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liteon semiconductor corporation lsp3100 1.5mhz, 800ma synchronous step-down converter rev1.3 1/12 applications cellular and smart phones pdas mp3 player digital still and video cameras portable instruments microprocessors and dsp core supplies wireless and dsl modems pin configuration (top view) pin description pin number pin name pin function 1 run regulator enable control input. drive r un above 1.5v to turn on the part. drive run below 0.3v to turn it off. in shutdown, all functions are disable drawing ! 1a supply current. do not leave run floating. 2 gnd ground 3 sw power switch output. it is the switch node connection to inductor. this pin connects to the drains of the inte rnal p-ch and n-ch mosfet switches. 4 v in supply input pin. must be closely decoup led to gnd, pin2, with a 2.2f or greater ceramic capacitor. 5 v fb /v out vfb (lsp3100): feedback input pin. connected v fb to the center point of the external resistor divider. the feedback threshold voltage is 0.6v. v out (lsp3100-1.8): output voltage feedback pin. an internal resistive divider divides the output voltage down for comparison to the internal reference voltage. features high efficiency : up to 96% 1.5mhz constant switching frequency 800ma output current at v in =3.0v integrated main switch and synchronous rectifier. no schottky diode required 2.5v to 6.5v input voltage range output voltage as low as 0.6v 100% duty cycle in dropout low quiescent current : 300a ! 1a shutdown current slope compensated current mode control fo r excellent line and load transient response short circuit and thermal fault protection space saving 5-pin sot23 package 5 4 1 2 3 v in v fb /v out sw gnd run general description the lsp3100 is a 1.5mhz constant frequency; slope compensated current mode pwm step-down converter. the device integrates a main switch and a synchronous rectifier for high efficiency without an external schottky diode. it is ideal for powering portable equipment that runs from a single cell lithium-ion (li+) battery. the lsp3100 can suppl y 800ma of load current from a 2.5v to 6.5v inpu t voltage. the output voltage can be regulated as low as 0.6v. the lsp3100 can also run at 100% duty cycle fo r low dropout operation, extending battery life in portable system. idle mode operati on at light loads provides very low output ripple voltage for noise sensitive applications. the lsp3100 is offered in a low profile 5-pin, so t package, and is available in an adjustable version and fixed output voltage of 1.8v.
liteon semiconductor corporation lsp3100 1.5mhz, 800ma synchronous step-down converter rev1.3 2/12 block diagram * v fb /v out note: for adjustable output, r1and r2 is external. thermal resistance (note 1) package ja ( /w) jc ( /w) sot23-5l 250 110 note 1: thermal resistance is specified with approximately 1 square of 1 oz cooper. absolute maximum ratings (note 2) parameter rating unit input supply voltage -0.3 to +7 v run, v fb voltages -0.3 to v in +0.3 v sw vout voltages -0.3 to v in +0.3 v peak sw sink and source current 1.5 a operating temperature range -40 to +85 junction temperature (note 3) +125 storage temperature range -65 to 150 lead temperature ( solding, 10 sec.) +300 note 2: absolute maximum ratings are those val ues beyond which the life of a device may be impaired. note 3: t j is calculated from the ambient temperature t a and power dissipation p d according to the following formula: t j =t a +p d ja
liteon semiconductor corporation lsp3100 1.5mhz, 800ma synchronous step-down converter rev1.3 3/12 electrical characteristics (note 4) (v in =v run =3.6v, t a =25 , unless otherwise noted) parameter condition min. typ. max. unit input voltage range 2.5 6.5 v input dc supply current active mode shutdown mode v fb =0.5v v fb =0v, v in =4.2v 270 0.08 400 1.0 a t a =+25 0.5880 0.6000 0.6120 v t a =0 ? t a ? 85 0.5865 0.6000 0.6135 v regulated feedback voltage t a =-40 ? t a ? 85 0.5850 0.6000 0.6150 v v fb input bias current v fb =0.65v 30 na reference voltage line regulation v in =2.5v to 6.5v, v out =v fb (r2=0) 0.11 0.40 %/v regulated output voltage LSP3100C18AD: -40 ? t a ? 85 1.746 1.800 1.854 v output voltage line regulation v in =2.5v to 6.5v, i out =10ma 0.11 0.40 %/v output voltage load regulation i out from 0 to 800ma 0.0015 %/ma maximum output current v in =3.0v 800 ma oscillator frequency v fb =0.6v or v out =100% 1.2 1.5 1.8 mhz r ds(on) of p-ch mosfet i sw =300ma 0.30 0.50 $ r ds(on) of n-ch mosfet i sw =-300ma 0.20 0.45 $ peak inductor current v in =3v, v fb =0.5v or v out =90%, duty cycle ! 35% 1.20 a sw leakage v run =0v, v sw =0v or 5v, v in =5v 0.01 1 a output over voltage lockout v ovl =v ovl -v fb 60 mv run threshold -40 ? t a ? 85 0.3 0.45 1.30 v run leakage current 0. 1 1 a note 4: 100% production test at +25 . specifications over the temperatur e range are guaranteed by design and characterization.
