Quad, Rail-to-Rail, Fault-Protected,

SPST Analog Switches

8

_______________________________________________________________________________________

0

0.5

1.5

1.0

2.5

2.0

3.0

010

15

5

20253035

LOGIC-LEVEL THRESHOLD vs. V+

V+ (V)

Typical Operating Characteristics (continued)

0

-10

-20

-120

0.01

0.1

1

10

100

1000

FREQUENCY RESPONSE

-90

-100

-110

MAX186-14A

FREQUENCY (MHz)

-70

-80

-50

-60

-30

-40

120

100

80

-120

-60

-80

-100

-20

-40

20

0

60

40

ON LOSS

OFF LOSS

ON PHASE

NAME

FUNCTION

1, 16,

9, 8

IN1–IN4

Logic Control Digital Inputs

2, 15,

10, 7

COM1–

COM4

Analog Switch Common* Terminals

PIN

3, 14,

11, 6

NO1–NO4

or

NC1–NC4

Analog Switch Fault-Protected Normally

Open* or Normally Closed* Terminals

4

V-

Negative Analog Supply Voltage Input.

Connect to GND for single-supply operation.

13

V+

Positive Analog and Digital Supply-Voltage

Input. Internally connected to substrate.

12

N.C.

No Connection—not internally connected

5

GND

Ground. Connect to digital ground. (Analog

signals have no ground reference.)

Pin Description

*

As long as the voltage on NO_ or NC_ does not exceed V+ or

V-, NO_ (or NC_) and COM_ pins are identical and interchange-

able. Either may be considered as an input or output; signals

pass equally well in either direction.

Detailed Description

Overview of Traditional

Fault-Protected Switches

The MAX4511/MAX4512/MAX4513 are fault-protected

CMOS analog switches with unusual operation and

construction. Traditional fault-protected switches are

constructed by three series FETs. This produces good

off characteristics, but fairly high on-resistance when

the signals are within about 3V of each supply rail. As

the voltage on one side of the switch approaches with-

in about 3V of either supply rail (a fault condition), the

switch impedance becomes higher, limiting the output

signal range (on the protected side of the switch) to

approximately 3V less than the appropriate polarity

supply voltage.

During a fault condition, the output current that flows

from the protected side of the switch into its load

comes from the fault source on the other side of the

switch. If the switch is open or the load is extremely

high impedance, the input current will be very low. If

the switch is on and the load is low impedance,

enough current will flow from the source to maintain the

load voltage at 3V less than the supply.