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Space-saving optocouplers reject noise

Edited by the Electronicstalk editorial team Oct 24, 2003

The FODM452 and the FODM453 are the first in a new family of high-speed transistor optocouplers providing the highest common mode noise rejection available, as well as the lowest package profile.

The FODM452 and the FODM453 are the first products in a new family of high-speed transistor optocouplers providing the highest common mode noise rejection (CMR) available, as well as the lowest package profile.

The advanced performance and small package size of these new optocouplers make them ideal for line receiver, output interface to CMOS-LSTTL-TTL, pulse transformer replacement, and wide-bandwidth analogue coupling applications.

Their unique coplanar construction allows these optocouplers to offer a CMR that is 30% superior to similar products, and their 5-pin, mini-flat packaging (MFP) housing reduces package volume by 35%, compared with commonly used 8-pin, SOIC-packaged optocouplers.

Additional performance benefits of the FODM452 and FODM453 include high bandwidth (1Mbit/s) and fast switching (less than 1us turn-on/turn-off).

The FODM452 and the FODM453 contain a high-speed transistor photodetector coupled with a high-efficiency, infra-red light emitting diode.

The products' photodiode is separated from the collector of the transistor to significantly improve bandwidth, compared with traditional phototransistor detectors.

These optocouplers are able to offer a superior CMR performance by using a proprietary shielding method on the silicon photodetector, as well as by using coplanar packaging construction; a technique that places the input and output lead frames on a single plane - as opposed to conventional over-under construction that places the input and output leadframes in parallel.

Coplanar packaging reduces the surface area across the isolation barrier and the separation between input and output leadframes, thus lowering the input to output capacitance.

This lower capacitance reduces the ability for noise to become coupled through the package.

"In today's factory environments, managing unwanted electrical noise is becoming increasingly challenging", said John Constantino, Strategic Marketing Manager for Fairchild's Optoelectronics group.

"Fairchild's new high speed optocouplers provide additional noise immunity, which reduces the probability of data errors caused by common mode noise".

The FODM452 and FODM453 are UL approved (VDE and CSA pending) and their performance is guaranteed over a 0 to 70C temperature range.