mic5255 micrel june 2002 1 mic5255 general descriptionthe mic5255 is an efficient, precise cmos voltage regulator optimized for ultra-low-noise applications. it offers 1% initial accuracy, extremely low dropout voltage (135mv at 150ma) and low ground current (typically 90 a). the mic5255 pro- vides a very low noise output, ideal for rf applications wherea clean voltage source is required. a noise bypass pin is also available for further reduction of output noise. designed specifically for handheld and battery-powered de- vices, the mic5255 provides a ttl-logic-compatible enable pin. when disabled, power consumption drops nearly to zero. the mic5255 also works with low-esr ceramic capacitors, reducing the amount of board space necessary for power applications, critical in hand-held wireless devices. key features include current limit, thermal shutdown, faster transient response, and an active clamp to speed up device turn-off. available in the ittybitty? sot-23-5 package and the new thin sot-23-5, which offers the same footprint as the standard ittybitty? sot-23-5, but only 1mm tall. the mic5255 offers a range of output voltages. typical application c out = 1.0 f c in = 1.0 f ceramic ceramic 152 3 4 c byp = 0.01 f enable shutdown en v out mic5255-x.xbm5 en (pin 3) may be connected directly to in (pin 1). v in ultra-low-noise regulator application mic5255 150ma low noise cap cmos ldo final information features? input voltage range: 2.7v to 6.0v ? thin sot package: 1mm height sot-23-5 ? ultralow output noise: 30 v(rms) ? stability with ceramic output capacitors ? ultralow dropout: 135mv @ 150ma ? high output accuracy: 1.0% initial accuracy2.0% over temperature ? low quiescent current: 90 a ? tight load and line regulation ? ttl-logic-controlled enable input ? zero off-mode current ? thermal shutdown and current limit protection applications? cellular phones and pagers ? cellular accessories ? battery-powered equipment ? laptop, notebook, and palmtop computers ? consumer/personal electronics micrel, inc. ? 1849 fortune drive ? san jose, ca 95131 ? usa ? tel + 1 (408) 944-0800 ? fax + 1 (408) 944-0970 ? http://www.mic rel.com downloaded from: http:///
mic5255 micrel mic5255 2 june 2002 pin configuration in out byp en lwxx 1 345 2 gnd mic5255-x.xbm5 (sot-23-5) pin description pin number pin name pin function 1 in supply input. 2 gnd ground. 3 en enable/shutdown (input): cmos compatible input. logic high = enable; logic low = shutdown. do not leave open. 4 byp reference bypass: connect external 0.01 f c byp 1.0 f capacitor to gnd to reduce output noise. may be left open. 5 out regulator output ordering information part number marking voltage junction temp. range package mic5255-2.5bm5 lw25 2.5v C40 c to +125 c sot-23-5 mic5255-2.6bm5 lw26 2.6v C40 c to +125 c sot-23-5 mic5255-2.7bm5 lw27 2.7v C40 c to +125 c sot-23-5 mic5255-2.8bm5 lw28 2.8v C40 c to +125 c sot-23-5 mic5255-2.85bm5 lw2j 2.85v C40 c to +125 c sot-23-5 mic5255-2.9bm5 lw29 2.9v C40 c to +125 c sot-23-5 mic5255-3.0bm5 lw30 3.0v C40 c to +125 c sot-23-5 mic5255-3.1bm5 lw31 3.1v C40 c to +125 c sot-23-5 mic5255-3.2bm5 lw32 3.2v C40 c to +125 c sot-23-5 mic5255-3.3bm5 lw33 3.3v C40 c to +125 c sot-23-5 mic5255-2.6bd5 nw26 2.6v C40 c to +125 c tsot-23-5 mic5255-3.3bd5 nw33 3.3v C40 c to +125 c tsot-23-5 other voltages available. contact micrel for details. in out byp en nwxx 1 345 2 gnd mic5255-x.xbd5 (tsot-23-5) downloaded from: http:///
mic5255 micrel june 2002 3 mic5255 electrical characteristics v in = v out + 1v, v en = v in; i out = 100 a; t j = 25 c, bold values indicate C40 c t j +125 c; unless noted. symbol parameter conditions min typical max units v o output voltage accuracy i out = 100 a C 11 % C 22 % ? v lnr line regulation v in = v out + 0.1v to 6v 0.02 0.05 %/v ? v ldr load regulation i out = 0.1ma to 150ma, note 5 1.5 2.5 % v in C v out dropout voltage, note 6 i out = 100 a 0.1 5 mv i out = 100ma 90 150 mv i out = 150ma 135 200 mv 250 mv i q quiescent current v en 0.4v (shutdown) 0.2 1 a i gnd ground pin current, note 7 i out = 0ma 90 150 a i out = 150ma 117 a psrr ripple rejection f = 10hz, c out = 1.0 f, c byp = 0.01 f6 0d b f = 100hz, v in = v out +1 60 db f = 10khz, v in = v out +1 50 db i lim current limit v out = 0v 160 425 ma e n output voltage noise c out = 1.0 f, c byp = 0.01 f, 