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SN74AVCH20T245_09 Datasheet, PDF (2/21 Pages) Texas Instruments – 20-BIT DUAL-SUPPLY BUS TRANSCEIVER WITH CONFIGURABLE VOLTAGE TRANSLATION AND 3-STATE OUTPUTS
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SN74AVCH20T245
20ĆBIT DUALĆSUPPLY BUS TRANSCEIVER
WITH CONFIGURABLE VOLTAGE TRANSLATION AND 3ĆSTATE OUTPUTS
SCES567F − MAY 2004 − REVISED APRIL 2005
description/ordering information (continued)
The SN74AVCH20T245 is designed for asynchronous communication between data buses. The device
transmits data from the A bus to the B bus or from the B bus to the A bus, depending on the logic level at the
direction-control (DIR) input. The output-enable (OE) input can be used to disable the outputs so that the buses
are effectively isolated.
The SN74AVCH20T245 is designed so that the control (1DIR, 2DIR, 1OE, and 2OE) inputs are supplied by
VCCA.
This device is fully specified for partial-power-down applications using Ioff. The Ioff circuitry disables the outputs,
preventing damaging current backflow through the device when it is powered down.
The VCC isolation feature ensures that if either VCC input is at GND, both outputs are in the high-impedance
state. The bus-hold circuitry on the powered-up side always stays active.
Active bus-hold circuitry holds unused or undriven inputs at a valid logic state. Use of pullup or pulldown resistors
with the bus-hold circuitry is not recommended.
To ensure the high-impedance state during power up or power down, OE should be tied to VCC through a pullup
resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.
GQL OR ZQL PACKAGE
(TOP VIEW)
123456
A
B
C
D
E
F
G
H
J
K
terminal assignments
1
2
3
4
5
6
A
1B1
1B2
1DIR
1OE
1A2
1A1
B
1B3
1B4
GND
GND
1A4
1A3
C
1B5
1B6
VCCB
VCCA
1A6
1A5
D
1B7
1B8
GND
GND
1A8
1A7
E
1B9
1B10
1A10
1A9
F
2B1
2B2
2A2
2A1
G
2B3
2B4
GND
GND
2A4
2A3
H
2B5
2B6
VCCB
VCCA
2A6
2A5
J
2B7
2B8
GND
GND
2A8
2A7
K
2B9
2B10
2DIR
2OE
2A10
2A9
FUNCTION TABLE
(each 10-bit section)
INPUTS
OE DIR
OPERATION
L
L
B data to A bus
L
H A data to B bus
H
X
Isolation
2
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