The Toshiba TLP388(D4GB-TR,E is a single-channel transistor-output optocoupler in a 6-SOIC 4-lead surface-mount package. Its 5000Vrms isolation rating suits designs requiring reinforced galvanic isolation between a low-voltage control side and a high-voltage load side — think motor-drive IGBT gate drives, industrial PLC I/O modules, or isolated sensor interfaces. The output transistor is rated for 350V collector-emitter voltage (VCEO), so it can directly switch 24V or 48V industrial loads, or drive a higher-voltage relay coil, without needing an external level shifter.
CTR range and switching speed — sizing the drive current
The current transfer ratio (CTR) is specified at 100% minimum and 600% maximum, both measured at 5mA LED forward current. A CTR of 100% means the output transistor can sink at least as much current as the LED draws — so a 5mA LED drive guarantees at least 5mA at the output, enough to pull a logic input low or drive a small relay. The 600% ceiling means the same 5mA input can produce up to 30mA output, giving plenty of headroom for degraded LED output over temperature or aging. Rise and fall times are 2µs and 3µs typical, with turn-on and turn-off times both 3µs typical — fast enough for 100 kHz switching in isolated gate drives or serial data isolation.
Temperature range and package — deployment context
The 6-SOIC 4-lead body (0.173" width, 4.40mm) is a standard surface-mount footprint shared with many Toshiba and competitor optocouplers, so a layout designed for a similar part often accepts this one without a board spin.
Sourcing and lifecycle
RoHS compliant.