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lp2950*/2951 100ma low-dropout voltage regulator * lp2950 discontinuance september 2007. micrel inc. ? 2180 fortune drive ? san jose, ca 95131 ? usa ? tel +1 ( 408 ) 944-0800 ? fax + 1 (408) 474-1000 ? http://www.micrel.com september 2008 m9999-091208 general description the lp2950 and lp2951 are micropower voltage regulators with very low dropout voltage (typically 40mv at light loads and 380mv at 100ma), and very low quiescent current (75a typical). the quiescent current of the lp2950 /lp2951 increases only slightly in dropout, thus prolonging battery life. this feature, among others, makes the lp2950 and lp2951 ideally suited for use in battery-powered systems. available in a 3-pin to-92 package, the lp2950 is pin- compatible with the older 5v regulators. additional system functions, such as programmable output voltage and logic- controlled shutdown, are ava ilable in the 8-pin dip and 8- pin soic versions of the lp2951. data sheets and support documentation can be found on micrel?s web site at: www.micrel.com. features ? high accuracy 5v, guaranteed 100ma output ? extremely low quiescent current ? low-dropout voltage ? extremely tight load and line regulation ? very low temperature coefficient ? use as regulator or reference ? needs only 1f for stability lp2951 versions only ? current and thermal limiting ? error flag warns of output dropout ? logic-controlled electronic shutdown ? output programmable from 1.24 to 29v applications ? automotive electronics ? voltage reference ? avionics ___________________________________________________________________________________________________________ block diagram lp2590 and lp2951 block diagram (pin numbers refer to lp2591)
micrel, inc. lp2950/2951 september 2008 2 m9999-091208 additional features available with the lp2951 also include an error flag output t hat warns of a low output voltage, which is often due to failing batteries on the input. this may also be used as a power-on reset. a logic-compatible shutdown input is also available which enables the regulator to be switched on and off. this part may also be pin-strapped for a 5v output, or programmed from 1.24v to 29v with the use of two external resistors. the lp2950 is available as either a -02 or -03 version. the -02 and -03 versions are guaranteed for junction temperatures from ?40c to +125c; the -02 version has a tighter output and reference voltage specification range over temperature. the lp2951 is available as an -02 or -03 version. the lp2950 and lp2951 have a tight initial tolerance (0.5% typical), a very low output voltage temperature coefficient which allows use as a low-power voltage reference, and extremely good load and line regulation (0.05% typical). this greatly reduces the error in the overall circuit, and is the result of careful design techniques and process control. ___________________________________________________________________________________________________________ ordering information part number voltage accuracy junction temperature range package lead finish lp2950-02bz* 5.0v 0.5% ?40 to +125c 3-pin to-92 plastic standard lp2950-03bz* 5.0v 1.0% ?40 to +125c 3-pin to-92 plastic standard lp2951-02bm 5.0v 0.5% ?40 to +125c 8-pin soic standard lp2951-03bm 5.0v 1.0% ?40 to +125c 8-pin soic standard lp2951-02bn 5.0v 0.5% ?40 to +125c 8-pin plastic dip standard lp2951-03bn** 5.0v 1.0% ?40 to +125c 8-pin plastic dip standard LP2951-02YM 5.0v 0.5% ?40 to +125c 8-pin soic pb-free lp2951-03ym 5.0v 1.0% ?40 to +125c 8-pin soic pb-free lp2951-02yn 5.0v 0.5% ?40 to +125c 8-pin plastic dip pb-free note: * to-92 package discontinuance notification issued september 2007. end-of-life-buy offer thru december 31, 2007. contact fa ctory for additional information. ** contact factory for pb-free version. pin configuration to-92 (z) (bottom view) dip (n) and soic (m) see mic2950 for a part with: 1) higher output (150ma), 2) trans ient protection (60v), and 3) reverse input protection to ?20v.
