LR8503 7 7 8 ? introduction: ? features: the LR8503 is a constant frequency, current mode 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 output voltage can be regulated as low as 0.6v. the LR8503 can also run at 100% duty cycle for low dropout operation, extending battery life in portable system. this device offers two operation modes, pwm control and pfm mode switching control, which allows a high efficiency over the wider range of the load. the LR8503 is offered in a low profile 5-pin, sot package, and is available in an adjustable version. z high efficiency :up to 96% z 1.5mhz constant frequency operation z 800ma output current z no schottky diode required z 2v to 6.5v input voltage range z output voltage as low as 0.6v z pfm mode for high efficiency in light load z 100% duty cycle in dropout operation z low quiescent current: 20 a z slope compensated current mode control for excellent line and load transient response z short circuit protection z thermal fault protection z inrush current limit and soft start z <1 a shutdown current z sot23-5 package ? applications ? z cellular and smart phones z pdas z wireless and dsl modems z digital still and video cameras z dtv z portable instruments ? pin configuration: ? order information: designator symbol description 7 a standard 8 m package ? sot23-5 800ma,2v-6.5v input,1.5mhz s y nchronous step-down converter LR8503 series leshan radio company, ltd. ver0.2 1/7
tabel1. pin description pin number pin name function m 1en chip enable pin. drive en above 1.5v to turn on the part. drive en below 0.3v to turn it off. do not leave en floating 2v ss analog grou nd pin 3sw power switch output. it is the switch node connection to inductor. this pin connects to the drains of the internal p-ch and n-ch mosfet switches. 4v in power supply input. must be closely decoupled to gnd with a 4.7 f or gre ater ceramic capacitor. 5fb output voltage feedb ack pin. an internal resistive divider divides the output voltage down for comparison to the internal reference voltage. ? absolute maximum ratings(note1) parameter symbol ratings units input voltage v in v ss -0.3~v ss +7.5 v ce,sw,fb/v out voltage v ss -0.3~v in +0.3 v power dissipation s ot23-5 p d 400 mw operating temperature t opr -40~+85 junction temperature t j 150 - storage te mperature t stg -40~+125 soldering te mperature & time t solder 260 , 10s esd hbm(human body mode) - 2 kv esd mm(machine mode) - 200 v leshan radio company , ltd. 2/7
? electrical characteristics LR8503 series (v in =v en =3.6v, v out =1.8v, t a = 25c, unless otherwise noted.) parameter conditions min typ max units input voltage 2.0 6.5 v input dc supply current note 4) v out = 90%, i load =0ma v out = 105%, i load =0ma v en = 0v, v in =4.2v - - - a pwm mode - 140 300 a pfm mode - 20 35 a shutdown mode - 0.1 1.0 a regulated feedback v oltage vfb t a = 25 0.588 0.600 0.612 v t a = 0 ? 0 t a 0 85 ? 0.586 0.600 0.613 v t a = -40 ? 0 t a 0 85 ? 0.585 0.600 0.615 v refere nce v o ltage line regulation v in =2.7v to 5.5v - 0.04 0.40 %/v output voltage line regul atio v in =2.7v to 5.5v 0.04 0.40 % output v o ltage loa d regulation 0.5 % oscillation frequency v out =100% v out =0v 1.5 mhz 300 khz on resistance of pmos i sw =100ma 300 450 m
on resistance of nmos i sw =-100ma 300 450 m
peak current limit v in = 3v, v out =90% 1.5 a turn on dela y time 0.2 ms ovp 7.3 v en "high" voltage (1) v enh 1.5 v in v en "low" voltage (2) v enl 0.4 v en leakage current 0.01 1.0 a sw leakage current v en =0v,v in =v sw =5v 0.01 1.0 a note 1: absolute maximum ratings are those va lues beyo n d which the life of a device may be impaired. note 2: t j is calculated from the am bient temperature t a and power dissipation p d according to the following formula: t j = t a + (p d ) x (250c/w). note 3: 100 % production test at +25c. specifications over the temperature range are guaranteed by design and characterization. note 4: dynamic supply current is higher due to the gate charge being delivered at the switching frequency. leshan radio company, ltd. 3/7
? typical applica tion circuits off on vss fb sw v in vin c in 10 f c1 22pf opt. r1 200k 1% r2 100k 1% v out c out 10 f l 2.2 h en figure1 basic application circuit
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l j f
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p ? typical perform ance characteristics (test figure1 above, unless other wise specified) leshan radio company , ltd. 4/7
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? functional block diagram figure2 block diagram leshan radio company , ltd. 6/7
? pa ckaging information z sot23-5 package outline dimensions symbol dimensions in millimeters dimensions in inches min max min max a 1.050 1.250 0.041 0.049 a1 0.000 0.100 0.000 0.004 a2 1.050 1.150 0.041 0.045 b 0.300 0.500 0.012 0.020 c 0.100 0.200 0.004 0.008 d 2.820 3.020 0.111 0.119 e 1.500 1.700 0.059 0.067 e1 2.650 2.950 0.104 0.116 e 0.950(bsc) 0.037(bsc) e1 1.800 2.000 0.071 0.079 l 0.300 0.600 0.012 0.024 0 e 8 e 0 e 8 e leshan radio company , ltd. leshan radio company , ltd. 7/7
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