Philips 74HCT646U, 74HCT646N, 74HCT646DB, 74HC646U, 74HC646N3 Datasheet
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DATA SH EET
Product specification
File under Integrated Circuits, IC06
September 1993
INTEGRATED CIRCUITS
74HC/HCT646
Octal bus transceiver/register;
3-state
For a complete data sheet, please also download:
•The IC06 74HC/HCT/HCU/HCMOS Logic Family Specifications
•The IC06 74HC/HCT/HCU/HCMOS Logic Package Information
•The IC06 74HC/HCT/HCU/HCMOS Logic Package Outlines
September 1993 2
Philips Semiconductors Product specification
Octal bus transceiver/register; 3-state 74HC/HCT646
FEATURES
• Independent register for A and B buses
• Multiplexed real-time and stored data
• Output capability: bus driver
• ICC category: MSI
GENERAL DESCRIPTION
The 74HC/HCT646 are high-speed Si-gate CMOS devices
and are pin compatible with low power Schottky TTL
(LSTTL). They are specified in compliance with JEDEC
standard no. 7A.
The 74HC/HCT646 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 internal registers. Data on the “A” or “B” bus will be
clocked into the registers as the appropriate clock
(CP
AB
and CPBA) goes to a HIGH logic level. Output
enable (OE) and direction (DIR) inputs are provided to
control the transceiver function. In the transceiver mode,
data present at the high-impedance port may be stored in
either the “A” or “B” register, or in both. The select source
inputs (SABand SBA) can multiplex stored and real-time
(transparent mode) data. The direction (DIR) input
determines which bus will receive data when OE is active
(LOW). In the isolation mode (OE = HIGH), “A” data may
be stored in the “B” register and/or “B” data may be stored
in the “A” register.
When an output function is disabled, the input function is
still enabled and may be used to store and transmit data.
Only one of the two buses, A or B, may be driven at a time.
The “646” is functionally identical to the “648”, but has
non-inverting data paths.
QUICK REFERENCE DATA
GND = 0 V; T
amb
=25°C; tr=tf= 6 ns
Notes
1. C
PD
is used to determine the dynamic power dissipation (PD in µW):
PD=CPD× V
CC
2
× fi+ ∑ (CL× V
CC
2
× fo) where:
fi= input frequency in MHz
fo= output frequency in MHz
∑ (CL× V
CC
2
× fo) = sum of outputs
CL= output load capacitance in pF
VCC= supply voltage in V
2. For HC the condition is VI= GND to V
CC
For HCT the condition is VI= GND to VCC− 1.5 V
ORDERING INFORMATION
See
“74HC/HCT/HCU/HCMOS Logic Package Information”
.
SYMBOL PARAMETER CONDITIONS
TYPICAL
UNIT
HC HCT
t
PHL
/ t
PLH
propagation delay An, Bn to Bn, A
n
CL= 15 pF; VCC=5V 11 13 ns
f
max
maximum clock frequency 69 85 MHz
C
I
input capacitance 3.5 3.5 pF
C
PD
power dissipation capacitance per channel notes 1 and 2 30 33 pF
September 1993 3
Philips Semiconductors Product specification
Octal bus transceiver/register; 3-state 74HC/HCT646
PIN DESCRIPTION
PIN NO. SYMBOL NAME AND FUNCTION
1CP
AB
A to B clock input (LOW-to-HIGH, edge-triggered)
2S
AB
select A to B source input
3 DIR direction control input
4, 5, 6, 7, 8, 9, 10, 11 A
0
to A
7
A data inputs/outputs
12 GND ground (0 V)
20, 19, 18, 17, 16, 15, 14, 13 B
0
to B
7
B data inputs/outputs
21
OE output enable input (active LOW)
22 S
BA
select B to A source input
23 CP
BA
B to A clock input (LOW-to-HIGH, edge-triggered)
24 V
CC
positive supply voltage
Fig.1 Pin configuration. Fig.2 Logic symbol. Fig.3 IEC logic symbol.
September 1993 4
Philips Semiconductors Product specification
Octal bus transceiver/register; 3-state 74HC/HCT646
Fig.4 Functional diagram.
FUNCTION TABLE
Notes
1. H = HIGH voltage level
L = LOW voltage level
X = don’t care
↑ = LOW-to-HIGH level transition
2. The data output functions may be enabled or disabled by various signals at the
OE and DIR inputs. Data input
functions are always enabled, i.e., data at the bus inputs will be stored on every LOW-to-HIGH transition on the clock
inputs.
INPUTS
(1)
DATA I/O
(2)
FUNCTION
OE DIR CP
AB
CP
BA
S
AB
S
BA
A0to A
7
B0to B
7
H
H
X
X
H or L↑H or L↑X
X
X
X
input input
isolation
store A and B data
L
L
L
L
X
X
X
H or LXX
L
H
output input
real-time B data to A bus
stored B data to A bus
L
L
H
H
X
H or LXX
L
H
X
X
input output
real-time A data to B bus
stored A data to B bus
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