The 1.5KE39A/54: It is a unidirectional Zener-type suppressor in the DO-201AA (DO-27) axial-lead package, rated for a 10/1000µs surge waveform up to 27.8A peak pulse current. The 33.3V reverse standoff voltage (V_RWM) means the diode stays transparent on a 24V or 28V bus, drawing negligible leakage. When a transient exceeds 37.1V (the minimum breakdown voltage), the device avalanches and clamps the surge to 53.9V maximum, shunting the energy to ground. This makes it suitable for general-purpose secondary protection on DC power rails, telecom line cards, and industrial control supplies where a single unidirectional TVS is needed per rail.
Lifecycle status and sourcing reality
Vishay lists the 1.5KE39A/54 as Obsolete. No official successor order code is recorded in the lifecycle data. For existing BOM lines, the 1.5KE39A/54 is available through independent surplus and broker channels. The DO-201AA axial package and 33.3V standoff voltage are the key fit parameters to verify against the board layout and rail voltage.
Package and thermal considerations for board fit
The DO-201AA (DO-27) axial package is a through-hole form factor with a 9.1mm body length and 5.3mm diameter typical. The leads are tin-plated copper. The junction temperature range spans -55°C to +175°C, covering industrial and military-temperature environments. The 1500W peak-pulse rating assumes a 25°C ambient; derating is required at elevated temperatures per the standard power-temperature curve for axial-lead TVS diodes.