The SMAJ170E3/TR13 is a unidirectional Zener TVS diode from Microchip Technology, rated for 170V reverse standoff voltage and 500W peak pulse power in the 10/1000µs waveform. It clamps transients to 304V maximum at 1.6A peak pulse current.
Minimum breakdown voltage is 189V, so the diode starts conducting between 189V and the 304V clamp ceiling. On a 170V rail, that gives roughly 19V of headroom before the TVS begins to avalanche — enough to ride through normal ripple without wearing the device. The 500W peak pulse rating at 10/1000µs is the standard telecom surge shape; for shorter pulses the diode can absorb more energy, but the 1.6A peak current is the hard limit at that waveform. If your application sees repetitive surges, derate the peak power — this is a one-shot clamp, not a continuous regulator.
Microchip lists the SMAJ170E3/TR13 as Active. For BOM quantities, we source per RFQ — no stock-holding claim, but the active status means lead times are predictable through distribution.
Surface-mount to DO-214AC (SMA) — the cathode band marks the unidirectional orientation. The 500W peak pulse is tested at 25°C; derate linearly above that per the datasheet curve.