The 1.5KE56AG is a unidirectional Zener TVS diode from the onsemi Mosorb™ family, rated for 1500W peak pulse power (10/1000µs waveform). It clamps a 47.8V reverse standoff rail to 77V maximum at 19.5A peak pulse current, making it a fit for protecting 48V nominal or 56V-max DC buses in industrial power supplies, telecom rectifiers, and automotive auxiliary circuits that can tolerate a through-hole axial package.
Clamping voltage and breakdown margin for a 56V rail
Minimum breakdown voltage is 53.2V; the device will start conducting around that threshold. On a 56V bus the TVS sits below the rail during normal operation (standoff 47.8V) but must not trigger on transient ripple. The 77V clamp at 19.5A is the voltage the protected circuitry must survive — if the downstream device's absolute maximum is below 77V, this part will not protect it.
onsemi lists the 1.5KE56AG as Obsolete. For a new design, select a current-production equivalent from the same Mosorb™ family with matching breakdown voltage and package. For an existing BOM, confirm the remaining quantity against your build forecast and source through verified distribution channels; the date-code and marking consistency should be checked on any broker-supplied material.
Junction temperature range is -65°C to 175°C, which covers military and high-reliability industrial environments. The DO-201AD axial package is a through-hole leaded format — it requires a drilled PCB and hand-solder or wave-solder assembly, not reflow. The copper lead diameter and body size are larger than SMD TVS packages; board layout must accommodate the hole pattern and lead spacing.