rev. 11/21/00 spx2954 250 ma low drop out voltage regulator features applications ? output accuracy 5v, 3.3v,@ 250ma output ? 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 ? current & thermal limiting ? portable instrumentation ? improved replacement with hight i out for lp2954 sockets ? automotive electronics ? smps post-regulator spx2954 version over lp2954 ? voltage reference ? error flag warns of output dropout ? avionics ? logic-controlled electronic shutdown ? output programmable from 1.24v to 29v ? input can withstand -20v reverse battery & +60 positive transient product description the spx2954 is a low power voltage regulator. this device is an excellent choice for use in battery-powered applications such as cordless telephones, radio control systems, and portable computers. the spx2954 features very low quiescent current (75 a typ.) and very low dropout voltage. this includes a tight initial tolerance of 0.5% max and 1% max., and very low output temperature coefficient, making the spx2954 useful as a low-power voltage reference. the key spx2954 features include protection against reversed battery, fold-back current limiting, and automotive load dump protection (60v positive transient). 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 spx2954 is o ffered in a 3-pin to-92and to-263 package compatible with other 5 volt regulators, in 8-pin plastic, so-8, (same pin out as spx2951), to- 220 and to-263. the regulator output voltage (of the 8-pin) may be pin-strapped for a 5vand 3.3v or programmed from 1.24v to 29v with an extern al pair of resistors. look for spx2951 for 150ma and lp2951 for 100ma applications. to-220-5 package front view spx2954 gnd shutdown error 1) 3) 4) 5) 2) output input 12345 front view to-220-3 package spx2954 123 v in v out gnd to-263-5 package top view 45 spx2954 to-263-3 package v in v out v adj gnd shutdown error 1) 3) 4) 5) 2) output input spx2954 top view 123 3 2 1 bottom view 13 2 output gnd input to-92 (n) top view 2 1 3 4 8 7 6 5 spx2954 shutdown gnd input 5v, 3.3v tap error feedback sense output 8-pin surface mount (s) spx2954 13 2 v out gnd sot-223 package front view v in pin connections
rev. 11/21/00 spx2954 absolute maximum ratings power dissipation..........................................internally limited input supply voltage ............................. ..........-20v to +60v lead temp. (soldering, 5 seconds) ................................ 260c feedback input voltage .................................. ...-1.5 to +30v storage temperature range ............................ -65 to +150c shutdown input voltage................................... ..-0.3 to +30v operating junction temperature range (note 9) error comparator output ...................................-0 .3 to +30v spx2954................................................ -40c to +125c esd rating ............................................ ................ 2kv min electrical characteristics at v s =15v, t a =25c , unless otherwise noted. boldface applies over the full operating temperature range. parameter conditions typical spx2954a min max spx2954 min max units output voltage t j =25 c -25 c t j +85 c -40 c t j +125 c 3.3 3.284 3.267 3.260 3.317 3.333 3.340 3.267 3.251 3.234 3.333 3.350 3.366 v output voltage 1ma i l 250ma t j t jmax 3.3 3.251 3.350 3.201 3.399 v output voltage t j =25 c -25 c t j +85 c -40 c t j +125 c 5.0 5.0 5.0 4.975 4.95 4.94 5.025 5.050 5.06 4.95 4.925 4.90 5.05 5.075 5.10 v output voltage 1ma i l 250ma t j t jmax 5.0 4.925 5.075 4.85 5.15 v output voltage temperature coefficient (note 1) 20 100 150 ppm/c line regulation (note 3) 6v v in 30v (note 4) 0.03 0.10 0.20 0.20 0.40 %max load regulation (note 3) i l = 1 to 250 ma i l = 0.1 to 1 ma 0.04 0.16 0.20 0.20 0.30 %max dropout voltage (note 5) i l = 1ma i l = 50ma i l = 100ma i l = 250 ma 60 220 250 375 100 150 250 420 300 450 450 600 100 150 250 420 300 450 450 600 mv ground current i l = 1ma i l = 50ma i l = 100ma i l = 250 ma 90 1 4.5 21 150 180 2 2.5 6 8 14 16 150 180 2 2.5 6 8 20 22 a ma current limit v out = 0 550 600 550 600 ma thermal regulation 0.05 0.2 0.2 %/w output noise, 10hz to 100khz i l = 100ma c l = 2.2 f c l = 33 f 400 260 v rms 8-pin versions only typical spx2954a spx2954 reference voltage 1.235 1.220 1.200 1.250 1.260 1.210 1.200 1.260 1.270 v reference voltage over temperature (note 6) 1.190 1.27 1.185 1.285 v feedback pin bias current 20 40 60 40 60 na reference voltage temperature coefficient (note 7) 50 ppm/c feedback pin bias current temperature coefficient 0.1 na/c
rev. 11/21/00 spx2954 (continued) parameter conditions (note 2) typical spx2954a min max spx2954 min max units applies for spx2954yt5-x, spx2954yu5-x and spx2954ys-x error comparator output leakage current v oh = 30v 0.01 100 2.00 100 2.00 a output low voltage v in = 4.5v i ol = 400 a 150 250 400 250 400 mv upper threshold voltage (note 8) 240 -320 -380 -150 -100 -320 -380 -150 -100 mv lower threshold voltage (note 8) 350 -450 -640 230 160 -450 -640 230 160 mv hysteresis (note 8) 60 mv shutdown input v sd output turn-on threshold voltage 1.155 1.140 1.305 1.320 1.155 1.140 1.305 1.320 v hysteresis(hyst) 6 mv input bias current(i b ) v in(sd) = 0v to 5v 10 -30 -50 -30 -50 -30 -50 -30 -50 na 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 are 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 spx2954 is tested at 150 c for i l = 1 ma. 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 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 a i l 250 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 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 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. note 8: v shutdown 2v, v in 30v, v out =0, feedback pin tied to 5v tap. note 9: 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. feedback input output unregulated dc shutdown ground error ______ 5v tap sense 5v @ 250ma max to cmos or ttl reference error comparator error amplifier 1.23v from cmos or ttl + + + + + + 60 mv 3 7 8 1 2 6 5 4 ? .. 60k 330k 180k ? .. ? .. .. 1f _ _ spx2954 block diagram v o
