The Toshiba TLP2309(E) is a single-channel, DC-input, transistor-output optocoupler in a Tube package with five leads. It provides 3750Vrms of galvanic isolation between the input LED and the output phototransistor, making it a fit for isolating logic signals, PLC digital inputs, motor-drive feedback, and AC-mains-referenced control circuits.
The 3750Vrms isolation voltage is the headline safety spec — it meets basic reinforced isolation requirements for many 240VAC applications, but check the creepage and clearance for your specific regulatory standard (UL/VDE/CSA). The 15% minimum current transfer ratio at 16 mA forward current is the floor for output drive: with a 5V pull-up and 8 mA output capability, the collector resistor should be sized to guarantee a logic-low at the load. The 1 µs turn-on and turn-off times (max) limit the part to switching frequencies below about 200 kHz — fine for 50/60 Hz line sync, relay coil drive, or 100 kHz isolated gate drive, but not for high-speed serial isolation (look at the TLP109 family for sub-microsecond switching). The 20V output maximum and 8 mA per-channel output current suit 5V or 12V logic families and low-power loads.
Package and footprint note
The 6-SOIC with five leads is a compact surface-mount package — the missing sixth pin is typically the base connection left unconnected (NC) in the transistor-output variant. The 4.55 mm body width matches standard SOIC-6 land patterns.