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rev. 8/6/01 lp2950/51 100ma low dropout voltage regulators ?copyright 2001 sipex corporation 1 input output unregulated dc shutdown ground error ______ sense 5v @ 100ma max to cmos or ttl reference error detection comparator error amplifier 1.23v from cmos or ttl + + + + + + 60 mv 3 7 8 1 2 6 5 4 60k w 330k w 180k w . . 1 m f _ _ feedback 5v tap lp2950/lp2951 100ma low dropout voltage regulators features applications 5.0v and 3.3v versions at 100ma output battery powered systems very low quiescent current cordless telephones low dropout voltage: 380mv at 100ma radio control systems extremely tight load and line regulation portable/palm top/notebook computers very low temperature coefficient portable consumer equipment current & thermal limiting portable instrumentation need only 1 m f for stability avionics offered in to-92 (lp2950) & soic (lp2951) smps post-regulator direct replacement for lp2950/lp2951 voltage reference automotive electronics lp2951 versions only error flag warns of output dropout logic-controlled electronic shutdown output programmable from 1.24 to 29v product description the lp2950 and lp2951 are low power voltage regulators. these devices are an excellent choice for use in battery-powered applications such as cordless telephones, radio control systems, and portable computers. the lp2950 and lp2951 feature low quiescent current and low dropout voltage (typ. 50mv at light load and 380 mv at 100ma). this includes a tight initial toleranc e (0.5% typ.), extremely good load and line regulation (0.05% typ.), and very low output temperature coefficient (20 ppm/?c typ.) , making the lp2950/lp2951 useful as a low-power voltage reference. the error flag output feature is used as a power-on reset for warning of a low output voltage, due to a falling input voltage. the logic- compatible shutdown feature enables the regulator to be switched on and off. the lp2950 is offered in a 3-pin to-92 package compatible with other 5v, 3.3v regulators. the lp2951 is available in an 8-lead soic package. block diagram of lp2951
rev. 8/6/01 lp2950/51 100ma low dropout voltage regulators ?copyright 2001 sipex corporation 2 lp2950/51 absolute maximum ratings power dissipation.....................................internally limited feedback input voltage................................. ............... -1.5v to +30v lead temp. (soldering, 5 seconds)............................260?c shutdown input voltage....................................... ........ -0.3v to +30v storage temperature range ......................... -65? to +150?c error comparator output ........................................ ..... -0.3v to +30v operating junction temperature range -40c to +125c esd rating ............................................................ .............2kv min input supply voltage..................................... -0.3v to +30v electrical characteristics v in =6v, i o =100a, c out =1f (note 2) t a =25c, unless otherwise noted . parameter conditions lp2950ac lp2951ac min. typ. max. lp2950c lp2951c min. typ. max. units 3.3 v versions output voltage t j = 25?c -25?c t j 85?c full operating temperature 3.284 3.267 3.260 3.3 3.3 3.3 3.317 3.333 3.340 3.267 3.251 3.234 3.3 3.3 3.3 3.333 3.350 3.366 v output voltage 100 m a i l 100 ma t j t jmax 3.254 3.3 3.346 3.221 3.3 3.379 v 5 v versions output voltage t j = 25?c -25?c t j 85?c full operating temperature 4.975 4.950 4.940 5.0 5.0 5.0 5.025 5.050 5.060 4.950 4.925 4.900 5.0 5.0 5.0 5.050 5.075 5.100 v output voltage 100 m a i l 100 ma t j t jmax 4.925 5.0 5.075 4.880 5.0 5.120 v all voltage options output voltage temperature coefficient (note 1) 20 120 50 150 ppm/?c line regulation (note 3) 6v v in 30v (note 4) 0.03 0.1 0.04 0.2 % load regulation (note 3) 100 m a i l 100 ma 0.04 0.1 0.1 0.2 % dropout voltage (note 5) i l = 100 m a i l = 100 ma 50 380 80 450 50 380 80 450 mv mv ground current i l = 100 m a i l = 100 ma 150 8 170 12 150 8 170 12 m a ma current limit v out = 0 150 200 150 200 ma thermal regulation 0.05 0.2 0.05 0.2 %/w output noise, c l = 1 m f 430 430 m v rms 10hz to 100khz c l = 200 m f 160 160 m v rms c l = 3.3 m f, bypass = 0.01f from pin 7 to pin 1 (lp2951) 100 100 m v rms 8-pin versions only lp2951ac lp2951c reference voltage 1.220 1.235 1.250 1.210 1.235 1.260 v reference voltage over temperature (note 6) 1.190 1.270 1.185 1.285 v feedback pin bias current 40 60 40 60 na
