What the 400W peak pulse rating means for your protection design
The SMAJ200AQ-13-F is a 400W Zener TVS diode in a DO-214AC (SMA) surface-mount package, designed to clamp transients on 200V nominal DC rails. At that waveform, the diode handles 1.2A peak pulse current before the clamping voltage reaches 324V. The -55°C to 150°C junction temperature range covers under-hood and engine-bay thermal profiles.
Clamping voltage and breakdown — the protection window
The reverse standoff voltage is 200V — the diode draws negligible leakage below this level, so it does not load the protected rail during normal operation. Breakdown starts at a minimum of 224V, and the maximum clamping voltage at rated peak pulse current is 324V. That 100V window between standoff and clamp defines the margin the downstream circuitry must survive without damage. Unidirectional (single-channel) clamping means the cathode is tied to the rail and the anode to ground — correct orientation matters. Reverse insertion blocks the transient path and leaves the rail unprotected.