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march 2002 1 mic37100/37101/37102 mic37100/37101/37102 micrel mic37100/37101/37102 1a low-voltage cap ldo regulator general description the mic37100, mic37101, and mic37102 are 1a low- dropout linear voltage regulators that provide low-voltage, high-current output from an extremely small package. utiliz- ing micrels proprietary super eta pnp? pass element, the mic37100/01/02 offers extremely low dropout (typically 280mv at 1a) and low ground current (typically 11ma at 1a). the mic37100 is a fixed output regulator offered in the sot-223 package. the mic37101 and mic37102 are fixed and adjustable regulators, respectively, in a thermally en- hanced power 8-lead soic (small outline package) and the sot-223 package. the mic37100/01/02 is ideal for pc add-in cards that need to convert from standard 5v to 3.3v, 3.3v to 2.5v or 2.5v to 1.8v or lower. a guaranteed maximum dropout voltage of 500mv over all operating conditions allows the mic37100/01/02 to provide 2.5v from a supply as low as 3v and 1.8v from a supply as low as 2.3v. the mic37100/01/02 is fully protected with overcurrent lim- iting and thermal shutdown. a fixed voltage of 1.5v is avail- able on mic37100/01 with adjustable output voltages to 1.24v on mic37102. for other voltages, contact micrel. typical applications features ? fixed and adjustable output voltages to 1.24v ? cap regulator, 10 f ceramic output capacitor stable ? 280mv typical dropout at 1a ideal for 3.0v to 2.5v conversion ideal for 2.5v to 1.8v, 1.65v or 1.5v conversion ? 1a minimum guaranteed output current ? 1% initial accuracy ? low ground current ? current limiting and thermal shutdown ? reversed-leakage protection ? fast transient response ? low-profile sot-223 package ? power so-8 package applications ? 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 microcontrollers and digital logic super eta pnp is a trademark of micrel, inc. 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 in 2.5v v in 3.3v 10 f ceramic out gnd mic37100 2.5v/1a regulator ordering information part number voltage junction temp. range package mic37100-1.5bs 1.5v C 40 c to +125 c sot-223 mic37101-1.5bm 1.5v C 40 c to +125 c soic-8 mic37102bm adj. C 40 c to +125 c soic-8 0 50 100 150 200 250 300 350 0 0.25 0.5 0.75 1 dropout (mv) output current ( a ) dropout vs. output current 2.5v out 3.3v out
mic37100/37101/37102 micrel mic37100/37101/37102 2 march 2002 pin configuration in out gnd 13 2 ta b gnd mic37100-x.x fixed sot-223 (s) 1 en in out flg 8 gnd gnd gnd gnd 7 6 5 2 3 4 mic37101-x.x fixed soic-8 (m) 1 en in out adj 8 gnd gnd gnd gnd 7 6 5 2 3 4 mic37102 adjustable soic-8 (m) pin description pin no. pin no. pin no. pin name pin function mic37100 mic37101 mic37102 sot-8 soic-8 soic-8 1 1 1 en enable (input): cmos-compatible control input. logic high = enable, logic low or open = shutdown. 2 2 in supply (input) 3 3 3 out regulator output 4 flg flag (output): open-collector error flag output. active low = output under voltage. 4 adj adjustment input: feedback input. connect to resitive voltage-divider network. 2, tab 5 C 85 C 8 gnd ground
march 2002 3 mic37100/37101/37102 mic37100/37101/37102 micrel electrical characteristics v in = v out + 1v; v en = 2.25v; t j = 25 c, bold values indicate C 40 c t j +125 c; unless noted symbol parameter condition min typ max units v out output voltage 10ma C 11% 10ma i out 1a, v out + 1v v in 6v C 22 % 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 1a, 0.2 1 % ? v out / ? t output voltage temp. coefficient, 40 ppm/ c note 5 v do dropout voltage, note 6 i out = 100ma, ? v out = C 1% 125 200 mv i out = 500ma, ? v out = C 1% 210 350 mv i out = 750ma, ? v out = C 1% 250 400 mv i out = 1a, ? v out = C 1% 280 500 mv i gnd ground current, note 7 i out = 100ma, v in = v out + 1v 650 a i out = 500ma, v in = v out + 1v 3.5 ma i out = 750ma, v in = v out + 1v 6.7 ma i out = 1a, v in = v out + 1v 11 25 ma i out(lim) current limit v out = 0v, v in = v out + 1v 1.6 2.5 a enable input v en enable input voltage logic low (off) 0.8 v logic high (on) 2.25 v i en enable input current v en = 2.25v 1 10 30 a v en = 0.8v 2 a 4 a flag output i flg(leak) output leakage current v oh = 6v 0.01 1 a 2 a v flg(do) output low voltage v in = 2.250v, i ol , = 250 a210 500 mv v flg low threshold % of v out 93 % high threshold % of v out 99.2 % hysteresis 1% absolute maximum ratings (note 1) supply voltage (v in ) ........................................ 0v to +6.5v enable voltage (v en ) ................................................. +6.5v storage temperature (t s ) ....................... C 65 c to +150 c lead temperature (soldering, 5 sec.) ....................... 260 c esd ......................................................................... note 3 operating ratings (note 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 ) ....................... C 40 c to +125 c package thermal resistance sot-223 ( jc ) ..................................................... 15 c/w soic-8 ( jc ) ....................................................... 20 c/w
