preliminary datasheet LP6252 lp 6252 C 00 version 1 . 0 aug . - 20 1 4 e - mail: marketing@lowpowersemi.com www.lowpowersemi.com page 1 of 8 high efficiency 2. 7 a synchronous boost convertor general description the LP6252 is a synchronous current mode boost dc - dc converter. its pwm circuitry with built - in 2. 7 a current power mosfet makes this converter highly power efficiently. selectable high switching frequency allows faster loop response and easy filtering with a low noise output. the non - inverting input its error amplifier is connected to an internal 8 00m v precision reference voltage. current mode control and external compensation network make it easy and flexible to stabilize the system. ordering information LP6252 f: pb - free package type b6 : sot23 - 6 qv : t dfn - 6 applications ? battery products ? host otg ? audio power features ? up to 9 5 % efficiency ? output to input disconnect at shutdown mode ? shut - down current:<1ua ? output voltage up to 5.5 v ? over output voltage protection ? over current p rotection ? over temperature protection ? internal compensation of soft - start ? 5 5 0k hz fixed frequency switching ? high switch on current: 2. 7 a ? available in sot23 - 6 and t dfn - 6 package ? pin configurations sot 23 - 6 t dfn - 6 marking information device marking package shipping LP6252b6f lps 5 v ywx sot23 - 6 3k/reel LP6252qvf lps 5tyw tdfn - 6 marking indicati on: y:production year w:production period x:production batch top view 1 2 3 6 5 4 l x g n d f b e n o u t v i n f b g n d l x e n o u t v i n 1 2 3 4 5 6 g n d
preliminary datasheet LP6252 lp 6252 C 00 version 1 . 0 aug . - 20 1 4 e - mail: marketing@lowpowersemi.com www.lowpowersemi.com page 2 of 8 typical application circuit functional pin description sot23 - 6 tdfn - 6 pin name description 6 1 fb regulation feedback input. connect to an external resistive voltage divider from the output to fb to set the output voltage. the pin is 0.8v. 5 2 gnd ground pin. 4 3 lx pin for switching . 3 4 vin voltage s upply input pin. 2 5 out voltage output pin. 1 6 en c hip enable pin . lp 6252 will turn on when en = high , and turn off when en = 0. function block diagram v i n v i n l x e n g n d o u t f b 5 v 6 8 k 1 3 k 1 0 u f * 2 4 . 7 u h 1 0 u f l p 6 2 5 2 3 3 p f / n c e n e n s l o p e c o m p e n s a i o n c u r r e n t s e n s e r c u r r e n t l i m i t i n t e r n a l c o m p e n s a t i o n c o n t r o l l o g i c o s c l x f b v i n v h i g h g n d b o d y a n d v h i c h s e l e c t o u t r e f
preliminary datasheet LP6252 lp 6252 C 00 version 1 . 0 aug . - 20 1 4 e - mail: marketing@lowpowersemi.com www.lowpowersemi.com page 3 of 8 absolute maximum ratings supply input voltage ------------------------------------------------------------------------- --------- ----------------------------- 6v power dissipation, pd @ ta = 25 c package thermal resistance sot23 - 6 , ja ----------------------------------------------------------------------- ----------------------------- --- -- ------ 2 5 0 c/w tdfn - 6, ja ----------------------------------------------------------------------------------------------- - ------------------ 95 c/ w lead temperature (soldering, 10 sec.) ------------------------------------------------------ -- -- -- -------- - ----- ------ 260c recommended operating conditions supply input voltage ------------------------------------------------------------ -- --- ---- ---- ----- - ---- -- - -------- --- -- 2.2 v to 5 .5 v en input voltage ----------------------------------------------- ------------------------------- ------ ------- --- - ----- ------ 0v to 5.5v operation junction temperature range ------------ -------------- ------------------- ------ ---------- -- - - ? 40c to 125c operation ambient temperature range -- ------------------- --------------------------- - ----------- --- - --- -- ? 40c to 85c electrical characteristics (vin= 3. 5 v,vout= 5 v,cin=10uf,cout= 22uf,l =4.7uh,r1= 52.5k, r2=10 k) par ameter conditions LP6252 units min typ max supply voltage 2.2 5.5 v output voltage range 2.5 5. 5 v uvlo 1. 4 2.0 v over output voltage protection 5.4 6 v supply current(shutdown) ven= 0v,v in =5v 0.05 1 ua feedback voltage 784 8 00 816 m v feedback input current vfb= 0.8 v 50 na switching frequency 55 0 k hz maximum duty cycle 80 90 9 5 % en input low voltage 0.4 v en input high voltage 1.4 v low - side current limit 2 . 7 3 a high - side on resist ance vout=3.3v 110 low - side on resistance 70
preliminary datasheet LP6252 lp 6252 C 00 version 1 . 0 aug . - 20 1 4 e - mail: marketing@lowpowersemi.com www.lowpowersemi.com page 4 of 8 typical operating characteristics vout=5v vin=3v iout vout=5v vin=3v iout 5 ma vout=5v v i n=3v iout 500 vout=5v v i n=3v iout 1 en vs vout
