Document Number: 70062

www.vishay.com

S11-0933-Rev. J, 16-May-11

11

This document is subject to change without notice.

DG408, DG409

Vishay Siliconix

APPLICATION HINTS

Overvoltage Protection

A very convenient form of overvoltage protection consists of

adding two small signal diodes (1N4148, 1N914 type) in

series with the supply pins (see figure 10). This arrangement

effectively blocks the flow of reverse currents. It also floats

the supply pin above or below the normal V+ or V- value. In

this case the overvoltage signal actually becomes the power

supply of the IC. From the point of view of the chip, nothing

has changed, as long as the difference VS - (V-) does not

exceed + 44 V. The addition of these diodes will reduce the

analog signal range to 1 V below V+ and 1 V above V-, but it

preserves the low channel resistance and low leakage

characteristics.

Fig. 10 - Overvoltage Protection Using Blocking Diodes

Fig. 11

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Technology and Package Reliability represent a composite of all qualified locations. For related documents such as package/tape drawings, part marking, and

1N4148

DG408

D

V-

V+

1N4148

EN

+ 15 V

(MUX On-Off Control)

Analog

Inputs

(Outputs)

Clock

In

NC

Enable In

Analog

Output

(Input)

+ 15 V

- 15 V

DG408

D

EN

GND

DM7493

V+

V-

NC

GND

+ 15 V

Analog

Inputs

(Outputs)

Analog

Outputs

(Inputs)

+ 15 V

- 15 V

DG409

GND

V+

V-

Differential

Differential

Clock

In

NC

GND

+ 15 V

NC

6

Reset Enable

J

K

CLK

J

K

CLK

CLEAR

CLEAR

Q

1/2 MM74C73

1/2 MM74C73

Q

Q

Q

8-Channel Sequential Multiplexer/Demultiplexer

Differential 4-Channel Sequential Multiplexer/Demultiplexer