74F845 8-Bit Transparent Latch
April 1988
Revised August 1999
74F845
8-Bit Transparent Latch
General Description
The 74F845 bus interface latch is designed to eliminate the
extra packages required to buffer existing latches and pro-
vide extra data width for wider address/data paths or buses
carrying parity.
The 74F845 is functionally- and pin-compatible with AMD’s
Am29845.
Features
s
3-STATE outputs
s
Direct replacement for AMD’s Am29845
Ordering Code:
Order Number
74F845SC
74F845SPC
Package Number
M24B
N24C
Package Description
24-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300 Wide
24-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-100, 0.300 Wide
Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.
Logic Symbols
Connection Diagram
IEEE/IEC
© 1999 Fairchild Semiconductor Corporation
DS009601
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74F845
Unit Loading/Fan Out
Pin Names
D
0
–D
7
O
0
–O
7
OE
1
–OE
3
LE
CLR
PRE
Description
Data Inputs
Data Outputs
Output Enables
Latch Enable
Clear
Preset
U.L.
HIGH/LOW
1.0/1.0
150/40
1.0/1.0
1.0/1.0
1.0/1.0
1.0/1.0
Input I
IH
/I
IL
Output I
OH
/I
OL
20
µA/−0.6
mA
−3.0 µA/24
mA
20
µA/−0.6
mA
20
µA/−0.6
mA
20
µA/−0.6
mA
20
µA/−0.6
mA
Functional Description
The 74F845 consists of eight D-type latches with 3-STATE
outputs. The flip-flops appear transparent to the data when
Latch Enable (LE) is HIGH. This allows asynchronous
operation as the output transition follows the data in transi-
tion. On the LE HIGH-to-LOW transition, the data that
meets the setup times is latched. Data appears on the bus
when the output Enable (OE) is LOW. When OE is HIGH,
the bus output is in the high impedance state.
Function Table
Inputs
CLR PRE OE
H
H
H
H
H
H
H
H
L
L
L
H
H
H
H
H
H
H
H
L
H
L
H
L
H
H
H
H
L
L
L
L
L
L
H
H
LE
X
H
H
L
H
H
L
X
X
X
L
L
D
X
L
H
X
L
H
X
X
X
X
X
X
Internal Output
Function
Q
X
L
H
NC
L
H
NC
H
L
H
L
H
O
Z
Z
Z
Z
L
H
NC
H
L
H
Z
Z
High Z
High Z
High Z
Latched
Transparent
Transparent
Latched
Preset
Clear
Preset
Latched
Latched
H
=
HIGH Voltage Level
L
=
LOW Voltage Level
X
=
Immaterial
Z
=
High Impedance
NC
=
No Change
Logic Diagram
Please note that this diagram is provided only for the understanding of logic operations and should not be used to estimate propagation delays.
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2
74F845
Absolute Maximum Ratings
(Note 1)
Storage Temperature
Ambient Temperature under Bias
Junction Temperature under Bias
V
CC
Pin Potential to Ground Pin
Input Voltage (Note 2)
Input Current (Note 2)
Voltage Applied to Output
in HIGH State (with V
CC
=
0V)
Standard Output
3-STATE Output
Current Applied to Output
in LOW State (Max)
twice the rated I
OL
(mA)
−0.5V
to V
CC
−0.5V
to
+5.5V
−65°C
to
+150°C
−55°C
to
+125°C
−55°C
to
+150°C
−0.5V
to
+7.0V
−0.5V
to
+7.0V
−30
mA to
+5.0
mA
Recommended Operating
Conditions
Free Air Ambient Temperature
Supply Voltage
0°C to
+70°C
+4.5V
to
+5.5V
Note 1:
Absolute maximum ratings are values beyond which the device
may be damaged or have its useful life impaired. Functional operation
under these conditions is not implied.
Note 2:
Either voltage limit or current limit is sufficient to protect inputs.
