1/ ? features z output voltage: 3.3v, 5.0v, 12v, and adjustable output version z adjustable version output voltage range:1.23v to 37v4% z 52khz15% fixed switching frequency z voltage mode non-synchronous pwm control z thermal-shutdown and current-limit protection z on/off shutdown control input z operating voltage can be up to 40v z output load current: 2a z low power standby mode z built-in switching transistor on chip z sop8-ep package ? general description the LSP3127 series are monolithic ic that design for a step-down dc/dc converter, and own the ability of 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 of 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 oscillator frequency. the output version included fixed 3.3v, 5v, 12v, and an adjustable type. the package is available in a standard sop8-ep package. ? applications z simple high-efficiency step-down regulator z on-card switching regulators z positive to negative converter ? 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 joint bay semiconductor co.,ltd . + = $ 3 : 0 % x f n ' & ' & & r q y h u w h u lsp312
2/ ? block diagram ? v cc supply voltage +45 v v sd on/off pin inpu t voltage -0.3 to +25 v v fb feedback pin voltage -0.3 to +25 v v out output voltage to grou nd -1 v p d power dissipation internally limited w t st storage temperatu re -65 to +150 t op operating temperature -40 to +125 v op operating voltage +4.5 to +40 v ? block diagram ? absolute maximum ratings symbol paramrter rating unit joint bay semiconductor co.,ltd . + = $ 3 : 0 % x f n ' & ' & & r q y h u w h u / 6 3
3/ ? electrical characteristics (all output voltage versions) e n. i load =0.5a unl ss otherwise specified, v in =12v for 3.3v,5v, adjustable version and v in =24v for the 12v versio 50 i b feedb v fb =1 le ack bias current .3v(adjustab version only) 40 100 na 4 4 52 60 f osc oscillator frequency khz 38 66 v sat saturation voltage i out =2a ide circuit v no outs v fb =0v force driver on 1.4 1.8 max.duty cycle(on) 100 v fb =0v force driver on dc % min.duty cycle(off) v fb =12v force driver off 0 i cl current limit it on 5.8 a peak current no outside circu v fb =0v force driver output=0 2 ma no outside circuit v fb =12v force driver off i l output output=-1 leakage current v in =40v 30 ma i q ur orce driver off quiescent c rent v fb =12v f 5 10 ma i y nt stb standby quiesie current on/off pin=5v v in =40v 80 200 a v il gultaor on) low(re 0.8 v ih on/off pin logic input 2.4 1.4 v threshold voltage high(regultaor off) i h input logic 30 on/off pin logic current v =2.5v(off) i l pin input v logic =0.5v(on) 10 a on/off current jc sistence so p n 10 /w thermal re p8-e junctio to case ja ce p8-ep t 50 /w thermal resisten with copper area of approximately 3 in 2 so junction o ambient electrical characteristics (continued) min. typ. max. unit ? parameter sy mbol test conditions 1.193 1.267 outp f v fb v out 3v 1.23 v ut eedback 4.5v v in 22v 0.2a i load 2a programmed for 1.18 1.28 efficiency LSP3127-adj v load 76 % in =12v, i = 2a 3.168 3.432 output f v fb in 3.3 v eedback 4.5v v 22v 0.2a i load 2a 3.135 3.465 efficiency LSP3127-3.3v v in load % =12v, i = 2a 78 4.8 5 .2 output f v fb in 0 5 eedback 7v v 22v .2a i load 2a 4.75 5.25 v efficiency LSP3127-5.0v v % in =12v, i load = 2a 83 11.52 11.4 v output f v fb 12 eedback 15v v in 22v 0.2a i load 2a 12.48 12.6 efficiency LSP3127-12v v in % =15v, i load = 2a 90 sp with boldface are for full operat ing e other typ re for t 5c ecifications temperature range, th e a j =2 ? 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 joint bay semiconductor co.,ltd . + = $ 3 : 0 % x f n ' & ' & & r q y h u w h u / 6 3
? 4/ typical performance characteristics switch saturation voltage 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 v in =12v switching frequency 130 135 140 145 150 -50 -25 0 25 50 75 100 125 junction temperature( ) 155 160 frequency (khz) -50 -25 0 25 50 75 100 125 3.50 4.00 4.50 5.00 5.50 v in =12v vout=5v switch current limit(a) switch current limit junction temperature( ) on/off threshold voltage -50 -25 0 25 50 75 100 125 0.0 0.5 1.0 1.5 2.0 2.5 threshold voltage(v) junction temperature( ) off on joint bay semiconductor co.,ltd . + = $ 3 : 0 % x f n ' & ' & & r q y h u w h u lsp312
