? 2000 fairchild semiconductor corporation ds006474 www.fairchildsemi.com august 1986 revised march 2000 dm74s182 look-ahead carry generator dm74s182 look-ahead carry generator general description these circuits are high-speed, look-ahead carry genera- tors, capable of anticipating a carry across four binary adders or groups of adders. they are cascadable to per- form full look-ahead across n-bit adders. carry, generate- carry, and propagate-carry functions are provided as shown in the pin designation table. when used in conjunction with the 181 arithmetic logic unit, these generators provide high-speed carry look-ahead capability for any word length. each dm74s182 generates the look-ahead (anticipated carry) across a group of four alu's and, in addition, other carry look-ahead circuits may be employed to anticipate carry across sections of four look-ahead packages up to n-bits. the method of cascad- ing circuits to perform multi-level look-ahead is illustrated under typical application data. carry input and output of the alu's are in their true form, and the carry propagate (p) and carry generate (g) are in negated form; therefore, the carry functions (inputs, out- puts, generate, and propagate) of the look-ahead genera- tors are implemented in the compatible forms for direct connection to the alu. reinterpretations of carry functions, as explained on the 181 data sheet are also applicable to and compatible with the look-ahead generator. positive logic equations for the dm74s182 are: c n + x = g 0 + p 0 c n c n + y = g 1 + p 1 g 0 + p 1 p 0 c n c n + z = g 2 + p 2 g 1 + p 2 p 1 g 0 + p 2 p 1 p 0 c n g = g 3 (p 3 + g 2) (p 3 + p 2 + g 1) (p 3 + p 2 + p 1 + g 0) p = p 3 p 2 p 1 p 0 features n typical propagation delay time 7 ns n typical power dissipation 260 mw ordering code: connection diagram pin designations order number package number package description dm74s182n n16e 16-lead plastic dual-in-line package (pdip), jedec ms-001, 0.300 wide designation pin nos. function g0, g1, g2, g3 3, 1, 14, 5 active low carry generate inputs p0, p1, p2, p3 4, 2, 15, 6 active low carry propagate inputs c n 13 carry input c n + x , c n + y , 12, 11, 9 carry outputs c n + z g 10 active low carry generate output p 7 active low carry propagate output v cc 16 supply voltage gnd 8 ground
www.fairchildsemi.com 2 dm74s182 logic diagram v cc = pin 16 gnd = pin 8 typical application 64-bit alu, full-carry look ahead in three levels a and b inputs, and f outputs of 181 are not shown.
3 www.fairchildsemi.com dm74s182 absolute maximum ratings (note 1) note 1: the absolute maximum ratings are those values beyond which the safety of the device cannot be guaranteed. the device should not be operated at these limits. the parametric values defined in the electrical characteristics tables are not guaranteed at the absolute maximum ratings. the recommended operating conditions table will define the conditions for actual device operation. recommended operating conditions electrical characteristics over recommended operating free air temperature (unless otherwise noted) note 2: all typicals are at v cc = 5v, t a = 25 c. note 3: not more than one output should be shorted at a time, and the duration should not exceed one second. note 4: i cch is measured with all outputs open, inputs p3 and g3 at 4.5v, and all other inputs grounded. note 5: i ccl is measured with all outputs open, inputs g0, g1, and g2 at 4.5v, and all other inputs grounded. supply voltage 7v input voltage 5.5v operating free air temperature range 0 c to + 70 c storage temperature range - 65 c to + 150 c symbol parameter min nom max units v cc supply voltage 4.75 5 5.25 v v ih high level input voltage 2 v v il low level input voltage 0.8 v i oh high level output current - 1ma i ol low level output current 20 ma t a free air operating temperature 0 70 c symbol parameter conditions min typ max units (note 2) v i input clamp voltage v cc = min, i i = - 18 ma - 1.2 v v oh high level v cc = min, i oh = max 2.7 3.4 v output voltage v il = max, v ih = min v ol low level v cc = min, i ol = max 0.5 v output voltage v ih = min, v il = max i i input current @ max input voltage v cc = max, v i = 5.5v 1 ma i ih high level v cc = max p0, p1 or g3 200 m a input current v i = 2.7v p3 100 p2 150 c n 50 g0, g2 350 g1 400 i il low level v cc = max p0, p1 or g3 - 8ma input current v i = 0.5v p3 - 4 p2 - 6 c n - 2 g0, g2 - 14 g1 - 16 i os short circuit output current v cc = max (note 3) - 40 - 100 ma i cch supply current with outputs high v cc = max (note 4) 39 55 ma i ccl supply currents with outputs low v cc = max (note 5) 69 109 ma
www.fairchildsemi.com 4 dm74s182 switching characteristics at v cc = 5v and t a = 25 c r l = 280 w symbol parameter from (input) c l = 15 pf c l = 50 pf units to (output) min max min min t plh propagation delay time gn or pn to c n + x, y, z 710ns low-to-high level output t phl propagation delay time gn or pn to c n + x, y, z 711ns high-to-low level output t plh propagation delay time gn or pn to g 7.5 11 ns low-to-high level output t phl propagation delay time gn or pn to g 10.5 14 ns high-to-low level output t plh propagation delay time pn to p 6.5 10 ns low-to-high level output t phl propagation delay time pn to p 10 14 ns high-to-low level output t plh propagation delay time c n to to c n + x, y, z 10 13 ns low-to-high level output t phl propagation delay time c n to to c n + x, y, z 10.5 14 ns high-to-low level output
5 www.fairchildsemi.com dm74s182 look-ahead carry generator physical dimensions inches (millimeters) unless otherwise noted 16-lead plastic dual-in-line package (pdip), jedec ms-001, 0.300 wide package number n16e fairchild does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and fairchild reserves the right at any time without notice to change said circuitry and specifications. life support policy fairchilds products are not authorized for use as critical components in life support devices or systems without the express written approval of the president of fairchild semiconductor corporation. as used herein: 1. life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be rea- sonably expected to result in a significant injury to the user. 2. a critical component in any component of a life support device or system whose failure to perform can be rea- sonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. www.fairchildsemi.com
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