mic37100/37101/37102 micrel mic37100/37101/37102 4 march 2002 symbol parameter condition min typ max units mic37102 only reference voltage 1.228 1.240 1.252 v 1.215 1.265 v adjust pin bias current 40 80 na 120 na note 1. exceeding the absolute maximum ratings may damage the device. note 2. the device is not guaranteed to function outside its operating rating. note 3. devices are esd sensitive. handling precautions recommended. note 4. p d(max) = (t j(max) C t a ) ja , where ja depends upon the printed circuit layout. see applications information. note 5. output voltage temperature coefficient is ? v out(worst case) (t j(max) C t j(min) ) where t j(max) is +125 c and t j(min) is C 40 c. note 6. 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 2.25v, dropout voltage is the input-to-output voltage differential with the minimum input voltage being 2.25v. minimum input operating voltage is 2.25v. note 7. i gnd is the quiescent current. i in = i gnd + i out . note 8. v en 0.8v, v in 6v, and v out = 0v.
march 2002 5 mic37100/37101/37102 mic37100/37101/37102 micrel typical characteristics 0 10 20 30 40 50 60 70 80 0.01 0.1 1 10 100 1000 psrr (db) frequency (khz) power supply rejection ratio i out = 1000ma c out = 10 f c in = 0 v in = 5v v out = 3.3v 0 10 20 30 40 50 60 70 80 0.01 0.1 1 10 100 1000 psrr (db) frequency (khz) power supply rejection ratio i out = 1000ma c out = 47 f c in = 0 v in = 5v v out = 3.3v 0 10 20 30 40 50 60 70 80 0.01 0.1 1 10 100 1000 psrr (db) frequency (khz) power supply rejection ratio i out = 1000ma c out = 10 f c in = 0 v in = 3.3v v out = 2.5v 0 10 20 30 40 50 60 70 80 0.01 0.1 1 10 100 1000 psrr (db) frequency (khz) power supply rejection ratio i out = 1000ma c out = 47 f c in = 0 v in = 3.3v v out = 2.5v 0 50 100 150 200 250 300 350 0 0.25 0.5 0.75 1 dropout (mv) output current ( a ) dropout vs. output current 2.5v out 3.3v out 0 50 100 150 200 250 300 350 400 450 -40 -20 0 20 40 60 80 100 120 dropout (mv) temperature ( c) dropout vs. temperature 2.5v out 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.5 1.7 1.9 2.1 2.3 2.5 output voltage (v) input voltage ( v ) dropout characteristics (1.5v) 10ma load 1000ma load 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 1.5 1.7 1.9 2.1 2.3 2.5 2.7 output voltage (v) input voltage (v) dropout characteristics (1.8v) 10ma load 1000ma load 0 0.5 1.0 1.5 2.0 2.5 3.0 1.5 2 2.5 3 3.5 output voltage (v) input voltage (v) dropout characteristics (2.5v) 10ma load 1000ma load 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 1.5 2 2.5 3 3.5 4 output voltage (v) input voltage (v) dropout characteristics (3.3v) 10ma load 1000ma load 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0123456 ground current (ma) input voltage ( v ) ground current vs. supply voltage (1.5v) 10ma 100ma 0 2 4 6 8 10 12 0 0.25 0.5 0.75 1 ground current (ma) output current ( a ) ground current vs. output current 1.5v out 3.3v out
mic37100/37101/37102 micrel mic37100/37101/37102 6 march 2002 0 2 4 6 8 10 12 14 16 18 0123456 ground current (ma) input voltage ( v ) ground current vs. supply voltage (1.5v) 1000ma 750ma 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0123456 ground current (ma) input voltage ( v ) ground current vs. supply voltage (1.8v) 100ma 10ma 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0123456 ground current (ma) input voltage ( v ) ground current vs. supply voltage (2.5v) 100ma 10ma 0 5 10 15 20 25 30 0123456 ground current (ma) input voltage ( v ) ground current vs. supply voltage (2.5v) 1000ma 750ma 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0123456 ground current (ma) input voltage ( v ) ground current vs. supply voltage (3.3v) 100ma 10ma 0 5 10 15 20 25 0123456 ground current (ma) input voltage ( v ) ground current vs. supply voltage (1.8v) 1000ma 750ma 0 5 10 15 20 25 30 0123456 ground current (ma) input voltage ( v ) ground current vs. supply voltage (3.3v) 750ma 500ma 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 -40 -20 0 20 40 60 80 100 120 ground current (ma) temperature ( c ) ground current vs. temperature 2.5v out i out =10ma 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 -40 -20 0 20 40 60 80 100 120 ground current (ma) temperature ( c ) ground current vs. temperature 2.5v out i out =500ma 0 2 4 6 8 10 12 14 16 -40 -20 0 20 40 60 80 100 120 ground current (ma) temperature ( c ) ground current vs. temperature 2.5v out i out =1000ma 2.4 2.45 2.5 2.55 2.6 -40 -20 0 20 40 60 80 100 120 output voltage (v) temperature ( c) output voltage vs. tem p erature 2.5v out 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.25 3 3.75 4.5 5.25 6 short circuit current (a) supply voltage (v) short circuit current vs. supply voltage
