High Performance, 4-/8-Channel,

Fault-Protected Analog Multiplexers

ADG438F/ADG439F

Rev. E

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FEATURES

All switches off with power supply off

Analog output of on channel clamped within power supplies

if an overvoltage occurs

Latch-up proof construction

Fast switching times

Fault and overvoltage protection: −40 V to +55 V

Break-before-make construction

TTL- and CMOS-compatible inputs

APPLICATIONS

Data acquisition systems

Industrial and process control systems

Avionics test equipment

Signal routing between systems

High reliability control systems

GENERAL DESCRIPTION

The ADG438F and ADG439F are CMOS analog multiplexers, with

the ADG438F comprising eight single channels and the ADG439F

comprising four differential channels. These multiplexers provide

fault protection. Using a series n-channel, p-channel, and

n-channel MOSFET structure, both device and signal source

protection is provided in the event of an overvoltage or power

loss. The multiplexer can withstand continuous overvoltage

inputs from −40 V to +55 V. During fault conditions with power

supplies off, the multiplexer input (or output) appears as an open

circuit and only a few nanoamperes of leakage current flows. This

protects not only the multiplexer and the circuitry driven by the

multiplexer, but also protects the sensors or signal sources which

drive the multiplexer.

The ADG438F switches one of eight inputs to a common output

as determined by the 3-bit binary address lines, A0, A1, and A2.

The ADG439F switches one of four differential inputs to a

common differential output as determined by the 2-bit binary

address lines, A0 and A1. An EN input on each device is used

to enable or disable the device. When disabled, all channels are

switched off.

FUNCTIONAL BLOCK DIAGRAM

S1

S8

A0

D

ADG438F

A1 A2 EN

1 OF 8

DECODER

Figure 1.

S1A

A0

DA

ADG439F

A1

S4A

S1B

S4B

DB

EN

1 OF 4

DECODER

Figure 2.

PRODUCT HIGHLIGHTS

1.

Fault Protection. The ADG438F and ADG439F can with-

stand continuous voltage inputs up to −40 V or +55 V.

When a fault occurs due to the power supplies being

turned off, all the channels are turned off and only a

leakage current of a few nanoamperes flows.

2.

On channel saturates while fault exists.

3.

4.

Fast Switching Times.

5.

Break-Before-Make Switching. Switches are guaranteed

break-before-make so that input signals are protected

against momentary shorting.

6.

Trench Isolation Eliminates Latch-Up. A dielectric trench

separates the p-channel and n-channel MOSFETs thereby

preventing latch-up.

7.

Improved Off Isolation. Trench isolation enhances the

channel-to-channel isolation of the ADG438F/ADG439F.