unisonic technologies co., ltd uc3380 cmos ic www.unisonic.com.tw 1 of 9 copyright ? 2010 unisonic technologies co., ltd qw-r502-099.c pwm step up dc-dc controller ? description the uc3380 is pwm step up dc-dc switching controller that operates from 0.9v. the low start up input voltage makes uc3380 specially designed for powering portable equipment from one or two cells battery packs. this device consist of a soft start circuit, a reference voltage source, an error amplifier, an oscillator, a phase compensation, a pwm controller and an output drive ci rcuit for driving external power transistor. additionally, a chip enable feature is provided to power down the converter for extended battery life. the device features a voltage mode pwm control loop, providing stable a nd high efficiency operation over a broad load current range. ? features * 0.9v low start-up input voltage at 1ma load * low operation current * 0.5ua low shutdown current * fix frequency pwm at 100khz * built in pwm switching contro l circuit ,duty ratio is 0~83% * output voltage:0.1v step setting is available between 2.0v and 6.5v * soft start time: 6ms * shutdown function ? applications *portable devices *electronic games *portable audio (mp3) *personal digital assistant (pda) *digital still cameras(dsc) *camcorders *white led driver *single and dual-cell battery operated products ? ordering information ordering number lead free halogen free package packing uc3380l-xx-af5-r UC3380G-XX-AF5-R sot-25 tape reel
uc3380 cmos ic unisonic technologies co., ltd 2 of 9 www.unisonic.com.tw qw-r502-099.c ? marking information package voltage code marking sot-25 18:1.8v 21:2.1v 25:2.5v 27:2.7v 30:3.0v 33:3.3v 40:4.0v 50:5.0v ? pin description pin no name description 1 shutdown shutdown control input, ?h? : normal operation ?l? : stop step up( whole circuit stop). 2 v out power supply and voltage output. 3 nc no connection. 4 v ss ground. 5 ext switching the circuit by connecting to a transistor.
uc3380 cmos ic unisonic technologies co., ltd 3 of 9 www.unisonic.com.tw qw-r502-099.c ? block diagram
uc3380 cmos ic unisonic technologies co., ltd 4 of 9 www.unisonic.com.tw qw-r502-099.c ? absolute maximum ratings parameter symbol ratings unit v out pin voltage v out 12 v shutdown pin voltage v shutdown v ss -0.3~12 v ext pin voltage v ext -0.3~ v out +0.3 v ext pin current i ext 80 ma power dissipation p d 250 mw operating ambient temperature t opr -40~+85 c storage temperature t stg -40~ +125 c note: absolute maximum ratings are those values bey ond which the device could be permanently damaged. absolute maximum ratings are stress ratings only and functional device oper ation is not implied. ? electrical characteristics refer to the test circuit, t opr =25oc , v in =v out (s)*0.6, i out =v out (s)/50 , unless otherwise specified. parameter symbol test circuit test condition min typ max unit total device output voltage v out 2 v out (s)*0.976 v out (s) v out (s)*1.024 v supply current 1 i s1 1 v out =v out (s)*0.95 39.8 66.4 ua supply current 2 i s2 1 v out =v in (s)+0.5v 6.3 12.5 ua input voltage v in 2 10 v operation holding voltage v hold 2 measured by decreasing v in voltage gradually, when i out =1ma. 0.7 v operation start voltage v st1 2 i out =1ma 0.9 v oscillation start voltage v st2 1 increase the v in until ext pin output the oscillating signal 0.8 v oscillation frequency f osc 1 v out =v out (s)*0.95 85 100 115 khz duty ratio duty 1 v out =v out (s)*0.95 75 83 90 % line regulation S lnr 2 vin=v out (s)*0.4 to *0.6 30 60 mv load regulation S ldr 2 i out =10ua to v out (s)/50*1.25 30 60 mv temperature coefficient e t 2 S v out /( S t opr *v out ) t opr =-40c to +85c 50 ppm/ c efficiency e f 2 86 % soft start time ts 2 3.0 6.0 12.0 ms shutdown shutdown supply current i ss 1 v shutdown =0 0.5 ua i sh v shutdown =v out (s)*0.95 0.1 ua shutdown pin input current i sl 1 v shutdown =0 -0.1 ua v ih shutdown pin ?l? to ?h? until ext output oscillating signal 0.75 v v il1 v out 1.5v 0.3 v shutdown pin input voltage threshold v il2 1 shutdown pin ?h? to ?l? until ext output oscillating signal v out < 1.5v 0.2 v ext i exth 1 v ext =v out (s) -0.4v -16.1 -32.3 ma ext pin current i extl 1 v ext = 0.4v 27.4 54.8 ma note: v out (s) is the value of the set output voltage.
