AC LINE MONITOR

LOGIC-OUT DEVICE

MID400

7/24/03

Page 4 of 11

© 2003 Fairchild Semiconductor Corporation

The input of the MID400 consists of two back-to-back LED diodes which will accept and convert alternating currents into light

energy. An integrated photo diode-detector amplifier forms the output network. Optical coupling between input and output provides

2500 VRMS voltage isolation. A very high current transfer ratio (defined as the ratio of the DC output current and the DC input cur-

rent) is achieved through the use of high gain amplifier. The detector amplifier circuitry operates from a 5 V DC supply and drives

an open collector transistor output. The switching times are intentionally designed to be slow in order to enable the MID400, when

used as an AC line monitor, to respond only to changes in input voltage exceeding many milliseconds. The short period of time

during zero-crossing which occurs once every half cycle of the power line is completely ignored. To operate the MID400, always

resistor can be determined by the following equation:

DESIGNATION

PIN #

FUNCTION

1,3

Input terminals

8

Supply voltage, output circuit.

AUX.

7

Auxiliary terminal.

Programmable capacitor input to

adjust AC voltage sensing level and

time delay.

6

Output terminal; open collector.

GND

5

Circuit ground potential.

Characteristics

Test Conditions

Symbol

Min

Typ

Max

Units

Steady State Isolation Voltage

Relative Humidity

1 Minute, 60 Hz

2500

VRMS

Isolation Resistance

Ω

Isolation Capacitance

(f = 1 MHz)

2pF

DESCRIPTION / APPLICATIONS

PIN DESCRIPTION

R

IN

V

IN

V

F

–

I

IN

-----------------------

=

4

5

1

AUX.

GND

2

3

8

7

6

NOTE: DO NOT CONNECT PINS 2 AND 4

SCHEMATIC DIAGRAM