
SN54HCT646, SN74HCT646
OCTAL BUS TRANSCEIVERS AND REGISTERS
WITH 3-STATE OUTPUTS
SCLS178C – MARCH 1984 – REVISED MARCH 2003
1
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
D Operating Voltage Range of 4.5 V to 5.5 V
D Low Power Consumption, 80-A Max ICC
D Typical tpd = 12 ns
D ±6-mA Output Drive at 5 V
D Low Input Current of 1 A Max
D Inputs Are TTL-Voltage Compatible
D Independent Registers for A and B Buses
D Multiplexed Real-Time and Stored Data
D True Data Paths
D High-Current 3-State Outputs Can Drive Up
To 15 LSTTL Loads
14 15 16 17
SN54HCT646 ...JT OR W PACKAGE
SN74HCT646 . . . DW OR NT PACKAGE
(TOP VIEW)
SN54HCT646 . . . FK PACKAGE
(TOP VIEW)
CLKAB
SAB
DIR
A1
A2
A3
A4
A5
A6
A7
A8
GND
VCC
CLKBA
SBA
OE
B1
B2
B3
B4
B5
B6
B7
B8
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
5
6
7
8
9
10
11
25
24
23
22
21
20
19
43
2 1 28
12 13
OE
B1
B2
NC
B3
B4
B5
A1
A2
A3
NC
A4
A5
A6
DIR
SAB
CLKAB
B8
B7
A8
GND
NC
CLKBA
SBA
V
A7
B6
18
27 26
CC
NC – No internal connection
description/ordering information
The ’HCT646 devices consist of bus-transceiver circuits with 3-state outputs, D-type flip-flops, and control
circuitry arranged for multiplexed transmission of data directly from the input bus or from the internal registers.
Data on the A or B bus is clocked into the registers on the low-to-high transition of the appropriate clock (CLKAB
or CLKBA) input. Figure 1 illustrates the four fundamental bus-management functions that can be performed
with the ’HCT646 devices.
Output-enable (OE) and direction-control (DIR) inputs control the transceiver functions. In the transceiver
mode, data present at the high-impedance port can be stored in either or both registers.
ORDERING INFORMATION
TA
PACKAGE
ORDERABLE
PART NUMBER
TOP-SIDE
MARKING
PDIP – NT
Tube
SN74HCT646NT
–40
°C to 85°C
SOIC
DW
Tube
SN74HCT646DW
HCT646
SOIC – DW
Tape and reel
SN74HCT646DWR
HCT646
CDIP – JT
Tube
SNJ54HCT646JT
–55
°C to 125°C
CFP – W
Tube
SNJ54HCT646W
LCCC – FK
Tube
SNJ54HCT646FK
Package drawings, standard packing quantities, thermal data, symbolization, and PCB design guidelines are
available at www.ti.com/sc/package.
Copyright
2003, Texas Instruments Incorporated
UNLESS OTHERWISE NOTED this document contains PRODUCTION
DATA information current as of publication date. Products conform to
specifications per the terms of Texas Instruments standard warranty.
Production processing does not necessarily include testing of all
parameters.
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.