mic5249 300ma cap ldo with programmable power-on reset delay micrel inc. ? 2180 fortune drive ? san jose, ca 95131 ? usa ? te l +1 (408) 944-0800 ? fax + 1 (408) 474-1000 ? http://www.micre l.com september 2006 1 m9999-090806 general description the mic5249 is an efficient, precise 300ma cmos voltage regulator with power-on reset delay which can be implemented via an external capacitor. it offers 1% initial accuracy, extremely-low-dropout voltage (typically 400mv @ 300ma), and low ground current (typically 85ma) over load. designed specifically for noise-critical applications in hand- held or battery-powered devices, the mic5249 comes equipped with a noise reduction feature to filter the output noise via an external capacit or. other features of the mic5249 include a logic compatible enable pin, current limit, thermal shutdown, ultra-fast transient response, and an active clamp to speed up device turnoff. the mic5249 also works with low-esr ceramic capacitors, reducing the amount of board space necessary for power applications, critical in hand-held wireless devices. the mic5249 is available in the msop-8 package. data sheets and support doc umentation can be found on micrel?s web site at www.micrel.com. features ? 300ma output current ? high psrr: 65db@120hz ? stable with ceramic output capacitor ? power-on reset output with adjustable delay time ? high output accuracy: ? 1.0% initial accuracy ? 3.0% over temperature ? low dropout voltage of 400mv @ 300ma ? low quiescent current: 85a ? zero current shutdown mode ? thermal shutdown protection ? current-limit protection ? tiny msop-8 package applications ? cellular phones ? pdas ? fiber optic modules typical application ultra-low noise application
micrel, inc. mic5249 september 2006 2 m9999-090806 ordering information part number standard pb-free voltage* junction temperature range package mic5249-1.8bmm mic5249-1.8ymm 1. 8v ?40c to +125c 8-pin msop mic5249-2.5bmm mic5249-2.5ymm 2. 5v ?40c to +125c 8-pin msop mic5249-2.6bmm mic5249-2.6ymm 2. 8v ?40c to +125c 8-pin msop mic5249-2.8bmm mic5249-2.8ymm 2. 8v ?40c to +125c 8-pin msop mic5249-2.85bmm mic5249-2.85ymm 2.85v ?40c to +125c 8-pin msop mic5249-3.0bmm mic5249-3.0ymm 3. 0v ?40c to +125c 8-pin msop mic5249-3.3bmm mic5249-3.3ymm 3. 3v ?40c to +125c 8-pin msop note : other voltage available. cont act micrel marketing for details. pin configuration 1 cbyp delay gnd vin 8 enable reset nc vout 7 6 5 2 3 4 8-pin msop (mm) pin description pin number pin name pin function 1 cbyp reference bypass: connect external 0.01f capacitor to gnd to reduce output noise. may be left open. 2 delay delay set input: connect external capacitor to gnd to set the delay of the error flag. 3 gnd ground. 4 vin supply input. 5 vout regulator output. 6 nc no connect. 7 reset reset output: open-drain output. acti ve low indicates an output undervoltage condition. 8 enable enable input: cmos compatible input. logic high = enable; logic low = shutdown. do not leave open.
