BL8851 BELLING | Alldatasheet
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www.bellin g.com.cn V1. Current Mode PWM Power Switch GENERAL DESCRI P TION BL8851 c o mb i nes a ded i c a ted c u rrent mode P W M controll e r. It is optim i z ed f or hi g h p e rformance, low stan d by power, and cost effective off line flyback conv e rter ap plicati o ns in 40W~ 0W ran g BL8851 o ffers c omplete prote c tion c o v erage with automatic s e lf r e covery feature inc l ud i ng Cycl e b y C y c l e cu rr e nt limiting O CP), C S s h ort prot e c tion, CS floating protecti o over load prot e c tion O LP), and VDD un d er voltage l o ckout (UV L over temperature prot e c tion O TP), over voltage(fixed or adj u s tab le prot e c tion (OVP). The tone e n e rgy at bel o w 20KHZ i s m i nimiz e d in the design a nd audio no i se is elimin a ted during operation. BL8851 i s offered in SOT2 6 pack a ge. FE A T URES Pow e r on S o ft Start Red u ci ng M OSF E T Vds Stress Fre q ue n cy s h uffling for EMI Extended B u rst M o de C o ntrol F o r I m proved Efficiency a nd Minim u m Standby Power D e sign Audio No i s e Free O p e ration Fixed 65KHZ Switchi n g Fr e que n cy Internal Synchron i z e d Slo p e Com p e n sa t ion Lead i ng Ed g e Blanki n g on C u rrent Sense Input Good Protection Covera g e With Auto Self R e co v ery o VDD Und e r Voltage L o c ko ut with Hysteres i s (UV L o Over T emp e r ature Prot e c tion O TP) with auto recovery o Cycl e by cyc l e over current thr e sho l d setting for const a nt out p ut power li m iting over univ e rs a l input voltage ran g e o Overlo a d Protecti o n O LP) with auto recovery o Over voltage Protecti o O VP) with auto recovery o Adjustab l e O VP through ex ternal Ze n er
APPLICATIONS
c onverter for AC/DC a dap t er PDA power suppli e s Digital Cam e ras a n d Ca mc ord e r Adapt e r VCR, SVR, STB, DVD&D V CD Player SMPS Set Top Box Power Auxiliary Power Supply for PC and Ser v er Open frame SMPS
www.bellin g.com.cn V1. TYPICAL APPLICA T ION Pin Configu ration The BL8851 is o f fered in S OT2 p ackage, sh o wn a s be l o w Pin Name I/O De s cription GND P Gro u nd FB I Feed b ack in p ut pin. The PWM duty cyc l e is determi n ed by voltage level into this pin and the curr e nt s e nse si gn al at Pin 3. RT I Dual fu n c tion pin. Either co n n e c ted throu g h a N T C r e s i stor to gro u nd for over temperature shut d own/latch control or con n ect e d throu g h Ze n er to VDD for adj u s table o v er voltage p r ot ection CS I Curr e nt se ns e input VDD P Pow e r Supp l y Gate O Totem pole g ate driver o utput for power Mosfet
www.bellin g.com.cn V1. Parameter V alue VDD DC Su p ply Voltage 40 V VDD Z e ner Clamp Voltage Note VDD Cl a m 0.1V VDD D C C la mp C u rr e nt 10 mA FB Input Voltage 0.3 to 7V Sen se In p ut Voltage 0.3 to 7V RT Input Voltage 0.3 to 7V Min/Max Op e rating Ju n c tion T em perat u re T J 20 to 150 o C Min/Max Storage Te m p e rat u re T s tg 55 to 160 o C RECOMMENDED OPER A TING CONDITION S y mbol Parameter Min/Max Unit VDD VDD Su p ply Voltage 10 to 30 V T A Operating