300ma cmos l.d.o. regulator lm1108 features extremel y low su pp l y current ( 50 a,t yp . ) ver y low dro p out volta ge 300ma out p ut current com p atible with mlcc hi g h out p ut volta g e accurac y +/- 1.4 % standardor custom out p ut volta g e s over currentand over tem p erature protection small in p ut/out p ut differential : 0.3v for full load moisture sensitivit y level 3 application s batter y o p erated s y stems portable com p uters portable cameras and video recorder s medical instruments instrumentation ordering information cellular/gsm/phs phones linear post-re g ulators for smps pa g er s ( "x.x" = output voltage = 1.5, 1.8, 2.5, 3.0, 3.3, 3.6, 5.0 ) description typical application circui t nov. 2010 - rev. 1.3.1 htc -1 - package sot-89 sot-23 5l marking 1108 x.x hxx bxx hxx hgxx sot-23 3l device lm1108f-x.x lm1108sf5-x.x lm1108bsf-x.x (b type) lm1108sf-x.x (a type) LM1108GSF-x.x (h/f) the lm1108 is a fixed output,high accuracy(typically 0.5%) cmos low drop-out regulator. total supply current is typically 50a at full load (20 to 60 times lower than in bipolar regulators). lm1108 key features include ultra low noise operation, very low dropout voltage (typically 240mv at full load), and fast response to step changes in load. the lm1108 in corporates both over temperature and over current protection. the lm1108 is stable with an output capacitor of only1f and has a maximum out put current of 300ma. it is available in a sot-23 & sot-89 package sot-23-5l ( sot-25 ) sot-89 1. gnd 2. vin 3. vout 4. nc 5. n c sot-23 ( 2.92*1.60*1.10 ) 1. gnd 2. vin 3. vout [a type] 1. vin 2. vout 3. gnd [b type] 1. gnd 2. vin 3. vout 1 3 2 1 2 3 4 5 1 2 3
300ma cmos l.d.o. regulator lm1108 absolute maximum rating electrical characteristic s note.1 : load regulation is measured using pulse techniques with duty cycle<5% htc - 2 - characteristic symbol value unit supply voltage output current v 260 vin +6.5 c 500 230 iout 300 ma v c operating ambient temperature topr -40 ~ +85 c storage temperature tstg -40 ~ +125 lead temperature (soldering, 5 sec) output voltage vout vss-0.3 to vin+0.3 mw sot89 pkg total power dissipation sot23 pkg pd %
300ma cmos l.d.o. regulator lm1108 detail descri p tion htc - 3 - - the lm1108 is aprecision, fixed output ldo. un like bipolar regulators, the lm1108?s supply current does not increase with load current. in addition,v out remains stable and with in regulation over theen tire 0ma to i out max operating load current range, (an important consideration in rtc and cmos ram battery back-up applications). figure3-1shows a typical application circuit. 1. output capacitor 1uf(min) capacitor from v out to ground is required. the output capacitor should have an effective series resistance greater than 0.1 ? and less than .0 ? . 1uf capacitor should be connected from v in to gnd if there is more than 10 inches of wire between the regulator and the ac filter capacitor or if a battery is used as the power source. aluminum electrolytic or tantalum capacitor types can be used. (since many aluminum electrolytic capacitors freeze at approximately -30c, solid tantalums are recommended for applications operating below -25c) when operating from sources other than batteries,supply-noise rejection and transient response can be improved by increasing the value of the input and output capacitors and employing passive filtering techniques. 2. thermal considerations 2.1 thermal shutdown integrated thermal protection circuitry shuts the regulator off when die temperature exceeds150c. the regulator remains off until the die temperature drops to approximately 140c. 2.2 power dissipation the amount of power the regulator dissipate is primarily a function of input and output voltage, and output current. the following equation is used to calculate worst case actual power dissipation: equation 2-1: table 2-1 : the maximum allowable power dissipation (equation 2-2) is a function of the maximum ambient temperature (t amax ), the maximum allowable die temperature (t jmax ) and the thermal resistance from junction-to-air( ja).
300ma cmos l.d.o. regulator lm1108 htc - 4 - equation 2-2: table 2-1 shows various values of ja for the lm1108 versus board copper area. table 2-1 : thermal resistance guidelines for lm1108 equation 2-1can be used in conjunction with equation 2-2 to ensure regulator thermal operation is within limits. for example: in this example, the lm1108 dissipates a maximum of 260mw; below the allow able limit of 508 mw. in a similar manner, equation 2-1 and equation 2-2 can be used to calculate maximum current and/or input voltage limits. for example, the maximum allowable v in , is found by sustituting the maximum allowable power dissipation of 508 mw into equation 2-1, from which v inmax = 4.6v.
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