liteon semiconductor corporation lsp3100 1.5mhz, 800ma synchronous step-down converter rev1.3 4/12 typical performance characteristics (test figure 1 below unless otherwise specified) input voltage (v) efficiency 55% 65% 75% 80% 90% 95% 234 5 6 efficiency vs input voltage 60% 70% 85% 100% 50% iload=100ma iload=500ma iload=10ma output current (ma) efficiency 10% 30% 50% 60% 80% 90% 0.1 1 10 100 1000 efficiency vs output current 20% 40% 70% 100% v in =2.7v v in =3.6v v in =4.2v v out =1.2v ta=25 output current (ma) efficiency 10% 30% 50% 60% 80% 90% 0.1 1 10 100 1000 efficiency vs output current 20% 40% 70% 100% v in =2.7v v in =3.6v v in =4.2v v out =1.5v ta=25 output current (ma) efficiency 10% 30% 50% 60% 80% 90% 0.1 1 10 100 1000 efficiency vs output current 20% 40% 70% 100% v in =2.7v v in =3.6v v in =4.2v v out =1.8v ta=25
liteon semiconductor corporation lsp3100 1.5mhz, 800ma synchronous step-down converter rev1.3 5/12 typical performance characteristics (continued) output current (ma) efficiency 10% 30% 50% 60% 80% 90% 0.1 1 10 100 1000 efficiency vs output current 20% 40% 70% 100% 0% v in =2.7v v in =3.6v v in =4.2v v out =2.5v ta=25 load current (ma) efficiency 10% 30% 50% 60% 80% 90% 0.1 1 10 100 1000 efficiency vs load current 20% 40% 70% 100% 0% 4.7h 2.2h 1.4h 10h v in =3.6v v out =1.8v ta=25 load current (ma) efficiency 10% 30% 50% 60% 80% 90% 0.1 1 10 100 1000 efficiency vs load current 20% 40% 70% 100% 0% 4.7h 2.2h 1.4h 10h v in =3.6v v out =2.5v ta=25 0 200 400 800 1000 1200 1.64 1.66 1.72 1.76 1.78 1.80 load current (ma) output voltage (v) output voltage vs load current 1.70 1.84 600 1.68 1.74 1.82 v in =3.6v v out =1.8v l=2.2h
liteon semiconductor corporation lsp3100 1.5mhz, 800ma synchronous step-down converter rev1.3 6/12 typical performance characteristics (continued) 2.73.153.6 4.54.95 5.4 1.36 1.37 1.4 1.42 1.43 1.44 input voltage (v) frequency (mhz) frequency vs input voltage 1.39 1.46 4.05 1.38 1.41 1.45 v out =1.8v i load =150ma l=2.2h 012 567 0.0 0.2 0.3 0.4 input voltage (v) r ds(on) (ohm) r ds(on) vs input voltage 0.5 3 0.1 4 main switch synchronous switch -50-30-10 507090 0.6008 0.6040 0.6056 0.6072 temperature ( ) reference voltage (v) reference voltage vs temperature 0.6080 10 0.6024 30 0.6016 0.6032 0.6048 0.6064 v in =3.6v -45 -30 -15 45 75 90 0.18 0.26 0.30 0.34 temperature ( ) r ds(on ) (ohm) r ds(on) vs temperature 0.36 15 0.22 30 0.20 0.24 0.28 0.32 v in =3.6v 0.38 060 n_r ds(on ) p_r ds(on)
liteon semiconductor corporation lsp3100 1.5mhz, 800ma synchronous step-down converter rev1.3 7/12 typical performance characteristics (continued) load transient response pwm mode only load transient response idle mode to pwm mode idle mode pwm 2.7 3 3.3 4.5 5.1 5.4 0.26 0.29 0.30 0.31 input voltage (v) in put curren t (ma) input voltage vs input current 0.32 3.9 0.28 4.2 0.27 0.28 0.29 0.31 0.32 3.6 4.8 5.7 v out =1.8v i load =0 l=2.2h -50 -25 50 75 100 1.10 1.30 1.40 1.50 temperature ( ) ocs frequency (mhz) frequency vs temperature 1.55 0 1.20 25 1.15 1.25 1.35 1.45 v in =3.6v 1.60 -50 -30 -10 50 70 90 200 260 280 300 supply current vs temperature 320 10 220 30 temperature ( ) supply current (a) 240