30 v(rms) f = 10hz to 100khz enable input v il enable input logic-low voltage v in = 2.7v to 5.5v, regulator shutdown 0.4 v v ih enable input logic-high voltage v in = 2.7v to 5.5v, regulator enabled 1.6 v i en enable input current v il 0.4v, regulator shutdown 0.01 a v ih 1.6v, regulator enabled 0.01 a shutdown resistance discharge 500 thermal protection thermal shutdown temperature 150 c thermal shutdown hysteresis 10 c note 1. exceeding the absolute maximum rating may damage the device. note 2. the device is not guaranteed to function outside its operating rating. note 3. the maximum allowable power dissipation of any t a (ambient temperature) is p d(max) = t j(max) Ct a / ja . exceeding the maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. the ja of the mic5255-x.xbm5 (all versions) is 235 c/w on a pc board (see thermal considerations section for further details). note 4. devices are esd sensitive. handling precautions recommended. note 5. regulation is measured at constant junction temperature using low duty cycle pulse testing. parts are tested for load regulation in the load range from 0.1ma to 150ma. changes in output voltage due to heating effects are covered by the thermal regulation specification . note 6. dropout voltage is defined as the input to output differential at which the output voltage drops 2% below its nominal value measured at 1v differential. for outputs below 2.7v, dropout voltage is the input-to-output voltage differential with the minimum input voltage 2.7v. minimum input operating voltage is 2.7v. note 7. ground pin current is the regulator quiescent current. the total current drawn from the supply is the sum of the load current plus the ground pin current. absolute maximum ratings (note 1) supply input voltage (v in ) .................................. 0v to +7v enable input voltage (v en ) ................................. 0v to +7v power dissipation (p d ) ............... internally limited, note 3 junction temperature (t j ) ....................... C40 c to +125 c storage temperature ............................... C65 c to +150 c lead temperature (soldering, 5 sec.) ....................... 260 c esd, note 4 .................................................................. 2kv operating ratings (note 2) input voltage (v in ) ......................................... +2.7v to +6v enable input voltage (v en ) .................................. 0v to v in junction temperature (t j ) ....................... C40 c to +125 c thermal resistance sot-23 ( ja ) .....................................................235 c/w downloaded from: http:///
mic5255 micrel mic5255 4 june 2002 typical characteristics 0 10 20 30 40 50 60 70 10 100 1000 10000 100000 1000000 psrr (db) frquency (hz) 100 a* 50ma* 100ma* 150ma* power supply rejection ratio *i load c out = 1 f ceramic 0 10 20 30 40 50 60 70 10 100 1000 10000 100000 1000000 psrr (db) frquency (hz) 100 a* 50ma* 100ma* 150ma* power supply rejection ratio * i load c out = 4.7 f ceramic 0 10 20 30 40 50 60 70 10 100 1000 10000 100000 1000000 psrr (db) frquency (hz) 0 f* 0.01 f* 0.1 f* 1.0 f* power supply rejection ratio * c byp i load = 50ma v in = v out + 0.5v c out = 1 f ceramic 0 10 20 30 40 50 60 70 80 0 200 400 600 800 1000 psrr (db) voltage drop (mv) psrr vs. voltage drop i load = 100 a i load = 150ma c out = 1 f c byp = 0.01 f 100 105 110 115 120 125 130 0.1 1 10 100 1000 ground current ( a) output current (ma) ground pin current v in = v out + 1v 95 97 99 101 103 105 107 109 111 113 115 -40 -20 0 20 40 60 80 100120140 ground current ( a) temperature ( c) ground pin current i load = 100 a 95 100 105 110 115 120 125 -40 -20 0 20 40 60 80 100120140 ground current ( a) temperature ( c) ground pin current i load = 150ma 0 20 40 60 80 100 120 140 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 ground current ( a) input voltage (v) ground pin current i load = 100 a 0 20 40 60 80 100 120 140 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 ground current ( a) input voltage (v) ground pin current i load = 150ma 0 0.5 1 1.5 2 2.5 3 3.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 output voltage (v) input voltage (v) dropout characteristics i load = 150ma i load = 100 a 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 -40 -20 0 20 40 60 80 100120140 dropout voltage (mv) temperature ( c) dropout voltage i load = 100 a 0 10 20 30 40 50 60 70 0 200 400 600 800 1000 psrr (db) voltage drop (mv) psrr vs. voltage drop i load = 100 a i load = 150ma c out = 1 f c byp = 0 downloaded from: http:///
