rev. 10/30/00 spx2975 180 ma low dropout voltage regulators features applications ? 3.0v, 3.3v and 5.0v fixed output voltages ? battery powered systems ? very low quiescent current ? cordless telephones ? low dropout voltage ? radio control systems ? extremely tight load and line regulation ? portable/palm top/notebook computers ? very low temperature coefficient ? portable consumer equipment ? needs only 1 f for stability ? portable instrumentation ? current & thermal limiting ? avionics ? unregulated dc input can withstand -20v reverse battery ? automotive electronics and +60v positive transients ? smps post-regulator ? similar replacement for lp2950/lp2951 sockets ? voltage reference spx2975 so-8 versions only ? error flag warns of output dropout ? logic- controlled electronic shutdown ? output programmable from 1.24 to 29v product description the spx2975 is a low power voltage regulator. this device is an excellent choice for use in battery-powered applications such a s cordless telephones, radio control systems, and portable computers. the spx2975 features very low quiescent current and very l ow dropout voltage (typ. 50mv at light load and 380 mv at 180 ma). this includes a tight initial tolerance of 0.5% typ., extremel y good load and line regulation 0.05% typ. and very low output temperature coefficient, making the spx2975 useful as a low-power volta ge reference. other additional key features include higher output current (150ma), positive transient protection up to 60v (load dump), and the ability to survive an unregulated input voltage transient of -20v below ground (reverse battery). the error flag output feature is used as power-on reset for warning of a low output voltage, due to falling voltage input of ba tteries. another feature is the logic-compatible shutdown input which enables the regulator to be switched on and off. the spx2975 is offered in a 3-pin to-92 package compatible with other 5v regulators. the spx2975 is available in 8-pin plastic, so-8 packages . top view 2 1 3 4 8 7 6 5 spx2975 8-pin surface mount (s) bottom view to-92 (n) 13 2 v out sense shutdown gnd error 5v tap feedback v in v in gnd v out pin connections
rev. 10/30/00 spx2975 absolute maximum ratings power dissipation..........................................internally limited input supply voltage (survival) .................. ....-20v to +60v lead temp. (soldering, 5 seconds) ................................ 260c feedback input voltage .................................. -1.5v to +30v storage temperature range ............................ -65 to +150c shutdown input voltage..................................- 0.3v to +30v operating junction temperature range (note 10) error comparator output ................................-0.3v to +30v spx2975................................................... -55 to +150c esd rating ........................................... .................. 2kv min spx2975ac/spx2975c .......................... -40 to +125c electrical characteristics at v s =15v, t a =25c, unless otherwise specified. boldface apply over the full operating temperature range. parameter conditions (note 2) spx2975ac min typ max spx2975c min typ max units output voltage t j = 25c -25c t j 85c -40c t j +125c 3.2835 3.267 3.2608 3.3 3.3165 3.333 3.3396 3.267 3.2505 3.2604 3.3 3.333 3.695 3.3396 v output voltage 100 a i l 180 ma t j t jmax 3.2505 3.3 3.3495 3.201 3.3 3.399 v output voltage t j = 25c -25c t j 85c -40c t j +125c 4.975 4.95 4.94 5.0 5.0 5.0 5.025 5.050 5.06 4.95 4.925 4.90 5.0 5.0 5.0 5.05 5.075 5.10 v output voltage 100 a i l 180 ma t j t jmax 4.925 5.0 5.075 4.85 5.0 5.15 v output voltage temperature coefficient (note 1) 20 50 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 a i l 180 ma 0.04 0.1 0.1 0.2 % dropout voltage (note 5) i l = 100 a i l = 100 ma i l = 180 ma 50 380 450 80 450 500 50 380 450 80 450 500 mv ground current i l = 100 a i l = 100 ma i l = 180 ma 150 8 18 170 12 22 150 8 18 170 12 22 a ma ma current limit v out = 0 130 200 130 200 ma thermal regulation 0.05 0.2 0.05 0.2 %/w output noise, 10hz to 100khz c l = 1 f c l = 200 f c l = 13.3 f (bypass = 0.01 f pins 7 to 1(spx2975)) 430 160 100 430 160 100 v rms 8-pin versions only spx2975ac spx2975c reference voltage 1.22 1.235 1.25 1.21 1.23 1.26 v reference voltage over temperature ( note 6) 1.19 1.27 1.18 1.28 v feedback pin bias current 40 60 40 60 na reference voltage temperature coefficient (note 7) 20 50 ppm/c feedback pin bias current temperature coefficient 0.1 0.1 na/c output leakage current v oh = 30v 0.01 1 0.01 1 a output low voltage v in = 4.5v i ol = 400 a 150 250 150 250 mv upper threshold voltage (note 8) 40 60 40 60 mv lower threshold voltage (note 8) 75 95 75 95 mv hysteresis (note 8) 15 15 mv
rev. 10/30/00 spx2975 parameter conditions (note 2) spx2975ac min typ max spx2975c min typ max units input logic voltage low (regulator on) high (regulator off) 2 1.3 0.7 2 1.3 0.7 v shut down pin input current v s = 2.4v v s = 30v 30 675 50 800 30 675 50 800 a regulator output current in shutdown (note 9) 3 10 3 10 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 a and c l = 1 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 spx2975 is tested at 150 c for i l = 1ma. for i l = 100 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 100mv below its nominal valu e 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 int o account. note 6: v ref v out (v in - 1v), 2.3 v in 30v, 100 a i l 100 ma, t j t jmax . note 7: comparator thresholds are expressed in terms of a voltage differential at the feedback terminal below the nominal reference vo ltage 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 95mv x 5v/1.235 = 384mv. thresholds remain co nstant 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 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. note 10: the junction -to-ambient thermal resistance of the to-92 package is 180 c/ w with 0.4? leads and 160 c/ w with 0.25? leads to a pc board. the thermal resistance of the 8-pin dip package is 105 c/w junction-to-ambient when soldered directly to a pc board. junction-to-ambient thermal resistance for the soic (s) package is 160 c/w. block diagram feedback input output unregulated dc shutdown ground error ______ 5v tap sense 5v @ 180ma 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 330k 180k ? ? ? ? .. ? ? ? ? .. .. 1 f _ _ spx2975 block diagram