micrel, inc. mic5249 september 2006 3 m9999-090806 absolute maximum ratings (1) supply voltage (v in ) ............................................. 0v to +7v power dissipation (p d ). .......................... inte rnally limited (3) junction temperature (t j ) ........................?40c to +125c lead temperature (solde ring, 5sec .) ......................... 260c storage temperature (t s ) .........................?65c to +150c eds rating (4) operating ratings (2) supply voltage (v in ) ........................................ +2.7v to +6v enable voltage (v en ).............................................. 0v to v in junction temperature (t j ) ........................ ?40c to +125c package thermal resistance msop ( ja )......................................................200 c/w electrical characteristics v in = v out + 1v; c out =1f, i out = 100a; t j = 25c, bold values indicate ?40c to +125c, unless noted. parameter condition min typ max units output voltage accuracy variation from nominal v out ?1.0 ?3.0 +1.0 +3.0 % % line regulation v in = v out +1v to 6v ?0.3 0.02 +0.3 %/v load regulation i out = 0.1ma to 300ma 1.5 3.0 % i out = 100a 1 mv i out = 150ma 160 225 275 mv mv dropout voltage i out = 300ma 340 500 600 mv mv i out = 0ma 85 150 a ground pin current i out = 300ma 100 200 a ground pin current in shutdown v en < 0.4v (regulator off) 0.35 1 a ripple rejection f = 120hz, c out = 2.2f 65 db current limit v out = 0v 300 440 ma enable input logic low (regulator shutdown) 0.4 v enable input voltage logic high (regulator enabled) 1.6 v v il < 0.4v (regulator shutdown) 0.01 a enable input current v ih > 1.6v (regulator enabled) 0.01 a delay input delay pin current source 0.55 1 a delay pin threshold voltage threshold for reset = logic high 1.40 v reset output low threshold, % of v out (flag on) 89 91 % v th high threshold, % of v out (flag off) 93 96 % v ol reset output logic ? low voltage; i reset = 100a output in fault condition 0.020 0.1 v i reset flag leakage current, flag off 0.01 a notes: 1. exceeding the absolute maximum rating may damage the device. 2. the device is not guaranteed to function outside its operating rating. 3. the maximum allowable power dissipation of any t a (ambient temperature) is p d(max) = t j(max) ? t a ) ja . exceeding the maximum allowable power dissipation will result in excessive die temper ature, and the regulator will go into thermal shutdown. 4. devices are esd sensitive. handling precautions re commended. human body model, 1.5k in series with 100pf.
micrel, inc. mic5249 september 2006 4 m9999-090806 functional diagram
micrel, inc. mic5249 september 2006 5 m9999-090806 application information enable/shutdown the mic5249 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 th is state, current consumed by the regulator goes 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 indeterminate state on the output. input capacitor the mic5249 is a high performance, high bandwidth device. therefore, it requ ires a well-bypassed input supply for optimal performance. a 1.0f capacitor is required from the input to ground to provide stability. low-esr ceramic capacitors provide optimal perform- ance at a minimum of space. additional high-frequency capacitors such as small valued npo dielectric type capacitors help to filter out high frequency noise and are good practice in any rf-based circuit. output capacitor the mic5249 require s an output capacitor for stability. the design requires 2.2f or greater on the output to maintain stability. the design is optimized for use with low-esr ceramic 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 2.2f ceramic output capacitor and does not improve significantly with larger capacitance. x7r/x5r dielectric-type ceramic capacitors are recom- mended because of their temperature performance. x7r-type capacitors change c apacitance by 15% over their operating 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 t heir operating temperature ranges. to use a ceramic chip capacitor with y5v dielectric, the value must be much higher than anx7r ceramic capacitor to ensure the same minimum capacitance over the equiva lent operating temperature range. delay pin input the power-on reset function can be implemented on the mic5249 by adding an external capacitor from the delay pinto ground. this external capacitor sets the delay time (tdelay) of the reset output. the capacitor value required can be easily calculated using the formula: ? ? ? ? ? ? ? ? = delay delay delay delay v i t c where idelay is 0.55a and the vdelay is 1.4v. when no capacitor is used, there will be no delay and the por output acts like a standard error flag output. reset output the reset output of the mi c5249 provides the power- on reset signal based on the capacitor from the delay pin to ground when input power is applied to the regulator. the reset signal stays low for a preset time period after power is applied to the regulator, and then goes high (see ?timing diagram?). the reset output is an active-low, open-drain output that drives low when a fault c ondition and an undervoltage detection occurs. internal circuitry intelligently monitors overcurrent, overtemperature and dropout conditions and ors these outputs together to indicate some fault condition. the output of that or gate is anded with an output voltage monitor that detects an undervoltage condition. the output drives an open-drain transistor to indicate a fault. this prevents chattering or inadvertent triggering of the reset. there set must be pulled up using a resistor form the reset pin to either the input or the output. bypass pin input a bypass capacitor is required from the noise bypass pin to ground to reduce output voltage noise. the capacitor bypasses the internal referenc e. a 0.01f capacitor is recommended for applications that require low-noise outputs. the bypass ca pacitor can be increased, further reducing noise and improving psrr. turn-on time increases slightly with respect to bypass capacitance. a unique quick-start circuit allo ws the mic5249 to drive a large capacitor on the bypass pin without significantly slowing the turn-on time. active shutdown the mic5249 also features an active shutdown clamp, which is a n-channel mosfet that turns on when the device is disabled. this allo ws the output capacitor and load to discharge, de-energizing the load. no-load stability the mic5249 will remain stable and in regulation with no load unlike many other volt age regulators. this is especially important in cmos ram keep-alive application.
