Datasheet

SNx4HCT245
DIR
Master Device
Low Drive Strength
(MCU, FPGA, CPU)
OE
A1
A2
A3
A4
A5
A6
A7
A8
B1
B2
B3
B4
B5
B6
B7
B8
Ribbon Cable
SNx4HC245
DIR
OE
A1
A2
A3
A4
A5
A6
A7
A8
B1
B2
B3
B4
B5
B6
B7
B8
Slave Device
or
Back Plane
Copyright © 2016, Texas Instruments Incorporated
10
SN54HCT245 , SN74HCT245
SCLS020F –MARCH 1984–REVISED AUGUST 2016 www.ti.com
Product Folder Links: SN54HCT245 SN74HCT245
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9 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
The SNx4HCT245 is a versatile device with many available applications. The application chosen as an example
here is connecting a master and slave device through a ribbon cable. This configuration is common due to losses
in this type of cable.
9.2 Typical Application
Logic transceivers are commonly seen in back plane and ribbon cable applications where a signal direct from an
FPGA or MCU would be too weak to reach the distant end. The transceiver acts as an amplifier to get the signal
across the line, and since it is bidirectional, data can be sent from master to slave or slave to master. The
additional buffer on the direction line is necessary to ensure the direction signal can always reach the distant
end.
Figure 4. Typical application for SNx4HC245
9.2.1 Design Requirements
This device uses CMOS technology and has balanced output drive. Care must be taken to avoid bus contention
because it can drive currents that would exceed maximum limits. Outputs can be combined to produce higher
drive, but the high drive also creates faster edges into light loads, so routing and load conditions must be
considered to prevent ringing.
9.2.2 Detailed Design Procedure
1. Recommended Input Conditions
– Rise time and fall time specs: See (Δt/ΔV) in the Recommended Operating Conditions.
– Specified high and low levels: See (VIH and VIL) in the Recommended Operating Conditions.
2. Recommended Output Conditions
– Load currents should not exceed 35 mA per output and 70 mA total for the part.
– Outputs should not be pulled above V
CC
.