A mbient Tem p erat u re 20 to 85 Absolute M aximum Ratings No t VDD_Clamp has a nomi n al val ue of V S tresses be y o n d those listed under “absol u te maximum ratings” m a y c a use perma n ent damage to the device. These are stress ratin g s on l y function a l operation of t h e device at these or a n y o t her conditions b e y ond those in di cated under “reco mmend e d operating conditions” is not implied. Expos ur e to absolute maximum rated co n ditions for extended periods may a f fect device reliabilit y BLOCK DIAGRAM
www.bellin g.com.cn V1. S y mbol Parameter Test Condit i ons Mi n T y p Max Unit Supply Voltage (VDD) Istartup VDD Start up Current VDD=11V, M easure Le a ka g e c u rr e nt into VDD uA I_VDD Op er ation Operation C u rr e nt V FB =3V mA UVL O O VDD Un d er V oltage L o ck o ut Enter V UVL O (OF F VDD Un d er V oltage L o ck o ut Exit (Recov er 14.3 15.3 16.3 V Vpull u p Pull up PM O S active V Vdd_c l amp Ivdd=10mA V OVP(ON) Over volt a ge p r ot e c tion voltage CS=0V,F B V Ramp u p VDD until gate cl oc k is off V Vlatch r el e ase Latch rele a s e voltage V Feed b ack I n put Se c t ion(FB Pin) V FB_ Open V FB Open Lo o p Voltage 3.9 4.2 V A v cs PWM input gain Δ VFB/ Δ VCS V/V Maximum duty c y cle Max duty c y c le VDD=14V,VFB 3V,VCS=0V Vref_green The thr e sho l d enter gr e en mode V Vref_b u rst H The thr e sh o ld exit burst mode 1.275 V Vref_b u rst L The thr e s h o l d enter b u rst mode 1.175 V I FB _Short FB pin sh o rt circuit c u rrent Short FB pin to GND and me a s u re curr e nt mA V T H _PL Pow e r L i miting FB Thr e s h old V o ltage 3.7 V T D _PL Pow e r limiting Deb o u n ce Time mSec Z FB _IN Input Imped a nce Kohm Curr e nt Se n se Input(Se n se Pin) Soft s t art time ms T_bla n ki n g Lead i ng ed g e blank i ng time 220 ns Z SENSE _IN Input Imped a nce Kohm T D _OC Over C u rr e nt Detection a nd Control De l ay From Ov e r Current Occurs till the Gatedrive output s tar t to turn off 120 nSec V T H O C Internal C u rr e nt Limiting Thr e s h old V o ltage FB=3.3V 0.75 V Vocp c l a mp e r CS voltage c l amp e r 0.9 V Oscillator F OSC Normal Oscillation Fre q ue n cy VDD=14V, FB 3V, CS=0V KHZ f OSC Fre q ue n cy jittering F_s h uffling Shuffling fre q ue n cy Hz f_Temp Fre q ue n cy Temperature Stability ELECTRICAL CHARACT E R IS TI CS A = 2 VDD= 6V, unless otherw i se noted)
www.bellin g.com.cn V1. V DD Fre q ue n cy Voltage Stability F_Burst Burst M ode B a se Fre q ue n cy KHZ Gate dri v er VOL Ouput l o w level VDD 14V, Io 5mA V VOH Ouput hi g h level VDD=14V, I o =20mA V V_cla m p Output c l a mp voltage V T_r Output ris i ng time 12V @ C L F 175 nS T_f Output falling time 12V @ C L p F nS O v er temperature p rotection IRT Output c u rre n t of R T pin 100 105 uA VOTP Thr e s h old vo l t age for OTP 0.95 1.05 V Td_OTP OTP deb o u n ce time Cycle VRT_ F L Float vol t age at R T pin 2.3 V Vth_OVP External O VP thres ho ld vol t age V
www.bellin g.com.cn V1. CHARAC T ERIZATION PLOTS VDD = 18V, TA = 25 c o ndition a p pli e s if not otherwise noted.
www.bellin g.com.cn V1. OUTLINE DRAWING