HD74HC91
8-bit Shift Register
Description
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.
Features
• High Speed Operation: t
pd
(Data Word Input to Output) = 21 ns typ (C
L
= 50 pF)
• High Output Current: Fanout of 10 LSTTL Loads
• Wide Operating Voltage: V
CC
= 2 to 6 V
• Low Input Current: 1 µA max
• Low Quiescent Supply Current: I
CC
(static) = 4 µA max (Ta = 25°C)
Function Table
Inputs Outputs
t
n
t
n + 8
AB Q
H
Q
H
HH L
LX L
XL H
X : Irrelevant
t
n
: Reference bit time, clock low
t
n + 8
: Bit time after 8 low-to-high clock transitions