january 2002 1 mic37500/37501/37502 mic37500/37501/37502 micrel mic37500/37501/37502 5a, low voltage cap ldo regulator advance information general description the micrel mic37500/01/02 is a 5a low-dropout linear volt- age regulator that provides a low voltage, high current output with a minimum of external components. it offers high preci- sion, ultra low dropout (500mv), and low ground current. the mic37500/01/02 operates from an input of 2.3v to 6.0v. it is designed to drive digital circuits requiring low voltage at high currents (i.e. plds, dsp, microcontroller, etc.). it is available in fixed and adjustable output voltages. fixed voltages include 1.5v. the adjustable version is capable of 1.24v to 5.5v. features of the mic37500/01/02 ldo include thermal and current limit protection, and reverse current & reverse battery protection. logic enable and error flag pins are available. junction temperature range of the mic37500/01/02 is from ?0 c to 125 c. for applications requiring input voltage greater than 6.0v, see mic3910x, mic3915x, mic3930x, and mic3950x ldos. typical application vout vin vout vin flg gnd ven c out 100 f, ceramic 100k mic37500 v in = 3.0v v out = 2.5v c in fixed 2.5v regulator with error flag features 5a minimum guaranteed output current 500mv maximum dropout voltage ideal for 3.0v to 2.5v conversion ideal for 2.5v to 1.8v, 1.65v, or 1.5v conversion stable with ceramic or tantalum capacitor wide input voltage range: v in : 2.3v to 6.0v 1.0% initial output tolerance fixed and adjustable output voltages excellent line and load regulation specifications logic controlled shutdown thermal shutdown and current limit protection reverse-leakage protection low profile s-pak package applications ldo linear regulator for low-voltage digital ic pc add-in cards high efficiency linear power supplies smps post regulator battery charger 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 superswitcher is a trademark of micrel, inc. vout vin vout vin adj gnd ven c out 100 f, ceramic r1 r2 1.3v mic37502 v in c in adjustable regulator
mic37500/37501/37502 micrel mic37500/37501/37502 2 january 2002 ordering information output part number current voltage* junction temp. range package mic37502br 5a adj. 40 c to +125 c s-pak-7 mic37501-1.5br 5a 1.5v 40 c to +125 c s-pak-7 *for other voltages contact micrel. pin configuration ta b 7 flg/adj 6 vout 5 vout 4 gnd 3 vin 2 vin 1en s-pak7 pin description pin number pin name pin function 1 en enable (input): cmos compatible input. logic high = enable, logic low = shutdown 2, 3 vin input voltage which supplies current to the output power device. connect pins 2 and 3 together externally. 4 gnd ground (tab is connected to ground on s-pak) 5, 6 vout regulator output. connect pins 5 and 6 together externally. 7 flg. error flag (output): open collector output. active low indicates an output fault condition. adj. adjustable regulator feedback input. connect to resistor voltage divider.
january 2002 3 mic37500/37501/37502 mic37500/37501/37502 micrel electrical characteristics t a = 25 c with v in = v out + 1v; v en = v in ; bold values indicate 40 c < t j < +125 c; unless otherwise noted. parameter condition min typ max units output voltage accuracy i l = 10ma -1 +1 % 10ma < i out < i l(max) , v out + 1 v in 6v -2 +2 % output voltage line regulation v in = v out +1.0v to 6.0v 0.06 0.5 % output voltage load regulation i l = 10ma to 5a 0.2 1 % v in v out ; dropout voltage ; i l = 2.5a 350 mv note 5 i l = 5a 330 500 mv ground pin current, note 6 i l = 5a 57 ma ground pin current in shutdown v il < 0.5v, v in = v out + 1v 1.0 a current limit v out = 0 7.5 a start-up time v en = v in , i out = 10ma, c out = 22 f170 500 s enable input enable input threshold regulator enable 2.25 v regulator shutdown 0.8 v enable pin input current v il < 0.8v (regulator shutdown) 2 a 4 a v ih > 2.25v (regulator enabled) 1 15 30 a 75 a flag output i flg(leak) v oh = 6v 1 a 2 a v flg(lo) v in = 2.25v, i ol = 250ua, note 7 210 mv mv v flg low threshold, % of vout below nominal 93 % hysteresis 2 % high threshold, % of vout below nominal 99.2 % mic37502 only reference voltage 1.228 1.240 1.252 v 1.215 1.265 v adjust pin bias current 40 80 na 120 na absolute maximum rating (note 1) supply voltage (v in ) .................................................... 6.5v enable input voltage (v en ) .......................................... 6.5v power dissipation .................................... internally limited junction temperature ........................ 40 c t j +125 c storage temperature ......................... 65 c t j +150 c lead temperature (soldering, 5 sec.) ....................... 260 c esd, note 3 operating maximum rating (note 2) supply voltage (v in ) ....................................... 2.3v to 6.0v enable input voltage (v en ) ................................ 0v to 6.0v junction temperature range ............. 40 c t j +125 c maximum power dissipation .. ............... note 4 package thermal resistance s-pak( jc ) ............. 2 c/w
mic37500/37501/37502 micrel mic37500/37501/37502 4 january 2002 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. device is esd sensitive. handling precautions recommended. note 4. p d(max) = (t j(max) t a ) / ja , where ja , depends upon the printed icurcuit layout. see applications information. note 5. v do = v in v out when v out decreased to 98% of its nominal output voltage with v in = v out +1v. for output voltages below 1.75v, dropout voltage specification does not apply due to a minimum input operating voltage of 2.3v. note 6. i gnd is the quiescent current. i in = i gnd + i out . note 7. for a 2.5v device, v in = 2.3v (device is in dropout).