rev. 8/6/01 lp2950/51 100ma low dropout voltage regulators ?copyright 2001 sipex corporation 3 lp2950/51 parameter conditions (note 2) lp2951ac min. typ. max. lp2951c min. typ. max. units 8-pin versions only (continued) reference voltage temperature coefficient 20 50 ppm/?c feedback pin bias current temperature coefficient 0.1 0.1 na/?c error comparator output leakage current v oh = 30v 0.01 1 0.01 1 m a output low voltage v in = 4.5v i ol = 400 m a 150 250 150 250 mv upper threshold voltage (note 7) 40 60 40 60 mv lower threshold voltage (note 7) 75 95 75 95 mv hysteresis (note 7) 15 15 mv shutdown input input logic voltage low (regulator on) high (regulator off) 2.0 1.3 0.7 2.0 1.3 0.7 v v shut down pin input current v s = 2.4v v s = 30v 30 675 50 800 30 675 50 800 m a m a regulator output current in shutdown (note 8) 3 10 3 10 m a note 1: output or reference voltage temperature coefficients defined as the worst case voltage change divided by the total temperature range. note 2: unless otherwise specified all limits guaranteed for t j = 25 c, v in = 6v, i l = 100 m a and c l = 1 m f. 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. note 3: regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. changes in output voltag e due to heating effects are covered under the specification for thermal regulation. note 4 : line regulation for the lp2951 is tested at i l = 1ma. for i l = 100 m a and t j = 125 c, line regulation is guaranteed by design to 0.2%. see typical performance characteristics for line regulation versus temperature and load current. note 5: dropout voltage is defined as the input to output differential at which the output voltage drops 100 mv below its nominal val ue measured at 1v differential. at very low values of programmed output voltage, the minimum input supply voltage of 2v (2.3v over temperature) must be taken into account. note 6: v ref v out (v in - 1v), 2.3 v in 30v, 100 m a i l 100ma, t j t jmax . note 7: comparator thresholds are expressed in terms of a voltage differential at the feedback terminal below the nominal reference v oltage measured at 6v input. to express these thresholds in terms of output voltage change, multiply by the error amplifier gain = v out /v ref = (r 1 + r 2 )/r 2 . 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 = 384 mv. thresholds remain c onstant as a percent of v out as v out is varied, with the dropout warning occurring at typically 5% below nominal, 7.5% guaranteed. note 8: v shutdown 3 2v, v in 30v, v out =0, feedback pin tied to 5v tap. note 9: all typical values are not guaranteed. the value could vary from lot to lot.
rev. 8/6/01 lp2950/51 100ma low dropout voltage regulators ?copyright 2001 sipex corporation 4 input current input current ( m a) 75 0 010 input voltage (volts) r l = 50k w 25 50 100 125 150 175 200 225 250 123 r l = 8 dropout characteristics output voltage (volts) 0 0 input voltage (volts) 123 456 1 2 3 4 5 6 r l =50k w r l =50k w 456789 load current (ma) quiescent current ground pin current (ma) 10 1 0.1 0.01 0.1 1 10 100 ground current ground current ( m a) 320 280 0 input voltage (volts) 240 80 40 0 12345678 120 160 200 i l = 1ma i l = 0 input voltage (volts) input current input current (ma) 160 150 140 130 70 50 0 120 110 100 90 80 60 40 30 20 10 0 12345678910 r l =50 w v out = 5v quiescent current 190 170 150 130 -75 -50 -25 0 25 50 75 100 125 150 temperature (oc) quiescent current ( m a) v in =6v i l =100ua ground current 16 14 12 0 1 2345678 input voltage ground current (ma) 10 8 6 4 2 0 i l =100ma ground current 16 12 8 4 -75 -50 -25 0 25 50 75 100 125 150 temperature (oc) ground current (ma) v in = 6v i l = 100ma lp2950/ lp2951 typical performance characteristic
