SN54/74LS85 4-BIT MAGNITUDE COMPARATOR The SN54/ 74LS85 is a 4-Bit Magnitude Camparator which compares two 4-bit words (A, B), each word having four Parallel Inputs (A0 - A3, B0 - B3); A3, B3 being the most significant inputs. Operation is not restricted to binary codes, the device will work with any monotonic code. Three Outputs are provided: "A greater than B" (OA > B), "A less than B" (OA < B), "A equal to B" (OA = B). Three Expander Inputs, IA > B, IA < B, IA = B, allow cascading without external gates. For proper compare operation, the Expander Inputs to the least significant position must be connected as follows: IA < B= IA > B = L, IA = B = H. For serial (ripple) expansion, the OA > B, OA < B and OA = B Outputs are connected respectively to the IA > B, IA < B, and IA = B Inputs of the next most significant comparator, as shown in Figure 1. Refer to Applications section of data sheet for high speed method of comparing large words. The Truth Table on the following page describes the operation of the SN54 / 74LS85 under all possible logic conditions. The upper 11 lines describe the normal operation under all conditions that will occur in a single device or in a series expansion scheme. The lower five lines describe the operation under abnormal conditions on the cascading inputs. These conditions occur when the parallel expansion technique is used. * Easily Expandable * Binary or BCD Comparison * OA > B, OA < B, and OA = B Outputs Available 4-BIT MAGNITUDE COMPARATOR LOW POWER SCHOTTKY J SUFFIX CERAMIC CASE 620-09 16 1 N SUFFIX PLASTIC CASE 648-08 16 1 CONNECTION DIAGRAM DIP (TOP VIEW) VCC 16 A3 15 B2 14 A2 13 A1 12 B1 11 A0 10 B0 9 D SUFFIX SOIC CASE 751B-03 16 1 NOTE: The Flatpak version has the same pinouts (Connection Diagram) as the Dual In-Line Package. 1 B3 2 3 IA<B IA=B ORDERING INFORMATION SN54LSXXJ SN74LSXXN SN74LSXXD 8 4 5 6 7 IA>B OA>B OA=B OA<B GND Ceramic Plastic SOIC LOGIC SYMBOL PIN NAMES LOADING (Note a) HIGH A0 - A3, B0 - B3 IA = B IA < B, IA > B OA > B OA < B OA = B Parallel Inputs A = B Expander Inputs A < B, A > B, Expander Inputs A Greater Than B Output (Note b) B Greater Than A Output (Note b) A Equal to B Output (Note b) 1.5 U.L. 1.5 U.L. 0.5 U.L. 10 U.L. 10 U.L. 10 U.L. 10 12 13 15 9 11 14 1 LOW 0.75 U.L. 0.75 U.L. 0.25 U.L. 5 (2.5) U.L. 5 (2.5) U.L. 5 (2.5) U.L. NOTES: a) 1 TTL Unit Load (U.L.) = 40 A HIGH/1.6 mA LOW. b) The Output LOW drive factor is 2.5 U.L. for Military (54) and 5 U.L. for Commercial (74) Temperature Ranges. FAST AND LS TTL DATA 5-84 4 2 3 A0 A1 A2 A3 B0 B1 B2 B3 OA>B IA>B OA<B IA<B OA=B IA=B VCC = PIN 16 GND = PIN 8 5 7 6 SN54/74LS85 LOGIC DIAGRAM A3 (15) B3 (1) (5) OA>B A2 B2 (13) (14) (2) A<B (3) A=B (4) A>B A1 B1 (6) OA=B (12) (11) (7) OA<B A0 B0 (10) (9) TRUTH TABLE CASCADING INPUTS 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 A2,B2 A1,B1 A0,B0 X X A2>B2 A2<B2 A2=B2 A2=B2 A2=B2 A2=B2 A2=B2 A2=B2 A2=B2 A2=B2 A2=B2 X X X X A1>B1 A1<B1 A1=B1 A1=B1 A1=B1 A1=B1 A1=B1 A1=B1 A1=B1 X X X X X X A0>B0 A0<B0 A0=B0 A0=B0 A0=B0 A0=B0 A0=B0 IA>B X X X X X X X X H L X H L IA<B X X X X X X X X L H X H L IA=B X X X X X X X X L L H L L OUTPUTS OA>B OA<B OA=B H L H L H L H L H L L L H L H L H L H L H L H L L H L L L L L L L L L L H L L H = HIGH Level L = LOW Level X = IMMATERIAL GUARANTEED OPERATING RANGES Min Typ Max Unit VCC Symbol Supply Voltage Parameter 54 74 4.5 4.75 5.0 5.0 5.5 5.25 V TA Operating