74LVX4245MTC 查看數據表（PDF） - Fairchild Semiconductor

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74LVX4245MTC

8-Bit Dual Supply Translating Transceiver with 3-STATE Outputs

Fairchild Semiconductor 

Applications: Mixed Mode Dual Supply Interface Solution

LVX4245 is designed to solve 3V/5V interfacing issues

when CMOS devices cannot tolerate I/O levels above their

applied VCC. If an I/O pin of 3V ICs is driven by 5V ICs, the

P-Channel transistor in 3V ICs will conduct causing current

flow from I/O bus to the 3V power supply. The resulting

high current flow can cause destruction of 3V ICs through

latchup effects. To prevent this problem, a current limiting

resistor is used typically under direct connection of 3V ICs

and 5V ICs, but it causes speed degradation.

In a better solution, the LVX4245 configures two different

output levels to handle the dual supply interface issues.

The “A” port is a dedicated 5V port to interface 5V ICs. The

“B” port is a dedicated port to interface 3V ICs. Figure 2

shows how LVX4245 fits into a system with 3V subsystem

and 5V subsystem.

This device is also configured as an 8-bit 245 transceiver,

giving the designer 3-STATE capabilities and the ability to

select either bidirectional or unidirectional modes. Since

the center 20 pins are also pin compatible to 74 series 245,

as shown in Figure 1, the designer could use this device in

either a 3V system or a 5V system without any further work

to re-layout the board.

FIGURE 1. LVX4245 Pin Arrangement is Compatible to

20-Pin 74 Series 245

FIGURE 2. LVX4245 Fits into a System with 3V Subsystem and 5V Subsystem

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