2.5

CMOS Analog Switches

_______________________________________________________________________________________

7

NAME

FUNCTION

MAX4661

1, 16, 9, 8

IN1, IN2,

IN3, IN4

Logic-Control Digital Inputs

2, 15,

10, 7

COM1, COM2,

COM3, COM4

Analog Switch Common Terminals

3, 14, 11, 6

NC1, NC2,

NC3, NC4

Analog Switch Normally Closed Terminals

4

V-

Negative Analog Supply-Voltage Input. Connect to GND for single-

supply operation.

—

NC2, NC3

Analog Switch Normally Closed Terminals

—

NO1, NO4

Analog Switch Normally Open Terminals

—

NO1, NO2,

NO3, NO4

Analog Switch Normally Open Terminals

13

V+

Positive Analog Supply Input

12

Logic-Supply Input

5

GND

Ground

Pin Description

MAX4662

1, 16, 9, 8

2, 15,

10, 7

—

4

—

—

3, 14, 11, 6

13

12

5

MAX4663

1, 16, 9, 8

PIN

2, 15,

10, 7

—

4

14, 11

3, 6

—

13

12

5

Applications Information

Overvoltage Protection

Proper power-supply sequencing is recommended for

all CMOS devices. Do not exceed the absolute maxi-

mum ratings because stresses beyond the listed rat-

ings can cause permanent damage to the devices.

Always sequence V+ on first, then V-, followed by the

logic inputs, NO, or COM. If power-supply sequencing

is not possible, add two small-signal diodes (D1, D2)

in series with the supply pins and a Schottky diode

1). Adding diodes reduces the analog signal range to

one diode drop below V+ and one diode drop above V-,

but does not affect the devices’ low switch resistance

and low leakage characteristics. Device operation is

unchanged, and the difference between V+ and V-

should not exceed 44V.

Off-Isolation at High Frequencies

In 50

Ω systems, the high-frequency on-response of

these parts extends from DC to above 100MHz with a

typical loss of -2dB. When the switch is turned off, how-

ever, it behaves like a capacitor and off-isolation

decreases with increasing frequency. (Above 300MHz,

the switch actually passes more signal turned off than

turned on.) This effect is more pronounced with higher

source and load impedances.

Above 5MHz, circuit board layout becomes critical and

it becomes difficult to characterize the response of the

switch independent of the circuit. The graphs shown in

the

Typical Operating Characteristics were taken using

a 50

Ω source and load connected with BNC connec-

tors to a circuit board deemed “average”; that is,

designed with isolation in mind, but not using stripline

or other special RF circuit techniques. For critical appli-

cations above 5MHz, use the MAX440, MAX441, and

MAX442, which are fully characterized up to 160MHz.

COM_

V-

V+

NO_

* INTERNAL PROTECTION DIODES

D2

D1

-15V

+15V

MAX4661

MAX4662

MAX4663

*

*

*

*

Figure 1. Overvoltage Protection Using External Blocking

Diodes