mic5255 micrel june 2002 5 mic5255 0 20 40 60 80 100 120 140 160 180 0 20 40 60 80 100 120 140 160 dropout voltage (mv) output current (ma) dropout voltage t = C 40c t = 25c t = 125c 0 100 200 300 400 500 600 3 3.5 4 4.5 5 5.5 6 short circuit current (ma) input voltage (v) short circuit current 400 410 420 430 440 450 460 470 480 490 500 -40 -20 0 20 40 60 80 100120140 short circuit current (ma) temperature ( c) short circuit current v in = v out + 1v 2.95 2.96 2.97 2.98 2.99 3.00 3.01 3.02 3.03 3.04 3.05 -40 -20 0 20 40 60 80 100120140 output voltage (v) temperature ( c) output voltage vs. temperature i load = 100 a 0.8 0.85 0.9 0.95 1 1.05 1.1 1.15 1.2 1.25 1.3 -40 -20 0 20 40 60 80 100120140 enable threshold voltage (v) temperature ( c) enable threshold vs. temperature i load = 100 a 0 50 100 150 200 250 300 350 400 450 500 100 1000 10000 100000 1000000 time ( s) bypass capacitance (pf) turn-on time vs. bypass capacitance prop delay rise time c in = 1 f ceramic c out = 1 f ceramic i load = 100 a 0 20 40 60 80 100 120 140 160 180 -40 -20 0 20 40 60 80 100120140 dropout voltage (mv) temperature ( c) dropout voltage i load = 150ma downloaded from: http:///
mic5255 micrel mic5255 6 june 2002 c in = 1 f ceramic c out = 1 f ceramic c byp = 0.01 f i out = 100 a line transient response time (400 s/div) output voltage (50mv/div) input voltage (1v/div) 4v 5v c in = 1 f ceramic c out = 1 f ceramic c byp = 0.01 f v in = 4v 100 a 150ma load transient response time (4 s/div) output current (100ma/div) output voltage (50mv/div) c in = 1 f ceramic c out = 1 f ceramic c byp = 0.01 f v in = 4v shutdown delay time (400 s/div) output voltage (1v/div) enable voltage (1v/div) c in = 1 f ceramic c out = 1 f ceramic c byp = 0.01 f i out = 100 a enable pin delay time (10 s/div) output voltage (1v/div) enable voltage (1v/div) downloaded from: http:///
mic5255 micrel june 2002 7 mic5255 block diagram reference voltage startup/ shutdown control en quickstart/ noise cancellation under- voltage lockout thermal sensor in fault error amplifier current amplifier gnd bypout active shutdown downloaded from: http:///
mic5255 micrel mic5255 8 june 2002 applications informationenable/shutdown the mic5255 comes with an active-high enable pin that allows the regulator to be disabled. forcing the enable pin low disables the regulator and sends it into a zero off-mode- current state. in this state, current consumed by the regulatorgoes nearly to zero. forcing the enable pin high enables the output voltage. this part is cmos and the enable pin cannot be left floating; a floating enable pin may cause an indetermi- nate state on the output. input capacitor the mic5255 is a high performance, high bandwidth device. therefore, it requires a well-bypassed input supply for opti- mal performance. a 1 f capacitor is required from the input to ground to provide stability. low-esr ceramic capacitorsprovide optimal performance at a minimum of space. addi- tional high-frequency capacitors, such as small valued npo dielectric type capacitors, help filter out high frequency noise and are good practice in any rf based circuit. output capacitor the mic5255 requires an output capacitor for stability. the design requires 1 f or greater on the output to maintain stability. the design is optimized for use with low-esrceramic chip capacitors. high esr capacitors may cause high frequency oscillation. the maximum recommended esr is 300m . the output capacitor can be increased, but performance has been optimized for a 1 f ceramic output capacitor and does not improve significantly with largercapacitance. x7r/x5r dielectric-type ceramic capacitors are recom- mended because of their temperature performance. x7r- type capacitors change capacitance by 15% over their oper- ating temperature range and are the most stable type of ceramic capacitors. z5u and y5v dielectric capacitors change value by as much as 50% and 60% respectively over their operating temperature ranges. to use a ceramic chip capaci- tor with y5v dielectric, the value must be much higher than an x7r ceramic capacitor to ensure the