preliminary datasheet LP6252 lp 6252 C 00 version 1 . 0 aug . - 20 1 4 e - mail: marketing@lowpowersemi.com www.lowpowersemi.com page 5 of 8 operation informat ion the LP6252 uses a synchronous 5 5 0k hz fixed frequency, current - mode regulation architecture to regulate the output voltage. the LP6252 measures the output voltage through an external resistive voltage divider and compares that to the internal 0. 8 v refe rence to generate the error voltage to the inductor current to regulate the output voltage. t he use of current - mode regulation improves transient response and control loop stability. when the LP6252 is disable (en=low), both power switches are off. there is no current path from sw to out. there f ore, the output voltage discharges to ground. when the LP6252 is enabled(en=high),a limited start - current charges the output voltage rising to sw, then th e part operates in force pwm mode for regulating the output v oltage to the target value. at the beginning of each cycle, the n - channel mosfet switch is turned on, forcing the inductor current to rise, the current at the source of the switch is internally measured and converted to a voltage by the current sense ampli fier. that voltage is compared to the error voltage. when the inductor current rises sufficiently, the pwm comparator turns off the switch, forcing the inductor current to the output capacitor through the internal p - channel mosfet rectifier, which forces t he inductor current to decrease. the peak inductor current i s controlled by the error voltage. thus the output voltage controls t he indu ctor current to satisfy the lode. setting the output voltage set the output voltage by selecting the resistive vo ltage divider ratio. the voltage divider drops the output voltage to t he 0. 8 v feedback voltage. use a 100k resistor for r2 of the voltage divider. determine t he high - side resistor r1 by the equation: vout=(r1/r2+1) x vfb pre - boost current and short ci rcuit protect initially output voltage is lower than battery voltage, and the LP6252 enters pre - boost phase. during pre - boost phase, the internal nmosfet/pmosfet is turned off/on and a constant current is provided from battery to output until the output voltage close to the battery voltage. the constant current is limited by internal controller. if the output short to ground, the LP6252 also limits the output current to avoid damage condition inductor selection for a better efficiency in high switching f requency converter, the inductor selection has to use a proper core material such as ferrite core to reduce the core loss and choose low esr wire to reduce copper loss. the most important point is to prevent the core saturated when handling the maximum pea k current. using a shielded inductor can minimize radiated noise in sensitive applications. the maximum peak inductor current is the maximum input current plus the half of inductor ripple current. the calculated peak current has to be smaller than the curr ent limitation in the electrical characteristics. a typical setting of the inductor ripple current is 20% to 40% of the maximum input current. if the selection is 40%, the maximum peak inductor current is
preliminary datasheet LP6252 lp 6252 C 00 version 1 . 0 aug . - 20 1 4 e - mail: marketing@lowpowersemi.com www.lowpowersemi.com page 6 of 8 the minimum inductance value is derived from th e following equation : depending on the application, the recommended inductor value is between 2.2h to 4.7 h. input capacitor selection for better input bypassing, low - esr ceramic capacitors are recommended for performance. a 10f input capacitor is s ufficient for most applications. for a lower output power requirement application, this value can be decreased. output capacitor selection for lower output voltage ripple, low - esr ceramic capacitors are recommended. the tantalum capacitors can be used as well, but the esr is bigger than ceramic capacitor. the output voltage ripple consists of two components: one is the pulsating output ripple current flows through the esr, and the other is the capacitive ripple caused by charging and discharging. layout guide for high frequency switching power supplies, the pcb layout is important step in system application design. in order to let ic achieve good regulation, high efficiency and stability, it is strongly recommended the power components should be placed as close as possible. the set races should be wide and short. the feedback pin and then works of feedback and compensation should keep away from the power loops, and be shielded with a ground trace or plane to prevent noise coupling.
preliminary datasheet LP6252 lp 6252 C 00 version 1 . 0 aug . - 20 1 4 e - mail: marketing@lowpowersemi.com www.lowpowersemi.com page 7 of 8 packaging information
preliminary datasheet LP6252 lp 6252 C 00 version 1 . 0 aug . - 20 1 4 e - mail: marketing@lowpowersemi.com www.lowpowersemi.com page 8 of 8
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