rev. 8/6/01 lp2950/51 100ma low dropout voltage regulators ?copyright 2001 sipex corporation 5 lp2951 comparator sink current sink current (ma) 2.5 1.5 output low voltage (v) 2.0 1.0 0.5 0.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 t a = -55oc t a = 25oc t a = 125oc line transient response time( m s) 100 0 200 400 600 800 input output voltage voltage change 4v 6v 8v -50 0 50 ~ ~ mv mv mv c l = 1 m f i l = 1ma v out = 5v error comparator output comparator output (v) 8 6 0 input voltage (v) 4 2 0 -2 12 345 v out = 5v pullup resistor to separate 5v supply hysteresis output impedance 10 0.5 0.1 0.02 10 100 1k 10k 100k 1m frequency (hz) output impedance (ohms) 5 0.2 0.05 0.01 1 2 i o = 100ma i o = 100 m a i o = 1ma v out = 5v c l = 1 m f ripple rejection 90 70 60 40 10 1 10 2 10 3 10 4 10 5 10 6 frequency (hz) ripple rejection (db) 80 50 20 30 i l = 100 m a i l = 0 c l = 1 m f v in = 6v v out = 5v ripple rejection frequency (hz) ripple rejection (db) 10 6 10 3 10 2 10 1 90 80 70 60 50 20 40 30 10 4 10 5 i l = 10ma i l = 1ma c l = 1 m f v in = 6v v out = 5v drop-out voltage 600 400 300 50 -75 -50 -25 0 25 50 75 100 125 150 temperature (oc) drop-out voltage (mv) 500 100 0 i l = 100ma i l = 100 m a ~ ~ drop-out voltage t j = 25oc output current drop-out voltage (mv) 100ma 10ma 1ma 100 m a 500 400 300 200 100 0 short circuit current short circuit current (ma) 170 150 130 110 -75 -50 -25 0 25 50 75 100 125 150 temperature (oc) 160 140 120 110 lp2950/lp2951 typical performance characteristics (continued)
rev. 8/6/01 lp2950/51 100ma low dropout voltage regulators ?copyright 2001 sipex corporation 6 lp2951 feedback bias current bias current (na) -30 -75 tempeature (oc) -50 0 50 75 100 150 -20 -10 0 10 20 -25 25 125 lp2951 feedback pin current feedback current ( m a) -150 -250 -2.0 -0.5 1.0 feedback voltage (v) -200 -100 -50 0 50 -1.5 -1.0 0 0.5 t a = 25oc t a = 55oc ta=1 25oc pin 7 driven by external source (regulator run open loop) lp2951 minimum operating voltage temperature minimum operating voltage (v) 2.3 2.1 1.9 1.7 -75 0 75 150 -50 -25 25 50 100 125 load transient response 250 100 -50 100 01 23 45 time (ms) load output voltage current change (mv) m a ~ ~ ma -100 0 50 150 200 c l = 1 m f v out = 5v 100 load transient response 80 20 -40 100 04 8121620 time (ms) load output voltage current change (mv) m a 100 -60 -20 0 40 60 m a c l = 10 m f v out = 5v ~ ~ lp2950 maxium rated output output current (ma) 120 80 0 010 20 30 input voltage (v) 25 15 5 t a = 85 oc t a =25 oc t jmax = 125 oc 0.25" leads soldered to-92 package to pc board 100 60 40 20 vout=5v lp2950 maxium rated output current output current (ma) 120 100 60 40 0 input voltage (v) 80 20 0 510 15 20 2530 t jmax = 125o c v out = 5v t a = 25oc t a = 50oc t a = 85oc 8-pin molded to pc board dip soldered enable transient 7 6 4 -100 0 100 200 300 400 500 600 700 time (us) shutdown output pinout voltage (v) voltage (v) 3 2 1 0 2 -2 0 5 out = 5v v in = 8v i l = 10ma v lp2951 divider resistance pin 2 to pin 4 resistance (k w ) 400 200 100 0 -75 0 75 150 temperature (oc) -50 -25 25 50 100 125 300 c l = 1 m f c l = 10 m f lp2950/lp2951 typical performance characteristics (continued)
rev. 8/6/01 lp2950/51 100ma low dropout voltage regulators ?copyright 2001 sipex corporation 7 shutdown threshold voltage shutdown threshold voltage (v) 1.8 1.6 1.0 -75 temperature (?c) 1.4 1.2 0.8 0.6 -50 -25 0 25 50 75 100 125 150 thermal response power output voltage dissipation (w) change (mv) 4 2 1 0 time ( m s) 0 -2 0 -1 10 20 30 40 50 5 1.25w ~ ~ output noise voltage noise spectral density ( m v/hz) 3.5 2.5 2.0 0.0 10 2 10 3 10 4 10 5 frequency (hz), c byp =0.1uf 3.0 1.5 1.0 0.5 c = 3.3 m f l ripple rejection ripple rejection (db) 80 60 40 10 10 1 10 3 10 4 10 6 frequency (hz) i l = 50 m a i l = 100ma c l = 1 m f v in = 6v v out = 5v 70 50 30 20 10 2 10 5 line regulation output voltage change (mv) 30 25 20 10 5 input voltage (v) 15 10 5 0 5 0 -5 -10 10 15 20 25 30 ~ ~ i l = 100 m a i l = 1ma t j = 150 ?c t j = 125 ?c i l = 100 m a c = 0.1 m f byp c l = 220 m f i l = 100ma c l = 1 m f lp2950/lp2951 typical applications
