Dual polarity input photocouplers for industrial applications

October 03, 2013 // By Graham Prophet
Toshiba Electronics has two new dual-polarity, high-speed photocouplers/optocouplers that can support both sink and source logic input signals. The TLP2395 and TLP2398 will help to significantly reduce component count and power consumption in industrial systems ranging from programmable logic controllers (PLCs) to instrumentation.

Requirements to support both sink and source logic inputs in modern PLC and instrumentation systems means that bridge circuitry is commonly employed upstream from the photocouplers used in high-speed digital interfaces. Now, however, by combining two LEDs in a reverse parallel configuration, the TLP2395 and TLP2398 eliminate the need for these bridge circuits. As a modern PLC can have multiple photocouplers - and, therefore, multiple bridge circuits - the devices will significantly reduce circuit size, power consumption and cost.

Both the TLP2395 (logic buffer output) and the TLP2398 (inverter output) photocouplers will accommodate a 3 to 20V power supply voltage range, which helps to reduce the need for DC-DC conversion circuitry. Each device also offers guaranteed operation at temperatures ranging from -40°C to 125°C. Toshiba’s new devices support a data transfer speed of 5 Mbps and combine a propagation delay of less than 250 nsec with a pulse width distortion below 80 nsec. As a result they are suitable for RS232C, RS422, RS485 and other commonly used industrial communication interfaces. Input current drive of 2.3 mA and a supply current of 3 mA contribute to application efficiency.

The couplers are supplied in SO6 surface mount packaging that integrates two GaAlAs LEDs coupled with a high-gain, high-speed photodetector. Dimensions are 7.0 x 3.7 x 2.3 mm, guaranteed minimum creepage and clearance distance is 5 mm and guaranteed minimum input-output withstand voltage is 3.5 kVrms. An internal Faraday shield ensures common-mode transient immunity of ±20 kV/μsec.

Toshiba; www.toshiba-components.com