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liteon semiconductor corporation LSP3127 52khz 2a pwm buck dc/dc converter rev1.2 1/9 pin configuration sop8-ep (top view) pin description name no. description vin 1 operating voltage input output 2 switching output fb 3 output voltage feedback control sd 4 on/off shutdown gnd 5 ground gnd 6 ground gnd 7 ground gnd 8 ground features output voltage: 3.3v, 5.0v, 12v, and adjustable output version adjustable version output voltage range:1.23v to 37v4% 52khz15% fixed switching frequency voltage mode non-synchronous pwm control thermal-shutdown and current-limit protection on/off shutdown control input operating voltage can be up to 40v output load current: 2a low power standby mode built-in switching transistor on chip sop8-ep package applications simple high-efficiency step-down regulator on-card switching regulators positive to negative converter general description the LSP3127 series are monolithic ic that design fo r a step-down dc/dc converter, and own the ability o f driving a 2a load without additional transistor component. due to reducing the number of external component, the board space can be saved easily. the external shutdown function can be controlled by logic level and then come into standby mode. the internal compensation makes feedback control have good line and load regulation without external design. regarding protected function, thermal shutdown is to prevent over temperature operating from damage, and current limit is against over current operating o f the output switch. the LSP3127 series operates at a switching frequency of 52 khz thus allowing smaller sized filter components than what would be needed with lower frequency switching regulators. other features include a guaranteed 4% tolerance on output voltage under specified input voltage and output load conditions, and 15% on the oscillato r frequency. the output version included fixed 3.3v, 5v, 12v, and an adjustable type. the package is available in a standard sop8-ep package. please be aware that an important notice concerning availability, disclaimers, and use in critical applications of lsc products is at the end of this document.
liteon semiconductor corporation LSP3127 52khz 2a pwm buck dc/dc converter rev1.2 2/9 block diagram absolute maximum ratings symbol paramrter rating unit v cc supply voltage +45 v v sd on/off pin input voltage -0.3 to +25 v v fb feedback pin voltage -0.3 to +25 v v out output voltage to ground -1 v p d power dissipation internally limited w t st storage temperature -65 to +150
t op operating temperature -40 to +125
v op operating voltage +4.5 to +40 v
liteon semiconductor corporation LSP3127 52khz 2a pwm buck dc/dc converter rev1.2 3/9 electrical characteristics (all output voltage versions) unless otherwise specified, v in =12v for 3.3v,5v, adjustable version and v in =24v for the 12v version. i load =0.5a symbol paramrter conditions min. typ. max. unit 50 i b feedback bias current v fb =1.3v(adjustable version only) 40 100 na 44 52 60 f osc oscillator frequency 38 66 khz v sat saturation voltage i out =2a no outside circuit v fb =0v force driver on 1.4 1.8 v max.duty cycle(on) v fb =0v force driver on 100 dc min.duty cycle(off) v fb =12v force driver off 0 % i cl current limit peak current no outside circuit v fb =0v force driver on 5.8 a output=0 no outside circuit v fb =12v force driver off 2 ma i l output=-1 output leakage current v in =40v 30 ma i q quiescent current v fb =12v force driver off 5 10 ma i stby standby quiesient current on/off pin=5v v in =40v 80 200 a v il low(regultaor on) 0.8 v ih on/off pin logic input threshold voltage high(regultaor off) 2.4 1.4 v i h on/off pin logic input current v logic =2.5v(off) 30 i l on/off pin input current v logic =0.5v(on) 10 a jc thermal resistence sop8-ep junction to case 10 /w
ja thermal resistence with copper area of approximately 3 in 2 sop8-ep junction to ambient 50 /w
electrical characteristics (continued) parameter symbol test conditions min. typ. max. unit 1.193 1.267 output feedback v fb 4.5v v in 22v 0.2a i load 2a v out programmed for 3v 1.18 1.23 1.28 v efficiency LSP3127-adj v in =12v, i load = 2a 76 % 3.168 3.432 output feedback v fb 4.5v v in 22v 0.2a i load 2a 3.135 3.3 3.465 v efficiency LSP3127-3.3v v in =12v, i load = 2a 78 % 4.8 5.2 output feedback v fb 7v v in 22v 0.2a i load 2a 4.75 5 5.25 v efficiency LSP3127-5.0v v in =12v, i load = 2a 83 % 11.52 11.4 v output feedback v fb 15v v in 22v 0.2a i load 2a 12.48 12 12.6 efficiency LSP3127-12v v in =15v, i load = 2a 90 % specifications with boldface are for full operat ing temperature range, the other type are for t j =25c
liteon semiconductor corporation LSP3127 52khz 2a pwm buck dc/dc converter rev1.2 4/9 typical performance characteristics 2 . 0 2.5 on/off threshold voltage ge(v) off 0.60 0.80 1.00 1.20 1.40 1.60 0.5 1 2 3 switch current(a) 1 2 3 saturation voltage(v) 1:-40 2:25 3:125 switch saturation voltage v in =12v 130 135 140 145 150 -50 -25 0 25 50 75 100 125 junction temperature( ) switching frequency 155 160 frequency (khz) 5.50 v in =12v vout=5v m it(a) switch current limit
liteon semiconductor corporation LSP3127 52khz 2a pwm buck dc/dc converter rev1.2 5/9 typical application circuits (1) fixed output circuit (2) adjustable output circuit vout=v fb *(1+r1/r2); v fb =1.23v; r2=1k typical remark: for input-output voltage greater than approximately 15v the additional capacitor cff 100nf is recommended between fb and vout. the capacitor type can be ceramic, plastic, etc.
