preliminary datasheet LP6223 LP6223 C00 version 1.0 datasheet jul.-2013 www.lowpowersemi.com - - page 1 of 6 high efficiency boost dc/dc convertor general description the LP6223 is a current mode boost dc-dc converter. its pwm circuitry with built-in 0.3 ? ,24v,1.5a 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 0.6v precision reference voltage. soft-start time can be programmed with an external capacitor, which sets the input current ramp rate. current mode control and external compensation network make it easy and flexible to stabilize the system. ordering information LP6223 - f: pb-free package type b6: sot23-6 typical application circuit 2.2uh 22pf + 22uf vin(3-5v) r1 300k r2 100k en 1 lx 4 fb 6 gnd 3 vdd 5 LP6223 vout_5v 10uf features up to 94% efficiency output to input disconnect at shutdown mode shut-down current:<1ua output voltage up to 28v internal compensation, soft-start 1.1mhz fixed frequency switching high switch on current:1.5a/30v available in sot23-6 package applications battery products host products panel pin configurations marking information please see website:www.lowpowersemi.com. l p622 3 b 6f 5 4 3 2 1 6
preliminary datasheet LP6223 LP6223 C00 version 1.0 datasheet jul.-2013 www.lowpowersemi.com - - page 2 of 6 functional pin description function block diagram pin number sot23-6 pin name pin name 1 en chip on/off(high enable) 2 ext external switch transistor driver output. 3 gnd ground. 4 lx pin for switching mos output. 5 vdd chip power supply. 6 fb feedback input pin, internal reference voltage for the error amplifier is 1.25v. LP6223
preliminary datasheet LP6223 LP6223 C00 version 1.0 datasheet jul.-2013 www.lowpowersemi.com - - page 3 of 6 absolute maximum ratings supply input voltage------------------------------------------- --------------------------------------------------------------- -----6v power dissipation, pd @ ta = 25 c sot23-6----------------------------------------------------------------------------------------------------------450mw package thermal resistance sot23-6, ja -------------------------------------------------- -------------------------------------------------------------16 5c/w lead temperature (soldering, 10 sec.) ------------------------- ---------------------------------------------------------260c recommended operating conditions supply input voltage------------------------------------------- ------------------------------------------------------2.2v to 6 v en input voltage ---------------------------------------------- ---------------------------------------------------------0v to 5.5v operation junction temperature range -------------------------- ----------------------------------------?40c to 125c operation ambient temperaturerange----------------------------- -----------------------------------------?40c to 85c electrical characteristics (vin=2.4v,vout=3.5v,cin=10uf,cout=22uf,l1=2.2uh,r1=178k,r2=100k) parameter conditions LP6223 units min typ max supply voltage 1.6 6 v output voltage range 2.5 28 v supply current(shutdown) ven=vout=0v,vsw=5v 0.05 1 ua supply current vfb=0.7v 0.19 ma feedback voltage 0.6 v feedback input current vfb=0.7v 50 na switching frequency 1.10 mhz maximum duty cycle 80 90 95 % en input low voltage 0.4 v en input high voltage 1.4 v high-side on resistance vout=3.3v 300 mosfet voltage 28 v mosfet current 1.5 a
preliminary datasheet LP6223 LP6223 C00 version 1.0 datasheet jul.-2013 www.lowpowersemi.com - - page 4 of 6 operation information the LP6223 uses a 1.1mhz fixed-frequency, current-mode regulation architecture to regulate the output voltage. the LP6223 measures the output voltage through an external resistive voltage divider and compares that to the internal 0.6v reference to generate the error voltage to the inductor current to regulate the output voltage. the use of current-mode regulation improves transient response and control loop stability. when the LP6223 is disable(en=low),both power switches are off. there is no current path from sw to out. there fore, the output voltage discharges to ground. when the LP6223 is enabled(en=high),a limited start-current charges the output voltage rising to sw, then the part operates in force pwm mode for regulating the output voltage 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 amplifier. that voltage is compared to the error voltage. when the inductor current rises sufficiently, the pwm comparator turns off the switch, forcin g the inductor current to the output capacitor through the internal p-channel mosfet rectifier, which forces the inductor current to decrease. the peak inductor current is controlled by the error voltage. thus the output voltage controls the inductor current to satisfy the lode. setting the output voltage set the output voltage by selecting the resistive voltage divider ratio. the voltage divider drops the output voltage to the 0.6v feedback voltage. use a 100k resistor for r2 of the voltage divider. determine the high-side resistor r1 by the equation: vout=(r1/r2+1) x v fb current limitation the internal power-mos switch current is monitored cycle-by-cycle and is limited to the value not exceed 1.5a (typ.). when the switch current reaches the limited value, the internal power-mos is turned off immediately until the next cycle. inductor selection for a better efficiency in high switching frequency 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 peak 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 ripp le current. the calculated peak current has to be smaller than the current 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 the minimum inductance value is derived from the following equation : depending on the application, the recommended inductor value is between 2.2 h to 4.7 h. diode selection to achieve high efficiency, schottky diode is good choice for low forward drop voltage and fast switching time. the output diode rating should be able to handle the maximum output voltage, average power dissipation and the pulsating diode peak current.
preliminary datasheet LP6223 LP6223 C00 version 1.0 datasheet jul.-2013 www.lowpowersemi.com - - page 5 of 6 input capacitor selection for better input bypassing, low-esr ceramic capacitors are recommended for performance. a 10 f input capacitor is sufficient 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 guideline 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 st ability, 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 LP6223 LP6223 C00 version 1.0 datasheet jul.-2013 www.lowpowersemi.com - - page 6 of 6 packaging information
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