ADG3308

–4–

REV. PrE

PRELIMINARY TECHNICAL DATA

GENERAL DESCRIPTION

The ADG3308 level translator allows the required level

shifting necessary for data transfer in a system where mul-

tiple voltages are used. The device requires two supplies,

each side of the device. The device translates data present

Power Supplies

both A and Y I/O’s will remain tri-stated.

Level Translator Architecture

The forward channel consists of a string of inverters and a

level translator, while the reverse channel consists simply

of inverters. A level translator is not required in the re-

tor is used in series with each channel to prevent any con-

tention issues, see figure 1.

One Shot

Generator

One Shot

Generator

VCCY

VCCA

A

Y

6k

6k

Figure 1. Simplified Functional Diagram of one channel.

As the driven side has to drive a load capacitance through

this 6k resistance, one shot generators are used to drive

large mos devices in the output stage to help speed up the

rate of switching. The output stage is inactive and three

state except when transistions are present on either side of

the translator. When this happens the one shot fires

turn-

ing on the output stage and driving the load capacitance

faster than if it were driven through the resistor. As the

device is bi-directional, both input stages will be active

during this period. While this design gives maximum

speed from the device, it can result in some current driv-

ing back into the source driving the input of the translator.

To ensure correct operation, the input driver should meet

the following requirements - 50

Ω maximum output im-

pedance with minimum of 20mA output current when

driving 20Mbps.

Enable Operation

When pulled low, the EN input allows the user to tri-state

both sides (A and Y) of the level translator. EN pin is