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Lighting the way for constant photocoupler current transfer ratios

When specifying photocouplers special care must be taken to ensure that the current transfer ratio (CTR) will guarantee the correct output current or else device malfunction may occur. The CTR, expressed as a percentage of the ratio of the output current divided by the input current, commonly varies with varying input current, the room temperature and age of the component.

This variation can prove particularly challenging in applications such as programmable Logic Controllers, AC adaptor and I/O boards as well as in lighting designs that use the Digital Addressable Lightning Interface (DALI)-Bus.

Fortunately, Toshiba has developed the TLP383 - a photocoupler that guarantees the same CTR (Current Transfer Ratio) across an input current range from 0.2mA to 8mA and across the temperature range of 25°C to 100°C.

This impressively constant CTR has already made the TLP383 a firm favourite amongst those designing DALI-bus lighting systems. In addition, it has a maximum operating temperature of 125°C providing plenty of thermal headroom for lighting systems.

The photocoupler incorporates Toshiba's original high output, low degradation GaAlAs infrared LEDs and features a faster switching speed than standard phototransistor couplers – achieving a turn-off time (tOFF) of just 30μs (at IF=1.6mA, VCC=5V, RL=4.7kΩ).

To learn more about the TLP383, please visit

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·Before creating and producing designs and using, customers must also refer to and comply with the latest versions of all relevant TOSHIBA information and the instructions for the application that Product will be used with or for.