Fairchild Semiconductor DM74LS645WMX, DM74LS645WM, DM74LS645N Datasheet
© 2000 Fairchild Semiconductor Corporation DS009056 www.fairchildsemi.com
August 1986
Revised March 2000
DM74LS645 Octal Bus Transceiver
DM74LS645
Octal Bus Transceiver
General Description
These octal bus transceivers ar e designed for asynchronous two-way communication between data buses. The
devices transmit data from t he A bus to the B bus o r from
the B bus to the A bus depending upo n the level at the
direction control (DIR) input. The enable input (G
) can be
used to disable the device so t hat the buses are effectively
isolated.
Features
■ Bi-directional bus transceivers in high-density 20-pin
packages
■ Hysteresis at bus inputs improves noise margins
■ 3-STATE outputs
Ordering Code:
Devices also availab le in Tape and Reel. Specify by appending th e s uffix let t er “X” to the ordering code.
Connection Diagram Function Table
H = HIGH Level
L = LOW Level
X = Irrelevant
Order Number Package Number Package Description
DM74LS645WM M20B 20-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300 Wide
DM74LS645N N20A 20-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
Control
Inputs DM74LS645
G
DIR
L L B data to A bus
L H A data to B bus
H X Isolation
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DM74LS645
Absolute Maximum Ratings(Note 1)
Note 1: The “Absolute Maximum Ratin gs” are those v alues beyon d which
the safety of the dev ice cannot be guaranteed. T he device sh ould not be
operated at these limits. The parametric values defined in the Electrical
Characteristics tables are not guaranteed at the absolute maximum ratings.
The “Recommend ed O peratin g Cond itions” t able w ill defin e the co ndition s
for actual device operation.
Recommended Operating Conditions
Note 2: Voltage values are w it h res pect to the network gr ound terminal.
Electrical Characteristics
over recommended operating free air temperature range (unless otherwise noted)
Note 3: For conditions shown as Min or Max , us e t he appropriate value specified under Recom m ended Operating Conditions.
Note 4: All typicals are at V
CC
= 5V, TA = 25°C.
Note 5: Not more than one output should be shorted at a time, and the duration should not exceed one second.
Supply Voltage 7V
Input Voltage 7V
Operating Free Air Temperature Range 0°C to +70°C
Storage Temperature Range −55°C to +150°C
Symbol Parameter Min Nom Max Units
V
CC
Supply Voltage (Note 2) 4.75 5 5.25 V
V
IH
HIGH Level Input Voltage 2 V
V
IL
LOW Level Input Voltage 0.6 V
I
OH
HIGH Level Output Current −15 mA
I
OL
LOW Level Output Current 24 mA
T
A
Free Air Operating Temperature 0 70 °C
Symbol Parameter Conditions (Note 3) Min
Typ
Max Units
(Note 4)
V
I
Input Clamp Voltage VCC = Min, II = 18 mA −1.5 V
H
YS
Hysteresis (VT+ − V−)V
CC
= Min 0.2 0.4 V
A or B Input
V
OH
HIGH Level Output Voltage VCC = Min, VIH = 2V, IOH = −3 mA 2.4 3.4
V
VIL = Max IOH = Max 2
V
OL
LOW Level Output Voltage VCC = Min, VIH = 2V, IOL = 12 mA 0.25 0.4
V
VIL = Max IOL = 24 mA 0.35 0.5
I
OZH
Off-State Output Current, VCC = Max, G at 2V,
20 µA
HIGH Level Voltage Applied VO = 2.7V
I
OZL
Off-State Output Current, VCC = Max, G at 2V
−400 µA
LOW Level Voltage Applied VO = 0.4V
I
I
Input Current at VCC = Max A or B VI = 5.5V 0.1
mA
Maximum Input Voltage DIR or G VI = 7V 0.1
I
IH
HIGH Level Input Current VCC = Max, VIH = 2.7 20 µA
I
IL
LOW Level Input Current VCC = Max, VIL = 0.4V −0.4 mA
I
OS
Short Circuit Output Current ( N ote 5) VCC = Max −40 −225 mA
I
CC
Total Supply Outputs HIGH VCC = Max, 48 70
Current Outputs LOW Outputs Open 62 90 mA
Outputs at Hi-Z 64 95
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