7491 Datasheet – 8-bit Shift Register

Part number : 7491, 74LS91, 74HC91

Functions : 8-bit Shift Register

Package : 14 Pin DIP type

Manufactures : Hitachi, Texas Instruments


7491 Shift Register


This serial-in, serial-out, 8-bit shift register is composed of eight R-S master-slave flip-flops, input gating, and a clock drive. Single-rail data and input control are gated through inputs A and B and an internal inverter to form the complementary inputs to the first bit of the shift register. Drive for the internal common clock line is provided by an inverting clock driver. This clock pulse inverter/driver causes these circuits to shift information one bit on the positive edge of an input clock pulse.


7491 datasheet pinout


1. High Speed Operation: tpd (Data Word Input to Output) = 21 ns typ (CL = 50 pF)
2. High Output Current: Fanout of 10 LSTTL Loads
3. Wide Operating Voltage: VCC = 2 to 6 V
4. Low Input Current: 1 µA max
5. Low Quiescent Supply Current: ICC (static) = 4 µA max (Ta = 25°C)

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Truth Table

7491 Truth Function Table


1. Digital Computer System
2. Data-Handling System
3. Control System

7491 Datasheet