5/ ? typical application circuits (1) fixed output circuit c3 104 vout=+5v/2a c4 104 r1 l1 150uh c2 470uf/25v c5 22nf on/off u1 LSP3127 5 1 2 3 4 sd vin output gnd fb c1 220uf/35v vin=24v d1 ss24 r3 10 r2 ) adjustable output circuit vout=v fb *(1+r1/r2); v fb =1.23v; r2=1k typical (2 c5 22nf c2 470uf/25v r4 r5 10 d1 ss24 u 1 LSP3127 5 1 2 3 4 sd vin output gnd fb r3 c1 220uf/35v c3 104 r2 c4 104 r1 vo ut=+5v/2a l1 150uh c6 2.2nf vin=24v on/off function description is the positive input supply for the ic switching regulator. a suitable input bypass capacitor must be present ound. switch. the voltage at this pin switches between (v in ? v sat ) and approximately ? 0.5v, with a duty egulated output voltage to complete the feedback loop. e control loop stability. ? pin function v in this at this pin to minimize voltage transients and to supply the switching currents needed by the regulator. ground circuit gr output internal 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 r add c6 capacitor (cff:feed forward capacitor) for adj version to add th joint bay semiconductor co.,ltd . + = $ 3 : 0 % x f n ' & ' & & r q y h u w h u lsp312
6/8 on/off switching regulator circui t to be shutdown using logic level signals thus dropping the total input nk under most conditi ons. the size of the heat sink depends on the input rises pper traces and generous amounts of printed circuit board copper should rature increme nts are all approximate. the increments are affected size, quantity and spacing of other se allows the supply current to approximately 150ua. pulling this pin be low 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/o ff 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 si voltage, the output voltage, the load current and the ambi ent temperature. the LSP3127 junction temperature above ambient temperature for a 2a load and different input and output voltages. the dat a for these curves was taken with the LSP3127(sop8l package) operating as a buck-switching regulator in an ambient temperature 25 (still air). these temperature incr ements are all approximate and are affected by many factors. higher ambient temperatures requires more heat sinker. for the best thermal performance, wi de co be used in the board layout. (one exception is the output (switch) pi n, which should not have large areas of copper.) large areas of copper provide the best transfer of heat (low er thermal resistance) to t he surrounding air, and moving air lowers the thermal resistance even further. package thermal resistance and junction tempe by a lot of factors. some of these fa ctors include board size, shape, thi ckness, position, location, and even board temperature. other factors are, trace width, total printed 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 t he components on the boa rd, as well as whether the su rrounding air is still or moving. furthermore, some of the components such as the catch diode will add heat to the pc board and the heat can va ry as the input voltage changes. for the inductor, depending on t he physical size, type of core materia l 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. joint bay semiconductor co.,ltd . + = $ 3 : 0 % x f n ' & ' & & r q y h u w h u lsp312
7/8 ? ordering in formation marking information ? joint bay semiconductor co.,ltd . + = $ 3 : 0 % x f n ' & ' & & r q y h u w h u lsp312
8/8 ? , e h e1 d1 c e b d a2 a a1 7 (4 ? ) 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. 1 4 0.51 0.013 0.0 6 1 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. 9 9 6.30 0.228 0.2 6 3 0.248 l 0.38 0.71 1.27 0.015 0.028 0.050 0 8 0 8 symbol min. nom. max. min. nom. max. ? package information dimensions in millimeters dimensions in inches joint bay semiconductor co.,ltd . + = $ 3 : 0 % x f n ' & ' & & r q y h u w h u lsp312
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