MAX367C/D Просмотр технического описания (PDF) - Maxim Integrated

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MAX367C/D

Signal-Line Circuit Protectors

Maxim Integrated 

Signal-Line Circuit Protectors

MAX366

V+ 8

1 IN1

OUT1 7

2 IN2

OUT2 6

3 IN3

4 V-

OUT3 5

SWITCHED +5V

P

+5V

100k

OP AMP

-5V

100mV

VIN IN_

MAX366

A

OUT_ VOUT

V- 4

V-

8

V+

V+

ADJUSTABLE ANALOG VOLTAGE

PATH RESISTANCE = 100mV/A

Figure 5. Power-Supply Sequencing

Figure 6 shows a circuit that can give reliable results.

This circuit uses a 100mV voltage source and a low-

voltage-drop ammeter as the measuring circuit, and an

adjustable supply to sweep the analog voltage across

its whole range. The ammeter must have a voltage

drop of less than one millivolt (at any current) for accu-

rate results. (A Keithley Model 617 Electrometer has a

suitable ammeter circuit, appropriate ranges, and a

built-in voltage source designed for this type of mea-

surement.) Measurements are made by setting the

analog voltage, measuring the current, and calculating

the path resistance. The procedure is repeated at

each analog voltage and supply voltage.

It is important to use a voltage source of 100mV or less.

As shown in Figure 4, this voltage is added to the VIN

voltage to form the VOUT voltage. Using a higher volt-

age could cause the OUT pin to go into a fault condi-

tion prematurely.

Figure 6. Path-Resistance Measuring Circuit

High-Frequency Performance

In 50Ω systems, signal response is reasonably flat up

to several megahertz (see Typical Operating

Characteristics). Above 5MHz, the response has sev-

eral minor peaks, which are highly layout dependent.

Because the path resistance is dependent on the sup-

ply voltage and signal amplitude, the impedance is not

controlled. Adjacent channel attenuation up to 5MHz is

about 3dB above that of a bare IC socket, and is due

entirely to capacitive coupling.

Pulse response is reasonable, but because the imped-

ance changes rapidly, fast rise times may induce ringing

as the signal approaches the fault voltage. At very high

amplitudes (such as noise spikes), the capacitive cou-

pling across the signal pins will transfer considerable

energy, despite the fact that the DC path is a virtual open

circuit.

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