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liteon semiconductor corporation lsp3122a 300khz 5a pwm buck dc/dc converter rev1.1 1/11 ? pin configuration (1) to220-5l (2) to263-5l (top view) (top view) symbol name descriptions 1 vin operating voltage input 2 output switching output 3 gnd ground 4 fb output voltage feedback control 5 sd on/off shutdown ? features z output voltage: 3.3 v, 5.0v, 12v, and adjustable output version z adjustable version output voltage range:1.23v to 37v3% z 300khz15% 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: 5a z low power standby mode z built-in switching transistor on chip z to220-5l,to263-5l packages ? applications z simple high-efficiency step-down regulator z on-card switching regulators z positive to negative converter ? general description the lsp3122a series are monolithic ic that design for a step-down dc/dc converter, and own the ability of driving a 5a load without additional transistor component. due to reducing the number of external component, the board space can be saved easily. the external s hutdown 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 lsp3122a series operates at a switching frequency of 300 khz thus allowing smaller sized filter components than what would be needed with lower frequency switching regulators. other features include a guaranteed 3% 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 packages are available in a standard 5-lead to-220 package and a 5-lead to-263 package. metal tab gnd 1 vin 2 output 3 gnd 4 fb 5 sd 1 2 3 4 5 vin output gnd fb sd metal tab gnd
liteon semiconductor corporation lsp3122a 300khz 5a pwm buck dc/dc converter rev1.1 2/11 ? 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 +40 v v fb feedback pin voltage -0.3 to +40 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 +45 v
liteon semiconductor corporation lsp3122a 300khz 5a pwm buck dc/dc converter rev1.1 3/11 ? electrical characteristics (a ll 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 i fb feedback bias current v fb =1.3v(adjustable version only) 15 50 na f osc oscillator frequency 255 300 345 khz v sat saturation voltage i out =5a no outside circuit v fb =0v force driver on 1.4 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 6.5 a output=0 no outside circuit v fb =12v force driver off 50 a i l output=-1 output leakage current v in =40v 2 30 ma i q quiescent current v fb =12v force driver off 4.5 10 ma i stby standby quiesient current on/off pin=5v v in =40v 80 200 a v il low(regultaor on) 0.6 v ih on/off pin logic input threshold voltage high(regultaor off) 2.0 1.3 v i h on/off pin logic input current v logic =2.5v(off) 5 15 i l on/off pin input current v logic =0.5v(on) 5 a to220-5l 2.5 jc thermal resistence to263-5l junction to case 3.5 /w to220-5l 28 ja thermal resistence with copper area of approximately 3 in 2 to263-5l junction to ambient 30 /w ? electrical characteristics (continued) symbol parameter conditions typ. limit unit v fb output feedback 5v v in 40v 0.2a i load 5a v out programmed for 3v 1.215 1.18 1.25 v v min v max lsp3122a-adj efficiency v in =12v, i load =5a 73 % v out output voltage 5.5v v in 40v 0.2a i load 5a 3.3 3.20 3.40 v v min v max lsp3122a-3.3v efficiency v in =12v, i load =5a 73 % v out output voltage 8v v in 40v 0.2a i load 5a 5 4.85 5.15 v v min v max lsp3122a-5v efficiency v in =12v, i load =5a 80 % v out output voltage 15v v in 40v 0.2a i load 5a 12 11.64 12.36 v v min v max lsp3122a-12v efficiency v in =15v, i load =5a 90 % specifications with boldface type are for full operating temperature range, the other type are for tj=25 o c.
