Isolated signal coupling for industrial and power interfaces
The Toshiba TLP184(TPR,SE is a single-channel photocoupler with a transistor output, designed to pass AC or DC signals across a 3750Vrms isolation barrier. Its 6-SOP package suits surface-mount assembly for motor drives, PLC I/O modules, and isolated power-supply feedback loops. With a current transfer ratio ranging from 50% to 600% at 5mA forward current, the designer can select the LED drive current to match the load without overdriving the input. The output transistor handles up to 80V and 50mA continuous, covering most low-power isolated switching and level-shifting tasks.
3750Vrms isolation — what it buys you
The 3750Vrms isolation rating is the one-minute withstand voltage between input LED and output phototransistor. That is enough for reinforced insulation in 240VAC mains-referenced circuits and for basic insulation in 400VAC drive systems. In a motor-drive I/O card or a PLC digital input module, this part keeps the low-voltage logic side safe from the high-voltage plant side. The 6-SOP package gives 4.40mm creepage width, which supports the clearance needed for that voltage class in clean indoor environments.
CTR spread and drive margin
The 50% to 600% CTR range at 5mA forward current is wide — typical for a standard CTR-grade photocoupler. At the low end (50%), a 5mA LED current yields at least 2.5mA of phototransistor collector current, enough to saturate the output into a 1kΩ pull-up. At the high end (600%), the same 5mA can drive 30mA into the load, which may let you reduce the LED current to save power. The turn-on and turn-off times are both 3µs typical, so this part is not for high-speed data — think 10kHz switching or slower for relay replacement, status feedback, or isolated 50/60Hz zero-cross detection.
Temperature range and handling
The 110°C upper limit is a junction temperature; in a 85°C ambient with modest self-heating (50mA output at 300mV Vce(sat) is only 15mW), derating is not a concern. The 300mV Vce(sat) maximum means the output transistor saturates hard at low collector currents, keeping the logic-side voltage drop predictable.
The TLP184 family includes several CTR-grade variants (TPL, GB-TPR, BL-TPL) that are pin-compatible and functionally identical; if your BOM specifies a particular CTR bin, verify the grade before substituting.