uc3380 cmos ic unisonic technologies co., ltd 5 of 9 www.unisonic.com.tw qw-r502-099.c ? application circuit ? test circuit 1. 2.
uc3380 cmos ic unisonic technologies co., ltd 6 of 9 www.unisonic.com.tw qw-r502-099.c ? application circuit information the following equations show the relati on of the basic desig n parameters. 1. refer to the application circuit, the increasing inductor current when the switch is turn on is given by the following equation 11 () llonins d iut uu ll f + = = ? ( in u :input voltage ; s u :transistor saturation voltage) the decreasing inductor current when the switch is turn off can derive by the equation below 11 1 () lloff odin d iut uuu ll f ? ? = =? + ? d u diode forward voltage according to 0 ll ii +? += ,the duty ratio is given by odin ods uuu d uuu +? = +? 2. the average current flowing through the inductor is 1 o l i i d = ? 3. we note that (1 ) ol i di =? then we can write: (1 ) l ol l i i di i =? ? substituting 1 lloff iut l = l i for equation above, output current is given by 11 (1 ) oloff i dut icr l =? ? ? ( i cr = l l i i ) 11 1 (1 ) ( ) odin d id uouu i cr l f ? =? ? ? + ? derive that 4. the peak current of the inductor is given by 1 2 p kl l i ii =+ 1 2 l p kl l l i i ii i =+ ? according to i cr = l l i i derive that 1 2 p kl l i iicri =+ ? then derive the following equation for peak current of inductor 1 (1 ) 2 pk l i iicr =+
uc3380 cmos ic unisonic technologies co., ltd 7 of 9 www.unisonic.com.tw qw-r502-099.c ? application circuit information (cont.) 5. charge stores in c3 during charging up is given by coff qi t =? we can write 1 () lo d qii f ? = ? ? 6. output ripple voltage is given by () p pc lo vuesrii = + ? ? (esr: equivalent series resistance of the output capacitor) () p plo q vesrii c =+ ?? then we give the following example about choosing exte rnal components by considering the design parameters. design parameters: in u =1.5v uo =2.1v o i =200ma p p v =100mv f=300khz icr=0.2 assume d u and s u are both 0.3v, the duty ratio is 2.1 0.3 1.5 0.429 2.1 0.3 0.3 odin ods uuu d uuu +? +? === +? +? in order to generate the desired output current and icr, the value of inductor should meets the following formula l (1 ? d ) 2 ( u o +u d -u in ) icr ? i o ? f = (1 ? 0.429 ) 2 ( 2.1v+0.3v-1.5v ) 0.20.2 a 300000 hz = 24.5 uh calculate the average current and the peak current of inductor 0.2 0.35 1 1 0.429 o l i a i a d == = ?? 11 (1 ) 0.35 (1 0.2) 0.385 22 pk l i iicr a a =+ = += so, we make a trial of choosing a 22uh inductor t hat allowable maximum current is lager than 0.385a. determine the delta charge stores in c3 during charging up 1 1 0.429 ( ) (0.35 0.2 ) 0.286 300000 lo d qii a a uc fhz ?? = ? ? = ? = assume the esr of c3 is 0.15 ? , determine the value of c3 6 0.286 10 3.69 ( ) 0.1 0.15 (0.35 0.2 ) pp l o qc cuf vesrii a a ? ? = = ??? ?? ? therefore, a tantalum capacitor with value of 10uf and esr of 0.15 ? can be used as output capacitor. however, the optimized value should be obtained by experiment.