9 + + + + 4.75v output voltage error* _______ input voltage 1.3v 5.0v * see application info. lp2950/51 application hints external capacitors the stability of the lp2950/lp2951 requires a 1.0 m f or greater capacitor between output and ground. oscillation could occur without this capacitor. most types of tantalum or aluminum electrolytic works fine here. for operations below -25 c solid tantalum is recommended since the many aluminum types have electrolytes that freeze at about -30 c. the esr of about 5 w or less and resonant frequency above 500khz are the most important parameters in the value of the capacitor. the capacitors value may be increased without limit. at lower values of output current, less output capacitance is required for stability. for the currents below 10ma the value of the capacitor can be reduced to 0.33 m f and 0.1 m f for 1ma. more output capacitance is needed for the 8-pin version at voltages below 5v since it runs the error amplifier at lower gain. at worst case 3.3 m f or greater must be used for the condition of 100ma load at 1.23v output. the lp2950/51 unlike other low dropout regulators will remain stable and in regulation with no load in addition to the internal voltage divider. this feature is especially important in applications like cmos ram keep-alive. when setting the output voltage of the lp2950/51 version with external resistors, a minimum load of 1 m a is recommended 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 then a 1 m a tantalum or aluminum electrolytic capacitor should be placed from the input to the ground. instability can occur if there is stray capacitance to the lp2951 feedback terminal (pin 7). this could cause more problems when using a higher value of external resistors to set the output voltage. this problem can be fixed by adding a 100pf capacitor between output and feedback and increasing the output capacitor to at least 3.3 m f. \ error detection comparator output the comparator produces a logic low output whenever the lp2951 output falls out of regulation by more than around 5%. this is around 60 mv offset divided by the 1.235 reference voltage. this trip level remains 5% below normal regardless of the programmed output voltage of the regulator. figure 1 shows the timing diagram depicting the error signal and the regulator output voltage as the lp2951 input is ramped up and down. the error signal becomes low at around 1.3v input, and goes high around 5v input (input voltage at which v out = 4.75). since the lp2951?s dropout voltage is load dependent, the input voltage trip point (around 5v) will vary with the load current. the output voltage trip point (approx. 4.75v) does not vary with load. the error comparator has an open-collector output, which requires an external pull-up resistor. depending on the system requirements the resistor may be returned to 5v output or other supply voltage. in determining the value of this resistor, note that the output is rated to sink 400 m a, this value adds to battery drain in a low battery condition. suggested values range from 100k to 1m w . if the output is unused this resistor is not required. programming the output voltage of 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 (feedback) to pin 6 (5v tap). also, it may be programmed for any output voltage between its 1.235v reference and its 30v maximum rating . as seen in figure 2, an external pair of resistors is required. refer to the below equation for the programming of the output voltage: v out = v ref (1 + r 1 /r 2 )+ i fb r 1 the v ref is 1.235 and i fb is the feedback bias current, nominally - 20na. the minimum recommended load current of 1 m a forces an upper limit of 1.2m w on value of r 2 . if no load is presented the i fb produces an error of typically 2% in v out which may be eliminated at room temperature by trimming r 1 . to improve the accuracy choose the value of r2 = 100k this reduces the error by 0.17% and increases the resistor program current by 12 m a. since the lp2951 typically draws 60 m a at no load with pin 2 open-circuited this is a small price to pay reducing output noise it may be an advantage to reduce the ac noise present at the output. one way is to reduce the regulator bandwidth by increasing the size of the output capacitor. this is the only way that noise can be reduced on the 3 lead lp2950 but is relatively inefficient, as increasing the capacitor from 1 m f to 220 m f only decreases the noise from 430 m v to 160 m v rms for a 100khz bandwidth at 5v output. noise could also be reduced fourfold by a bypass capacitor across r 1 , since it reduces the high frequency gain from 4 to unity. pick c bypass @ 1 / 2 p r 1 200 hz or choose 0.01 m f. when doing this, the output capacitor must be increased to 3.3 m f to maintain stability. these changes reduce the output noise from 430 m v to 100 m v rms for a 100khz 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 rev. 8/6/01 lp2950/51 100ma low dropout voltage regulators ?copyright 2001 sipex corporation 8
