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ꢃ ꢊꢋꢌ ꢍ ꢀꢎ ꢁꢅꢄꢏꢐ ꢁꢐ ꢑꢀ ꢑꢒꢓ ꢔꢐ ꢕ ꢁ ꢋꢌ ꢁꢖꢏꢎ ꢅ ꢐꢑ ꢁ ꢍꢗ ꢏꢀ
SCLS121D − DECEMBER 1982 − REVISED OCTOBER 2003
SN54HC191 . . . J OR W PACKAGE
SN74HC191 . . . D, N, OR NS PACKAGE
(TOP VIEW)
D
D
D
D
D
D
D
D
Wide Operating Voltage Range of 2 V to 6 V
Outputs Can Drive Up To 10 LSTTL Loads
Low Power Consumption, 80-µA Max I
CC
B
V
A
1
2
3
4
5
6
7
8
16
15
CC
Typical t = 13 ns
pd
4-mA Output Drive at 5 V
Q
B
A
Q
14 CLK
Low Input Current of 1 µA Max
Single Down/Up Count-Control Line
13
12
11
10
9
CTEN
D/U
RCO
MAX/MIN
LOAD
C
Q
C
Q
D
GND
Look-Ahead Circuitry Enhances Speed of
Cascaded Counters
D
D
Fully Synchronous in Count Modes
D
Asynchronously Presettable With Load
Control
SN54HC191 . . . FK PACKAGE
(TOP VIEW)
description/ordering information
The ’HC191 devices are 4-bit synchronous,
reversible,
up/down
binary
counters.
3
2
1
20 19
18
CLK
RCO
NC
Q
4
5
6
7
8
A
Synchronous counting operation is provided by
having all flip-flops clocked simultaneously so that
the outputs change coincident with each other
when instructed by the steering logic. This mode
of operation eliminates the output counting spikes
CTEN
NC
17
16
15 MAX/MIN
14
9 10 11 12 13
D/U
LOAD
Q
C
normally
associated
with
asynchronous
(ripple-clock) counters.
The outputs of the four flip-flops are triggered on
a low- to high-level transition of the clock (CLK)
input if the count-enable (CTEN) input is low. A
high at CTEN inhibits counting. The direction of
the count is determined by the level of the
down/up (D/U) input. When D/U is low, the counter
counts up, and when D/U is high, it counts down.
NC − No internal connection
ORDERING INFORMATION
ORDERABLE
PART NUMBER
TOP-SIDE
MARKING
†
PACKAGE
T
A
PDIP − N
SOIC − D
Tube of 25
Tube of 40
Reel of 2500
Reel of 250
Reel of 2000
Tube of 25
Tube of 150
Tube of 55
SN74HC191N
SN74HC191N
SN74HC191D
SN74HC191DR
SN74HC191DT
SN74HC191NSR
SNJ54HC191J
SNJ54HC191W
SNJ54HC191FK
−40°C to 85°C
HC191
SOP − NS
CDIP − J
HC191
SNJ54HC191J
SNJ54HC191W
SNJ54HC191FK
−55°C to 125°C
CFP − W
LCCC − FK
†
Package drawings, standard packing quantities, thermal data, symbolization, and PCB design guidelines are
available at www.ti.com/sc/package.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
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Copyright 2003, Texas Instruments Incorporated
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