AN2433 Freescale Semiconductor / Motorola, AN2433 Datasheet - Page 15

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

MOTOROLA
5V System
5V System
(TTL comp.)
(TTL comp.)
V
V
GND
GND
DD
DD
IN/OUT
IN/OUT
Figure 12. Interfacing of 3V and 5V system with bus switch
5V
5V
By supplying 4.3V to the V
limited to 3.3V maximum, even under light loading. A 4.3V V
by adding a diode with a voltage drop of approximately 0.7V between the 5V
supply and the device. The QS3384 device has an internal 10 k
between the diode's cathode and ground to provide a current path for the diode.
In other types of bus switches, like the QS3861, the diode D1 and the resistor
R1 are not available inside the chip, therefore those components are required
externally, see
When there is not the option of controlling the data flow direction in the bi-
directional interfacing between 5V and 3.3V systems, special level translators
like the MAX3370/1 shown in
are available in space-saving 5-pin and 6-pin SC70 packages respectively.
Freescale Semiconductor, Inc.
For More Information On This Product,
GND
GND
5V to 3V Design Considerations
R1 10k
R1 10k
Go to: www.freescale.com
11
11
14
14
17
17
18
18
21
21
22
22
13
13
Figure 12
3
3
4
4
7
7
8
8
1
1
U1
U1
A0
A0
A1
A1
A2
A2
A3
A3
A4
A4
A5
A5
A6
A6
A7
A7
A8
A8
A9
A9
BEA
BEA
BEB
BEB
1N4148
1N4148
.
CC
D1
D1
GND
GND
Figure 13
pin of the Bus Switch, the driven output will be
B0
B0
B1
B1
B2
B2
B3
B3
B4
B4
B5
B5
B6
B6
B7
B7
B8
B8
B9
B9
QS3861
QS3861
VDD 5V
VDD 5V
2
2
5
5
6
6
9
9
10
10
15
15
16
16
19
19
20
20
23
23
can be used. The MAX3370/MAX3371
3.3V System
3.3V System
IN/OUT
IN/OUT
V
V
DD
DD
GND
GND
3.3V
3.3V
Bi-directional Translation
CC
can be created
resistor
AN2433/D
15