preliminary datasheet LP3315 LP3315C 00 version1.0 datasheet feb.-2012 www.lowpowersemi.com page 1 of 8 1.2mhz,30v/1a high perfor mance, boost converter general description the LP3315 is a 1.2mhz pwm boost switching regulator designed for constant-voltage boost applications. the LP3315 can drive a string of up to 30v. the LP3315 implements a constant frequency 1.2mhz pwm control scheme. the high frequency pwm operation also saves board space by reducing external component sizes. to improve efficiency, the feedback voltage is set to 1250mv, which reduces the power dissipation in the voltage setting resistor. highly integration and internal compensation network minimizes as 5 external component counts. optimized operation frequency can meet the requirement of small lc filters value and low operation current with high efficiency. ordering information LP3315 f: pb-free package: b5: sot23-5 pin configurations features ? high efficiency: 90% ? 1.2mhzfixed-frequency pwm operation ? maximum output voltage up to 30v ? guaranteed 13v/200ma output with 5v input ? operating range : 2.7v to 5.5v ? shutdown supply current:<1ua ? programmable soft-star ? available in sot23-6/sot23-5 package ? minimize the external component ? rohs compliant and 100% lead (pb)-free applications ? ? panel bais voltage supply ? ? oled backlight driver ? notebook computers ? ? portable applications ? ? mid/ptv typical application circuit off on vout vin 4.7uh LP3315 gnd 2 shdn 4 fb 3 vin 5 lx 1 c2 2.2uf c3 1nf c1 4.7uf r1 210k r2 30k marking information please view website . x represents the date( year month day)of the producing day of the products. device no. marking package shipping LP3315b5f lps fbxxx sot23-5 3k/reel
preliminary datasheet LP3315 LP3315C 00 version1.0 datasheet feb.-2012 www.lowpowersemi.com page 2 of 8 functional pin description sot-23-5 pin name pin function 1 lx switch pin. connect this pin to inductor and catch diode. minimize the track area to reduce emi. 2 gnd ground pin 3 fb feedback reference voltage pin. series connect a resistor between vout and ground as a voltage sense. the feedback voltage is 1250mv. 4 shdn chip enable (active high). voltage sensing input to trigger the function of over voltage protection. note that this pin is high impedance. there should be a pull low 100k resistor connected to gnd when the control signal is floating. 5 vin supply input voltage pin. bypass 1uf capacitor to gnd to reduce the input noise. function block diagram vin fb lx gnd en + + + - - -
preliminary datasheet LP3315 LP3315C 00 version1.0 datasheet feb.-2012 www.lowpowersemi.com page 3 of 8 absolute maximum ratings supply input voltage--------------------------------------------------------------------------------------------------- ? 0.3v to 6.0v lx input voltage -------------------------------------------------------------------------------------------------------- ? 0.3v to 30v the other pins ---------------------------------------------------------------------------------------------------------- ? 0.3v to 5.5v power dissipation, p d @ t a = 25c tsot-23-5/6-----------------------------------------------------------------------0.455w lead temperature (soldering, 10 sec.) -------------------------------------------------------------------------------- 260c operation temperature range --------------------------------------------------------------------------------- ? 40c to 80c storage temperature range ---------------------------------------------------------------------------------------- ? 65c to 150c electrical characteristics parameter symbol test condition min typ. max units system supply input operation voltage range v dd 2.7 6 v under voltage lock out v dd 2.2 2.4 2.6 v supply current i dd fb=1.2v, switch 430 550 ua shut down current i dd v en < 0.4v 0.1 1 ua line regulation v in : 3.0~4.3v 2 % oscillator operation frequency f osc 1.2 mhz maximum duty cycle 93 % feedback voltage LP3315 1.22 1.25 1.28 v mosfet on resistance of mosfet r ds(on) 0.4 sw current limit ilm 1 a protection shut down voltage v en 0.3 v enable on voltage v en 1.0 v
preliminary datasheet LP3315 LP3315C 00 version1.0 datasheet feb.-2012 www.lowpowersemi.com page 4 of 8 typical operating characteristics
preliminary datasheet LP3315 LP3315C 00 version1.0 datasheet feb.-2012 www.lowpowersemi.com page 5 of 8
preliminary datasheet LP3315 LP3315C 00 version1.0 datasheet feb.-2012 www.lowpowersemi.com page 6 of 8 applications information inductor selection the recommended value of inductor for 30v applications are 4.7 to 22h. small size and better efficiency are the major concerns for portable device, such as LP3315 used for mob ile phone. the inductor should have low core loss at 1.2mhz and low dcr for better efficiency. to avoid indu ctor saturation current rating should be considered. constant output voltage control the output voltage of the LP3315 can be adjusted by the divider circuit on the fb pin. typical fb voltage is 1250mv. the output voltage can be calculated by the following e quations. power sequence in order to assure the normal soft start function for suppressi ng the inrush current the input voltage should be ready before en pulls high. soft-start the function of soft-start is made for suppressing the inrush c urrent to an acceptable value at the beginning of power on. the LP3315 provides a built-in soft-start function by clamping the output voltage of error amplifier so that the duty cycle of the pwm w ill be increased gradually in t he soft-start period. current limiting the current flow through inductor as charging period is detecte d by a current sensing circuit. as the value comes across the current limiting threshold, the n-mosfet will be tur ned off so that the inductor will be forced to leave charging stage and enter discharging stage. therefore, the indu ctor current will not increase over the current limiting threshold. ovp/uvlo/otp the over voltage protection is detected by a junction breakdown detecting circuit. once vout goes over the detecting voltage, lx pin stops switching and the power n-mosfe t will be turned off. then, the vout will be clamped to be near vovp. as the output voltage is higher than a specified value or input voltage is lower than a specified value, the chip will enter protection mode to prevent abnormal function. as the die temperature is higher the n 160c, the chip also will enter protection mode. the power mosfet will be turned off during protection mode to p revent abnormal operation. thermal considerations for continuous operation, do not exceed absolute maximum operat ion junction temperature. the maximum power dissipation depends on the thermal resistance of ic package, pc b layout, the rate of surroundings airflow and temperature difference between junction to ambient. the maximum power dissipation can be calculated by following formula : where tj(max) is the maximum operation junction temperature, ta is the ambient temperature and the qja is the
preliminary datasheet LP3315 LP3315C 00 version1.0 datasheet feb.-2012 www.lowpowersemi.com page 7 of 8 junction to ambient thermal resistance. for the recommended operating conditions specification of lp331 5, the maximum junction temperature of the die is 125c. the junction to ambient thermal resistance qja is lay out dependent. the junction to ambient thermal resistance for sot23-5 package is 255c/w and for wdfn-8l 2x2 p ackage is 165c/w on the standard jedec 51-3 single layer thermal test board. the maximum power dissipa tion at ta = 25c can be calculated by following formula : layout consideration for best performance of th e LP3315, the following guidelines must be strictly followed. - input and output capacitors should be placed close to the ic and connected to ground plane to reduce noise coupling. - the gnd and exposed pad should be connected to a strong groun d plane for heat sinking and noise protection. - keep the main current traces as possible as short and wide. - lx node of dc-dc converter is with high frequency voltage swi ng. it should be kept at a small area. - place the feedback components as close as possible to the ic and keep away from the noisy devices.
preliminary datasheet LP3315 LP3315C 00 version1.0 datasheet feb.-2012 www.lowpowersemi.com page 8 of 8 packing information
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