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fremont micro devices preliminary FT825 ? 2013 fremont micro devices inc. confidential rev0.82 ds825-a-page1 primary-side control led driver with high pfc features description ? primary feedback control without secondary feedback circuit ? high power factor >0.9 over the universal input ? high current accuracy 3% ? boundary conduction mode operation ? ultra-low start up current ? cycle-by-cycle current limit ? over-voltage protection ? short-circuit protection ? under voltage lock out ? available in a sop8/dip8 package applications ? isolated, solid state lighting ? industrial and commercial lighting ? residential lighting the FT825 is a primary-side-control offline led lighting controller which can achieve high power factor and accurate led current for an isolated lighting application in a single stage converter. the real current control method can control the led current accurately from the primary side information. it can significantly simplif y the led lighting system design by eliminating the secondary side feedback components and the opto-coupler. the FT825 works in boundary conduction mode for reducing the mosfet switching losses. the extremely low start-up current and the quiescent current can reduce the power consumption thus lead to an excellent efficiency performance. the multi-protection function of FT825 can greatly enhance the system reliability and safety. the FT825 features over-voltage protection, short-circuit protection, cycle-by-cycle current limit, vcc uvlo protection. the FT825 is available in sop8/dip8 package. fremont usa use only
fremont micro devices preliminary FT825 ? 2013 fremont micro devices inc. conf idential rev0.82 ds825-a-page2 typical application circuit figure 1: typical application circuit absolute maximum ratings vcc to gnd????????????????????????????????????-0.3v to +27v analog inputs and outputs???????????????????????????.???.. -0.3v to 7v zcd pin maximum current????????????????????????-5ma (source) / 5ma(sink) max. gate source current??????????????????????????????????1.0a max. gate sink current???????????????????????????????????-1.2a operating temperature range???????????????????????????-40 to +125 junction temperature? ????????????? ??????????????...........-40 to +150 storage temperature range ???????????????????????????-60 to +150 esd protection hbm??????????????????????????????????.?.2000v esd protection mm?????????????????????????????... ???......?.. 200v * stresses exceed those listed under ?absolute maximum ratings? may cause permanent damage to the device. functional operation of the device at conditions beyond those listed in the specification is not guaranteed. prolonged exposure to extrem e conditions may affect device reliability or functionality. fremont usa use only
fremont micro devices preliminary FT825 ? 2013 fremont micro devices inc. conf idential rev0.82 ds825-a-page3 pin configuration nc comp mult cs vcc gate gnd zcd top view 1 2 3 45 6 7 8 figure 2: pin assignments terminal description no. pin function 1 nc this pin can be nc or connects to gnd. 2 comp loop compensation pin. connects a compensation network to stabilize the led driver and get an accurate led current of the led driver. 3 mult main input to the multiplier. this pin is connected to the rectified mains voltage via a resistor divider and provides the sinu soidal reference to the current loop. 4 cs current sense pin. the mosfet current is sensed via a resistor, the resulting voltage compared to the internal sinusoid shaped current reference signal to determine when the mosfet turns off. 5 zcd zero current detection pin. a negative going edge triggers the turn on signal of the external mosfet, connects this pin throu gh a resistor divider from the auxiliary winding to gnd. over-voltage condition is detected through zcd, if zcd voltage is higher than the over-voltage protection (ovp) threshold after a blanking time 1us, the over-voltage condition is detected. 6 gnd ground. 7 gate gate drive output pin. the totem pole output stage is able to drive high power mosfet with a peak current of 1a source capability and 1.2a sink capability. the high level voltage of this pin is clamped to 13v to avoid excessive gate drive voltage. 8 vcc supply voltage of both the signal part of the ic and the gate driver. table1 fremont usa use only