uc3380 cmos ic unisonic technologies co., ltd 8 of 9 www.unisonic.com.tw qw-r502-099.c ? external components 1. diode (d1) the diode is the largest source of loss in dc-dc conver ters. the most important par ameters which affect the efficiency are the forward voltage drop d u and the reverse recovery time. the forward voltage drop creates a loss just by having a voltage across the dev ice while a current flowing through it. the reverse recovery time generates a loss when the diode is reverse biased, and the current appears to actually flow backwards through the diode due to the minority carriers being swept from the p-n junction. a schottky diode with the following characteristics is recommended: *low forward voltage: 0.3 d uv < *fast reverse recovery time/switchi ng speed: 50 ns *rated current: p k i > *reverse voltage: od uu + 2. inductor (l1) low inductance values supply higher output current, but also increase the ripple and reduce efficiency. choose a low dc-resistance inductor to minimize loss. it is necessary to choose an inductor with saturation current greater than the peak current that the inductor will encounter in the application. saturati on occurs when the inductor?s magnetic flux density reaches the maximum level the core can support and inductance falls. 3. capacitor (c1, c3) the input capacitor c1 improves the efficiency by re ducing the power impedance and stabilizing the input current. select a c1 value according to the impedance of the power supply used. small equivalent series resistance (esr) tantalum or ceramic capacitor with an appropriate value should be suitable the output capacitor is used for smoot hing the output voltage and sustaining t he output voltage when the switch is on. select an appropriate capacitor depending on the ripple volt age that increases in case of a higher output voltage or a higher load current. the capacitor value should be 10uf minimum. small esr should be used to reduce output ripple voltage. however, the best esr may depend on l, capacitance, wiring and applications (output load). therefore, fully evaluate esr under an act ual condition to determine the best value. 4. external transistor (q1 r1 c2) an enhancement n-channel mosfet or a bipolar npn transi stor can be used as the external switch transistor. *bipolar npn transistor the h fe value of npn transistor and the r1 value determi ne the driving capacity to increase the output current using a bipolar transistor. 1k ? is recommended for r1. r1 is selected from the following calculation. calculate the necessary base current (ib) from the bipolar transistor h fe using p k b fe i i h = 0.7 0.4 1 || bexth vout r ii ? =?
uc3380 cmos ic unisonic technologies co., ltd 9 of 9 www.unisonic.com.tw qw-r502-099.c ? external components(cont.) since the pulse current flows through the transistor , the exact rb value should be finely tuned by the experiment. generally, a small rb value can increase the output current capability, but the efficiency will decrease due to more energy is used to drive the transistor. moreover, a speed up capacitor, c2, should be connected in parallel with r1 to reduce switching loss and improve efficiency. c2 can be calculated by the equation below: 1 2 21 0.7 osc c rf it is due to the variation in the characteristics of t he transistor used. the calculated value should be used as the initial test value and the optimized value should be obtained by the experiment. *enhancement mos fet for enhancement n-channel mosfet, since enhancement mosf et is a voltage driven, it is a more efficient switch than a bjt transistor. however, the mosfet requires a higher voltage to turn on as compared with bjt transistors. an enhancement n-channel mosfet c an be selected by the following guidelines: - input capacitance less than 700pf. - low gate threshold voltage. - low on-resistance. - the allowable maximum current of drain shoul d be larger than peak current of inductor. utc assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all utc products described or contained herein. utc products are not designed for use in life support appliances, devices or systems where malfunction of these products can be reasonably expected to result in personal injury. reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. the information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice.
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