micrel, inc. lp2950/2951 september 2008 3 m9999-091208 absolute maximum ratings (1) if military/aerospace specified devices are required, contact your local micrel representative/distributor for availability and specifications. power dissipation .....................................in ternally limited lead temperature (solde ring, 5 se c.)........................ 260c storage temperature ................................?65c to +150c operating junction temperature range (8) lp2950, lp2951 ................................. ?40c to +125c input supply voltage ........................................?0.3 to +30v feedback input voltage (9, 10) ............................?1.5 to +30v shutdown input voltage (9) ................................?0.3 to +30v error comparator output voltage (9) .................?0.3 to +30v esd rating is to be determined electrical characteristics (1) t a = 25c except as noted. parameter condition min typ max units lp295x-02 (0.5%) 4.975 5.000 5.025 v lp295x-03 (1%) 4.950 5.000 5.050 v output voltage t j = 25c lp2951-4.8 (1%) 4.802 4.850 4.899 v lp295x-02 (0.5%) 4.950 5.050 v lp295x-03 (1%) 4.925 5.075 v output voltage ?25c t j +85c lp2951-4.8 (1%) 4.777 4.872 v lp295x-02 (0.5%) 4.940 5.060 v lp295x-03 (1%) 4.900 5.100 v output voltage over full temperature range ?40c to +125c lp2951-4.8 (1%) 4.753 4.947 v lp295x-02 (0.5%), 100a i l 100ma, t j t j(max) 4.930 5.070 v lp295x-03 (1%), 100a i l 100ma, t j t j(max) 4.880 5.120 v output voltage over load variation lp2951-4.8 (1%), 100a i l 100ma, t j t j(max) 4.733 4.967 v lp295x-02 (0.5%), note 12 20 100 ppm/c lp295x-03 (1%), note 12 50 150 ppm/c output voltage temperature coefficient lp2951-4.8 (1%), note 12 50 150 ppm/c lp295x-02 (0.5%), notes 14, 15 0.03 0.10 0.20 % % lp295x-03 (1%), notes 14, 15 0.04 0.20 0.40 % % line regulation lp2951-4.8 (1%), notes 14, 15 0.04 0.20 0.40 % % lp295x-02 (0.5%), note 14 , 100a i l 100ma 0.04 0.10 0.20 % % lp295x-03 (1%), note 14 , 100a i l 100ma 0.10 0.20 0.30 % % load regulation lp2951-4.8 (1%), note 14 , 100a i l 100ma 0.10 0.20 0.30 % %
micrel, inc. lp2950/2951 september 2008 4 m9999-091208 parameter condition min typ max units note 5 , i l = 100a 50 80 150 mv mv dropout voltage note 5 , i l = 100ma 380 450 600 mv mv i l = 100a 100 150 200 a a ground current i l = 100ma 8 12 14 ma ma dropout current v in = 4.5v, i l = 100a 180 250 310 a a current limit v out = 0v 160 220 220 ma ma thermal regulation note 13 0.05 0.20 %/w 10hz to 100khz, c l = 1f 430 v rms 10hz to 100khz, c l = 200f 160 v rms output noise 10hz to 100khz, c l = 3.3f, 0.01f bypass feedback to output 100 v rms lp295x-02 (0.5%) 1.220 1.200 1.235 1.250 1.260 v v lp295x-03 (1%) 1.210 1.200 1.235 1.260 1.270 v v reference voltage lp2951-4.8 (1%) 1.210 1.200 1.235 1.260 1.270 v v lp295x-02 (0.5%), note 7 1.190 1.270 v lp295x-03 (1%), note 7 1.185 1.285 v reference voltage lp2951-4.8 (1%), note 7 1.185 1.285 v feedback bias current 20 40 60 na na lp295x-02 (0.5%), note 12 20 ppm/c lp295x-03 (1%), note 12 50 ppm/c reference voltage lp2951-4.8 (1%), note 12 50 ppm/c feedback bias current temperature coefficient 0.1 na/c output leakage current v oh = 30v 0.01 1.00 2.00 a a output low voltage (flag) v in = 4.5v, i ol = 200a 150 250 400 mv mv upper threshold voltage note 6 40 25 60 mv mv lower threshold voltage note 6 75 95 140 mv mv hysteresis note 6 15 mv
micrel, inc. lp2950/2951 september 2008 5 m9999-091208 parameter condition min typ max units lp295x-02 (0.5%) low high 2.0 1.3 0.7 v v v lp295x-03 (1%) low high 2.0 1.3 0.7 v v v input logic voltage lp2951-4.8 (1%) low high 2.0 1.3 0.7 v v v v shutdown = 2.4v 30 50 100 a a shutdown input current v shutdown = 30v 450 600 700 a a regulator output current in shutdown note 11 3 10 20 a a notes: 1. boldface limits apply at temperature extremes. 2. unless otherwise specified all limits guaranteed for t j = 25c, v in = 6v, i l = 100a and c l = 1f. additional conditions for the 8-pin versions are feedback tied to 5v tap and output tied to output sense (v out = 5v) and v shutdown 0.8v. 3. guaranteed and 100% production tested. 4. guaranteed but not 100% production tested. t hese limits are not used to calculate outgoing aql levels. 5. dropout voltage is defined as the input to output differ ential at which the output voltage drops 100mv below its nominal value measured at 1v differential. at very low values of programmed out put voltage, the minimum input supply voltage of 2v (2.3v over temper ature) must be taken into account. 