liteon semiconductor corporation lsp3122a 300khz 5a pwm buck dc/dc converter rev1.1 4/11 ? typical performance characteristics
liteon semiconductor corporation lsp3122a 300khz 5a pwm buck dc/dc converter rev1.1 5/11 ? typical performanc e characteristics ( continued )
liteon semiconductor corporation lsp3122a 300khz 5a pwm buck dc/dc converter rev1.1 6/11 ? typical application circuits (1) fixed output circuit (2) adjustable output circuit vout=v fb *(1+r1/r2); v fb =1.23v; r2=1k typical (3) delay start circuit
liteon semiconductor corporation lsp3122a 300khz 5a pwm buck dc/dc converter rev1.1 7/11 ? 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 40v) 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 lsp3122a is available in three packages, a 5-pin to-220, and a 5-pin surface mount to-263. the to-220 package needs a heat sink under most conditions. the size of the heat sink depends on the input voltage, the output voltage, the load current and the ambient temperature. the lsp3122a junction temperature rises above ambient temperature for a 5a load and different input and output voltages. the data for these curves was taken with the lsp3122a (to-220 package) operatin g as a buck switching regulator in an ambient temperature of 25 o c (still air). these temperature rise numbers are all approximate and there are many factors that can affect these temperat ures. higher ambient temperatures require more heat sinking. the to-263 surface mount package tab is designed to be soldered to the copper on a printed circuit board. the copper and the board are the heat sink for this package and the other heat producing components, such as the catch diode and inductor. the pc board copper area that the package is soldered to should be at least 0.4 in 2 , and ideally should have 2 or more square inches of 2 oz. additional copper area improves the thermal characteristics, but with copper areas greater than approximately 6 in 2 , only small improvements in heat dissipation are realized. if further thermal improvemen ts are needed, double sided, multilayer pc board with large copper areas and/or airflow are recommended. the lsp3122a (to-263 package) junction temperature ri se above ambient temperature with a 2a load for various input and output voltages. this data was taken with the circuit operating as a buck switching regulator with all components mounted on a pc board to simulate the junction temperature under actual operating conditions. this curve can be used for a quick check fo r the approximate junction temperature for various conditions, but be aware that there are many factors that can affect the junction temperature. when load currents higher than 3a are used, double sided or multilay er pc boards with large copper areas and/or airflow might be needed, especially for high ambient temperatures and high output voltages. for the best thermal performance, wide copper traces and generous amounts of printed circuit board copper should be used in the board layout. (once exception to this is the output (switch) pin, which should not have large areas of copper.) large areas of copper provide the best transfer of hea t (lower thermal resistance) to the surrounding air, and moving air lowers the thermal resistance even further. package thermal resistance and junction temperature ri se numbers are all approximate, and there are many factors that will affect these numbers. some of thes e factors include board size, shape, thickness, position, location, and even board temperature. other factors are, trace width, total printed circuit copper area, copper thickness, single or double-sided, multilayer 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 ma terial and the dc resistance, it could either act as a heat sink taking heat away from the boar d, or it could add heat to the board.
liteon semiconductor corporation lsp3122a 300khz 5a pwm buck dc/dc converter rev1.1 8/11 ? ordering information ? marking in formation 1) to220-5l 2) to263-5l
liteon semiconductor corporation lsp3122a 300khz 5a pwm buck dc/dc converter rev1.1 9/11 ? package information 1) to220-5l dimensions in millimeters dimensions in inches symbol min. nom. max. min. nom. max. a 4.07 4.45 4.82 0.160 0.175 0.190 b 0.76 0.89 1.02 0.030 0.035 0.040 c 0.36 0.50 0.64 0.014 0.020 0.025 d 14.22 14.86 15.50 0.560 0.585 0.610 e 9.78 10.16 10.54 0.385 0.400 0.415 e 1.57 1.71 1.85 0.062 0.067 0.073 e1 6.68 6.81 6.93 0.263 0.268 0.273 f 1.14 1.27 1.40 0.045 0.050 0.055 h1 5.46 6.16 6.86 0.215 0.243 0.270 j1 2.29 2.74 3.18 0.090 0.108 0.125 l 13.21 13.97 14.73 0.520 0.550 0.580 p 3.68 3.81 3.94 0.145 0.150 0.155 q 2.54 2.73 2.92 0.100 0.107 0.115 a f c j1 e1 l d q e h1 e b p
liteon semiconductor corporation lsp3122a 300khz 5a pwm buck dc/dc converter rev1.1 10/11 2) to263-5l dimensions in millimeters dimensions in inches symbol min. nom. max. min. nom. max. a 4.07 4.46 4.85 0.163 0.176 0.194 b 0.51 0.84 1.02 0.020 0.033 0.041 c 0.36 0.50 0.74 0.014 0.020 0.030 c2 1.14 1.27 1.65 0.046 0.050 0.066 d 8.20 9.15 9.65 0.328 0.360 0.380 e 9.65 10.16 10.67 0.386 0.400 0.427 e 1.57 1.71 1.85 0.063 0.068 0.074 l 14.45 15.24 15.88 0.578 0.600 0.635 l1 1.78 2.54 2.79 0.071 0.100 0.110 l2 2.92 0.115 e b e d l2 l l1 c c2 a 9.10 land pattern recommendation (unit: mm) 10.90 15.70 2.50 1.70 1.00
liteon semiconductor corporation lsp3122a 300khz 5a pwm buck dc/dc converter rev1.1 11/11 ? update history date version descriptions 20090417 v1.1 add the vout calculation formula of adj version in page6 (by fredwu);

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