liteon semiconductor corporation lsp3100 1.5mhz, 800ma synchronous step-down converter rev1.3 8/12 functional description operation lsp3100 is a monolithic switching mode step-down dc-dc converter. it utilizes internal mosfets to achieve high efficiency and can generate very low output voltage by usi ng internal reference at 0. 6v. it operates at a fixed switching frequency, and uses the slope compensated current mode architecture. this step-down dc-dc converter suppliers 800ma output current at vin=3. 6v with input voltage range from 2.5v to 6.5v. current mode pwm control slope compensated current mode pwm control provides st able switching and cycle-by-cycle current limit for excellent load and line responses and protection of the internal main switch (p-ch mosfet) and synchronous rectifier (n-ch mosfet). during normal operation, the inte rnal p-ch mosfet is turned on for a certain time to ramp the inductor current at each rising edge of the in ternal oscillator, and switched off when the peak inductor current is above the error voltage. the current comparator, i comp , limits the peak inductor current. when the main switch is off, the synchronous rectifier will be turned on immediately and stay on until either the inductor current starts to reverse, as indicated by the current reversal comparator, i zero , or the beginning of the next clock cycle. the ovdet comparator controls output tran sient overshoots by turning the main switch off and keeping it off until the faults is no longer present. idle mode operation at very light loads, the lsp3100 automat ically enters idle mode. in the idle mode, the inductor current may reach zero or reverse on each pulse. the pwm control loop will automatically skip pulses to maintain output regulation. the bottom mosfet is turned off by the current reversal comparator, i zero , and the switch voltage will ring. this is discontinuous mode operation, and is norma l behavior for the switching regulator. dropout operation when the input voltage decreases toward the value of t he output voltage, the lsp3100 allows the main switch to remain on for more than one switching cycle and increases the duty cycle until it reaches 100%. the duty cycle d of a step-down converter is defined as: out on osc in v d=t f 100% 100% v where t on is the main switch on time and f osc is the oscillator frequency (1.5mhz). the output voltage then is the input voltage minus the voltage drop across the main switch and the inductor. at low input supply voltage, the r ds(on) of the p-channel mosfet increase, and the efficiency of the converter decreases. caution must be exercised to ensure the heat dissipated not to exceed the maximum junction temperature of the ic. maximum load current the lsp3100 will operate with input supply voltages as lo w as 2.5v, however, the maximum load current decreases at lower input due to large ir drop on the main switch and synchronous rectifier. the slope compensation signal reduces the peak inductor current as a function of the dut y cycle to prevent sub harmoni c oscillations at duty cycles greater than 50%. conversely the current lim it increases as the duty cycle decreases.
