4.7 V clamp at 500 mW — SOD-323F footprint
The ROHM UFZVTE-174.7B is a 4.7 V Zener diode rated for 500 mW continuous power dissipation in the SOD-323F package. The ±2.78% tolerance on the nominal voltage means this part holds the regulation band tighter than the standard ±5% grade — relevant when the clamp voltage must stay within a narrow window for downstream logic or ADC reference protection.
Leakage and impedance at the operating point
Reverse leakage is specified at 5 µA maximum when biased at 1 V — well below the knee, so this diode draws negligible current from the protected rail until it enters breakdown. The maximum Zener impedance (Zzt) is 25 Ohms at the test current, which sets the dynamic resistance the upstream current-limiting resistor sees once the diode conducts.