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mic2937a/29371/29372 micrel, inc. may 2006 1 mic2937a/29371/29372 features ? high output voltage accuracy ? guaranteed 750ma output ? low quiescent current ? low dropout voltage ? extremely tight load and line regulation ? very low temperature coef?cient ? current and thermal limiting ? input can withstand C20v reverse battery and +60v posi - tive transients ? error ?ag warns of output dropout ? logic-controlled electronic shutdown ? output programmable from 1.24v to 26v(mic29372) ? available in to-220, to-263, to-220-5, and to-263-5 packages. applications ? battery powered equipment ? cellular telephones ? laptop, notebook, and palmtop computers ? pcmcia v cc and v pp regulation/switching ? bar code scanners ? automotive electronics ? smps post-regulator/ dc to dc modules ? high ef?ciency linear power supplies pin con?guration ground output input to-220-5 package (mic29371/29372bt/wt) to-220 package (mic2937a-xxbt/wt) general description the mic2937a family are bulletproof ef?cient voltage regu - lators with very low dropout voltage (typically 40mv at light loads and 300mv at 500ma), and very low quiescent current (160a typical). the quiescent current of the mic2937a in - creases only slightly in dropout, thus prolonging battery life. key mic2937a features include protection against reversed battery, fold-back current limiting, and automotive load dump protection (60v positive transient). the mic2937 is available in several con?gurations. the mic2937a-xx devices are three pin ?xed voltage regulators with 3.3v, 5v, and 12v outputs available. the mic29371 is a ?xed regulator offering logic compatible on/off switching input and an error ?ag output. this ?ag may also be used as a power-on reset signal. a logic-compatible shutdown input is provided on the adjustable mic29372, which enables the regulator to be switched on and off. to-263 package (mic2937a-xxbu/wu) ground output input to-263-5 package (mic29371/29372bu/wu) five lead package pin functions: mic29371 mic29372 1) error adjust 2) input shutdown 3) ground ground 4) output input 5) shutdown output the tab is ground on the to-220 and to-263 packages. mic2937a/29371/29372 750ma low-dropout voltage regulator micrel, inc. ? 2180 fortune drive ? san jose, ca 95131 ? usa ? tel + 1 (408) 944-0800 ? fax + 1 (408) 474-1000 ? http://www.micrel.com 2 1 3 1 2 3 4 5 2 1 3 1 2 3 4 5
mic2937a/29371/29372 micrel, inc. mic2937a/29371/29372 2 may 2006 ordering information part number voltage junction temp. range package standard rohs compliant* mic2937a-3.3bu mic2937a-3.3wu 3.3v C 40 oc to +125 o c to-263-3 mic2937a-3.3b t mic2937a-3.3 w t 3.3v C 40 oc to +125 o c to-220-3 mic2937a-5.0bu mic2937a-5.0wu 5.0v C 40 oc to +125 o c to-263-3 mic2937a-5.0bt mic2937a-5.0wt 5.0v C 40 oc to +125 o c to-220-3 mic2937a-12bu mic2937a-12wu 12v C 40 oc to +125 o c to-263-3 mic2937a-12bt mic2937a-12wt 12v C 40 oc to +125 o c to-220-3 mic29371-3.3bu mic29371-3.3wu 3.3v C 40 oc to +125 o c to-263- 5 mic29371-3.3b t mic29371-3.3 w t 3.3v C 40 oc to +125 o c to-220- 5 mic29371-5.0bu mic29371-5.0wu 5.0v C 40 oc to +125 o c to-263- 5 mic29371-5.0bt mic29371-5.0wt 5.0v C 40 oc to +125 o c to-220- 5 mic29371-12bu mic29371-12wu 12v C 40 oc to +125 o c to-263- 5 mic29371-12bt mic29371-12wt 12v C 40 oc to +125 o c to-220- 5 mic29372bu mic29372wu adj C 40 oc to +125 o c to-263- 5 mic29372bt mic29372wt adj C 40 oc to +125 o c to-220- 5 * rohs compliant with high-melting solder exemption.