6. comparator thresholds are expressed in terms of a volt age differential at the feedback terminal below the nominal referen ce voltage measured at 6v input. to express these thresholds in terms of output voltage change, multiply by the error amplifier 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 95mv x 5v/1.235v = 384mv. thresholds remain constant as a percent of v out as v out is varied, with the dropout warning occurring at typically 5% below nominal, 7.5% guaranteed. 7. v ref v out (v in ? 1 v), 2.3v v in 30v, 100a < i l 100ma, t j t jmax . 8. the junction-to-ambient thermal resistance of the to-92 package is 180c/w with 0.4? leads and 160c/w with 0.25? leads t o a pc board. the thermal resistance of the 8-pin dip package is 105c/w junction-to-ambient when soldered di rectly to a pc board. juncti on-to-ambient thermal resistance for the soic (m) package is 160c/w. 9. may exceed input supply voltage. 10. when used in dual-supply systems where the output terminal sees loads returned to a negative supply, the output voltage sh ould be diode-clamped to ground. 11. v shutdown 2v, v in 30 v, v out = 0, with feedback pin tied to 5v tap. 12. output or reference voltage temperature coefficient is defined as the worst case voltage change divided by the total tempe rature range. 13. thermal regulation is defined as the change in output volt age at a time t after a change in power dissipation is applied, excluding load or line regulation effects. specif ications are for a 50ma load pulse at v in = 30v (1.25w pulse) for t = 10ms. 14. regulation is measured at constant j unction temperature, using pulse testing with a low duty cycle. changes in output vol tage due to heating effects are covered in the specification for thermal regulation. 15. line regulation for the lp2951 is tested at 150c for i l = 1ma. for i l = 100a and t j = 125c, line regulation is guaranteed by design to 0.2%. see typical performance characteristics fo r line regulation versus temperature and load current.
micrel, inc. lp2950/2951 september 2008 6 m9999-091208 typical characteristics
micrel, inc. lp2950/2951 september 2008 7 m9999-091208 typical characteristics (continued)
micrel, inc. lp2950/2951 september 2008 8 m9999-091208 typical characteristics (continued)
micrel, inc. lp2950/2951 september 2008 9 m9999-091208 application information external capacitors a 1.0f (or greater) capacit or is required between the lp2950/lp2951 output and ground to prevent oscillations due to in stability. most types of tantalum or aluminum electrolytics will be adequate; film types will work, but are costly and therefore not recommended. many aluminum electrolyti cs have electrolytes that freeze at about ?30c, so solid tantalum capacitors are recommended for operation below ?25c. 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 0.33f for current below 10ma or 0.1f for currents below 1ma. using the 8-pin versions at voltages below 5v runs the error amplifier at lower gains so that more output capacitance is needed. for the worst-case situation of a 100ma load at 1.23v output (output shorted to feedbac k) a 3.3f (or greater) capacitor should be used. the lp2950 will remain stable and in regulation with no load in addition to the internal voltage divider, unlike many other voltage regulator s. this is especially important in cmos ram keep-alive applications. when setting the output voltage of the lp2951 version with external resistors, a minimum load of 1a is recomm- ended. a 0.1f capacitor should be placed from the lp2950/lp2951 input to ground if there is more than 10 inches of wire between the input and the ac filter capacitor or if a battery is used as the input. stray capacitance to the lp2951 feedback terminal (pin 7) can cause instability. this may especially be a problem when using high value external resistors to set the output voltage. adding a 100pf capacitor between output and feedback and increasing the output capacitor to at least 3.3f will remedy this. error detection comparator output a logic low output will be pr oduced by the comparator whenever the lp2951 output falls out of regulation by more than approximately 5%. this figure is the comparator?s built-in offset of about 60mv divided by the 1.235v reference voltage. (ref er to the block diagram on page 1). this trip level remains ?5% below normal? regardless of the programmed output voltage of