liteon semiconductor corporation LSP3127 52khz 2a pwm buck dc/dc converter rev1.2 6/9 function description pin function v in this is the positive input supply for the ic switching regulator. a suitable input bypass capacitor must be present at this pin to minimize voltage transients and to supply the switching currents needed by the regulator. ground circuit ground. output internal switch. the voltage at this pin switches between (v in ? v sat ) and approximately ? 0.5v, with a duty cycle of approximately v out / v in . to minimize coupling to sensitiv e circuitry, the pc board copper area connected to this pin should be kept a minimum. feedback senses the regulated output voltage to complete the feedback loop. on/off allows the switching regulator circuit to be shutdown using logic level signals thus dropping the total input supply current to approximately 150ua. pulling this pin below a threshold voltage of approximately 1.3v turns the regulator on, and pulling this pin above 1.3v (up to a maximum of 25v) shuts the regulator down. if this shutdown feature is not needed, the on/off pin can be wired to the ground pin or it can be left open, in either case the regulator will be in the on condition. thermal considerations the sop8l package needs a heat sink under most conditi ons. the size of the heatsink depends on the input voltage, the output voltage, the load cu rrent and the ambient temperature. t he LSP3127 junction temperature rises above ambient temperature for a 2a load and different i nput and output voltages. the data for these curves was taken with the LSP3127(sop8l package) operating as a bu ck-switching regulator in an ambient temperature 25 (still air). these temperature increments are all approxim ate and are affected by many factors. higher ambient temperatures requires more heat sinker. for the best thermal performance, wi de copper traces and generous amounts of printed circuit board copper should be used in the board layout. (one exception is the output (switch) pin, which shou ld not have large areas of copper.) large areas of copper provide the best transfer of heat (low er thermal resistance) to the surrounding air, and moving air lowers the thermal resistance even further. package thermal resistance and junction temperature increm ents are all approximate. t he increments are affected by a lot of factors. some of these factors include boar d size, shape, thickness, position, location, and even board temperature. other factors are, trace width, total pr inted circuit copper area, copper thickness, single or double-sided, multi-layer board and the amount of solder on the board. the effectiveness of the pc board to dissipate heat also depends on the size, quantity and spacing of other components on the board, as well as whether the surrounding air is still or moving. furthermore, some of these components such as the catch diode will add heat to the pc board and the heat can vary as the input voltage changes. for the inductor, depending on the physical size, type of core material and the dc resistance, it could either act as a heat sink taking heat away from the board, or it could add heat to the board.
liteon semiconductor corporation LSP3127 52khz 2a pwm buck dc/dc converter rev1.2 7/9 ordering information marking information
liteon semiconductor corporation LSP3127 52khz 2a pwm buck dc/dc converter rev1.2 8/9 package information dimensions in millimeters dimensions in inches symbol min. nom. max. min. nom. max. a 1.35 1.60 1.75 0.053 0.063 0.069 a1 0.05 0.15 0..002 0.006 a2 1.35 1.45 1.55 0.053 0.057 0.061 b 0.33 0.41 0.51 0.013 0.016 0.020 c 0.19 0.20 0.25 0.0075 0.008 0.010 d 4.70 4.90 5.10 0.185 0.196 0.200 d1 3.202 3.402 0.126 0.134 e 3.80 3.90 4.00 0.148 0.154 0.160 e1 2.313 2.513 0.091 0.099 e 1.27typ. 0.050typ. h 5.80 5.99 6.30 0.228 0.236 0.248 l 0.38 0.71 1.27 0.015 0.028 0.050 0 8 0 8 e h e1 d1 l , view ?a? e b d a2 a a1 7 (4 ? ) 0.015 ? 45 c view ?a? 7 (4 ? )
liteon semiconductor corporation LSP3127 52khz 2a pwm buck dc/dc converter rev1.2 9/9 important notice and disclaimer lsc reserves the right to make changes to this document and its product s and specifications a t any time without notice. customers should obta in and confirm the latest product informatio n and specifications before final design, purchase or use. lsc makes no warranty, representation or guarant ee regarding the suitability of its products fo r any particular purpose, nor does lsc assume any lia bility for application assistance or custome r p roduct design. lsc does not warr ant or accept any liability w ith products which are purchase d or used for any unintended or unauthorized application. n o license is granted by implication or otherwise under any intellectual property rights of lsc. lsc products are not authorized for use as critical components in life support devices or systems without express written approval of lsc.

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