liteon semiconductor corporation lsp3100 1.5mhz, 800ma synchronous step-down converter rev1.3 9/12 application information r2 316k r1 2 c3 10f 5 3 4 1 vout 1.8v gnd vfb sw run 2.2h vin 2.7v-4.2v l1 22pf c2 c1 4.7f 632k vin fig.1 basic application circuit with lsp3100 adjustable version 2 c3 10f 5 3 4 1 vout 1.8v gnd vout sw run 2.2h vin 2.5v-5.5v l1 c1 4.7f vin fig.2 basic application circui t with fixed output versions setting the output voltage figure 1 above shows the basic application circuit with l sp3100 adjustable output version. the external resistor sets the output voltage according to the following equation: ? ? ? ? ? ? ? ? + = 2 1 out r r 1 v 6 . 0 v for example, fixed r1=300k for all outputs; r2=300k for v out =1.2v, r2=200k for v out =1.5v, r2=150k for v out =1.8v and r2=95.3k for v out =2.5v. inductor selection for most designs, the lsp3100 operates with inductors of 1h to 4.7h. low inductance values are physically smaller but require faster switching, which results in some efficiency loss. the inductor value can be derived from the following equation: () out in out in l osc vvv l vif ? = ? where ? i l is inductor ripple current. large value inductors lo wer ripple current and small value inductors result in high ripple currents. choose inductor ripple current approximately 35% of the maximum load current 800ma, or ? i l =280ma. for output voltages above 2.0v, when light-load efficiency is important, the minimum recommended inductor is 2.2h. for optimum voltage-positioning load transients, choose an inductor with dc series resistance in the 50m to 150m range. for higher efficiency at heavy loads (above 200 ma), or minimal load regulation (but some transient overshoot), the resistance should be kept below 100m . the dc current rating of the inductor should be at least equal to the maximum load current plus half the ripple cu rrent to prevent core saturation (800ma+140ma). table 1 lists some typical surface mount inductors t hat meet target applications for the lsp3100.
liteon semiconductor corporation lsp3100 1.5mhz, 800ma synchronous step-down converter rev1.3 10/12 part # l (h) max dcr (m ? ) rated d.c. current (a) size wlh (mm) sumida cr43 14 2.2 3.3 4.7 56.2 71.2 86.2 108.7 2.52 1.75 1.44 1.15 4.54.03.5 sumida cdrh4d18 1.5 2.2 3.3 4.7 75 110 162 1.32 1.04 0.84 4.74.72.0 to k o d312c 1.5 2.2 3.3 4.7 120 140 180 240 1.29 1.14 0.98 0.79 3.63.61.2 input capacitor selection the input capacitor reduces the surge current drawn from the input and switch ing noise from the device. the input capacitor impedance at the switching frequency shall be less than input source imp edance to prevent high frequency switching current passing to the input. a low esr input capacitor sized for minimum rms current must be used. ceramic capacitors with x5r or x7r dielectrics are highly recommended because of their low esr and small temperature coefficients. a 4.7f ceramic capa citor for most applications is sufficient. output capacitor selection the output capacitor is requires to keep the output volt age ripple small and to ensure regulation loop stability. the output capacitor must have low impedance at the switch ing frequency. ceramic capacitors with x5r or x7r dielectrics are recommended due to their low esr and high ripple current. the output ripple v out is determined by: () out in out out in osc osc vvv 1 vesr vf l 8f c3 ? ?? ? + ?? ?? ? ordering information
liteon semiconductor corporation lsp3100 1.5mhz, 800ma synchronous step-down converter rev1.3 11/12 marking information
liteon semiconductor corporation lsp3100 1.5mhz, 800ma synchronous step-down converter rev1.3 12/12 package information dimensions in millimeters symbol min typ max a 1.05 1.20 1.35 a1 0.05 0.10 0.15 a2 1.00 1.10 1.20 b 0.30 - 0.50 c 0.08 - 0.22 d 2.80 2.90 3.00 e 2.60 2.80 3.00 e1 1.50 1.60 1.70 e 0.95 bsc e1 1.90 bsc l 0.30 0.45 0.55 l1 0.60 ref l2 0.25 bsc ? m1 3 q 5 q 7 q ? m2 6 q 8 q 10 q l l1 l2 a 2 a a 1 m2 e1 e e e1 d b c m1 gauge plane seating plane

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