Precision, CMOS Analog Switches

6

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PIN

NAME

FUNCTION

MAX317

MAX318

MAX319

1

1

1

COM

Analog-switch common terminal

2

2

—

N.C.

No connect — not internally connected

—

—

8

NO

Analog-switch normally open terminal

3

3

3

GND

Logic ground

4

4

4

V+

Analog-signal positive supply input

5

5

5

VL

Logic-level positive supply input

6

6

6

IN

Logic-level input

7

7

7

V-

Analog-signal negative supply input

8

—

2

NC

Analog-switch normally closed terminal

—

8

—

NO

Analog-switch normally open terminal

_______________________________________________________________________Pin Description

__________Applications Information

Operation with Supply Voltages

Other Than ±15V

The main limitation of supply voltages other than ±15V

is analog signal range reduction. The MAX317/

MAX318/MAX319 switches operate with bipolar sup-

plies of ±5V to ±20V. Typical Operating Characteristics

graphs show typical on resistance for ±15V, ±10V, and

±5V supplies. Switching times increase by a factor of

two

or

more

for

operation

at

±5V.

The

MAX317/MAX318/MAX319 can operate from unipolar

supplies of +10V to +30V. Both parts can also operate

from unbalanced supplies such as +24V and -5V.

Connect V- to 0V when operating with a single supply.

This means that VL must be connected to +5V to be

TTL compatible, or to V+ for CMOS logic input levels.

Overvoltage Protection

Proper power-supply sequencing is recommended for

all CMOS devices. It is important not to exceed the

absolute maximum ratings because stresses beyond

the listed ratings may cause permanent damage to the

devices. Always sequence V+ on first, followed by VL,

V-, and logic inputs. If power-supply sequencing is not

possible, protect the devices from overvoltage by

adding two small signal diodes in series with the sup-

ply pins (Figure 1). Adding the diodes reduces the

analog signal range to 1V below V+ and 1V below V-,

but low switch resistance and low leakage characteris-

tics are unaffected. Device operation is unchanged,

and the difference between V+ to V- should not exceed

+44V.

V+

COM_

V-

NO_

Vg

V+

V-

Figure 1. Overvoltage Protection Using Blocking Diodes