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mic3775 750ma cap low-voltage low-dropout regulator powerpc is a trademark of ibm corp. super eta pnp is a registered trademark of micrel, inc. micrel inc. 2180 fortune drive san jose, ca 95131 usa tel +1 ( 408 ) 944-0800 fax + 1 (408) 474-1000 http://www.micrel.com december 2006 1 m9999-121906 general description the mic3775 is a 750ma low-dropout linear voltage regulators that provides low- voltage, high-current output from an extremely small package. utilizing micrels proprietary super eta pnp ? pass element, the mic3775 offers extremely low-dropout (typically 280mv at 750ma) and low ground current (typically 7.5ma at 750ma). the mic3775 is ideal for pc add-in cards that need to convert from standard 5v to 3.3v or 3.0v, 3.3v to 2.5v or 2.5v to 1.8vor 1.65v. a guaranteed maximum dropout voltage of 500mv over all operating conditions allows the mic3775 to provide 2.5v from a supply as low as 3.0v and 1.8v or 1.5v from a supply as low as 2.25v. the mic3775 is fully protected with overcurrent limiting, thermal shutdown, and reversed-leakage protection. fixed and adjustable output voltage options are available with an operating temperature range of C40c to +125c. data sheets and support doc umentation can be found on micrels web site at www.micrel.com. features ? fixed and adjustable output voltages to 1.24v ? 280mv typical dropout at 750ma C ideal for 3.0v to 2.5v conversion C ideal for 2.5v to 1.8v or 1.65v conversion ? stable with ceramic capacitor ? 750ma minimum guaranteed output current ? 1% initial accuracy ? low ground current ? current limiting and thermal shutdown ? reversed-leakage protection ? fast transient response ? low-profile power msop-8 package applications ? fiber optic modules ? ldo linear regulator for pc add-in cards ? powerpc? power supplies ? high-efficiency linear power supplies ? smps post regulator ? multimedia and pc processor supplies ? battery chargers ? low-voltage microcontro llers and digital logic ___________________________________________________________________________________________________________ typical application 1.25v/750ma adjustable regulator downloaded from: http:///
micrel, inc. mic3775 december 2006 2 m9999-121906 ordering information part number standard pb-free voltage junction temp. range package mic3775-1.5bmm mic3775-1.5ymm 1. 5v C40 to +125c 8-pin msop mic3775-1.65bmm mic3775-1.65ymm 1.65v C40 to +125c 8-pin msop mic3775-1.8bmm mic3775-1.8ymm 1. 8v C40 to +125c 8-pin msop mic3775-2.5bmm mic3775-2.5ymm 2. 5v C40 to +125c 8-pin msop mic3775-3.0bmm mic3775-3.0ymm 3. 0v C40 to +125c 8-pin msop mic3775-3.3bmm mic3775-3.3ymm 3. 3v C40 to +125c 8-pin msop mic3775bmm mic3775ymm adj. C40 to +125c 8-pin msop note : for other voltages. contact micrel marketing for details. pin configuration mic3775-x.x (fixed) 8-pin msop (mm) mic3775 (adjustable) 8-pin msop (mm) pin description pin number pin name pin function 1 en enable (input): cmos-compatible cont rol input. logic high = enable, logic low or open = shutdown. 2 in supply (input). flg flag (output): open-collector error flag output. active low = output under- voltage. 3 adj adjustment input: feedback input. connect to resistive voltage-divider network. 4 out regulator output. 5 C 8 gnd ground. downloaded from: http:///
micrel, inc. mic3775 december 2006 3 m9999-121906 absolute maximum ratings (1) supply voltage (v in ) ......................................................6.5v enable voltage (v en ).....................................................6.5v lead temperature (solde ring, 5 se c.)........................ 260c storage temperature (t s ) .........................C65c to +150c eds rating................................................................ note 3 operating ratings (2) supply voltage (v in )...................................... +2.25v to +6v enable voltage (v en )............................................ 0v to +6v maximum power dissipation (p d(max) ) ...................... note 4 junction temperature (t j ) ........................ C40c to +125c package thermal resistance msop-8 ( ja ) .....................................................80c/w electrical characteristics (5) v in = v out + 1v; v en = 2.25v; t j = 25c, bold values indicate C40c< t j < +125c, unless noted. symbol parameter condition min typ max units v out output voltage 10ma 10ma i out 750ma, v out + 1v v in 6v C1 C2 1 2 % % line regulation i out = 10ma, v out + 1v v in 6v 0.06 0.5 % load regulation v in = v out + 1v, 10ma i out 750ma 0.2 1 % ? v out / ? t output voltage temp. coefficient, note 6 40 ppm/c i out = 100ma, ? v out = C1% 125 200 250 mv mv i out = 500ma, ? v out = C1% 210 mv v do dropout voltage, note 7 i out = 750ma, ? v out = C1% 280 500 mv i out = 100ma, v in = v out + 1v 700 a i out = 500ma, v in = v out + 1v 3.7 ma i gnd ground current, note 8 i out = 750ma, v in = v out + 1v 7.5 15 ma i out(lim) current limit v out = 0v, v in = v out + 1v 1.6 2.5 a enable input logic low (off) 0.8 v v en enable input voltage logic high (on) 2.25 v v en = 2.25v 1 10 30 a i en enable input current v en = 0.8v 2 4 a a flag output i flg(leak) output leakage current v oh = 6v 0.01 1 2 a a v flg(do) output low voltage v in = 2.250v, i ol , = 250a 250 500 mv low threshold % of v out 93 % high threshold % of v out 99.2 % v flg hysteresis 1 % adjustable output only reference voltage 1.227 1.215 1.240 1.2521.265 v v adjust pin bias current 40 80 120 na na downloaded from: http:///
micrel, inc. mic3775 december 2006 4 m9999-121906 notes: 1. exceeding the absolute maximum rating may damage the device. 2. the device is not guaranteed to function outside its operating rating. 3. devices are esd sensitive. handling precautions recommended. 4. p d(max) = (t j(max) C t a ) ja , where ja depends upon the printed circuit layout. see applications information. 5. specification for packaged product only. 6. output voltage temperature coefficient is ? v out(worst case) (t j(max) C t j(min) ) where t j(max) is +125c and t j(min) is C40c. 7. v do = v in C v out when v out decreases to 98% of its nominal output voltage with v in = v out + 1v. for output voltages below 1.75v, dropout voltage is the input-to-output voltage differential with the minimu m input voltage being 2.25v. minimum input operating voltage is 2 .25v. 8. i gnd is the quiescent current. i in = i gnd + i out . downloaded from: http:///
micrel, inc. mic3775 december 2006 5 m9999-121906 typical characteristics downloaded from: http:///
micrel, inc. mic3775 december 2006 6 m9999-121906 typical characteristics (cont.) downloaded from: http:///
micrel, inc. mic3775 december 2006 7 m9999-121906 typical characteristics (cont.) downloaded from: http:///
micrel, inc. mic3775 december 2006 8 m9999-121906 functional characteristics downloaded from: http:///
micrel, inc. mic3775 december 2006 9 m9999-121906 functional diagrams mic3775 fixed regulator with flag and enable block diagram mic3775 adjustable regulator block diagram downloaded from: http:///
micrel, inc. mic3775 december 2006 10 m9999-121906 application information the mic3775 is a high-performance low-dropout voltage regulator suitable for moderate to high-current voltage regulator applications. its 500mv dropout voltage at full load and overtemperature makes it especially valuable in battery-powered systems and as high-efficiency noise filters in post-regulator applications. unlike older npn- pass transistor designs, where the minimum dropout voltage is limited by the base-to-emitter voltage drop and collector-to-emitter saturati on voltage, dropout perform- ance of the pnp output of t hese devices is limited only by the low v ce saturation voltage. a trade-off for the low-dropout voltage is a varying base drive requirement. micrels super eta pnp ? process reduces this drive requirement to only 2% of the load current. the mic3775 regulator is fu lly protected from damage due to fault conditions. linear current limiting is provided. output current dur ing overload conditions is constant. thermal shutdown disables the device when the die temperature exceeds the maximum safe operating temperature. the output structure of these regulators allows voltages in excess of the desired output voltage to be applied wi thout reverse current flow. figure 1. capacitor requirements output capacitor the mic3775 requires an output capacitor for stable operation. as a cap ldo, the mic3775 can operate with ceramic output capacitors as long as the amount of capacitance is 10f or greater. for values of output capacitance lower than 10f, the recommended esr range is 200m ? to 2 ? . the minimum value of output capacitance recommended for the mic3775 is 4.7f. for 10f or greater the esr range recommended is less than 1 ? . ultra-low esr ceramic capacitors are recommended for output capacitance of 10f or greater to help improve transient response and noise reduction at high frequency. x7r/x5r dielectric-type ceramic capacitors are recommended because of their temperature performance. x7r-type capacitors change capacitance 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 their operating temperature ranges. to use a ceramic chip capacitor with y5v dielectric, the value must be much higher than an x7r ceramic capacitor to ensure the same minimum capacitance over the equivalent operating temperature range. input capacitor an input capacitor of 1f or greater is recommended when the device is more than 4 inches away from the bulk ac supply capacitance or when the supply is a battery. small, surface mount, ceramic chip capacitors can be used for bypassing. larger values will help to improve ripple rejection by bypassing the input to the regulator, further improving the integrity of the output voltage. error flag the mic3775 features an error flag (flg), which monitors the output voltage and signals an error condition when this voltage drops 5% below its expected value. the error flag is an open-collector output that pulls low under fault conditions and may sink up to 10ma. low output voltage signifies a number of possible problems, including an overcurr ent fault (the device is in current limit) or low input voltage. the flag output is inoperative during overtemperature conditions. a pull-up resistor from flg to either v in or v out is required for proper operation. for inform ation regarding the minimum and maximum values of pull-up resistance, refer to the graph in the typical characteristics section of the data sheet. enable input the mic3775 features an active-high enable input (en) that allows on-off control of the regulator. current drain reduces to zero when the device is shutdown, with only microamperes of leakage current. the en input has ttl/cmos compatible thresholds for simple logic interfacing. en may be directly tied to v in and pulled up to the maximum supply voltage. transient response and 3.3v to 2.5v or 2.5v to 1.8v or 1.65v conversion the mic3775 has excellent transient response to variations in input volt age and load current. the device has been designed to respond quickly to load current variations and input voltage variations. large output capacitors are not required to obtain this performance. a standard 10f output capacitor, is all that is required. larger values help to improve performance even further. by virtue of its low-dropout voltage, this device does not saturate into dropout as readily as similar npn-based designs. when converting from 3.3v to 2.5v or 2.5v to 1.8v or 1.65v, the npn- based regulators are already operating in dropout, with typical dropout requirements of 1.2v or greater. to conv ert down to 2.5v or 1.8v without operating in dropout, npn-based regulators require an input voltage of 3. 7v at the very least. the mic3775 regulator will prov ide excellent performance downloaded from: http:///
micrel, inc. mic3775 december 2006 11 m9999-121906 with an input as low as 3.0v or 2.5v respectively. this gives the pnp-based regulat ors a distinct advantage over older, npn-bas ed linear regulators. minimum load current the mic3775 regulator is spec ified between finite loads. if the output current is t oo small, leakage currents dominate and the output voltage rises. a 10ma minimum load current is necessary for proper regulation. adjustable regulator design ? ? ? ? ? ? + = r2 r1 1 1.240v v out figure 2. adjustable regulator with resistors the mic3775 allows programming the output voltage anywhere between 1.24v and the 6v maximum operating rating of the family. two resistors are used. resistors can be quite large, up to 1m ? , because of the very high input impedance and low bias current of the sense comparator. the resistor values are calculated by: ? ? ? ? ? ? ? ? ? = 1 1.240 v r2 r1 out where v o is the desired output voltage. figure 2 shows component definition. applications with widely varying load currents may scale the resistors to draw the minimum load current required for proper operation (see above). power msop-8 thermal characteristics one of the secrets of the mi c3775s performance is its power msop-8 package featuring half the thermal resistance of a standard msop-8 package. lower thermal resistance means more output current or higher input voltage for a given package size. lower thermal resistance is achieved by joining the four ground leads with the die attach paddle to create a single-piece electrical and thermal conductor. this concept has been used by mosfet manufacturers for years, proving very reliable and cost effective for the user. thermal resistance consists of two main elements, jc (junction-to-case thermal resistance) and ca (case-to- ambient thermal resistance). see figure3. jc is the resistance from the die to the leads of the package. ca is the resistance from the leads to the ambient air and it includes cs (case-to- sink thermal resistance) and sa (sink-to-ambient thermal resistance). using the power msop-8 reduces the jc dramatically and allows the user to reduce ca . the total thermal resistance, ja (junction-to-ambient thermal resistance) is the limiting factor in ca lculating the maximum power dissipation capability of the device. typically, the power msop-8 has a ja of 80c/w, this is significantly lower than the standard msop-8 wh ich is typically 160c/w. ca is reduced because pins 5 through 8 can now be soldered directly to a ground plane which significantly reduces the case-to-sink thermal resistance and sink-to- ambient thermal resistance. low-dropout linear regulators from micrel are rated to a maximum junction temperature of 125c. it is important not to exceed this maximum junction temperature during operation of the device. to prevent this maximum junction temperature from being exceeded, the appropriate ground plane heatsink must be used. figure 3. thermal resistance figure 4 shows copper area versus power dissipation with each trace corresponding to a different temperature rise above ambient. from these curves, the minimum area of copper necessary for the part to operate safely can be deter- mined. the maximum allowable temperature rise must be calculated to determine operation along which curve. figure 4. copper area vs. power-msop power dissipation ( ? t ja ) downloaded from: http:///
micrel, inc. mic3775 december 2006 12 m9999-121906 figure 5. copper area vs. power-msop power dissipation (t a ) ? t = t j(max) C t a(max) t j(max) = 125c t a(max) = maximum ambient operating temperature for example, the maximum ambient temperature is 50c, the ? t is determined as follows: ? t = 125c C 50c ? t = 75c using figure 4, the minimum amount of required copper can be determined based on the required power dissipation. power dissipation in a linear regulator is calculated as follows: p d = (v in C v out ) i out + v in i gnd if we use a 2.5v output device and a 3.3v input at an output current of 750ma, then our power dissipation is as follows: p d = (3.3v C 2.5v) 750ma + 3.3v 7.5ma p d = 600mw + 25mw p d = 625mw from figure 4, the minimum amount of copper required to operate this application at a ? t of 75c is 160mm 2 . quick method determine the power dissipation requirements for the design along with the maximum ambient temperature at which the device will be operated. refer to figure 5, which shows safe operating curves for three different ambient temperatures: 25c, 50c and 85c. from these curves, the minimum amount of copper can be determined by knowing the maximum power dissipation required. if the maximum ambient temperature is 50c and the power dissipation is as above, 625mw, the curve in figure 5 shows that the required area of copper is 160mm 2 .the ja of this package is ideally 80c/w, but it will vary depending upon the availability of copper ground plane to which it is attached. downloaded from: http:///
micrel, inc. mic3775 december 2006 13 m9999-121906 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 appliances, 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 purchasers use or sale of micrel produc ts for use in life support app liances, devices or systems is a purchasers own risk and purchaser agrees to fully indemnify micrel for any damages resulting from such use or sale. ? 2002 micrel, incorporated. downloaded from: http:///

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