AN2433 Freescale Semiconductor / Motorola, AN2433 Datasheet - Page 14

• Manufacturer Part Number: AN2433
• Description: 5V to 3V Design Considerations
• Manufacturer: Freescale Semiconductor / Motorola

AN2433/D
Bi-directional Translation
14
5V System
5V System
5V System
GND
GND
GND
IN/OUT
IN/OUT
IN/OUT
Figure 11. Interfacing of the 3.3V and 5V system bus
Similar TTL compatible product inputs offer additional protection when the
V
withstand up to 7V input voltage regardless of the V
feature simplifies power-up and power-down sequences of 5V and 3V parts of
the system because 5V parts can be powered down while 3V parts are running
without excessive currents on the 5V inputs.
When bi-directional connections of 3.3V and 5V devices are required, special
level shifters are normally used, see
of transceiver is that the direction of the data flow (DIR pin) needs to be
controlled and requires an additional port pin from the master MCU.
Another alternative for interfacing 5V and 3V systems is to use a Bus Switch
such as the QS3384. The main advantages of such a device are very low
propagation delay (0.25 ns) and the fact that the control of the data direction is
not necessary. The disadvantage of this solution is that the 5V system must
have TTL compatible levels because that Bus Switch only limits voltage to 3V
levels, in the same way as limiting resistors do. Therefore, contrary to the
MC74LVX4245 and other similar transceivers, it does not provide additional
drive capability.
DD5
Freescale Semiconductor, Inc.
VDD 5V
VDD 5V
VDD 5V
For More Information On This Product,
supply is powered down and the V
GND
GND
GND
5V to 3V Design Considerations
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MC74LVX4245
MC74LVX4245
MC74LVX4245
A1
A1
A1
A2
A2
A2
A3
A3
A3
A4
A4
A4
A5
A5
A5
A6
A6
A6
A7
A7
A7
A8
A8
A8
DIR
DIR
DIR
OE
OE
OE
VCCA
VCCA
VCCA
VCCB
VCCB
VCCB
VCCB
VCCB
VCCB
GND
GND
GND
GND
GND
GND
GND
GND
GND
B1
B1
B1
B2
B2
B2
B3
B3
B3
B4
B4
B4
B5
B5
B5
B6
B6
B6
B7
B7
B7
B8
B8
B8
Figure 11
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VDD 3.3V
VDD 3.3V
VDD 3.3V
DD3
GND
GND
GND
supply is applied; they can
. The disadvantage of this kind
DD5
3.3V System
3.3V System
3.3V System
IN/OUT
IN/OUT
IN/OUT
value provided. This
GND
GND
GND
MOTOROLA