micrel, inc. mic5249 september 2006 6 m9999-090806 thermal consideration the mic5249 is designed to provide 300ma of continuous current in a very small package. maximum power dissipation can be calc ulated based on the output current and the voltage drop across the device. to determine the maximum power dissipation of the package, use the junction-to- ambient thermal resistance of the device and the fo llowing basic equation: ? ? ? ? ? ? ? ? ? = ja a j(max) d(max) t t p t j(max) is the maximum junction temperature of the die, 125c and t a is the ambient operating temperature. ja is layout dependent; table 1 shows examples of the junction-to-ambient thermal re sistance for the mic5249. package ja recommended minimum footprint msop-8 200c/w table 1. msop-8 thermal resistance the actual power dissipation of the regulator circuit can be determined using the equation: p d = (v in ? 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 the maximum operating conditions for the regulator circuit. for example, when operati ng the mic5249-3.0bmm at 50c with a minimum footprint layout, the maximum input voltage for a set output current can be determined as follows: ? ? ? ? ? ? ? = c/w 200 c 50 c 125 p d(max) the junction-to-ambient thermal resistance for the minimum footprint is 200c/w, from table 1. the maximum power dissipation must not be exceeded for proper operation. using the output voltage of 3.0v, and an output current of 300ma, the maximum input voltage can be determined. because this device is cmos and the ground current is typically 90a over the load range, the power dissipation contri buted by the ground current is < 1.0% and can be ignored for this calculation. 375mw = (v in ? 3.0v) 300ma 375mw = v in 300ma ? 900mw 1275mw = v in 300ma v in(max) = 4.25v therefore, a 3.0v applicati on at 300ma of output current can accept a maximum input voltage of 4.25v in the msop-8 package. for a full discussion of heat sinking and thermal effects on the voltage regulators, refer to the ?regulator thermals? section of micrel?s designing with low-dropout voltage regulators handbook .
micrel, inc. mic5249 september 2006 7 m9999-090806 package information 8-pin msop (mm) micrel, inc. 2180 fortune drive san jose, ca 95131 usa tel +1 (408) 944-0800 fax +1 (408) 474-1000 web http:/www.micrel.com the information furnished by micrel in this data sheet is belie ved to be accurate and reliable. however, no responsibility is a ssumed by micrel for its use. micrel reserves the right to change circuitry and specifications at any time without notification to the customer. micrel products are not designed or authori zed for use as components in life support app liances, devices or systems where malfu nction of a product can reasonably be expected to result in personal injury. life suppo rt devices or systems are devices or systems that (a) are in tended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significan t injury to the user. a purchaser?s use or sale of micrel produc ts for use in life support app liances, devices or systems is a purchaser?s own risk and purchaser agrees to fully indemnify micrel for any damages resulting from such use or sale. ? 2002 micrel, incorporated.
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