same minimum capaci- tance over the equivalent operating temperature range. bypass capacitor a capacitor can be placed from the noise bypass pin to ground to reduce output voltage noise. the capacitor by- passes the internal reference. a 0.01 f capacitor is recom- mended for applications that require low-noise outputs. thebypass capacitor can be increased, further reducing noise and improving psrr. turn-on time increases slightly with respect to bypass capacitance. a unique quick-start circuit allows the mic5255 to drive a large capacitor on the bypass pin without significantly slowing turn-on time. refer to the typical characteristics section for performance with different bypass capacitors. active shutdown the mic5255 also features an active shutdown clamp, which is an n-channel mosfet that turns on when the device is disabled. this allows the output capacitor and load to dis- charge, de-energizing the load. no-load stabilitythe mic5255 will remain stable and in regulation with no load unlike many other voltage regulators. this is especially important in cmos ram keep-alive applications. thermal considerations the mic5255 is designed to provide 150ma of continuous current in a very small package. maximum power dissipation can be calculated based on the output current and the voltage drop across the part. to determine the maximum power dissipation of the package, use the junction-to-ambient ther- mal resistance of the device and the following basic equation: p tt d(max) j(max) a ja = ? ?? ? ?? ? t j(max) is the maximum junction temperature of the die, 125 c, and t a is the ambient operating temperature. ja is layout dependent; table 1 shows examples of junction-to-ambient thermal resistance for the mic5255. package ja recommended ja 1" square jc minimum footprint copper clad sot-23-5 235 c/w 185 c/w 145 c/w (m5 or d5) table 1. sot-23-5 thermal resistance the actual power dissipation of the regulator circuit can bedetermined using the equation: p d = (v in C v out ) i out + v in i gnd substituting p d(max) for p d and solving for the operating conditions that are critical to the application will give themaximum operating conditions for the regulator circuit. for example, when operating the mic5255-3.0bm5 at 50 c with a minimum footprint layout, the maximum input voltage for aset output current can be determined as follows: p 125 c 50 c 235 c/w d(max) = ? ?? ? ?? ? p d(max) = 315mw the junction-to-ambient thermal resistance for the minimumfootprint is 235 c/w, from table 1. the maximum power dissipation must not be exceeded for proper operation. usingthe output voltage of 3.0v and an output current of 150ma, the maximum input voltage can be determined. because this device is cmos and the ground current is typically 100 a over the load range, the power dissipation contributed by the ground current is < 1% and can be ignored for this calculation. 315mw = (v in C 3.0v) 150ma 315mw = v in 150ma C 450mw 810mw = v in 150ma v in(max) = 5.4v therefore, a 3.0v application at 150ma of output current canaccept a maximum input voltage of 5.4v in a sot-23-5 package. for a full discussion of heat sinking and thermal effects on voltage regulators, refer to the regulator thermals section of micrel s designing with low-dropout voltage regu- lators handbook. downloaded from: http:///
mic5255 micrel june 2002 9 mic5255 package information 0.20 (0.008)0.09 (0.004) 0.60 (0.024)0.10 (0.004) 3.02 (0.119)2.80 (0.110) 10 0 3.00 (0.118)2.60 (0.102) 1.75 (0.069)1.50 (0.059) 0.95 (0.037) ref 1.30 (0.051)0.90 (0.035) 0.15 (0.006)0.00 (0.000) dimensions: mm (inch) 0.50 (0.020)0.35 (0.014) 1.90 (0.075) ref sot-23-5 (m5) 1.90bsc 1.90bsc 1.90bsc 1.60bsc 1.60bsc dimensions: millimeter 2.90bsc 0.100.01 0.200.12 0.300.50 0.300.45 0.900.80 1.000.90 tsot-23-5 (d5) micrel, inc. 1849 fortune drive san jose, ca 95131 usa tel + 1 (408) 944-0800 fax + 1 (408) 944-0970 web http://www.micrel.com this information is believed to be accurate and reliable, however no responsibility is assumed by micrel for its use nor for any infringement of patents or other rights of third parties resulting from its use. no license is granted by implication or otherwise under any patent or patent right of micrel, inc. ? 2002 micrel, incorporated downloaded from: http:///
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