MID400

www.onsemi.com

4

APPLICATION INFORMATION

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 VACRMS

voltage isolation. A very high current transfer ratio (defined

as the ratio of the DC output current and the DC input

current) 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 add a resistor, RIN, in series with the input

(as shown in figure 2) to limit the current to the required

value. The value of the resistor can be determined by the

following equation:

RIN +

VIN * VF

IIN

(eq. 1)

Where,

VIN (RMS) is the input voltage.

VF is the forward voltage drop across the LED.

IIN (RMS) is the desired input current required to sustain a

logic “O” on the output.

PIN DESCRIPTION

Pin

Number

Pin

Name

Description

1, 3

VIN1, VIN2 Input terminals

2, 4

N/C

No Connect

8

VCC

Supply voltage, output circuit.

7

AUX

Auxiliary terminal.

Programmable capacitor input to adjust

AC voltage sensing level and time delay.

6

VO

Output terminal; open collector.

5

GND

Circuit ground potential.

SCHEMATIC DIAGRAM

45

1

VIN1

N/C

N/C

VIN2

VCC

AUX.

GND

VO

2

3

8

Figure 1. Schematic Diagram

7

6

GLOSSARY

Voltages

VIN (ON_RMS)

On−State RMS Input Voltage

The RMS voltage at an input terminal for a specified input

current with output conditions applied according to the

product specification will cause the output switching

element to be sustained in the on−state within one full cycle.

VIN (OFF_RMS)

Off−State RMS Input Voltage

The RMS voltage at an input terminal for a specified input

current with output conditions applied according to the

product specification will cause the output switching

element to be sustained in the off−state within one full cycle.

VOL

Low−Level Output Voltage

The voltage at an output terminal for a specific output

current IOL, with input conditions applied according to the

product specification will establish a low−level at the output.

VOH

High−Level Output Voltage

The voltage at an output terminal for a specific output

current IOH, with input conditions applied according to the

product specification will establish a high−level at the

output.

VF

LED Forward Voltage

The voltage developed across the LED when input current

IF is applied to the anode of the LED.

Currents

IIN (ON_RMS)

On−State RMS Input Current

The RMS current flowing into an input with output

conditions applied according to the product specification

will cause the output switching element to be sustained in the

on−state within one full cycle.

IIN (OFF_RMS)

Off−state RMS Input Current

The RMS current flowing into an input with output

conditions applied according to the product specification

will cause the output switching element to be sustained in the

off−state within one full cycle.

IOH

High−Level Output Current

The current flowing into an output with input conditions

applied according to the product specification will establish

high−level at the output.