fremont micro devices preliminary FT825 ? 2013 fremont micro devices inc. conf idential rev0.82 ds825-a-page4 ordering information FT825 x - xx package temperature range hsf packaging ordering code tube FT825-rb rohs t&r FT825-rt tube FT825-gb sop8 -40 -125 green t&r FT825-gt rohs tube FT825a-rb dip8 -40 -125 green tube FT825a-gb table 2 marking rule figure 3 marking rule ????? for internal reference circuit type package blank: sop8 a: dip8 hsf and packaging rb: rohs and tube rt: rohs and t&r gb: green and tube gt: green and t&r fremont usa use only
fremont micro devices preliminary FT825 ? 2013 fremont micro devices inc. conf idential rev0.82 ds825-a-page5 block diagram voltage regulator multiplier - + internal reference & bias vcc zcd gate cs mult comp vcc 0.9v/0.4v zero current detection uvlo 13v starter logic & driver + - 18v/ 9.2v real current control fb current sense 7 4 1 gnd pwm/pfc control 8 5 3 2 ovp latch ovp latch 6 fremont usa use only
fremont micro devices preliminary FT825 ? 2013 fremont micro devices inc. conf idential rev0.82 ds825-a-page6 electrical characteristics (tj = 25c, vcc = 16v, unless otherwise specified) symbol parameter test condition min typ max unit supply voltage vcc operating range after turn-on 9.5 20 v vcc on turn-on threshold 17.8 v vcc off turn-off threshold 9.2 v vcc ovp vcc over voltage 24 v supply current istart-up start-up current before turn-on,vcc= 16v 6 ua iq quiescent current after turn-on, no switch 1.3 ma icc operating supply current @ 70 khz 1.8 ma multiplier input i mult input bias current v mult = 0 to 3 v -1 ua v mult linear operation range 0 to 3 v v cs / v mult output max slope v mult = 0 to 1v v comp = upper clamp 2.4 v/v k gain (1) v mult = 1 v, v comp = 3 v 0.72 1/v error amplifier v fb voltage feedback input threshold 0.4 v v ea voltage gain 400 v/v g ea transconductance 100 100ua/v source current 45 ua i comp sink current -65 ua upper clamp voltage 5.2 v v comp lower clamp voltage 1.2 v current sense comparator t d (h-l) delay to output 100 ns v cs clamp current sense reference clamp 2.4 v fremont usa use only
fremont micro devices preliminary FT825 ? 2013 fremont micro devices inc. conf idential rev0.82 ds825-a-page7 electrical characteristics (tj = 25c, vcc = 16v, unless otherwise specified) symbol parameter test condition min typ max unit zero current detector v zcd_t zero current detect threshold (2) 0.4 v v zcd_hy zero current detect hysterestic (2) 0.5 v v zcd_ovp output over voltage threshold 1us delay after turn-off 5.3 v logic t start start timer period 130 us t leb leading edge blanking time 300 ns t off_min minimum off time 3.5 us gate driver igate-source max source current 1 a igate-sink max sink current -1.2 a voclamp output clamp voltage 12 v table 4 (1) the multiplier output is given by: vcs = k * v mult * (v comp ? 1.2) (2) parameters guaranteed by design, functionality tested in production. fremont usa use only
fremont micro devices preliminary FT825 ? 2013 fremont micro devices inc. conf idential rev0.82 ds825-a-page8 functional description under-voltage lockout(uvlo) the turn-on and turn-off threshold voltages are fixed inte rnally at 17.8v and 9.2v respectively for FT825. this hysteresis behavior will guarantee a one shot start-up, as long as a pr oper start-up resistor and hold-up capacitor are used. line compensation an offset current proportional to instantaneous main s voltage streams out cs pin. a compensation resistor inverse proportional to the offset current is added between zcd pin and transformer auxiliary winding to achieve extremely low thd and line compensation, the compensation resistor can be adjusted externally. zero current switching the ic is switched on when the transformer is demag netized after mosfet?s minimum off time about 3.5us typically. internal circuitry connected to the zcd pin de tects the end of the secondary stroke. after mosfet?s minimum off time, if no demagnetization signal is detect ed on the zcd pin, the controller generates a startup signal 130us typically after the last gate signal. leading edge blanking (leb) a turn on spike on cs pin will inevitably appear when the power mosfet is switched on. at the beginning of each switching pulse, the current-limit comparator is disabled for around 300nsec to avoid premature termination. the gate driver output ca nnot be switched off during the blanking period. however, it is strongly recommended to add a small rc filter for higher power appl ication to avoid the cs pin from damage by the negative turn-on spike. output driver with a low on-resistance and a high current driving capability, the output driver can easily driver a big mosfet or igbt. cross conduction currents are avoided to minimize heat dissipation, allowing the efficiency and reliability to be improved. over voltage protection (ovp) under steady-state condition, system output voltage is controlled by l oad connection, the voltage of zcd pin set by r1, r2 and auxiliary winding (see figure 4) does not exceeds 5.3v, when sy stem output is open, the voltage of output increases, due to the coupling polarit y between auxiliary winding and secondary winding of a transformer, zcd voltage will increase also. once the zcd voltage exceeds 5.3v and last for about 1us to guarantee the leakage inductance ringing has been fully damped, ovp of ic is triggered, the ic stops switching, it can be reset by re-starting the voltage on pin vcc. the ovp voltage can be adjusted by setting r1, r2 and auxiliary winding. fremont usa use only
