器件名称:
74HC148
功能描述:
8-to-3-line Octal Priority Encoder
文件大小:
45.29KB 共8页
简 介:
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 A max Low Quiescent Supply Current: ICC (static) = 4 A 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 A A I OL = 4 mA I OL = 5.2 mA Vin = VCC or GND Vin = VCC or GND, Iout = 0 A V I OH = –4 mA I OH = –5.2 mA Vin = VIH or VIL I OL = 20 A V Vin = VIH or VIL I OH = –20 A……
