74LVXC3245 查看數據表（PDF） - Fairchild Semiconductor

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74LVXC3245

8-Bit Dual Supply Configurable Voltage Interface Transceiver with 3-STATE Outputs

Fairchild Semiconductor 

Power Up Considerations

To insure the system does not experience unnecessary ICC

current draw, bus contention, or oscillations during power

up, the following guidelines should be adhered to (refer to

Table 1):

• Power up the control side of the device first. This is the

VCCA side.

• OE should ramp with or ahead of VCCA. This will help

guard against bus contention.

• The Transmit/Receive control pin (T/R) should ramp with

VCCA, this will ensure that the A Port data pins are con-

figured as inputs. With VCCA receiving power first, the A

I/O Port should be configured as inputs to help guard

against bus contention and oscillations.

• A side data inputs should be driven to a valid logic level.

This will prevent excessive current draw.

The above steps will ensure that no bus contention or oscil-

lations, and therefore no excessive current draw occurs

during the power up cycling of these devices. These steps

will help prevent possible damage to the translator devices

and potential damage to other system components.

TABLE 1. Low Voltage Translator Power Up Sequencing Table

Device Type

VCCA

VCCB

T/R

OE

A Side I/O

B Side I/O

Floatable Pin

Allowed

74LVXC3245

3V

(power up 1st)

3V to 5.5V

configurable

ramp

with VCCA

ramp

with VCCA

logic

0V or VCCA

outputs

yes, VCCB and B

I/O’s w/ OE HIGH

Please reference Application Note AN-5001 for more detailed information on using Fairchild’s LVX Low Voltage Dual

Supply CMOS Translating Transceivers.

Configurable I/O Application for PCMCIA Cards

Block Diagram

The LVXC3245 is a 24-pin dual supply device well suited

for PCMCIA configurable I/O applications. Ideal for low

power notebook designs, the LVXC3245 consumes less

than 1 mW of quiescent power in all modes of operation.

The LVXC3245 meets all PCMCIA I/O voltage require-

ments at 5V and 3.3V operation. By tying VCCB of the

LVXC3245 to the card voltage supply, the PCMCIA card

will always experience rail to rail output swings, maximizing

the reliability of the interface.

The VCCA pin on the LVXC3245 must always be tied to a

3V power supply. This voltage connection provides internal

references needed to account for variations in VCCB. When

connected as in the figure above, the LVXC3245 meets all

the voltage and current requirements of the ISA bus stan-

dard (IEEE P996).

www.fairchildsemi.com

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