march 2002 7 mic37100/37101/37102 mic37100/37101/37102 micrel 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 -40 -20 0 20 40 60 80 100 120 short circuit current (a) temperature ( c) short circuit current vs. temperature 2.5v in 0 0.2 0.4 0.6 0.8 1.0 0 0.5 1 1.5 2 2.5 3 3.5 4 flag voltage (v) flag current (ma) flag voltage vs. flag current 3.3v in 5v in 2.5v in 0 50 100 150 200 250 300 350 -40 -20 0 20 40 60 80 100 120 flag low voltage (mv) temperature ( c) flag low voltage vs. temperature fla g current = 250 ? ) error flag pull-up resistor flag high (ok) v in =5v flag low (fault) 0 1 2 3 4 5 6 7 8 9 -40 -20 0 20 40 60 80 100 120 enable current ( a) temperature ( c ) enable current vs. temperature 2.5v en
mic37100/37101/37102 micrel mic37100/37101/37102 8 march 2002 functional characteristics load transient response time (400 s/div.) load current (500ma/div) output voltage (200mv/div) v in = 3.3v v out = 2.5v c out = 10 f ceramic 1000ma 100ma load transient response time (400 s/div.) load current (500ma/div) output voltage (200mv/div) v in = 3.3v v out = 2.5v c out = 10 f ceramic 1000ma 10ma line transient response time (400 s/div.) output voltage (50mv/div) input voltage (2v/div) v out = 2.5v c out = 10 f ceramic load=100ma 5v 3.3v enable transient response time (10 s/div.) output voltage (1v/div) enable voltage (2v/div) v in = 3.3v v out = 2.5v i out = 100ma c out = 10 f ceramic
march 2002 9 mic37100/37101/37102 mic37100/37101/37102 micrel functional diagrams ref. thermal shut- down 1.240v in out mic37100 mic37100 fixed regulator block diagram ref. thermal shut- down 1.240v 1.180v en in flag gnd out mic37101 mic37101 fixed regulator with flag and enable block diagram ref. thermal shut- down 1.240v en in gnd out adj mic37102 mic37102 adjustable regulator block diagram
mic37100/37101/37102 micrel mic37100/37101/37102 10 march 2002 applications information the mic37100/01/02 is a high-performance low-dropout voltage regulator suitable for moderate to high-current volt- age 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 tran- sistor designs, where the minimum dropout voltage is limited by the base-to-emitter voltage drop and collector-to-emitter saturation voltage, dropout performance of the pnp output of these 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. micrel s super eta pnp ? process reduces this drive requirement to only 2% of the load current. the mic37100/01/02 regulator is fully protected from dam- age due to fault conditions. linear current limiting is provided. output current during overload conditions is constant. ther- mal 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 without reverse current flow. mic37100-x.x in out gnd c in c out v in v out figure 1. capacitor requirements output capacitor the mic37100/01/02 requires an output capacitor to main- tain stability and improve transient response. as a cap ldo, the mic37100/01/02 can operate with ceramic output capaci- tors as long as the amount of capacitance is 10 f or greater. for values of output capacitance lower than 10 f, the recom- mended esr range is 200m ? to 2 ? . the minimum value of output capacitance recommended for the mic37100/01/02 is 4.7 f. for 10 f or greater the esr range recommended is less than 1 ? . ultra-low esr ceramic capacitors are recommended for output capacitance of 10 f or greater to help improve tran- sient response and noise reduction at high frequency. 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. input capacitor an input capacitor of 1 f 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 bypass- ing the input to the regulator, further improving the integrity of the output voltage. error flag the mic37101 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 overcurrent 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 information 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 mic37101 and mic37102 versions feature 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, 1.65v or 1.5v conversion the mic37100/01/02 has excellent transient response to variations in input voltage 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 10 f 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 de- signs. when converting from 3.3v to 2.5v or 2.5v to 1.8v, or lower, the npn based regulators are already operating in dropout, with typical dropout requirements of 1.2v or greater. to convert 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 mic37100 regulator will provide excellent
