The BZX55B2V4-TR is a 2.4 V Zener diode from Vishay's BZX55 series, rated for 500 mW continuous dissipation in a DO-35 (DO-204AH) axial-lead package. The ±2% tolerance on the Zener voltage makes it a tighter-grade selection than the standard ±5% BZX55 parts — useful when the bias or reference voltage needs to stay within a narrow window across temperature and load. It carries AEC-Q101 qualification, which means it has passed the stress tests for automotive-grade semiconductor devices — thermal cycling, high-temperature reverse bias, and humidity bias life. The operating temperature range of -65°C to 175°C covers under-hood and engine-bay environments where the ambient temperature can climb well above the 85°C industrial ceiling.
500 mW in a DO-35 — thermal budget for the board
500 mW is the maximum power at 25°C lead temperature. In a real board the lead length and copper trace area set the thermal resistance; for a DO-35 soldered into a typical PCB with 10 mm lead length, derating to about 300 mW at 85°C ambient is a safe working limit. The 85 Ohms maximum Zener impedance (Zzt) at the test current means the regulation slope is moderate — for a 2.4 V rail the voltage will shift a few tens of millivolts as the current varies, which is fine for clamping or bias but not for a precision reference.
Active production — no LTB clock ticking
ROHS3 compliant — no exemption issues for EU or similar markets.