. 4 4 cs current sense pin, connect it to sense the mosfet current 5 2 vcc supply voltage pin 6 1 out gate drive output to drive the external mosfet
ld7536 3 leadtrend technology corporation www.leadtrend.com.tw ld7536-ds-02a december 2011 block diagram
ld7536 4 leadtrend technology corporation www.leadtrend.com.tw ld7536-ds-02a december 2011 absolute maximum ratings supply voltage vcc -0.3v ~29v comp, rt, cs -0.3v ~6v out -0.3v ~vcc+0.3v maximum junction temperature 150 c operating ambient temperature -40 c to 85 c operating junction temperature -40 c to 125 c storage temperature range -65 c to 150 c package thermal resistance (sot-26, ja ) 250 c/w package thermal resistance (dip-8, ja ) 100 c/w power dissipation (sot-26, at ambient temperature = 85 c) 250mw power dissipation (dip-8, at ambient temperature = 85 c) 650mw lead temperature (soldering, 10sec) 260 c esd voltage protection, human body model 2.5 kv esd voltage protection, machine model 250 v gate output current 300ma caution: stresses beyond the ratings specified in ?a bsolute maximum ratings? may cause permanent damage to the device. this is a stress only rating and operation of the device at these or any other conditions above t hose indicated in the operational sections of this s pecification is not implied. recommended operating conditions item min. max. unit supply voltage vcc 11 24 v start-up resistor value 540k 1.8 m
ld7536 5 leadtrend technology corporation www.leadtrend.com.tw ld7536-ds-02a december 2011 electrical characteristics (t a = +25 c unless otherwise stated, v cc =15.0v) parameter conditions min typ max units supply voltage (vcc pin) startup current 12 20 a v comp =0v 1.0 ma v comp =3v 2.0 ma olp tripped/ auto 0.4 ma ovp tripped/latch 0.85 ma operating current (with 1nf load on out pin) otp pin tripped/latch 0.85 ma holding current vcc=7v (latched) 430 a uvlo (off) 9 10 11 v uvlo (on) 15 16 17 v ovp level 25 26 27 v voltage feedback (comp pin) short circuit current v comp =0v 0.25 ma open loop voltage comp pin open 5.4 v green mode threshold vcomp 2.2 v zero duty threshold vcomp 1.4 v zero duty hysteresis 100 mv current sensing (cs pin) maximum input voltage, v cs_off 0.8 0.85 0.9 v leading edge blanking time 230 ns internal slope compensation 0% to d max . (linearly increase) 300 mv input impedance 1 m delay to output 100 ns oscillator for switching frequency frequency, freq 60 65 70 khz green mode frequency, freqg 22 khz trembling frequency 4.0 khz temp. stability (-20 c ~85 c) 5 % voltage stability (vcc=11v-25v) 1 %
ld7536 6 leadtrend technology corporation www.leadtrend.com.tw ld7536-ds-02a december 2011 parameter conditions min typ max units gate drive output (out pin) output low level vcc=15v, io=20ma 1 v output high level vcc=15v, io=20ma 8 v rising time load capacitance=1000pf -- 170 350 ns falling time load capacitance=1000pf 50 100 ns max. duty 75 % olp (over load protection) olp trip level 4.3 4.5 4.7 v olp delay time 55 65 75 ms otp pin latch protection (otp pin) otp pin source current 77 85 92 a turn-on trip level 1.00 1.05 1.10 v turn-off trip level 0.9 0.95 1.0 v otp pin de-bounce time 250 s on chip otp (over temperature) otp level 140 c otp hysteresis 30 c soft start duration soft start duration 2 ms
ld7536 7 leadtrend technology corporation www.leadtrend.com.tw ld7536-ds-02a december 2011 typical performance characteristics uvlo (on) (v) fig. 1 uvlo (on) vs. temperature temperature ( c) 14.0 14.8 15.6 16.4 17.2 18.0 -40 0 40 80 120 125 uvlo (off) (v) temperature ( c) fig. 2 uvlo (off ) vs. temperature 8 9.6 10.4 12 8.8 -40 0 40 80 120 125 11. 2 frequency (khz) fig. 3 frequency vs. temperature temperature ( c) -40 60 62 64 66 68 70 0 40 80 120 125 green mode frequency (khz) temperature ( c) fig. 4 green mode frequency vs. temperature 16 18 20 22 24 26 -40 0 40 80 120 125 frequency (khz) vcc (v) fig. 5 frequency vs. vcc 12 14 16 18 20 22 24 60 11 25 62 64 66 68 70 green mode frequency (khz) vcc (v) fig. 6 green mode frequency vs. vcc 12 14 16 18 20 22 24 11 25 19 21 23 25 17 15