mic2937a/29371/29372 micrel, inc. may 2006 3 mic2937a/29371/29372 electrical characteristics limits in standard typeface are for t j = 25c and limits in boldface apply over the full operating temperature range. unless other - wise speci?ed, v in = v out + 1v, i l = 5ma, c l = 10f. the mic29372 are programmed for a 5v output voltage, and v shutdown 0.6v (mic29371-xx and mic29372 only). symbol parameter conditions min typical max units v o output voltage variation from factory trimmed v out C1 1 % accuracy C2 2 5ma i l 500ma C2.5 2.5 mic2937a-12 and 29371-12 only: C1.5 1.5 C3 3 5ma i l 500ma C4 4 v o output voltage ( note 2 ) 20 100 ppm/c t temperature coef. output voltage > 10v 80 350 v o line regulation v in = v out + 1v to 26v 0.03 0.10 % v o 0.40 v o load regulation i l = 5 to 500ma 0.04 0.16 % v o ( note 3) 0.30 v in C v o dropout voltage i l = 5ma 80 150 mv ( note 4) 180 i l = 100ma 200 output voltage > 10v 240 i l = 500ma 300 output voltage > 10v 420 i l = 750ma 370 600 750 i gnd ground pin current i l = 5ma 160 250 a ( note 5) 300 i l = 100ma 1 2.5 ma 3 i l = 500ma 8 13 16 i l = 750ma 15 25 i gnddo ground pin v in = 0.5v less than designed v out 200 500 a current at dropout (v out 3.3v) ( note 5) i o = 5ma i limit current limit v out = 0v 1.1 1.5 a ( note 6) 2 v o thermal regulation ( note 7) 0.05 0.2 %/w p d e n output noise c l = 10f 400 v rms voltage (10hz to 100khz) c l = 100f 260 i l = 100ma absolute maximum ratings power dissipation ( note 1 )...............................................internally limited lead temperature (soldering, 5 seconds).........................................260c storage temperature range.............................................C65c to +150c operating junction temperature range ..........................C40c to +125c to-220 jc .....................................................................................2.5c/w to-263 jc .....................................................................................2.5c/w input supply voltage..............................................................C20v to +60v operating input supply voltage..................................................2v ? to 26v adjust input voltage ( notes 9 and 10 ).................................C1.5v to +26v shutdown input voltage .......................................................C0.3v to +30v error comparator output voltage.........................................C0.3v to +30v ? across the full operating temperature, the minimum input volta ge range for full output current is 4.3v to 26v. output will remain in-regulation at lower output voltages and low current loads down to an input of 2v at 25c.
mic2937a/29371/29372 micrel, inc. mic2937a/29371/29372 4 may 2006 electrical characteristics (continued) mic29372 parameter conditions min typical max units reference voltage 1.223 1.235 1.247 v 1.210 1.260 v max reference voltage ( note 8 ) 1.204 1.266 v adjust pin 20 40 na bias current 60 reference voltage ( note 7 ) 20 ppm/c temperature coef?cient adjust pin bias 0.1 na/c current temperature coef?cient error comparator output leakage v oh = 26v 0.01 1.00 a current 2.00 output low v in = 4.5v 150 250 mv voltage i ol = 250a 400 upper threshold ( note 9 ) 40 60 mv voltage 25 lower threshold ( note 9 ) 75 95 mv voltage 140 hysteresis ( note 9 ) 15 mv shutdown input input logic voltage 1.3 v low (on) 0.7 high (off) 2.0 shutdown pin v shutdown = 2.4v 30 50 a input current 100 v shutdown = 26v 450 600 a 750 regulator output ( note 10 ) 3 10 a current in shutdown 20 mic29371 mic29371/mic29372
mic2937a/29371/29372 micrel, inc. may 2006 5 mic2937a/29371/29372 note 1: absolute maximum ratings indicate limits beyond which damage to the component may occur. electrical speci?cations do not apply when operating the device outside of its rated operating conditions. the maximum allowable power dissipation is a function of the maximum junction temperature, t j (max) , the junction-to-ambient thermal resistance, ja , and the ambient temperature, t a . the maximum allowable power dissipation at any ambient temperature is calculated using: p (max) = (t j(max) C t a ) / ja. exceeding the maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. note 2: output voltage temperature coef?cient is de?ned as the worst case voltage change divided by the total temperature range. note 3: regulation is measured at constant junction temperature using low duty cycle pulse testing. changes in output voltage due to heating effects are covered by the thermal regulation