the lp2951. for example, the error flag 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, current limiting, or thermal limiting. figure 1 is a timing diagram depicting the /error signal and the regulated output voltage as the lp2951 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 = 4.75v). since the lp2951?s 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 (approximately 4.75v) does not vary with load. the error comparator has an open-collector output which requires an external pull-up resistor. depending on system requirements, this re sistor 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 400a, 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 (lp2951) the lp2951 may be pin-strapped for 5v using its internal voltage divider by tying pin 1 (output) to pin 2 (sense) and pin 7 (feedbac k) to pin 6 (5v tap). alternatively, it may be programmed for any output voltage between its 1.235v reference and its 30v maximum rating. an external pai r of resistors is required, as shown in figure 2. the complete equation for the output voltage is: 2 fb 2 1 ref out r i r r 1 v v + ? ? ? ? ? ? + = where v ref is the nominal 1.235 reference voltage and i fb is the feedback pin bias current, nominally 20na. the minimum recommended 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 2% 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 lp2951 typically draws 60a at no load with pin 2 open-circuited, this is a small price to pay. 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 the only method by which noise can be reduced on the 3-pin lp2950 and is relatively inefficient, as increasing the capacitor from 1f to 220f only decreases the noise from 430v to 160vrms for a 100khz bandwidth at 5v output.
micrel, inc. lp2950/2951 september 2008 10 m9999-091208 noise can be reduced fourfold by a bypass capacitor across r 1 , since it reduces the high frequency gain from 4 to unity. pick: 200hz r 2 1 c 1 bypass ? ? or about 0.01f. when doing this, the output capacitor must be increased to 3.3f to maintain stability. these changes reduce the output noise from 430v to 100vrms for a100khz bandwidth at 5v output. with the bypass capacitor added, noise no longer scales with output voltage so that improvements are more dramatic at higher output voltages. figure 1. error output timing figure 2. adjustable regulator
micrel, inc. lp2950/2951 september 2008 11 m9999-091208 typical applications wide input voltage range current limiter 5v regulator with 2.5v sleep function low drift current source 5v current limiter
micrel, inc. lp2950/2951 september 2008 12 m9999-091208 typical applications regulator with early warn ing and auxiliary output
micrel, inc. lp2950/2951 september 2008 13 m9999-091208 typical applications latch off when error flag occurs open circ uit detector for 4ma to 20ma current loop regulator with state-of-charge indicator
micrel, inc. lp2950/2951 september 2008 14 m9999-091208 typical applications low battery disconnect system over temperature protection circuit
micrel, inc. lp2950/2951 september 2008 15 m9999-091208 schematic diagram
micrel, inc. lp2950/2951 september 2008 16 m9999-091208 package information 8-pin soic (m) 0.380 (9.65) 0.370 (9.40) 0.135 (3.43) 0.125 (3.18) pin 1 dimensions: inch (mm) 0.018 (0.57) 0.100 (2.54) 0.013 (0.330) 0.010 (0.254) 0.300 (7.62) 0.255 (6.48) 0.245 (6.22) 0.380 (9.65) 0.320 (8.13) 0.0375 (0.952) 0.130 (3.30) 8-pin plastic dip (n)
micrel, inc. lp2950/2951 september 2008 17 m9999-091208 3 2 1 10 typ. 5 typ. 5 typ. 0.185 (4.699) 0.175 (4.445) 0.185 (4.699) 0.175 (4.445) 0.085 (2.159) diam . 0.500 (12.70) min. 0.090 (2.286) typ. 0.0155 (0.3937 ) 0.0145 (0.3683 ) seat ing plane 0.025 (0.635) max uncontrolled lead diamet er 0.016 (0.406) 0.014 (0.356) 0.105 (2.667) 0.095 (2.413) 0.055 (1.397) 0.045 (1.143) 0.090 (2.286) radius, typ . 0.145 (3.683) 0.135 (3.429) 0.055 (1.397) 0.045 (1.143) bottom view to-92 (z) 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 specific ations at any time without notification to the customer. micrel products are not designed or authorized for use as components in life suppor t appliances, devices or systems where malfu nction of a product can reasonably be expected to result in pers onal injury. life support devices or system s 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 re sulting from such use or sale. ? 1999 micrel, incorporated.

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