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 wide 3V 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 5Mbps and combine a propagation delay of less than 250ns with a pulse width distortion below 80ns. As a result they are ideal for RS232C, RS422, RS485 and other commonly used industrial communication interfaces. A low input current drive of 2.3mA and a supply current of just 3mA contribute to application efficiency.
The two new couplers are supplied in SO6 surface mount packaging that integrates two GaAlAs LEDs coupled with a high-gain, high-speed photodetector. Despite board mounting dimensions of only 7.0mm x 3.7mm x 2.3mm, guaranteed minimum creepage and clearance distance is 5mm and guaranteed minimum input-output withstand voltage is 3.5kVrms. An internal Faraday shield ensures common-mode transient immunity of ±20kV/μs.