IL3285/IL3222

12

NVE Corporation

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

Phone: (952) 829-9217

www.isoloop.com

iso-info@nve.com

iso-apps@nve.com

Fail-Safe Biasing

Power Supply Decoupling

Both VDD1 and VDD2 should be bypassed with 0.1 µF typical (0.047 µF minimum) capacitors placed as close as possible to

the VDD pins.

Maintaining Creepage

Creepage distances are often critical in isolated circuits. In addition to meeting JEDEC standards, NVE isolator packages have

unique creepage specifications. Standard pad libraries often extend under the package, compromising creepage and clearance.

Similarly, ground planes, if used, should be spaced to avoid compromising clearance. Package drawings and recommended pad

layouts are included in this datasheet.

Magnetic Field Immunity

IsoLoop Isolators operate by imposing a magnetic field on a GMR sensor, which translates the change in field into a change in

logic state. A magnetic shield and a Wheatstone Bridge configuration provide good immunity to external magnetic fields.

Immunity to external magnetic fields can be enhanced by proper orientation of the device with respect to the field direction and

larger boost capacitors.

An applied field in the “H1” direction is the worst case for magnetic immunity. In this case the external field is in the same

direction as the applied internal field. In one direction it will tend to

help switching; in the other it will hinder switching. This can cause

unpredictable operation.

An applied field in the direction of “H2” has considerably less effect

on the sensor and will result in significantly higher immunity levels as

shown in Table 1.

The greatest magnetic immunity is achieved by adding a larger boost

capacitor across the input resistor. Very high immunity can be

achieved with this method.

R

B

V

DD

GND

A

5 V

IL32xx

Fail-Safe

RT

Loading

Operation?

None

Four eighth-unit loads (96 kΩ ea.)

283 mV

Yes

120 Ω

Four eighth-unit loads (96 kΩ ea.)

1 mV

No

560 Ω

120 Ω

Four eighth-unit loads (96 kΩ ea.)

254 mV

Yes

510 Ω

120 Ω

256 eighth-unit loads (96 kΩ ea.)

243 mV

Yes

Nominal VA-B

(inactive)

RFS-EXT

Internal Only

Internal Only

Figure 3. Orientation of External Magnetic Field

V

DD1

V

COIL2

GND

1

V

COIL1

GND

2

R

NC

RE

B

DE

A

D

V

DD2

NC

GND

1

GND

2

H1

H2