rev. 10/30/00 spx2975 application hints external capacitors the stability of the spx2975 requires a 1.0 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 a bout -30 c. the esr of about 5 ? 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 f and 0.1 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 f or greater must be used for the condition of 10ma load at 1.23v output. the spx2975, 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 spx2975, a minimum load of 1 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 a tantalum or aluminum electrolytic capacitor should be pl aced from the input to the ground. instability can occur if there is stray capacitance to the spx2975 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 100 pf capacitor between output and feedback and increasing the output capacitor to at least 3.3 f. error detection comparator output the comparator produces a logic low output whenever the spx2975 output falls out of regulation by more than around 5%. this is around 60mv 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 spx2975 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 vout = 4.75 ). since the spx2975 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 a, this value adds to battery drain in a low battery condition. suggested values range from 100k to 1m ? . if the output is unused this resistor is not required. programming the output voltage of spx2975 the spx2975 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 a forces an upper limit of 1.2 m ? 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 r 2 = 100k this reduces the error by 0.17% and increases the resistor program current by 12 a. since the spx2975 typically draws 60 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 spx2975 but is relatively inefficient, as increasing the capacitor from 1 f to 220 f only decreases the noise from 430 v to 160 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 r 1 200 hz or choose 0.01 f. when doing this, the output capacitor must be increased to 3.3 f to maintain stability. these changes reduce the output noise from 430 v to 100 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.
rev. 10/30/00 spx2975 typical performance characteristics
rev. 10/30/00 spx2975 typical performance characteristics (continued)
rev. 10/30/00 spx2975 typical applications + + + + 4.75v output voltage error* _______ input voltage 1.3v 5.0v figure 1. error output timing _______ * see application if 100k output error error ______ sd v out gnd fb +v in +v in 1.23v 1.2 to 30v r 1 .01uf 3.3uf r 2 v ref 3 8 5 1 4 7 shutdown input + figure 2. adjustable regulator spx2975 470k error ______ sd v out gnd +v in +v in r 1 1 f r 2 3 8 5 1 4 + fb 7 v out ? ? ? ? .. ? ? ? ? .. 470k spx2975 latch off when error flag occurs output error error ______ sd v out gnd fb +v in +v in *v out = v in 3 8 5 1 4 7 shutdown input spx2975 wide input voltage range current limiter * minimum input-output voltage ranges from 4mv to 400mv. d epending on load current, current limit is typically 160ma
rev. 10/30/00 spx2975 typical applications (continued) 100k ? ? ? ? sense sd v out gnd +v in 3 8 1 1 f + 4 400k ? ? ? ? 120k ? ? ? ? 1.5k ? ? ? ? 6v sealed lead- acid battery source fb for 5.5 v + 1n457 2 20k ? ? ? ? ni-cad backup battery memory v+ main v- spx385 low battery disconnect spx2975 gnd 4 3 5 8 2 1 7 6 sd tap fb +v in sense v out error _ ____ _ reset 100? 100? 100? 100? 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** - + + + + - - - +v out = 5v 1 f + regulator with state-of-charge indicator * optional latch off when dropout occurs. adjust r3 for c2 switching when v in is 6.0v spx2975 ** outputs go low when v in drops below designated thresholds
rev. 10/30/00 spx2975 typical applications (continued) 330k in v out fb 3 5 1 4.7uf + 7 ? .. ? .. 27k spx2975 v tap gnd sense 4 2 unregulated input 2n5432 5v output load 50ma to 300 ma 300 ma regulator with 0.75 dropout 360k 0.1uf v out min voltage = 4v +v in 8 1 fb 7 1n4001 20ma 1n457 4.7ma +5v output 2 gnd 4 4 open circuit detector for 4ma to 20ma current loop spx2975 ? .. 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 shutdown off on spx35 + system over temperature protection circuit spx2975
rev. 10/30/00 spx2975 ordering information ordering no. precision output voltage packages spx2975n-3.0 1% 3.0v 3 lead to-92 spx2975n-3.3 1% 3.3v 3 lead to-92 spx2975n-5.0 1% 5.0v 3 lead to-92 spx2975acn-3.0 0.5% 3.0v 3 lead to-92 spx2975acn-3.3 0.5% 3.3v 3 lead to-92 spx2975acn-5.0 0.5% 5.0v 3 lead to-92 spx2975cp-3.0 1% 3.0v 8 lead soic spx2975cp-3.3 1% 3.3v 8 lead soic spx2975cp-5.0 1% 5.0v 8 lead soic spx2975acp-3.0 0.5% 3.0v 8 lead soic spx2975acp-3.3 0.5% 3.3v 8 lead soic spx2975acp-5.0 0.5% 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 liab ility arising 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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