? semiconductor components industries, llc, 2002 january, 2002 rev. 2 1 publication order number: mc34268/d mc34268 800 ma, 2.85 v, scsi-2 active terminator, low dropout voltage regulator the mc34268 is a medium current, low dropout positive voltage regulator specifically designed for use in scsi2 active termination circuits. this device offers the circuit designer an economical solution for precision voltage regulation, while keeping power losses to a minimum. the regulator consists of a 1.0 v dropout composite pnp/npn pass transistor, current limiting, and thermal limiting. these devices are packaged in the 8pin sop8 and 3pin dpak and sot223 surface mount power packages. applications include active scsi2 terminators and post regulation of switching power supplies. ? 2.85 v output voltage for scsi2 active termination ? 1.0 v dropout ? output current in excess of 800 ma ? thermal protection ? short circuit protection ? output trimmed to 1.4% tolerance ? no minimum load required ? space saving dpak, sot223 and sop8 surface mount power packages simplified block diagram input thermal limiting control circuit current limit output ground see detailed ordering and shipping information in the package dimensions section on page 3 of this data sheet. ordering information 8 1 8 7 6 5 1 2 3 4 gnd sop8 d suffix case 751 dpak dt suffix case 369a input nc nc 123 (top view) (top view) 1 3 output output heatsink surface (shown as terminal 4 in case outline drawing) is connected to pin 2. sot223 st suffix case 318e 1 3 pin 1. ground 2. output 3. input 4. output 4 marking diagrams alyw 34268 1 8 34268 alyww ayw 268st a = assembly location l = wafer lot y = year w = work week http://onsemi.com
mc34268 http://onsemi.com 2 maximum ratings rating symbol value unit power supply input voltage v in 15 v power dissipation and thermal characteristics dt suffix, plastic package, case 369a t a = 25 c, derate above t a = 25 c thermal resistance, junctiontocase thermal resistance, junctiontoair d suffix, plastic package, case 751 t a = 25 c, derate above t a = 25 c thermal resistance, junctiontocase thermal resistance, junctiontoair st suffix, plastic package, case 318e t a = 25 c, derate above t a = 25 c thermal resistance, junctiontocase thermal resistance, junctiontoair p d r q jc r q ja p d r q jc r q ja p d r q jc r q ja internally limted 5.0 87 internally limited 22 140 internally limited 15 245 w c/w c/w w c/w c/w w c/w c/w operating junction temperature range t j 0 to +150 c storage t emperature t stg 55 to +150 c electrical characteristics (v in = 4.25 v, c o = 10 m f, for typical values t j = 25 c, for min/max values t j = 0 c to +125 c, unless otherwise noted.) characteristic symbol min typ max unit output voltage (t j = 25 c, i o = 0 ma) output voltage, over line, load, and temperature (v in = 3.9 v to 15 v, i o = 0 ma to 490 ma) v o 2.81 2.76 2.85 2.85 2.89 2.93 v line regulation (v in = 4.25 v to 15 v, i o = 0 ma, t j = 25 c) reg line e e 0.3 % load regulation (i o = 0 ma to 800 ma, t j = 25 c) reg load e e 0.5 % dropout voltage (i o = 490 ma) v in v o e 0.95 1.1 v ripple rejection (f = 120 hz) rr 55 e e db maximum output current (v in = 5.0 v) i (max) 800 e e ma bias current (v in = 4.25 v, i o = 0 ma) i b e 5.0 to 3.0 8.0 ma minimum load current to maintain regulation (v in = 15 v) i l(min) e e 0 ma i o , output load current (ma) in v o -v figure 1. dropout voltage versus output load current 1.5 1.3 1.1 0.9 0.7 0.5 0 200 400 600 800 1000 figure 2. transient load regulation , dr o p o ut v o lta g e (v) t j = 25 c 20 ms/div v in = 5.0 v c o = 10 m f t a = 25 c , output current i o v o , output voltage deviation d
mc34268 http://onsemi.com 3 figure 3. typical scsi application 1n5819 to scsi bus mc34268 scsi regulator 110 w 10 10 5.0v v in v o gnd c o figure 3 is a circuit of a typical scsi terminator application. the mc34268 is designed specifically to provide 2.85 v required to drive a scsi2 bus. the output current capability of the regulator is in excess of 800 ma; enough to drive standard scsi2, fast scsi2, and some wide scsi2 applications. the typical dropout voltage is less than 1.0 v, allowing the ic to regulate to input voltages less than 4.0 v. internal protective features include current and thermal limiting. the mc34268 requires an external 10 m f capacitor with an esr of less than 10 w for stability over temperature. with economical electrolytic capacitors, cold temperature operation can pose a stability problem. as temperature decreases, the capacitance also decreases and the esr increases, which could cause the circuit to oscillate. tantalum capacitors may be a better choice if small size is a requirement. also, the capacitance and esr of a tantalum capacitor is more stable over temperature. , thermal resistance junctiontoair ( c/w) figure 4. sop8 thermal resistance versus p.c.b. copper length 0 10203040 l, length of copper (mm) figure 5. dpak thermal resistance versus p.c.b. copper length 0 102030405060 l, length of copper flags (mm) q ja , thermal resistance junctiontoair ( c/w) q ja 70 90 80 70 60 50 40 180 160 120 80 40 0 l l 2.0 oz copper l 9.0 mm p.c. board heatsink example l l 2.0 oz copper p.c. board heatsink example ordering information device package shipping information mc34268d so8 98 units / rail mc34268dr2 so8 2500 units / tape & reel mc34268dt dpak 75 units / rail mc34268dtrk dpak 2500 units / tape & reel mc34268stt3 sot223 4000 units / tape & reel
