Fault-Protected, High-Voltage

Signal-Line Protectors

_______________________________________________________________________________________

7

8-Pin

DIP/SO

18-Pin

DIP/SO

NAME*

1, 2, 3

1, 2, 3

IN1, IN2, IN3

PIN

–

4–8

IN4, IN5, IN6, IN7, IN8

4

9

V-

–

–

N.C.

8

18

V+

5, 6, 7

15, 16, 17

OUT3, OUT2, OUT1

–

10–14

OUT8, OUT7, OUT6, OUT5, OUT4

Pin Description

FUNCTION

Signal Inputs 1, 2, 3

Signal Inputs 4, 5, 6, 7, 8

Negative Supply Voltage Input

No Connection. Not internally connected.

Positive Supply-Voltage Input

Signal Outputs 3, 2, 1

Signal Outputs 8, 7, 6, 5, 4

20-Pin

SSOP

1, 2, 4

5–9

10

3, 18

20

16, 17, 19

11–15

MAX4506

MAX4507

*

Connect all unused inputs to a hard voltage within the supply range (e.g., V+, V-, or GND).

Detailed Description

The MAX4506/MAX4507 protect other ICs from over-

voltage by clamping its output voltage to the supply

rails. If the power supplies to the device are off, the

device clamps the output to 0V. The MAX4506/

MAX4507 provide protection for input signals up to

±36V with the power supplies on and ±40V with the

power supplies off.

The MAX4506/MAX4507 protect other integrated cir-

cuits connected to its output from latching up. Latchup

is caused by parasitic SCR(s) within the IC turning on,

and can occur when the supply voltage applied to the

IC exceeds the specified operating range. Latchup can

also occur when signal voltage is applied before the

power-supply voltage. When in a latchup state, the cir-

cuit draws excessive current and may continue to draw

excessive current even after the overvoltage condition

is removed. A continuous latchup condition may dam-

age the device permanently. Such “faults” are com-

monly encountered in modular control systems where

power supplies to interconnected modules may be

interrupted and reestablished at random. Faults can

happen during production testing, maintenance, start-

up, or a power failure.

Figure 1 shows the normal complementary pair (N1 and

P1) found in many common analog switches. In addi-

tion to these transistors, the MAX4506/MAX4507 also

contain comparators and sensing and clamping circuitry

to control the state of N1 and P1. During normal opera-

tion, N1 and P1 remain on with a typical 65

Ω on-resis-

tance between IN and OUT.

The on-board comparators and sensing circuitry moni-

tor the input voltage for possible overvoltage faults.

-15V

-15V

+15V

P-CHANNEL

DRIVER

N-CHANNEL

DRIVER

+15V

N3

P3

IN

N1

CLAMP

OUT

CLAMP

+V(+15V)

-V(-15V)

N2

P2

P1

COMPARATOR

COMPARATOR

SENSE

SWITCH

SENSE

SWITCH

Figure 1. Simplified Internal Structure