fremont micro devices FT838NB/ft838rna ? 2012 fremont micro devices inc. confidential rev. 0.8 ds838nb/838rna-a-page1 low-power off-line cc/cv switch features description ? constant-current (cc) and constant-voltage (cv) with primary side control ? proprietary technology enabling high efficiency and fast dynamic response ? no audible noise over entire operating range ? built-in power npn ? built-in cable compensation ? built-in line compensation ? primary-side feedback eliminates opto-coupler and tl431 ? cycle-by-cycle current limiting ? over temperature protection ? vcc over voltage protection ? open circuit protection typical application ? adapter/charger for cell/cordless phones, pdas, mp3 and other portable apparatus ? standby and auxiliary power supplies set top boxes (stb) ? ac/dc led driver applications the FT838NB/ft838rna controller device is optimized for high-performance, low power switching mode power supply applications. the FT838NB/ft838rna facilit ates cc/cv charger design by eliminating an opto-coupler and tl431. its highly integrated functions such as under voltage lockout (uvlo), leading edge blanking (leb) and built-in cable compensation offer the users a high efficiency and low cost solution for ac/dc power applications. power supplies built with FT838NB can achieve both highest average efficiency and fast dynamic load response. ft838rna is optimized for led driver applications with slightly higher (~22ua) standby current. furthermore, FT838NB/ft838rna features fruitful protections like open circuit protection and over temperature protection to eliminate the external protection circuits and provide reliable operations. FT838NB/ft838rna is available in sop8 package. fremontmicro usa use only
fremont micro devices FT838NB/ft838rna typical application circuit figure 1: typical application circuit absolute maximum ratings fb to gnd?????????? ??...???????????? ?.??.???.?.... -0.3v to +7v cs to gnd???????????????...????? ??????????.??.....-0.3v to +7v vcc to gnd?????????????.????.????????????????-0.3v to +30v c to gnd????????? ????...???????????. ???.????......-0. 3v to +700v operating temperat ure range??? ?????...???????????????...-40 to +125 junction temperature????????????..??????????????.... -40 to +150 storage temperature range ???????????..????????????.?.-60 to +150 esd protection hbm??????..... ??????????????????.?????????.2000v esd protection mm??????..???????????????????????.???????.200v stresses exceeding maximum ratings may damage the device. maximum ratings are stress ratings only. functional operation above the recommended op erating conditions is not implied. extended exposure to stresses above the recommended oper ating conditions may affect device reliability . ? 2012 fremont micro devices inc. confid ential rev. 0.8 ds838nb/838rna-a-page2 fremontmicro usa use only
fremont micro devices FT838NB/ft838rna pin configuration figure 2: pin assignments terminal description pin name description 1 cs primary current sense 2 fb output voltage feedback pin 3 vcc supply voltage 4 nc no connection 5 6 gnd ground. 7 8 c the collector of the power npn. this pin is connected to the primary lead of the transformer table 1 ordering information FT838NB x x - xx circuit type cable com p 0: 0% 1: 3% 2: 6% 3: 9% package blank: sop8 hsf and packaging rb: rohs and tube rt: rohs and t&r gb: green and tube gt: green and t&r ? 2012 fremont micro devices inc. confid ential rev. 0.8 ds838nb/838rna-a-page3 fremontmicro usa use only
fremont micro devices FT838NB/ft838rna ft838rna x - xx FT838NB /ft838rna table 2 marking rule figure 3: marking rule : represents version (0,1,2 or 3) ??? : for internal reference device designator symbol options 0 cable comp = 0% 1 cable comp = 3% 2 cable comp = 6% FT838NB 3 cable comp = 9% ft838rna cable comp = 0% for led driver applications circuit type package blank : sop8 hsf and packaging rb: rohs and tube rt: rohs and t&r gb: green and tube gt: green and t&r ? 2012 fremont micro devices inc. confid ential rev. 0.8 ds838nb/838rna-a-page4 fremontmicro usa use only
fremont micro devices FT838NB/ft838rna block diagram figure4: FT838NB/ft838rna block diagram ? 2012 fremont micro devices inc. confid ential rev. 0.8 ds838nb/838rna-a-page5 fremontmicro usa use only
fremont micro devices FT838NB/ft838rna electrical characteristics ( for typical values tj=25 , vcc=12v, unless otherwise noted ) characteristic symbol min typ max unit current sense maximum current threshold vcs_max 541 552 563 mv leading edge blanking duration tleb 350 400 450 ns propagation delay (out=1.0nf to gnd) tpd 200 ns feedback section feedback voltage threshold vfb 2.856 2.9 2.944 v ccm protection threshold level vcp 100 mv supply section start up threshold voltage vcc_on 16.5 17.6 18.5 v under voltage lockout voltage vcc_off 6 6.6 7 v FT838NB 2 5 ua vcc start up current ft838rna istart_up 14 22 30 operating current iop 0.4 0.5 0.7 ma protection section feedback loop open protection ifb_open 120 140 160 ua vcc over voltage protection vcc_ovp 26 27.5 29 v over temperature protection t_otp 145 compensation line compensation (ifb=1ma) vline 30 33 36 mv 0 0 1 3 2 6 cable compensation 3 kcab 9 % power npn section characteristic test condition symbol min typ max unit collector-base breakdown voltage ic=0.1ma vcbo 700 v collector-emitter breakdown voltage ic=1ma vceo 400 v emitter-base breakdown voltage ie=0.1ma vebo 9 v collector-emitter saturation voltage ib=0.25a,ic=1a vcesat 0.3 0.9 v base-emitter saturation voltage ib=0.25a,ic=1a vbesat 0.9 1.2 v maximum collector current vc=2v icm 0.4 0.45 a table 3 ? 2012 fremont micro devices inc. confid ential rev. 0.8 ds838nb/838rna-a-page6 fremontmicro usa use only
