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DM74LS85 4-Bit Magnitude Comparator
August 1986 Revised March 2000
DM74LS85 4-Bit Magnitude Comparator
General Description
These 4-bit magnitude comparators perform comparison of straight binary or BCD codes. Three fully-decoded decisions about two, 4-bit words (A, B) are made and are externally available at three outputs. These devices are fully expandable to any number of bits without external gates. Words of greater length may be compared by connecting comparators in cascade. The A > B, A < B, and A = B outputs of a stage handling less-significant bits are connected to the corresponding inputs of the next stage handling more-significant bits. The stage handling the leastsignificant bits must have a high-level voltage applied to the A = B input. The cascading path is implemented with only a two-gate-level delay to reduce overall comparison times for long words.
Features
s Typical power dissipation 52 mW s Typical delay (4-bit words) 24 ns
Ordering Code:
Order Number DM74LS85M DM74LS85N Package Number M16A N16E Package Description 16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow 16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
Devices also available in Tape and Reel. Specify by appending the suffix letter "X" to the ordering code.
Connection Diagram
(c) 2000 Fairchild Semiconductor Corporation
DS006379
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DM74LS85
Function Table
Comparing Inputs A3, B3 A3 > B3 A3 < B3 A3 = B3 A3 = B3 A3 = B3 A3 = B3 A3 = B3 A3 = B3 A3 = B3 A3 = B3 A3 = B3 A3 = B3 A3 = B3 A3 = B3 A2, B2 X X A2 > B2 A2 < B2 A2 = B2 A2 = B2 A2 = B2 A2 = B2 A2 = B2 A2 = B2 A2 = B2 A2 = B2 A2 = B2 A2 = B2 A1, B1 X X X X A1 > B1 A1 < B1 A1 = B1 A1 = B1 A1 = B1 A1 = B1 A1 = B1 A1 = B1 A1 = B1 A1 = B1 A0, B0 X X X X X X A0 > B0 A0 < B0 A0 = B0 A0 = B0 A0 = B0 A0 = B0 A0 = B0 A0 = B0 A>B X X X X X X X X H L L X H L Cascading Inputs AB H L H L H L H L H L L L L H AH = HIGH Level, L = LOW Level, X = Don't Care
Logic Diagram
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DM74LS85
Absolute Maximum Ratings(Note 1)
Supply Voltage Input Voltage Operating Free Air Temperature Range Storage Temperature Range 7V 7V 0C to +70C -65C to +150C
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
Symbol VCC VIH VIL IOH IOL TA Supply Voltage HIGH Level Input Voltage LOW Level Input Voltage HIGH Level Output Current LOW Level Output Current Free Air Operating Temperature 0 Parameter Min 4.75 2 0.8 -0.4 8 70 Nom 5 Max 5.25 Units V V V mA mA C
Electrical Characteristics
over recommended operating free air temperature range (unless otherwise noted) Symbol VI VOH VOL Parameter Input Clamp Voltage HIGH Level Output Voltage LOW Level Output Voltage II Input Current @ Max Input Voltage IIH HIGH Level Input Current IIL LOW Level Input Current IOS ICC Short Circuit Output Current Supply Current Conditions VCC = Min, II = -18 mA VCC = Min, IOH = Max VIL = Max, VIH = Min VCC = Min, IOL = Max VIL = Max, VIH = Min IOL = 4 mA, VCC = Min VCC = Max VI = 7V VCC = Max VI = 2.7V VCC = Max VI = 0.4V VCC = Max (Note 3) VCC = Max (Note 4) AB Others AB Others AB Others -20 10 2.7 3.4 0.35 0.25 0.5 0.4 0.1 0.1 0.3 20 20 60 -0.4 -0.4 -1.2 -100 20 mA mA mA A mA Min Typ (Note 2) Max -1.5 Units V V
V
Note 2: All typicals are at VCC = 5V, TA = 25C. Note 3: Not more than one output should be shorted at a time, and the duration should not exceed one second. Note 4: ICC is measured with all outputs OPEN, A = B grounded and all other inputs at 4.5V.
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DM74LS85
Switching Characteristics
at VCC = 5V and TA = 25C From Symbol Parameter Input To Output A < B, A>B A=B tPHL Propagation Delay Time HIGH-to-LOW Level Output tPLH tPHL tPLH tPHL tPLH tPHL Propagation Delay Time LOW-to-HIGH Level Output Propagation Delay Time HIGH-to-LOW Level Output Propagation Delay Time LOW-to-HIGH Level Output Propagation Delay Time HIGH-to-LOW Level Output Propagation Delay Time LOW-to-HIGH Level Output Propagation Delay Time HIGH-to-LOW Level Output Any A or B Data Input A < B, A>B A=B A < B or A = B A < B or A = B A=B A=B A > B or A = B A > B or A = B A>B A>B A=B A=B Awww.fairchildsemi.com
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DM74LS85
Physical Dimensions inches (millimeters) unless otherwise noted
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow Package Number M16A
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DM74LS85 4-Bit Magnitude Comparator
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
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 FAIRCHILD'S 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 reasonably expected to result in a significant injury to the user. www.fairchildsemi.com 6 2. A critical component in any component of a life support device or system whose failure to perform can be reasonably 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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