january 2002 5 mic37500/37501/37502 mic37500/37501/37502 micrel applications information the mic37500/01/02 is a high-performance low-dropout voltage regulator suitable for moderate to high-current regu- lator applications. its 500mv dropout voltage at full load makes it especially valuable in battery-powered systems and as high-efficiency noise filters in post-regulator applications. unlike older npn-pass transistor designs, there the minimum dropout voltage is limited by the based-to-emiiter voltage drop and collector-to-emitter saturation voltage, dropout per- formance 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 beta pnp process reduces this drive requirement to only 2% to 5% of the load current. the mic37500/01/02 regulator is fully protected from dam- age due to fault conditions. current limiting is provided. this limiting is linear; output current during overload conditions is constant. thermal shutdown disables the device when the die temperature exceeds the maximum safe operating tem- perature. transient protection allows device (and load) sur- vival even when the input voltage spikes above and below nominal. the output structure of these regulators allows voltages in excess of the desired output voltage to be applied without reverse current flow. thermal design linear regulators are simple to use. the most complicated design parameters to consider are thermal characteristics. thermal design requires the following application-specific parameters: maximum ambient temperature (t a ) output current (i out ) output voltage (v out ) input voltage (v in ) ground current (i gnd ) first, calculate the power dissipation of the regulator from these numbers and the device parameters from this datasheet. p d = (v in v out ) i out + v in i gnd where the ground current is approximated by using numbers from the electrical characteristics or typical characteris- tics. then the heat sink thermal resistance is determined with this formula: sa = ((t j(max) t a )/ p d ) ( jc + cs ) where t j(max) 125 c and cs is between 0 c and 2 c/w. the heat sink may be significantly reduced in applications where the minimum input votlage is known and is large compared with the dropout voltage. use a series input resistor to drop excessive voltage and distribute the heat between this resistor and the regulator. the low dropout properties of micrel super beta pnp regulators allow signifi- cant reductions in regulator power dissipation and the asso- ciated heat sink without compromising performance. when this technique is employed, a capacitor of at least 1.0 f is needed directly between the input and regulator ground. refer to application note 9 for further details and examples on thermal design and heat sink applications. output capacitor the mic37500/01/02 requires an output capacitor for stable operation. as a cap ldo, the mic37500/01/02 can operate with ceramic output capacitors as long as the amount of capacitance is 100 f or greater. for values of output capaci- tance lower than 100 f, the recommended esr range is 200m ? to 2 ? . the minimum value of output capacitance recommended for the mic37500/01/02 is 47 f. for 100 f or greater the esr range recommended is less than 1 ? ultra-low esr ceramic capacitors are recommended for output capacitance of 100 f or greater to help improve transient 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 op- erating 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. the mic37500/01/02 has excellent transient response to varia- tions 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 47 f output capacitor, is all that is required. larger values help to improve performance even further. input capacitor an input capacitor of 1.0 f or greater is recommended when the device is more than 4 inches away from the bulk ad supply capacitance, or when the supply is a battery. small, surface- mount chip capacitors can be used for the bypassing. the capacitor should be place within 1 of the device for optimal performance. larger values will help to improve ripple rejec- tion by bypassing the input to the regulator, further improving the integrity of the output voltage. transient response and 3.3v to 2.5v, 2.5v to 1.8v or 1.65v, or 2.5v to 1.5v conversions the mic37500/01/02 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 47 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, 2.5v to 1.8v or 1.65v, or 2.5v to 1.5v, the npn-based regulators are already operating in dropout, with typical dropout requirements of 1.2v or greater. to convert down to 2.5v without operating in dropout, npn-based regulators require an input voltage of 3.7v at the very least. the mic37500/01/02 regulator will provide excellent performance with an input as low as 3.0v or 2.25v, respectively. this gives the pnp-based regulators a distinct advantage over older, npn-based linear regulators.
mic37500/37501/37502 micrel mic37500/37501/37502 6 january 2002 minimum load current the mic37500/01/02 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 operation. error flag the mic37501 features an error flag circuit that monitors the output voltage and signals an error condition when the voltage 5% below the nominal output voltage. the error flag is an open-collector output that can sink 10ma during a fault condition. low output voltage can be caused by a number of problems, including an overcurrent fault (device in current limit) or low input voltage. the flag is inoperative during overtemperature shutdown. enable input the mic37501/37502 also feature an enable input for on/off control of the device. its shutdown state draws zero current (only micoamperes of leakage). the enable input is ttl/ cmos compatible for simple logic interface, but can be connected to up to v in . when enabled, it draws approxi- mately 15 a. adjustable regulator design in r1 v out v in c out r2 en out adj gnd mic37502 enable shutdown v 1.240v 1 r1 r2 out =+ ? ? ? ? ? ? figure 2. adjustable regulator with resistors the mic37502 allows programming the output voltage any- where between 1.24v and the 5.5v 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 =? ? ? ? ? ? ?
january 2002 7 mic37500/37501/37502 mic37500/37501/37502 micrel package information scale 20:1 0.375 (9.52) 0.365 (9.27) 0.360 (9.14) 0.350 (8.89) 0.080 (2.03) 0.070 (1.78) 0.010 bsc (0.25 bsc) 0.045 (1.14) 0.035 (0.89) 0.316 bsc (8.03 bsc) 0.256 bsc (6.50 bsc) 0.031 (0.79) 0.025 (0.63) 0.005 (0.13) 0.001 (0.03) 6 0 0.010 bsc (0.25 bsc) 0.050 bsc (1.27 bsc) 0.420 (10.67) 0.410 (10.41) 0.050 (1.27) 0.030 (0.76) 0.320 (8.13) 0.310 (7.87) dimensions: inch (mm) 7-lead s-pak (r)
mic37500/37501/37502 micrel mic37500/37501/37502 8 january 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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