speci?cation. note 4: dropout voltage is de?ned as the input to output differential at which the output voltage drops 100 mv below its nominal value measured at 1v differential. at low values of programmed output voltage, the minimum input supply voltage of 4.3v over temperature must be taken into account. the mic2937a operates down to 2v of input at reduced output current at 25c. note 5: ground pin current is the regulator quiescent current. the total current drawn from the source is the sum of the load current plus the ground pin current. note 6: the mic2937a family features fold-back current limiting. the short circuit (v out = 0v) current limit is less than the maximum current with normal output voltage. note 7: thermal regulation is de?ned as the change in output voltage at a time t after a change in power dissipation is applied, exclud - ing load or line regulation effects. speci?cations are for a 200ma load pulse at v in = 20v (a 4w pulse) for t = 10ms. note 8: v ref v out (v in C 1 v), 4.3v v in 26v, 5ma < i l 750 ma, t j t j max. note 9: comparator thresholds are expressed in terms of a voltage differential at the adjust terminal below the nominal reference voltage measured at 6v input (for a 5v regulator). to express these thresholds in terms of output voltage change, multiply by the error ampli?er gain = v out /v ref = (r1 + r2)/r2. for example, at a programmed output voltage of 5v, the error output is guaranteed to go low when the output drops by 95 mv x 5v/1.235 v = 384 mv. thresholds remain constant as a percent of v out as v out is varied, with the dropout warning occurring at typically 5% below nominal, 7.7% guaranteed. note 10: circuit of figure 3 with r1 150k. v shutdown 2v and v in 26v,v out = 0. note 11: when used in dual supply systems where the regulator load is returned to a negative supply, the output voltage must be diode clamped to ground. note 12: maximum positive supply voltage of 60v must be of limited duration (< 100ms) and duty cycle ( 1%). the maximum continu - ous supply voltage is 26v. feedback sense q15a out q24 q26 r27 v tap r28 r18 20 k ? q25 q23 q22 r15 100 k ? r16 30 k ? q29 q28 r17 10 ? r21 8 ? r17 12 k ? q31 q30 r23 60 k ? shdn r24 50 k ? r22 150 k ? q21 q19 c2 40 pf r14 350 k ? q14 r13 100 k ? q18 r12 110 k ? q20 q9 q15b q8 q7 r11 20.6 k ? q5 r8 31.4 k ? r10 150 k ? r9 27.8 k ? q11 q12 q13 r6 140 k ? r5 180 k ? r4 13 k ? r3 50 k ? q2 c1 20 pf q4 q3 r11 18 k ? q6 q1 10 r1 20 k ? r2 50 k ? q41 r30 30 k ? q40 q34 gnd q36 q37 r25 2.8 k ? q38 error r26 60 k ? q39 q42 q16 q17 50 k ? 10 k ? in denotes connection on mic2937a-xx and mic29371-xx versions only schematic diagram
mic2937a/29371/29372 micrel, inc. mic2937a/29371/29372 6 may 2006 typical characteristics 0 100 200 300 400 500 0 20 0 40 0 60 0 800 ) v m ( e g a t l o v t u o p o r d output current (ma) dropout voltage vs. output current 0 100 200 300 400 500 600 700 -6 0 -3 0 0 3 0 6 0 9 0 12 0 150 ) v m ( e g a t l o v t u o p o r d temperature ( c) dropout voltage vs. temperature i load = 750ma 0 1 2 3 4 5 6 0 1 2 3 4 5 6 ) v ( e g a t l o v t u p t u o input voltage (v) dropout characteristics i load = 5ma i load = 750ma 0.1 1 10 30 1 1 0 10 0 1000 ) a m ( t n e r r u c d n u o r g output current (ma) ground current vs. output current 0 50 100 150 200 0 1 2 3 4 5 6 7 8 ( t n e r r u c d n u o r g ) a supply voltage (v) ground current vs. supply voltage fixed 5v version i load = 5ma 0 5 10 15 20 25 30 0 2 4 6 8 10 ) a m ( t n e r r u c d n u o r g input voltage (v) ground current vs. supply voltage fixed 5v i load = 750ma 0.00 0.05 0.10 0.15 0.20 0.25 -6 0 -3 0 0 3 0 6 0 9 0 12 0 150 ) a m ( t n e r r u c d n u o r g temperature ( c) ground current vs. temperature i load = 5ma 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 -6 0 -3 0 0 3 0 6 0 9 0 12 0 150 ) a m ( t n e r r u c d n u o r g temperature ( c) ground current vs. temperature i load = 100ma 0 5 10 15 20 25 30 -6 0 -3 0 0 3 0 6 0 9 0 12 0 150 ) a m ( t n e r r u c d n u o r g temperature ( c) ground current vs. temperature i load = 750ma 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 -6 0 -3 0 0 3 0 6 0 9 0 12 0 150 ) a ( t n e r r u c temperature ( c) short circuit and maximum current vs. temperature v out = v nominal C 0.5v v out = 0v fixed 5v version -100 0 100 200 300 400 500 -3 0 -2 0 -1 0 0 1 0 2 0 30 ( t n e r r u c d n u o r g ) a input voltage (v) ground current vs. input voltage r load = 100 ? 3.20 3.22 3.24 3.26 3.28 3.30 3.32 3.34 3.36 3.38 3.40 -6 0 -3 0 0 3 0 6 0 9 0 12 0 150 ) v ( e g a t l o v t u p t u o temperature ( c) fixed 3.3v output voltage vs. temperature