march 2002 11 mic37100/37101/37102 mic37100/37101/37102 micrel performance with an input as low as 3.0v or 2.5v respec- tively. this gives the pnp based regulators a distinct advan- tage over older, npn based linear regulators. minimum load current the mic37100/01/02 regulator is specified between finite loads. if the output current is too small, leakage currents dominate and the output voltage rises. a 10ma minimum load current is necessary for proper regulation. adjustable regulator design in r1 v out v in c out r2 en out adj gnd mic37102 enable shutdown v 1.240v 1 r1 r2 out =+ ? ? ? ? ? ? figure 2. adjustable regulator with resistors the mic37102 allows programming the output voltage any- where 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: r1 r2 v 1.240 1 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 soic-8 thermal characteristics one of the secrets of the mic37101/02 s performance is its power so-8 package featuring half the thermal resistance of a standard so-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-ambi- ent thermal resistance). see figure 3. 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 soic-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 calculating the maximum power dissipation capabil- ity of the device. typically, the power soic-8 has a jc of 20 c/w, this is significantly lower than the standard soic-8 which is typically 75 c/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 resis- tance and sink to ambient thermal resistance. low-dropout linear regulators from micrel are rated to a maximum junction temperature of 125 c. it is important not to exceed this maximum junction temperature during opera- tion of the device. to prevent this maximum junction tempera- ture from being exceeded, the appropriate ground plane heat sink must be used. 0 100 200 300 400 500 600 700 800 900 0 0.25 0.50 0.75 1.00 1.25 1.50 copper area (mm 2 ) power dissipation (w) 40 c 50 c 55 c 65 c 75 c 85 c 100 c ? t ja = figure 4. copper area vs. power so-8 power dissipation 0 100 200 300 400 500 600 700 800 900 0 0.25 0.50 0.75 1.00 1.25 1.50 copper area (mm 2 ) power dissipation (w) t a = 85 c 50 c 25 c t j = 125 c figure 5. copper area vs. power-soic power dissipation
mic37100/37101/37102 micrel mic37100/37101/37102 12 march 2002 ja jc ca printed circuit board ground plane heat sink area soic-8 ambient 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 determined. the maxi- mum allowable temperature rise must be calculated to deter- mine operation along which curve. ? t = t j(max) C t a(max) t j(max) = 125 c t a(max) = maximum ambient operating temperature for example, the maximum ambient temperature is 50 c, the ? t is determined as follows: ? t = 125 c C 50 c ? t = 75 c 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 fol- lows: 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 1a, then our power dissipation is as follows: p d = (3.3v C 2.5v) 1a + 3.3v 11ma p d = 800mw + 36mw p d = 836mw from figure 4, the minimum amount of copper required to operate this application at a ? t of 75 c 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: 25 c, 50 c and 85 c. from these curves, the minimum amount of copper can be determined by knowing the maxi- mum power dissipation required. if the maximum ambient temperature is 50 c and the power dissipation is as above, 836mw, the curve in figure 5 shows that the required area of copper is 160mm 2 . the ja of this package is ideally 63 c/w, but it will vary depending upon the availability of copper ground plane to which it is attached.
march 2002 13 mic37100/37101/37102 mic37100/37101/37102 micrel package information 16 10 0.84 (0.033) 0.64 (0.025) 1.04 (0.041) 0.85 (0.033) 2.41 (0.095) 2.21 (0.087) 4.7 (0.185) 4.5 (0.177) 6.70 (0.264) 6.30 (0.248) 7.49 (0.295) 6.71 (0.264) 3.71 (0.146) 3.30 (0.130) 3.15 (0.124) 2.90 (0.114) 10 max 0.10 (0.004) 0.02 (0.0008) 0.38 (0.015) 0.25 (0.010) c l dimensions: mm (inch) c l 1.70 (0.067) 1.52 (0.060) 0.91 (0.036) min sot-223 (s) 45 0 C 8 0.244 (6.20) 0.228 (5.79) 0.197 (5.0) 0.189 (4.8) seating plane 0.026 (0.65) max ) 0.010 (0.25) 0.007 (0.18) 0.064 (1.63) 0.045 (1.14) 0.0098 (0.249) 0.0040 (0.102) 0.020 (0.51) 0.013 (0.33) 0.157 (3.99) 0.150 (3.81) 0.050 (1.27) typ pin 1 dimensions: inches (mm) 0.050 (1.27) 0.016 (0.40) 8-lead soic (m)
mic37100/37101/37102 micrel mic37100/37101/37102 14 march 2002 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 an y 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 pat ent right of micrel inc. ? 2002 micrel incorporated

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