DC Electrical Characteristics
Symbol
V
IH
V
IL
V
CD
V
OH
Parameter
Input HIGH Voltage
Input LOW Voltage
Input Clamp Diode Voltage
Output HIGH
Voltage
10% V
CC
10% V
CC
5% V
CC
5% V
CC
V
OL
I
IH
I
BVI
I
CEX
V
ID
I
OD
I
IL
I
OZH
I
OZL
I
OS
I
ZZ
I
CCZ
Output LOW Voltage
Input HIGH Current
Input HIGH Current
Breakdown Test
Output HIGH
Leakage Current
Input Leakage
Test
Output Leakage
Circuit Current
Input LOW Current
Output Leakage Current
Output Leakage Current
Output Short-Circuit Current
Bus Drainage Test
Power Supply Current
63
−60
4.75
3.75
−0.6
50
−50
−150
500
85
10% V
CC
2.5
2.4
2.7
2.7
0.5
5.0
7.0
50
V
µA
µA
µA
V
µA
mA
µA
µA
mA
µA
mA
Min
Max
Max
Max
0.0
0.0
Max
Max
Max
Max
0.0V
Max
V
Min
Min
2.0
0.8
−1.2
Typ
Max
Units
V
V
V
Min
V
CC
Conditions
Recognized as a HIGH Signal
Recognized as a LOW Signal
I
IN
= −18
mA
I
OH
= −1
mA
I
OH
= −3
mA
I
OH
= −1
mA
I
OH
= −3
mA
I
OL
=
24 mA
V
IN
=
2.7V
V
IN
=
7.0V
V
OUT
=
V
CC
I
ID
=
1.9
µA
All Other Pins Grounded
V
IOD
=
150 mV
All Other Pins Grounded
V
IN
=
0.5V
V
OUT
=
2.7V
V
OUT
=
0.5V
V
OUT
=
0V
V
OUT
=
5.25V
V
O
=
HIGH Z
3
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74F845
AC Electrical Characteristics
T
A
= +25°C
Symbol
Parameter
Min
t
PLH
t
PHL
t
PLH
t
PHL
t
PLH
t
PHL
t
PZH
t
PZL
t
PHZ
t
PLZ
Propagation Delay
D
n
to O
n
Propagation Delay
LE to O
n
Propagation Delay
PRE to O
n
Propagation Delay
CLR to O
n
Output Enable Time
OE to O
n
Output Disable Time
OE to O
n
2.5
1.5
5.0
2.0
3.0
V
CC
= +5.0V
C
L
=
50 pF
Typ
4.8
3.6
8.1
4.4
5.9
Max
8.0
6.5
12.0
7.5
10.0
T
A
=
0°C to
+70°C
V
CC
= +5.0V
C
L
=
50 pF
Min
2.0
1.5
4.5
2.0
2.5
Max
9.0
7.0
13.5
8.0
11.0
ns
ns
ns
Units
3.0
2.5
2.5
1.0
1.0
6.5
5.8
7.6
3.1
2.8
10.0
9.5
12.0
7.5
6.5
2.5
2.0
2.0
1.0
1.0
11.0
10.5
13.0
8.5
7.5
ns
ns
ns
AC Operating Requirements
T
A
= +25°C
Symbol
Parameter
V
CC
= +5.0V
Min
t
S
(H)
t
S
(L)
t
H
(H)
t
H
(L)
t
W
(H)
t
W
(L)
t
W
(L)
t
REC
t
REC
Setup Time, HIGH or LOW
D
n
to LE
Hold Time, HIGH or LOW
D
n
to LE
LE Pulse Width, HIGH
PRE Pulse Width, LOW
CLR Pulse Width, LOW
PRE Recovery Time
CLR Recovery Time
2.0
2.0
2.5
3.0
4.0
5.0
5.0
10.0
12.0
Max
T
A
=
0°C to
+70°C
V
CC
= +5.0V
Min
2.5
2.5
3.0
3.5
4.0
5.0
5.0
10.0
13.0
Max
ns
ns
ns
ns
ns
ns
ns
Units
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4
74F845
Physical Dimensions
inches (millimeters) unless otherwise noted
24-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300 Wide
Package Number M24B
5
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