rev. 11/21/00 spx2954 application hints external capacitors for the stability of the spx2954 requires a 2.2 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 of below -25 c solid tantalum is recommended since the many aluminum types have electrolytes the 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 capacitor value can 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 0.5 f and 0.15 f for 1ma. more output capacitance needed for the 8-pin version at voltages below 5v since it runs the error amplifier at lower gain. at worst case 5 f or greater must be used for the condition of 250ma load at 1.23v output. the spx2954, 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 application like cmos ram keep-alive. when setting the output voltage of the spx2954, 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 spx2954 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 f. error detection comparator output the comparator produces a logic low output whenever the spx2954 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 spx2954 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 spx2954?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 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 spx2954 the spx2954 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). + + + + 4.75v output voltage error* _______ input voltage 1.3v 5.0v figure 1. error output timing _______ * see application info . 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 spx2954
rev. 11/21/00 spx2954 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 c hoose the value of r 2 = 100k this reduces the error by 0.17% and increases the resistor program current by 12 a. since the lp2951 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 spx2954 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. heatsink requirements depending on the maximum ambient temperature and maximum power dissipation a heatsink may be required with the spx2954. the junction temperature range has to be within the range specified under absolute maximum ratings under all possible operating conditions. to find out if a heatsink is required, the maximum power dissipation of the device needs to be calculated. this is the maximum specific ac voltage that must be taken into consideration at input. figure 3 shows the condition and power dissipation which should be calculated with the following formula: p total = (v in - 5) i l + (v in )i g next step is to calculate the temperature rise t r ( max ). t j ( max ) maximum allowable junction temperature, t a ( max ) maximum ambient temperature : t r ( max ) = t j ( max ) - t a ( max ) junction to ambient thermal resistance (j-a) can be calculated after determining of p total & t r ( max ): (j-a) = t r (max)/p (max) if the (j-a) is 60 c/w or higher, the device could be operated without a heatsink. if the value is below 60 c/w then the heatsink is required and the thermal resistance of the heatsink can be calculated by the following formula, (j-c) junction to case, (c-h) case to heatsink, (h-a) heatsink to ambient: (j-a) = (j-c) + (c-h) + (h-a) + 2.2 uf + spx2954 i in v in i g i l 5v in out gnd load i in = i l + i g figure 3. 5v regulator circuit
rev. 11/21/00 spx2954 typical applications output error error ______ sd v out gnd fb +v in +v in *v out = v in 3 8 5 1 4 7 shutdown input spx2954 wide input voltage range cu rrent limited * minimum input-output voltage ranges from 4mv to 400mv. depending on load current. current limit is typically 160ma v out gnd +v in +v in *v out = 5v 4 spx2954 10uf + spx2954 fixed +5v regulator
rev. 11/21/00 spx2954 ordering information ordering no. precision output voltage packages spx2954t3-3.3 1% 3.3v 3 lead to-263 spx2954t3-5.0 1% 5.0v 3 lead to-263 spx2954at3-3.3 0.5% 3.3v 3 lead to-263 spx2954at3-5.0 0.5% 5.0v 3 lead to-263 spx2954t5-3.3 1% 3.3v 5 lead to-263 spx2954t5-5.0 1% 5.0v 5 lead to-263 spx2954at5-3.3 0.5% 3.3v 5 lead to-263 spx2954at5-5.0 0.5% 5.0v 5 lead to-263 spx2954n-3.3 1% 3.3v 3 lead to-92 spx2954n-5.0 1% 5.0v 3 lead to-92 spx2954an-3.3 0.5% 3.3v 3 lead to-92 spx2954an-5.0 0.5% 5.0v 3 lead to-92 spx2954u3-3.3 1% 3.3v 3 lead to-220 spx2954u3-5.0 1% 5.0v 3 lead to-220 spx2954au3-3.3 0.5% 3.3v 3 lead to-220 spx2954au3-5.0 0.5% 5.0v 3 lead to-220 spx2954u5-3.3 1% 3.3v 5 lead to-220 spx2954u5-5.0 1% 5.0v 5 lead to-220 spx2954au5-3.3 0.5% 3.3v 5 lead to-220 spx2954au5-5.0 0.5% 5.0v 5 lead to-220 spx2954s-3.3 1% 3.3v 8 lead soic spx2954s-5.0 1% 5.0v 8 lead soic spx2954as-3.3 0.5% 3.3v 8 lead soic spx2954as-5.0 0.5% 5.0v 8 lead soic spx2954m3-3.3 1% 3.3v 3 lead sot-223 spx2954m3-5.0 1% 5.0v 3 lead sot-223 spx2954am3-3.3 0.5% 3.3v 3 lead sot-223 spx2954am3-5.0 0.5% 5.0v 3 lead sot-223 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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