rev. 8/6/01 lp2950/51 100ma low dropout voltage regulators ?copyright 2001 sipex corporation 9 lp2950/lp2951 typical applications 100k output error error ______ sd v out gnd fb +v in +v in 1.23v 1.2 to 30v r 1 .01 m f 3.3 m f r 2 v ref 3 8 5 1 4 7 shutdown input + lp2951 470k w error ______ sd v out gnd +v in +v in r 1 1 m f r 2 3 8 5 1 4 + fb 7 v out 470k w lp2951 reset output error error ______ sd v out gnd fb +v in +v in *v out = v in 3 8 5 1 4 7 shutdown input lp2951 *minimum input-output voltage ranges from 40mv to 400mv. depending on load current. current limit is typically 150ma figure 2. adjustable regulator figure 3. latch off when error flag occurs figure 4. wide input voltage range current limiter
rev. 8/6/01 lp2950/51 100ma low dropout voltage regulators ?copyright 2001 sipex corporation 10 lp2950/lp2951 typical applications (continued) 100k w sense sd v out gnd +v in 3 8 1 1 m f + 4 400 k w 120k w 1.5k w 6v sealed lead- acid battery source fb for 5.5 v + 1n457 2 20k w ni-cad backup battery memory v+ main v+ spx385 lp2951 gnd 4 3 5 8 2 1 7 6 sd tap fb +v in sense v out error ______ reset 100k 100k 100k 1k 100k 10k 20k 1k 39k 39k c3 c1 c2 c4 1% 1% 1% 1% 6v lead- acid battery r 3 <6.2v** <5.8v** <6.0v** - + + + + - - - w .. w .. w .. w .. w .. w .. w .. w .. w .. w .. +v out = 5v 1uf + * optional latch off when dropout occurs. adjust r3 for c2 switching when v in is 6.0v * outputs go low when v in drops below desgnated threshholds lp2951 figure 5. low battery disconnect figure 6. regulator with state-of charge indicator
rev. 8/6/01 lp2950/51 100ma low dropout voltage regulators ?copyright 2001 sipex corporation 11 external circuit protected from over temperature (v+ goes off when temp > 125) or relay 8.2k temp sensor gnd v out fb sd +v in +v in 10k 5 degree shutdown flag error _______ 3 5 8 4 7 1 aux shutdow input off on w as35 + - lp2951 w . . 330k in v out fb 6 8 1 4.7 m f + 7 w w 27k lp2951 v ta p gnd sense 4 2 unregulated input 2n5432 5v output load 50ma to 300 ma (2) 360k 0.1 m f v out min voltage = 4v +v in 8 1 fb 7 1n4001 20ma 1n457 4.7ma +5v output 2 gnd 4 4 lp2951 w lp2950/lp2951 typical applications (continued) figure 7. system over temperature protection figure 8. open circuit detector for 4ma to 20ma current loop figure 9. 300ma regulator with 0.75v
rev. 8/6/01 lp2950/51 100ma low dropout voltage regulators ?copyright 2001 sipex corporation 12 lp2950/lp2951 schematic diagram
rev. 8/6/01 lp2950/51 100ma low dropout voltage regulators ?copyright 2001 sipex corporation 13 lp2950/lp2951 package diagram to-92 (n) 8-pin surface mount (s) alpha as293 0 1 lp2951 top view 2 3 4 5 6 7 8 output sense shutdown ground input feedback 5v or 3.3v output error lp2950 bottom view 13 2 v in ground v out ordering information ordering no. accuracy output voltage packages lp2950acn-3.3 0.5% 3.3v 3 lead to-92 lp2950acn-5.0 0.5% 5.0v 3 lead to-92 lp2950cn-3.3 1% 3.3v 3 lead to-92 lp2950cn-5.0 1% 5.0v 3 lead to-92 lp2951acs-3.3 0.5% 3.3v 8 lead soic lp2951acs-5.0 0.5% 5.0v 8 lead soic lp2951cs-3.3 1% 3.3v 8 lead soic lp2951cs-5.0 1% 5.0v 8 lead soic signal processing excellence sipex corporation headquarters and main offices: 22 linnell circle billerica, ma 01821 tel: (978) 667-8700 fax: (978) 670-9001 e-mail: sales@sipex.com 233 south hillview drive milpitas, ca 95035 tel: (408) 935-7600 fax: (408) 934-7500 sipex corporation reserves the right to make changes to any products described herein. sipex does not assume any liability ari sing out of the application or use of any product or circuit described hereing; neither does it convey any license under its patent rights nor the rights of others. corporation

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