mic2937a/29371/29372 micrel, inc. may 2006 7 mic2937a/29371/29372 0 25 50 75 100 125 -6 0 -3 0 0 3 0 6 0 9 0 12 0 150 ( t n e r r u c e l b a n e ) a temperature ( c) mic29371/2 shutdown current vs. temperaure v en = 5v v en = 2v -300 -150 0 150 300 ? ) v m ( t u p t u o -250 0 250 500 750 1000 -5 0 5 10 ) a m ( t u p t u o time (ms) load transient c out = 10 f 5ma -200 -100 0 100 200 ? ) v m ( t u p t u o -250 0 250 500 750 1000 -5 0 5 10 ) a m ( t u p t u o time (ms) load transeint c out = 100 f 5ma 0 10 20 30 40 50 -6 0 -3 0 0 3 0 6 0 9 0 12 0 150 ) a n ( t n e r r u c n i p t s u j d a temperature ( c) mic29372/3 adjust pin current vs. temperature i load = 1ma -40 -20 0 20 40 ? ) v m ( t u p t u o 4 6 8 10 -0.2 0. 0 0. 2 0. 4 0. 6 0. 8 1. 0 1. 2 1.4 ) v ( t u p n i time (ms) line transient c out = 10 f i l = 5ma -10 0 10 20 ? ) v m ( t u p t u o 4 6 8 10 -0.2 0. 0 0. 2 0. 4 0. 6 0. 8 1. 0 1. 2 1.4 ) v ( t u p n i time (ms) line transient c out = 100 f i l = 5ma 0.01 0.1 1 10 0 1 x 1 0 0 1 x 0 1 0 0 1 x 0 0 1 0 0 1 x 1 3 0 1 x 0 1 3 0 1 x 0 0 1 3 0 1 x 1 6 ( e c n a d e p m i t u p t u o ? ) frequency (hz) output impedance vs. frequency i load = 10ma
mic2937a/29371/29372 micrel, inc. mic2937a/29371/29372 8 may 2006 applications information external capacitors a 10f (or greater) capacitor is required between the mic2937a output and ground to prevent oscillations due to instability. most types of tantalum or aluminum electrolytics will be adequate; ?lm types will work, but are costly and therefore not recom - mended. many aluminum electrolytics have electrolytes that freeze at about C30c, so solid tantalums are recommended for operation below C25c. the important parameters of the capacitor are an effective series resistance of about 5 or less and a resonant frequency above 500khz. the value of this capacitor may be increased without limit. at lower values of output current, less output capacitance is required for output stability. the capacitor can be reduced to 0.5f for current below 10ma or 0.15f for currents below 1 ma. adjusting the mic29372 to voltages below 5v runs the error ampli?er at lower gains so that more output capacitance is needed. for the worst-case situation of a 750ma load at 1.23v output (output shorted to adjust) a 22f (or greater) capacitor should be used. the mic2937a/29371 will remain in regulation with a minimum load of 5ma. when setting the output voltage of the mic29372 version with external resistors, the current through these resis - tors may be included as a portion of the minimum load. a 0.1f capacitor should be placed from the input to ground if there is more than 10 inches of wire between the input and the ac ?lter capacitor or if a battery is used as the input. error detection comparator output (mic29371) a logic low output will be produced by the comparator when - ever the mic29371 output falls out of regulation by more than approximately 5%. this ?gure is the comparators built-in offset of about 75mv divided by the 1.235v reference volt - age. (refer to the block diagram on page 1). this trip level remains 5% below normal regardless of the programmed output voltage of the mic29371. for example, the error ?ag trip level is typically 4.75v for a 5v output or 11.4v for a 12v output. the out of regulation condition may be due either to low input voltage,extremely high input voltage, current limit - ing, or thermal limiting. figure 1 is a timing diagram depicting the error signal and the regulated output voltage as the mic29371 input is ramped up and down. the error signal becomes valid (low) at about 1.3v input. it goes high at about 5v input (the input voltage at which v out = 4.75). since the mic29371s dropout voltage is load-dependent (see curve in typical performance characteristics), the input voltage trip point (about 5v) will vary with the load current. the output voltage trip point (ap - proximately 4.75v) does not vary with load. * see applications information figure 1. error output timing the error comparator has an npn open-collector output which requires an external pull-up resistor. depending on system requirements, this resistor may be returned to the 5v output or some other supply voltage. in determining a value for this resistor, note that while the output is rated to sink 250a, this sink current adds to battery drain in a low battery condition. suggested values range from 100k to 1m. the resistor is not required if this