fremont micro devices FT838NB/ft838rna functional description operating description FT838NB/ft838rna is a cost effective and high-performance ac-dc power supply controller for off-line low power ac-dc applications including battery chargers, adaptors and led light ing. the constant voltage (cv) and constant current (cc) control are achieved ac curately without the secondary feedback circuit. start up control start-up current of FT838NB is very lo w so that a start-up resistor with high resistance and low-wattage is allowed to supply the start-up power for the controller. the large value startup resistor minimizes the power loss in operations and allows quick start up. ft838rna increa ses the start-up current slightly to ensure the smooth shutting down operations in led lighting applic ations with relaxed requirement on external board design. operating current the operating current of FT838NB/ft8 38rna is as low as 500ua. good efficiency is achieved with the low operating current. low operating current also reduces the vcc hold-up capacitance requirement. constant voltage (cv) and constant current (cc) operation the FT838NB/ft838rna can accurately achieve cv/ cc characteristic output without secondary side voltage and current-feedback circuits. it operates in cv mode to regulate the output voltage by capturing the auxiliary winding feedback voltage at fb pin. the aux iliary winding feedback voltage is proportional to secondary winding, so it provides controller the feedback signal from secondary side and achieves constant-voltage output. in cc mode, the controller det ects the secondary discharger peak current and the discharger time, which determines the off-time of the base driver to make the output average current constant. primary peak current modulation primary peak current is constant at constant current mode. and primary peak current is modulated at constant voltage mode for the purposes of good dynamic load response and no audible noise over entire operating range. according to the output loadi ng current the current threshold volt age is modulated from 0.55v to 0.27v. the current threshold voltage is 0.55v at rated load and 0.27v at light load. leading edge blanking each time the power npn transistor is switched on, a turn-on spike occurs at the sense resistor. to avoid premature termination of the switching pulse, a 400ns leading edge blanking time is built in. conventional rc filtering can therefore be omitted. during this blanking period, the current limit comparator is disabling and cannot switch off the base driver. under voltage lockout (uvlo) FT838NB/ft838rna turn-on vcc_on and turn-off vcc_off are 17.6 v and 6.6 v, respectively. during start-up, the hold-up capacitor must to be charged to 17.6v th rough the start-up resistor. the hold-up capacitor continues to supply vcc unt il power can be delivered from the auxiliary winding of the transformer. vcc must not drop below 6.6 v during this start-up process. th is uvlo hysteresis windo w ensures that hold-up capacitor is sufficient to supply vcc during start-up. ? 2012 fremont micro devices inc. confid ential rev. 0.8 ds838nb/838rna-a-page7 fremontmicro usa use only
fremont micro devices FT838NB/ft838rna protection control with rich protection features of FT838NB/ft838rna, excellent power supply system reliability can be achieved. the protection features including cycle by cy cle current limiting, vcc over voltage protection and clamp, over temperature protection, feedback loop o pen circuit protection and vcc under voltage lockout. integrated npn power npn is integrated in FT838NB/ft838rna fo r low cost and/or space limited applications. output cable compensation the output cable compensation provides a constant output voltage at the end of the c able over the entire load rang in constant voltage mode. as the converter load in crease from no-load to the peak current load, the voltage drop introduced across the output cable is co mpensated by increasing the feedback pin reference voltage. ? 2012 fremont micro devices inc. confid ential rev. 0.8 ds838nb/838rna-a-page8 fremontmicro usa use only
fremont micro devices FT838NB/ft838rna dip8 package outline dimensions sop8 package 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 ? 2012 fremont micro devices inc. confid ential rev. 0.8 ds838nb/838rna-a-page9 fremontmicro usa use only
fremont micro devices FT838NB/ft838rna ? 2012 fremont micro devices inc. confiden tial rev. 0.8 ds838nb/838rna-a-page10 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. fremontmicro usa use only
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