HD74HC149 8-to-8-line Priority Encoder Description The HD74HC149 is priority encoder which has 8 input lines (0 - 7) and 8 output lies (Y0 - Y7). It is the logical combination of a HD74HC148 8-3 line priority encoder driving a HD74HC138 3-8 line decoder. Only one request output can be low at a time. The output that is low is dependent on the highest priority request that is low. The order of priority is 7 highest and 0 lowest. When E input is high, all outputs are high. When a output (Y0 - Y 7) is low, P output is low and this indicates active condition. Features • • • • • High Speed Operation: tpd (0 - 7 to Y) = 16 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) HD74HC149 Function Table Inputs Outputs 0 1 2 3 4 5 6 7 E Y0 Y1 Y2 Y3 Y4 Y5 Y6 Y7 P X X X X X X X X H H H H H H H H H H H H H H H H H H L H H H H H H H H H X X X X X X X L L H H H H H H H L L X X X X X X L H L H H H H H H L H L X X X X X L H H L H H H H H L H H L X X X X L H H H L H H H H L H H H L X X X L H H H H L H H H L H H H H L X X L H H H H H L H H L H H H H H L X L H H H H H H L H L H H H H H H L L H H H H H H H L L H H H H H H H L H : L : X : High level Low level Irrelevant Pin Arrangement Inputs 0 1 20 VCC 1 2 19 Y0 2 3 18 Y1 3 4 17 Y2 4 5 16 Y3 5 6 15 Y4 6 7 14 Y5 7 8 13 Y6 E 9 12 Y7 11 P GND 10 (Top view) 2 Outputs HD74HC149 Logic Diagram 7 Y7 6 Y6 5 4 3 Y5 Y4 Y3 2 Y2 1 Y1 0 Y0 P E 3 HD74HC149 DC Characteristics Ta = –40 to +85°C Ta = 25°C Item Symbol VCC (V) Min Typ Max Min Max Unit Input voltage VIH 2.0 1.5 — — 1.5 — V 4.5 3.15 — — 3.15 — 6.0 4.2 — — 4.2 — 2.0 — — 0.5 — 0.5 4.5 — — 1.35 — 1.35 6.0 — — 1.8 — 1.8 2.0 1.9 2.0 — 1.9 — 4.5 4.4 4.5 — 4.4 — 6.0 5.9 6.0 — 5.9 — 4.5 4.18 — — 4.13 — I OH = –4 mA 6.0 5.68 — — 5.63 — I OH = –5.2 mA 2.0 — 0.0 0.1 — 0.1 4.5 — 0.0 0.1 — 0.1 6.0 — 0.0 0.1 — 0.1 4.5 — — 0.26 — 0.33 I OL = 4 mA 6.0 — — 0.26 — 0.33 I OL = 5.2 mA VIL Output voltage VOH VOL Test Conditions V V V Vin = VIH or VIL I OH = –20 µA Vin = VIH or VIL I OL = 20 µA Input current Iin 6.0 — — ±0.1 — ±1.0 µA Vin = VCC or GND Quiescent supply current I CC 6.0 — — 4.0 40 µA Vin = VCC or GND, Iout = 0 µA 4 — HD74HC149 AC Characteristics (CL = 50 pF, Input tr = tf = 6 ns) Ta = –40 to +85°C Ta = 25°C VCC (V) Min Typ Max Min Max Unit Test Conditions Propagation delay t PLH 2.0 — — 140 — 175 ns 0 - 7 to Y, P time 4.5 — 16 28 — 35 6.0 — — 24 — 30 t PLH 2.0 — — 155 — 195 ns E to Y, P t PHL 4.5 — 13 31 — 39 6.0 — — 26 — 33 Item Symbol t PHL Output rise/fall t TLH 2.0 — — 75 — 95 time t THL 4.5 — 5 15 — 19 6.0 — — 13 — 16 — — 5 10 — 10 Input capacitance Cin ns pF 5 Unit: mm 24.50 25.40 Max 6.30 11 1 7.00 Max 20 10 1.30 2.54 ± 0.25 0.48 ± 0.10 0.51 Min 1.27 Max 2.54 Min 5.08 Max 0.89 7.62 + 0.11 0.25 – 0.05 0° – 15° Hitachi Code JEDEC EIAJ Weight (reference value) DP-20N — Conforms 1.26 g Unit: mm 12.6 13 Max 11 1 10 1.27 *0.42 ± 0.08 0.40 ± 0.06 0.10 ± 0.10 0.80 Max *0.22 ± 0.05 0.20 ± 0.04 2.20 Max 5.5 20 0.20 7.80 +– 0.30 1.15 0° – 8° 0.70 ± 0.20 0.15 0.12 M *Dimension including the plating thickness Base material dimension Hitachi Code JEDEC EIAJ Weight (reference value) FP-20DA — Conforms 0.31 g Unit: mm 12.8 13.2 Max 11 1 10 0.20 ± 0.10 0.935 Max 1.27 *0.42 ± 0.08 0.40 ± 0.06 *0.27 ± 0.05 0.25 ± 0.04 2.65 Max 7.50 20 0.25 10.40 +– 0.40 1.45 0° – 8° 0.57 0.70 +– 0.30 0.15 0.12 M *Dimension including the plating thickness Base material dimension Hitachi Code JEDEC EIAJ Weight (reference value) FP-20DB Conforms — 0.52 g Cautions 1. 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