fremont micro devices preliminary FT825 ? 2013 fremont micro devices inc. conf idential rev0.82 ds825-a-page9 zcd 5 FT825 r1 r2 figure4 circuit ovp power factor correction the mult pin is connected to the tap of the resistor divider from the rectified instantaneous line voltage and fed as one input of the multiplier. the output of the multiplier will be sha ped as sinusoid too. this signal provides the reference for the current comparator and comparing with the primary side inductor current which sets the primary peak current shaped as sinusoid with the input line voltage, high power factor can be achieved. the maximum voltage of the multiplier output to the current comparator is clamped to 2.4v to get a cycle-by-cycle current limitation. minimum off time the FT825 operates with variable switching frequency, the frequency is changing with the input instantaneous line voltage. to limit the maximum frequency and get a good emi performance, FT825 employs an internal minimum off time limiter?3.5 s. output short circuit protection when the output short circuit happens, the positive plat eau of auxiliary winding voltage is also near zero, the vcc can not be held on and it will drop below vcc uvlo. the ic will shut do wn and restart again. fremont usa use only
fremont micro devices preliminary FT825 ? 2013 fremont micro devices inc. conf idential rev0.82 ds825-a-page10 dip8 package outline dimensions dimensions in millimeters dimensions in inches symbol min max min max a 3.710 4.310 0.146 0.170 a1 0.510 0.020 a2 3.200 3.600 0.126 0.142 b 0.380 0.570 0.015 0.022 b1 1.524bsc 0.060 bsc c 0.204 0.360 0.008 0.014 d 9.000 9.400 0.354 0.370 e 6.200 6.600 0.244 0.260 e1 7.320 7.920 0.288 0.312 e 2.540 (bsc) 0.100 bsc l 3.000 3.600 0.118 0.142 e2 8.400 9.000 0.331 0.354 fremont usa use only
fremont micro devices preliminary FT825 ? 2013 fremont micro devices inc. conf idential rev0.82 ds825-a-page11 sop8 package outline dimensions dimensions in millimeters dimensions in inches symbol min max min max a 1.350 1.750 0.053 0.069 a1 0.100 0.250 0.004 0.010 a2 1.350 1.550 0.053 0.061 b 0.330 0.510 0.013 0.020 c 0.170 0.250 0.006 0.010 d 4.700 5.100 0.185 0.200 e 3.800 4.000 0.150 0.157 e1 5.800 6.200 0.228 0.244 e 1.270 (bsc) 0.050 (bsc) l 0.400 1.270 0.016 0.050 0 8 0 8 fremont usa use only
fremont micro devices preliminary FT825 ? 2013 fremont micro devices inc. conf idential rev0.82 ds825-a-page12 fremont micro devices (sz) limited #5-8, 10/f, changhong building, ke-ji nan 12 road, nanshan district, shenzhen tel: (86 755) 86117811 fax: (86 755) 86117810 fremont micro devices (hong kong) limited #16, 16/f, blk b, veristrong industrial centre, 34- 36 au pui wan street, fotan, shatin, hong kong tel: (852) 27811186 fax: (852) 27811144 fremont micro devices (usa), inc. 42982 osgood road fremont, ca 94539 tel: (1-510) 668-1321 fax: (1-510) 226-9918 web site: http://www.fremontmicro.com/ * information furnished is believed to be accurate and reliable. however, fremont micro devices, incorporated (bvi) assumes no responsibility for the c onsequences of use of such information or for any infringement of patents of other rights of third parties which may result from its use. no license is granted by implication or otherwise under any patent rights of fremont micro devices, incorporated (bvi). specifications mentioned in this publication are subject to change without notice. this publication supersedes and replaces all information previously supplied. fremont micro devices, incorporated (bvi) products are not authorized for use as critical com ponents in life support devices or systems without express written approval of fremont micro devices, incorporated (bvi). the fmd logo is a registered trademark of fremont micro devices, incorporated ( bvi). all other names are the property of their respective owners. fremont usa use only

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