ld7536 8 leadtrend technology corporation www.leadtrend.com.tw ld7536-ds-02a december 2011 max duty (%) temperature ( c) fig. 7 max duty vs. temperature -40 0 40 80 120 125 65 70 75 80 85 60 v cs (off) (v) temperature ( c) fig. 8 v cs (off) vs. temperature 0.80 0.82 0.84 0.86 0.88 0.90 -40 0 40 80 120 125 ste istartup ( a) temperature ( c) fig. 9 startup current (istartup) vs. temperature -40 0 40 80 120 125 3 6 9 12 15 0 18 vcc ovp ( v) temperature ( c) fig. 10 vcc ovp vs. temperature 10 15 20 25 30 35 -40 0 40 80 120 125 v comp (v) temperature ( c) fig. 11 v comp open loop voltage vs. temperature -40 0 40 80 12 0 12 5 4.0 4.5 5.0 5.5 6.0 6.5 olp (v) temperature ( c) fig. 12 olp-trip level vs. temperature -40 0 40 80 120 125 3.0 3.5 4.0 4.5 5.0 6.0
ld7536 9 leadtrend technology corporation www.leadtrend.com.tw ld7536-ds-02a december 2011 application information operation overview the ld7536 meets the green-po wer requirement and is intended for the use in those modern switching power suppliers and adaptors which demand higher power efficiency and power-saving. it integrated more functions to reduce the external components counts and the size. its major features are described as below. under voltage lockout (uvlo) an uvlo comparator is impl emented in it to detect the voltage on the vcc pin. it would assure the supply voltage enough to turn on the ld7536 pwm controller and further to drive the power mosfet. as shown in fig. 13, a hysteresis is built in to prevent the shutdown from the voltage dip during startup. the turn-on and turn-off threshold level are set at 16.0v and 10.0v, respectively. vcc uvlo(on) uvlo(off) t t i(vcc) startup current (~ua) operating current (~ ma) fig. 13 startup current and startup circuit the typical startup circuit to generate v cc of the ld7536 is shown in fig. 14. during the startup transient, the v cc is below uvlo threshold. before it has sufficient voltage to develop out pulse to drive the power mosfet, r1 will provide the startup current to charge the capacitor c1. once v cc obtain enough voltage to turn on the ld7536 and further to deliver the gate drive signal, it will enable the auxiliary winding of the transformer to provide supply current. lower startup current requirement on the pwm controller will help to increas e the value of r1 and then reduce the power consumption on r1. by using cmos process and the special circuit design, the maximum startup current for ld7536 is only 20 a. if a higher resistance value of the r1 is chosen, it will usually take more time to start up. to carefully select the value of r1 and c1 will optimize the power consumption and startup time. emi filter fig. 14 current sensing and leading-edge blanking the typical current mode of pwm controller feedbacks both current signal and voltage signal to close the control loop and achieve regulation. as shown in fig. 15, the ld7536 detects the primary mo sfet current from the cs pin, which is not only for the peak current mode control but also for the pulse-by-pulse current limit. the maximum voltage threshold of the current sensing pin is set at 0.85v. from above, the mosfet p eak current can be obtained from below. s ) max ( peak r v 85 . 0 i =
