IL600 Series Isolators

10

NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344-3617

(952) 829-9217

www.nve.com

YouTube.com/NveCorporation

iso-apps@nve.com

Applications Information

IL600-Series Isolators are current mode devices. Changes in current flow into the input coil result in logic state changes at the

output. As shown in Figure 1, output logic high is the zero input current state.

Coil Polarity

The device switches to logic low if current flows from (In−) to (In+).

Note that the designations “In−“ and “In+” refer to logic levels, not

current flow. Positive values of current mean current flow into

the In− input.

Input Resistor Selection

Resistors set the coil input current (see Figure 2). There is no limit to

input voltages because there are no semiconductor input structures.

Worst-case logic low threshold current is 8 mA, which is for single-

ended operation with a 3 V supply. In differential mode, where the

input current reverses, the logic low threshold current is 5 mA for the

range of supplies. A “boost capacitor” creates current reversals at edge

transitions, reducing the input logic low threshold current to the

differential level of 5 mA.

Typical Resistor Values

The table shows typical values for the

external resistor for 5 mA coil current.

The values are approximate and should

be adjusted for temperature or other

application specifics.

Single-Ended or Differential Input

The IL610, IL611, IL613, and channel 1 of the IL614 can be run with

single-ended or differential inputs (see Test Circuits on page 5). In the

differential mode, current will naturally flow through the coil in both

directions without a boost capacitor, although the capacitor can still be

used for increased external field immunity or improved PWD.

Absolute Maximum recommended coil current in single-ended mode

is 25 mA while differential mode allows up to ±75 mA to flow. The

difference in specifications is due to the risk of electromigration of

coil metals under constant current flow. In single ended mode, long-

term DC current flow above 25 mA can cause erosion of the coil

metal. In differential mode, erosion takes place in both directions as each current cycle reverses and has a net effect of zero up to

the absolute maximum current.

An advantage over optocouplers and other high-speed couplers in differential mode is that no reverse bias protection for the input

structure is required for a differential signal.

One of the more common applications is for an isolated Differential Line Receiver. For example, RS-485 can drive an IL610

directly for a fraction of the cost of an isolated RS-485 node (see Illustrative Applications).

3.5

5

High

Low

Logic State

Coil Current

mA

1.5

J

J

Figure 1. Typical IL600-Series Transfer Function

V

INH

V

INL

I

COIL

R1

85

Input

Coil

Figure 2. Limiting Resistor Calculation

Equivalent Circuit

VCOIL

Coil

Resistor

3.3 V

510 Ω

5 V

820 Ω