4-195 fast and ls ttl data 8-bit identity comparator the mc54/74f521 is an expandable 8-bit comparator . it compares two words of up to eight bits each and provides a low output when the two words match bit for bit. the expansion input i a = b also serves as an active-low en - able input. ? compares two 8-bit words in 6.5 ns typical ? expandable to any word length ? 20-pin package 10 2 3 4 5 6 7 8 9 14 15 17 18 19 20 16 11 12 13 1 v cc o a = b b 7 a 7 b 6 b 5 a 6 b 0 i a = b a 0 a 1 b 1 b 2 a 2 connection diagram (top view) a 5 a 4 b 4 a 3 gnd b 3 guaranteed operating ranges symbol parameter min typ max unit v cc supply voltage 54, 74 4.5 5.0 5.5 v t a operating ambient temperature range 54 55 25 125 c 74 0 25 70 i oh output current ? high 54,74 1.0 ma i ol output current ? low 54, 74 20 ma 8-bit identity comparator fast ? schottky ttl 20 1 dw suffix soic case 751d-03 20 1 n suffix plastic case 738-03 j suffix ceramic case 732-03 20 1 mc54/74f521 ordering information mc54fxxxj ceramic mc74fxxxn plastic mc74fxxxdw soic
4-196 fast and ls ttl data mc54/74f521 logic diagram note: this diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays. a 0 b 0 a 1 b 1 a 2 b 2 a 3 b 3 a 4 b 4 a 5 b 5 a 6 b 6 a 7 b 7 i a = b o a = b logic symbol v cc = pin 20 gnd = pin 10 1 18 17 16 15 14 13 12 11 9 8 7 6 5 4 3 2 19 o a = b i a = b b 7 a 7 b 6 a 6 b 5 a 5 b 3 a 3 b 4 a 4 b 2 a 2 b 1 a 1 b 0 a 0 dc characteristics over operating temperature range (unless otherwise specified) limits symbol parameter min typ max unit test conditions v ih input high voltage 2.0 v guaranteed input high voltage v il input low voltage 0.8 v guaranteed input low voltage v ik input clamp diode voltage 1.2 v i in = 18 ma v cc = min v oh output high voltage 54, 74 2.5 3.4 v i oh = 1.0 ma v cc = 4.5 v 74 2.7 3.4 v i oh = 1.0 ma v cc = 4.75 v v ol output low voltage 0.35 0.5 v i ol = 20 ma v cc = min 20 m a v in = 2.7 v v cc = max i ih input high current 100 m a v in = 7.0 v i il input low current 0.6 ma v in = 0.5 v v cc = max i os output short circuit current (note 2) 60 150 ma v out = 0 v v cc = max i cc power supply current 21 32 ma i a = b = gnd v cc = max notes: 1. for conditions shown as min or max, use the appropriate value specified under guaranteed operating ranges. 2. not more than one output should be shorted at a time, nor for more than 1 second.
4-197 fast and ls ttl data mc54/74f521 function table inputs output i a = b a, b o a = b l a = b* l l a b h h a = b* h h a b h h = high voltage level l = low voltage level *a 0 = b 0 , a 1 = b 1 , a 2 = b 2 , etc. ac characteristics 54/74f 54f 74f t a = +25 c t a = 55 c to +125 c t a = 0 c to +70 c v cc = +5.0 v v cc = 5.0 v 10% v cc = 5.0 v 10% c l = 50 pf c l = 50 pf c l = 50 pf symbol parameter min typ max min max min max unit t plh propagation delay 2.5 6.5 10 2.5 15 2.5 11 ns t phl a n or b n to o a = b 3.0 6.5 10 3.0 12 3.0 11 t plh propagation delay 2.5 4.5 6.5 2.5 8.5 2.5 7.5 ns t phl i a = b to o a = b 3.5 5.0 9.0 3.5 10 3.5 10 figure 1. applications parallel expansion ripple expansion a 0 b 0 a 7 b 7 a 8 b 8 a 15 b 15 a 16 b 16 a 23 b 23 enable low ...... ....... ....... ...... ....... ....... i a = b o a = b i a = b o a = b i a = b o a = b i a = b o a = b i a = b o a = b i a = b o a = b a 0 b 0 a 7 b 7 a 8 b 8 a 15 b 15 a 16 b 16 a 23 b 23
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