ld7536 10 leadtrend technology corporation www.leadtrend.com.tw ld7536-ds-02a december 2011 fig. 15 a 230ns leading-edge blanking (leb) time is included in the input of cs pin to prevent the false-trigger from the current spike. in the low pow er application, if the total pulse width of the turn-on spikes is less than 230ns and the negative spike on the cs pin below -0.3v, the r-c filter is free to eliminate. (as shown in fig.16). however, the total pulse widt h of the turn-on spike is determined according to output power, circuit design and pcb layout. it is strongly recommended to adopt a smaller r-c filter (as shown in fig. 17) for larger power application to avoid the cs pin being damaged by the negative turn-on spike. output stage and maximum duty-cycle an output stage of a cmos buffer, with typical 300ma driving capability, is incorporated to drive a power mosfet directly. and the maximum duty-cycle of ld7536 is limited to 75% to avoid the transformer saturation. voltage feedback loop the voltage feedback signal is provided from the tl431 at the secondary side through the photo-coupler to the comp pin of the ld7536. similar to uc3842, the ld7536 would carry a diode voltage offset at the stage to feed the voltage divider at the ratio of ra and rb, that is, ) v v ( rb ra rb v f comp ) pwm ( comparator ? + = ? a pull-high resistor is embedded internally and can be eliminated externally. fig. 16 fig. 17
ld7536 11 leadtrend technology corporation www.leadtrend.com.tw ld7536-ds-02a december 2011 internal slope compensation in the conventional applic ations, the problem of the stability is a critical issue fo r current mode controlling, when it operates over 50% duty-cycle. as uc384x, it takes slope compensation from injecting the ramp signal of the rt/ct pin through a coupling capacitor. it therefore requires no extra design for the ld7536 since it has integrated it already. on/off control the ld7536 can be turned off by pulling comp pin lower than 1.4v. the gate output pin of the ld7536 will be disabled immediately under such condition. the off-mode can be released when the pull-low signal is removed. over load protection (olp) - auto recovery to protect the circuit from damage due to over-load condition and short or open-loop condition, the ld7536 is implemented with smart olp function. it also features auto recovery function, see fi g. 18 for the waveform. in case of fault condition, the feedback system will force the voltage loop toward the saturation and then pull the voltage high on comp pi n (vcomp). when the v comp ramps up to the olp threshold of 4.5v and continues over olp delay time, the protection will be activated and then turn off the gate output to stop the switching of power circuit. with the protection mechanis m, the average input power will be minimized to remain the component temperature and stress within the safe operating area. vcc uvlo(on) uvlo(off) t t comp olp 4.5v t out olp delay time switching switching non-switching olp trip level uvlo(off) olp reset fig. 18 ovp (over voltage protection) on vcc - latch mode the vcc ovp function of ld75 36 is in latch mode. as soon as the voltage of the vcc pin rises above ovp threshold, the output gate driv e circuit will be shutdown simultaneous to latch off the power mosfet. on the contrast, if the voltage on vcc pin drops below ovp threshold and starts ac-recycling again, it will soon resume to normal operation. fig. 19 shows its operation. fig. 19