Ambient Temperature Range 54 74 - 55 0 25 25 125 70 C IOH IOL Output Current -- High 54, 74 - 0.4 mA Output Current -- Low 54 74 4.0 8.0 mA FAST AND LS TTL DATA 5-85 A0 A1 A2 A3 B0 B1 B2 B3 OA > B IA > B IA < B SN54/74LS85 OA < B OA = B IA = B L L H Bn B n1 B n2 B n3 An A n1 A0 A1 A2 A3 B0 B1 B2 B3 A n2 A n3 SN54/74LS85 A0 A1 A2 A3 B0 B1 B2 B3 IA > B OA > B IA < B SN54/74LS85 OA < B OA = B IA = B A>B A<B A=B L = LOW LEVEL H = HIGH LEVEL Figure 1. Comparing Two n-Bit Words APPLICATIONS Figure 2 shows a high speed method of comparing two 24-bit words with only two levels of device delay. With the technique shown in Figure 1, six levels of device delay result when comparing two 24-bit words. The parallel technique can be expanded to any number of bits, see Table 1. Table 1 WORD LENGTH NUMBER OF PKGS. 1 - 4 Bits 5 - 24 Bits 25 - 120 Bits 1 2-6 8 - 31 NOTE: The SN54/74LS85 can be used as a 5-bit comparator only when the outputs are used to drive the A0-A3 and B0-B3 inputs of another SN54/74LS85 as shown in Figure 2 in positions #1, 2, 3, and 4. INPUTS (LSB) A0 A1 A2 A3 B0 B1 B2 B3 L A0 A1 A2 A3 B0 B1 B2 B3 IA > B OA > B #5 OA < B IA < B H IA = B L (MSB) A20 A21 A22 A23 B20 B21 B22 B23 A19 B19 L OA = B A0 A1 A2 A3 B0 B1 B2 B3 IA > B OA > B IA < B #1 OA < B IA = B OA = B NC INPUTS A5 A6 A7 A8 B5 B6 B7 B8 A4 B4 L A0 A1 A2 A3 B0 B1 B2 B3 OA > B IA > B #4 IA < B OA < B IA = B OA = B A15 A16 A17 A18 B15 B16 B17 B18 A10 A11 A12 A13 B10 B11 B12 B13 A9 B9 NC L A0 A1 A2 A3 B0 B1 B2 B3 OA > B IA > B #3 OA < B IA < B IA = B OA = B A14 B14 NC L A0 A1 A2 A3 B0 B1 B2 B3 OA > B IA > B #2 OA < B IA < B IA = B OA = B A0 A1 A2 A3 B0 B1 B2 B3 IA > B OA > B IA < B OA < B #6 IA = B OA = B MSB = MOST SIGNIFICANT BIT LSB = LEAST SIGNIFICANT BIT L = LOW LEVEL H = HIGH LEVEL NC = NO CONNECTION Figure 2. Comparison of Two 24-Bit Words FAST AND LS TTL DATA 5-86 OUTPUTS NC SN54/74LS85 DC CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE (unless otherwise specified) Limits Symbol Parameter VIH Input HIGH Voltage VIL Input LOW Voltage VIK Input Clamp Diode Voltage VOH Output HIGH Voltage VOL Output LOW Voltage Min Typ Unit 2.0 54 V V Guaranteed Input LOW Voltage for All Inputs V VCC = MIN, IIN = - 18 mA 0.8 - 0.65 - 1.5 Test Conditions Guaranteed Input HIGH Voltage for All Inputs 0.7 74 54 2.5 3.5 V 74 2.7 3.5 V VCC = MIN, IOH = MAX, VIN = VIH or VIL per Truth Table 54, 74 0.25 0.4 V IOL = 4.0 mA 74 0.35 0.5 V IOL = 8.0 mA 20 60 A VCC = MAX, VIN = 2.7 V mA VCC = MAX, VIN = 7.0 V - 0.4 - 1.2 mA VCC = MAX, VIN = 0.4 V -100 mA VCC = MAX 20 mA VCC = MAX Input HIGH Current A < B, A > B Other Inputs IIH Max A < B, A > B Other Inputs 0.1 0.3 IIL Input LOW Current A < B, A > B Other Inputs IOS Output Short Circuit Current (Note 1) ICC Power Supply Current - 20 VCC = VCC MIN, VIN = VIL or VIH per Truth Table Note 1: Not more than one output should be shorted at a time, nor for more than 1 second. AC CHARACTERISTICS (TA = 25C, VCC = 5.0 V) Limits Symbol Parameter Min Typ Max Unit tPLH tPHL Any A or B to A < B, A > B 24 20 36 30 ns tPLH tPHL Any A or B to A = B 27 23 45 45 ns tPLH tPHL A < B or A = B to A > B 14 11 22 17 ns tPLH tPHL A = B to A = B 13 13 20 26 ns tPLH tPHL A > B or A = B to A < B 14 11 22 17 ns Test Conditions VCC = 5.0 V CL = 15 pF AC WAVEFORMS VIN 1.3 V 1.3 V tPHL VOUT 1.3 V VIN 1.3 V 1.3 V tPHL tPLH 1.3 V VOUT Figure 3 1.3 V Figure 4 FAST AND LS TTL DATA 5-87 tPLH 1.3 V