output is unused. programming the output voltage (mic29372) the mic29372 may programmed for any output voltage be - tween its 1.235v reference and its 26v maximum rating. an external pair of resistors is required, as shown in figure 3. the complete equation for the output voltage is v out = v ref x { 1 + r 1 /r 2 } C | i fb | r 1 where v ref is the nominal 1.235 reference voltage and i fb is the adjust pin bias current, nominally 20na. the minimum rec - ommended load current of 1a forces an upper limit of 1.2m on the value of r 2 , if the regulator must work with no load (a condition often found in cmos in standby), i fb will produce a C2% typical error in v out which may be eliminated at room temperature by trimming r 1 . for better accuracy, choosing r 2 = 100k reduces this error to 0.17% while increasing the resistor program current to 12a. since the mic29372 typically draws 100a at no load with shutdown open-circuited, this is a negligible addition. reducing output noise in reference applications it may be advantageous to reduce the ac noise present at the output. one method is to reduce the regulator bandwidth by increasing the size of the output capacitor. this is relatively inef?cient, as increasing the capaci - tor from 1f to 220f only decreases the noise from 430v to 160v rms for a 100khz bandwidth at 5v output. noise can be reduced by a factor of four with the adjustable regulators * * output voltage input voltage error not valid not valid 5v 1.3v 4.75v
mic2937a/29371/29372 micrel, inc. may 2006 9 mic2937a/29371/29372 automotive applications the mic2937a is ideally suited for automotive applications for a variety of reasons. it will operate over a wide range of input voltages with very low dropout voltages (40mv at light loads), and very low quiescent currents (100a typical). these features are necessary for use in battery powered systems, such as automobiles. it is a bulletproof device with the abil - ity to survive both reverse battery (negative transients up to 20v below ground), and load dump (positive transients up to 60v) conditions. a wide operating temperature range with low temperature coef?cients is yet another reason to use these versatile regulators in automotive designs. figure 2. mic2937a-5.0 fixed +5v regulator figure 3. mic29372 adjustable regulator typical applications figure 5. mic29372 5.0v or 3.3v selectable regulator with shutdown. figure 4. mic29372 wide input voltage range current limiter *minimum input-output voltage ranges from 40 m v to 400 m v, depending on load current. shutdown pin low= enable output. q1 on = 3.3v, q1 off = 5.0v. c bypass ? 1 2 r 1 ? 200 hz with a bypass capacitor across r 1 , since it reduces the high frequency gain from 4 to unity. pick or about 0.01f. when doing this, the output capacitor must be increased to 10f to maintain stability. these changes reduce the output noise from 430v to 100v rms for a 100 khz bandwidth at 5v output. with the bypass capacitor added, noise no longer scales with output voltage so that improve - ments are more dramatic at higher output voltages. gnd +v in out v v 10 f + in v out = 5v in out gn d adjust shutdown v v shutdown input out v 1.2v 26v 1 r .01 f 10 f 2 r 1.23v ref v v out = v ref x (1 + ) 1 r 2 r off on out gn d adjust v v in +v in v out v in shutdown v gnd out +v in adjust shutdown input 100pf 2n2222 1% 300k ? +5v to +7v 1% 180k ? + 10 f 470 k ? off on 5v 3.3v 220k ? 1% v cc out input output 0 3.3v 1 5.0v
mic2937a/29371/29372 micrel, inc. mic2937a/29371/29372 10 may 2006 package information 3-pin to-263 (u) 3-pin to-220 (t)
mic2937a/29371/29372 micrel, inc. may 2006 11 mic2937a/29371/29372 1 1 3 4 1 2 3 4 2 1 5-pin to-263 (u) 5-pin to-220 (t)
mic2937a/29371/29372 micrel, inc. mic2937a/29371/29372 12 may 2006 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 this information furnished by micrel in this data sheet is believed to be accurate and reliable. however no responsibility is assumed by micrel for its use. micrel reserves the right to change circuitry and speci?cations at any time without noti?cation to the customer. micrel products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. life support devices or systems are devices or systems that (a) are intended 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 signi? cant injury to the user. a purchaser's use or sale of micrel products for use in life support appliances, 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. ? 1999 micrel , inc.

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