mc34268 http://onsemi.com 4 package dimensions sop8 d suffix case 75107 issue w dpak dt suffix case 369a13 issue ab seating plane 1 4 5 8 n j x 45 k notes: 1. dimensioning and tolerancing per ansi y14.5m, 1982. 2. controlling dimension: millimeter. 3. dimension a and b do not include mold protrusion. 4. maximum mold protrusion 0.15 (0.006) per side. 5. dimension d does not include dambar protrusion. allowable dambar protrusion shall be 0.127 (0.005) total in excess of the d dimension at maximum material condition. a b s d h c 0.10 (0.004) dim a min max min max inches 4.80 5.00 0.189 0.197 millimeters b 3.80 4.00 0.150 0.157 c 1.35 1.75 0.053 0.069 d 0.33 0.51 0.013 0.020 g 1.27 bsc 0.050 bsc h 0.10 0.25 0.004 0.010 j 0.19 0.25 0.007 0.010 k 0.40 1.27 0.016 0.050 m 0 8 0 8 n 0.25 0.50 0.010 0.020 s 5.80 6.20 0.228 0.244 x y g m y m 0.25 (0.010) z y m 0.25 (0.010) z s x s m d a k b r v s f l g 2 pl m 0.13 (0.005) t e c u j h t seating plane z dim min max min max millimeters inches a 0.235 0.250 5.97 6.35 b 0.250 0.265 6.35 6.73 c 0.086 0.094 2.19 2.38 d 0.027 0.035 0.69 0.88 e 0.033 0.040 0.84 1.01 f 0.037 0.047 0.94 1.19 g 0.180 bsc 4.58 bsc h 0.034 0.040 0.87 1.01 j 0.018 0.023 0.46 0.58 k 0.102 0.114 2.60 2.89 l 0.090 bsc 2.29 bsc r 0.175 0.215 4.45 5.46 s 0.020 0.050 0.51 1.27 u 0.020 --- 0.51 --- v 0.030 0.050 0.77 1.27 z 0.138 --- 3.51 --- notes: 1. dimensioning and tolerancing per ansi y14.5m, 1982. 2. controlling dimension: inch. 123 4
mc34268 http://onsemi.com 5 package dimensions sot223 st suffix case 318e04 issue k h s f a b d g l 4 123 0.08 (0003) c m k j dim a min max min max millimeters 0.249 0.263 6.30 6.70 inches b 0.130 0.145 3.30 3.70 c 0.060 0.068 1.50 1.75 d 0.024 0.035 0.60 0.89 f 0.115 0.126 2.90 3.20 g 0.087 0.094 2.20 2.40 h 0.0008 0.0040 0.020 0.100 j 0.009 0.014 0.24 0.35 k 0.060 0.078 1.50 2.00 l 0.033 0.041 0.85 1.05 m 0 10 0 10 s 0.264 0.287 6.70 7.30 notes: 1. dimensioning and tolerancing per ansi y14.5m, 1982. 2. controlling dimension: inch.
mc34268 http://onsemi.com 6 notes
mc34268 http://onsemi.com 7 notes
mc34268 http://onsemi.com 8 on semiconductor and are trademarks of semiconductor components industries, llc (scillc). scillc reserves the right to make changes without further notice to any products herein. scillc makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does scillc assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages. atypicalo parameters which may be provided in scill c data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. all operating parameters, including atypicalso must be validated for each customer application by customer's technical experts. scillc does not convey any license under its patent rights nor the rights of others. scillc products are not designed, intended, or authorized for use as components in systems intended for surgical implant into t he body, or other applications intended to support or sustain life, or for any other application in which the failure of the scillc product could create a sit uation where personal injury or death may occur. should buyer purchase or use scillc products for any such unintended or unauthorized application, buyer shall indem nify and hold scillc and its of ficers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and re asonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized u se, even if such claim alleges that scillc was negligent regarding the design or manufacture of the part. scillc is an equal opportunity/affirmative action employ er. publication ordering information japan : on semiconductor, japan customer focus center 4321 nishigotanda, shinagawaku, tokyo, japan 1410031 phone : 81357402700 email : r14525@onsemi.com on semiconductor website : http://onsemi.com for additional information, please contact your local sales representative. mc34268/d literature fulfillment : literature distribution center for on semiconductor p.o. box 5163, denver, colorado 80217 usa phone : 3036752175 or 8003443860 toll free usa/canada fax : 3036752176 or 8003443867 toll free usa/canada email : onlit@hibbertco.com n. american technical support : 8002829855 toll free usa/canada
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