SN54/74LS147 SN54/74LS148 SN54/74LS LINE-TO-4-LINE AND 8-LINE-TO-3-LINE PRIORITY ENCODERS

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1 -LINE-TO--LINE AND 8-LINE-TO--LINE PRIORITY ENCODERS The SN/LS and the SN/LS8 are Priority Encoders. They provide priority decoding of the inputs to eure that only the highest order data line is encoded. Both devices have data inputs and s which are active at the low logic level. The LS encodes nine data lines to four-line (8---) BCD. The implied decimal zero condition does not require an input condition because zero is encoded when all nine data lines are at a high logic level. The LS8 encodes eight data lines to three-line (--) binary (octal). By providing cascading circuitry (Enable Input and Enable Output ) octal expaion is allowed without needing external circuitry. The SN/ LS8 is a proprietary Motorola part incorporating a built-in deglitcher network which minimizes glitches on the. The glitch occurs on the negative going traition of the input when data inputs are at logical ones. The only dc parameter differences between the LS8 and the LS8 are that () Pin (input ) has a fan-in of on the LS8 versus a fan-in of on the LS8; () Pi,,,,, and (inputs,,,,,, ) have a fan-in of on the LS8 versus a fan-in of on the LS8. The only ac difference is that from to is changed from to. SN/ LS (TOP VIEW) OUTPUT OUTPUT VCC NC D 9 A 9 D 9 A 8 C B 8 8 C B GND SN/LS SN/LS8 SN/LS8 -LINE-TO--LINE AND 8-LINE-TO--LINE PRIORITY ENCODERS LOW POWER SCHOTTKY J SUFFIX CERAMIC CASE -9 N SUFFIX PLASTIC CASE 8-8 ORDERING INFORMATION SNLSXXXJ SNLSXXXN SNLSXXXD D SUFFIX SOIC CASE B- Ceramic Plastic SOIC SN/ LS8 SN/ LS8 (TOP VIEW) VCC A OUTPUT 9 A A A 8 E A A GND -

2 SN/LS SN/LS8 SN/LS8 SN/ LS FUNCTION TABLE 8 9 D C B A H H H H H H H H H H H H H X X X X X X X X L L H H L X X X X X X X L H L H H H X X X X X X L H H H L L L X X X X X L H H H H L L H X X X X L H H H H H L H L X X X L H H H H H H L H H X X L H H H H H H H H L L X L H H H H H H H H H L H L H H H H H H H H H H H L H = HIGH Logic Level, L = LOW Logic Level, X = Irrelevant SN/ LS8 SN/ LS8 FUNCTION TABLE A A A H X X X X X X X X H H H H H L H H H H H H H H H H H H L L X X X X X X X L L L L L H L X X X X X X L H L L H L H L X X X X X L H H L H L L H L X X X X L H H H L H H L H L X X X L H H H H H L L L H L X X L H H H H H H L H L H L X L H H H H H H H H L L H L L H H H H H H H H H H L H FUNCTIONAL BLOCK DIAGRAMS () () (9) A () () () () () () () (8) A () () B () () () () A () C () 8 () A 9 () () D SN/ LS SN/ LS8 -

3 SN/LS SN/LS8 SN/LS8 FUNCTIONAL BLOCK DIAGRAMS (continued) G () () () () () () () () G G G G G G G8 G G9 G G G G () G9 (9) G8 () G G8 A A A SN/ LS8 -

4 SN/LS SN/LS8 SN/LS8 GUARANTEED OPERATING RANGES Symbol Parameter Min Typ Max Unit VCC Supply Voltage TA Operating Ambient Temperature Range IOH Output Current High,. IOL Output Current Low DC CHARACTERISTICS OVER OPERATING TEMPERATURE RANGE (unless otherwise specified) Symbol Parameter Min Typ Max Unit Test Conditio VIH Input HIGH Voltage. V VIL Input LOW Voltage..8 V Guaranteed Input HIGH Voltage for All Inputs Guaranteed Input LOW Voltage for All Inputs VIK Input Clamp Diode Voltage.. V VCC = MIN, IIN = 8 V C VOH VOL Output HIGH Voltage Output LOW Voltage.. V VCC = MIN, IOH = MAX, VIN = VIH.. V or VIL per Truth Table,.. V IOL =. VCC = VCC MIN, VIN =VIL or VIH.. V IOL = 8. per Truth Table IIH IIL Input HIGH Current Input (LS8) Inputs (LS8) Inputs (LS8) Input (LS8) Inputs (LS8) Inputs (LS8) Input LOW Current Input (LS8) Inputs (LS8) Inputs (LS8) µa VCC = MAX, VIN =. V IOS Short Circuit Current (Note ) VCC = MAX VCC = MAX, VIN =. V VCC = MAX, VIN =. V ICCH Power Supply Current Output HIGH VCC = MAX, All Inputs =. V ICCL Output LOW Note : Not more than one should be shorted at a time, nor for more than second. VCC = MAX, Inputs & E = GND All Other Inputs =. V -

5 SN/LS SN/LS8 SN/LS8 AC CHARACTERISTICS (VCC =. V, TA = C) SN/ LS Symbol From (Input) To (Output) Waveform Min Typ Max Unit Test Conditio In-phase 8 8 Out-of-phase CL L = pf, RL =. kω SN/ LS8 SN/ LS8 Symbol From (Input) thru A, A, or A thru A, A, or A thru thru To (Output) Waveform Min Typ Max Unit Test Conditio A, A, or A In-phase 8 Out-of-phase 9 Out-of-phase. 8 In-phase 9. In-phase In-phase In-phase 8 (LS8) (LS8) CL = pf, RL =. kω -