8-to-3-line Octal Priority Encoder
HD74HC148
8-to-3-line Octal Priority Encoder
Description
The HD74HC148 encodes eight data lines to three-line (4-2-1) b...
Description
HD74HC148
8-to-3-line Octal Priority Encoder
Description
The HD74HC148 encodes eight data lines to three-line (4-2-1) binary (octal). Cascading circuitry (enable input EI and enable output EO) is provided to allow octal expansion without the need for external circuitry. The data inputs and outputs are active at the low logic level.
Features
High Speed Operation: tpd (0 - 7 to A0 - A2) = 15 ns typ (CL = 50 pF) High Output Current: Fanout of 10 LSTTL Loads Wide Operating Voltage: VCC = 2 to 6 V Low Input Current: 1 µA max Low Quiescent Supply Current: ICC (static) = 4 µA max (Ta = 25°C)
Function Table
Inputs EI H L L L L L L L L L H : L : X : 0 X H X X X X X X X L 1 X H X X X X X X L H High level Low level Irrelevant 2 X H X X X X X L H H 3 X H X X X X L H H H 4 X H X X X L H H H H 5 X H X X L H H H H H 6 X H X L H H H H H H 7 X H L H H H H H H H Outputs A2 H H L L L L H H H H A1 H H L L H H L L H H A0 H H L H L H L H L H GS H H L L L L L L L L EO H L H H H H H H H H
HD74HC148
Pin Arrangement
4 1 5 2 Inputs 6 3 7 4 EI 5 A2 6 Outputs A1 7 GND 8 (Top view) A1 A0 0 5 6 7 EI A2 4 EO GS 3 2 1
16 VCC 15 EO Outputs 14 GS 13 3 12 2 Inputs 11 1 10 0 9 A0 Output
2
HD74HC148
DC Characteristics
Ta = 25°C Item Input voltage Symbol VIH Ta = –40 to +85°C Max — — — 0.5 1.35 1.8 — — — — — 0.1 0.1 0.1 0.33 0.33 ±1.0 40 µA µA I OL = 4 mA I OL = 5.2 mA Vin = VCC or GND Vin = VCC or GND, Iout = 0 µA V I OH = –4 mA I OH = –5.2 mA Vin = VIH or VIL I OL = 20 µA V Vin = VIH or VIL I O...
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