ld7536 12 leadtrend technology corporation www.leadtrend.com.tw ld7536-ds-02a december 2011 otp pin --- latched mode protection to protect the power circuit from damage due to system failure, over temperature prot ection (otp) is required. the otp circuit is implemented to sense a hot-spot of power circuit like power mosfet or output rectifier. it can be easily achieved by connecting a ntc with otp pin of ld7536. as the device temperature or ambient temperature rises, the resi stance of ntc decreases. so, the voltage on the otp pin could be written as below. ntc otp r a 85 v ? = when the v otp is below the defined voltage threshold (typ. 0.95v), ld7536 will shutdown the gate output and latch off the power supply. there are 2 conditions required to restart it successfully. first, cool down the circuit so that ntc resistance will increase and raise v otp up above 1.05v. then, remove the ac power cord and restart ac power-on recycling. oscillator and switching frequency the ld536 is implemented with frequency swapping function which helps the power supply designers to both optimize emi performance and lower system cost. the switching frequency substant ially centers at 65khz, and swap between a range of 4khz. green-mode operation by using the green-mode contro l, the switching frequency can be reduced under the light l oad condition. this feature helps to improve the efficiency in light load conditions. the green-mode control is leadtrend technology?s own property. fault protection there are several critical pr otections integrated in the ld7536 to prevent from damage to the power supply. those damages usually come from open or short conditions on the pins of ld7536. in case under such conditions listed below, the gate output will turn off immediately to protect the power circuit. 1. cs pin floating 2. comp pin floating
ld7536 13 leadtrend technology corporation www.leadtrend.com.tw ld7536-ds-02a december 2011 reference application circuit --- 40w (19v/2.1a) adapter br1 kbp206 f1 3.15a/250v c4 nc l n t1a rm8 c7 470uf/25v pc817b t1b c11 4.7u/50v d1 gs1002fl d2 pr1007 r9 51k/1206 c6 102pf/1206 r4 0/0805 c1 330p/1206 +vo rtn u1a smd c12 104p/0805 cy1 102p c10 104p/0805 r5 620k/1206 r6 620k/1206 c13 3.3nf/0805 r13 100r/0805 q1 2sk3562 r16 1.4/1206 r1 2.2meg/1206 r2 2.2meg/1206 l2 22mh cx1 0.22uf d5 20120 c14 100pf/0805 c5 82uf/400v c8 470uf/25v 19v / 2.1a r3 51r/1206 r16a 1.4/1206 r10 51k/1206 r12 200r/0805 c16 473p/0805 r25 1k/0805 r28 62k/0805 r29 4.3k/0805 r30 /0805 r31 330/0805 d6 d4148 l1 120uh r11 22r/1206 ic432 r32 5.6k/0805 dz2/6.8v zener1 c13 100p/0805 r12b 10r/0805 otp 3 cs 4 comp 2 out 6 gnd 1 vcc 5 ld7536 r16b 1.4/1206
ld7536 14 leadtrend technology corporation www.leadtrend.com.tw ld7536-ds-02a december 2011 package information sot-26 dimension in millimeters dimensions in inches symbol min max min max a 2.692 3.099 0.106 0.122 b 1.397 1.803 0.055 0.071 c ------- 1.450 ------- 0.057 d 0.300 0.500 0.012 0.020 f 0.95 typ 0.037 typ h 0.080 0.254 0.003 0.010 i 0.050 0.150 0.002 0.006 j 2.600 3.000 0.102 0.118 m 0.300 0.600 0.012 0.024 0 10 0 10
ld7536 15 leadtrend technology corporation www.leadtrend.com.tw ld7536-ds-02a december 2011 package information dip-8 dimension in millimeters dimensions in inches symbol min max min max a 9.017 10.160 0.355 0.400 b 6.096 7.112 0.240 0.280 c ----- 5.334 ------ 0.210 d 0.356 0.584 0.014 0.023 e 1.143 1.778 0.045 0.070 f 2.337 2.743 0.092 0.108 i 2.921 3.556 0.115 0.140 j 7.366 8.255 0.29 0.325 l 0.381 ------ 0.015 -------- important notice leadtrend technology corp. reserves the right to make changes or corrections to its products at any time without notice. custom ers should verify the datasheets are current and complete before placing order.
ld7536 16 leadtrend technology corporation www.leadtrend.com.tw ld7536-ds-02a december 2011 revision history rev. date change notice 00 2/25/2010 original specification 00a 3/15/2010 start-up resistor value (max): 1.8m otp source current (min.) 77 a 02 7/1/2010 olp trip level (min.) (max.) 02a 12/15/2011 olp delay time (min.) (max.) operating ambient temperature (min.)

▲Up To Search▲

Price & Availability of LD7536GL

	To Download LD7536GL Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .