What causes a diode to fail?
The common reasons for a diode failure are excessive forward current and a large reverse voltage. Usually, large reverse voltage leads to a shorted diode while overcurrent makes it fail open.
Do TVS diodes fail short?
The problem is that the diodes often fail shorted and ruin the boards. This happens more often then static damage ever did, so they’re actually making the reliability WORSE. The TVS diode (D11) is a Littelfuse SMAJ12A.
How do zener diodes fail?
Most of the zener diodes fail due to the excess power dissipation across it. Each zener has a rated power dissipation by manufacturer when the power dissipation is greater than the rated then it fails. The power dissipation is the product of voltage drop across the zener and the current flow through it.
What happens when a diode breaks down?
1 Answer. At reverse breakdown voltage on a PN junction diode, you get a large increase in reverse current (normally close to zero) for a small further increase in voltage. Breakdown is non destructive – provided thermal effects do not destroy the diode.
What happens when a TVS diode fails?
If the circuit or system is not properly fused, a shorted TVS device can become a safety hazard conducting operating currents through the return path. TVS devices will fail in one of three modes. These are shorts, opens, and degraded devices. In most applications, the preferred method of failure is a short.
How do I know if my Zener diode is broken?
If a zener diode reads high resistance in both directions, this is a sign that the diode is open. A diode should not measure very high resistance in the forward biased direction. The diode should be replaced in the circuit.
How do ESD protection diodes work?
The ESD diode absorbs the short-duration voltage pulses during the ESD strike. It breaks down and forms a low impedance between the interface and the IC. The high peak currents from the ESD strike flow to the ground through the ESD diode and limit the ESD strike voltages from damaging the IC or USB.
How do you know if a diode is defective?
A diode is reverse-biased when the positive (red) test lead is on the cathode and the negative (black) test lead is on the anode. The reverse-biased resistance of a good diode displays OL on a multimeter. The diode is bad if readings are the same in both directions.
What happens if a blocking diode fails short?
Figure 3: ESD damaged blocking diode fails short, allowing battery discharge path at night Failure of even one of these diodes in the field is very expensive for companies to replace due to the need for a qualified service technician, as most installations will require code requirements to be met.
Does the diode design type determine the risk of ESD?
Figure 25: Minimum, maximum and average pulse current during failure for all tested diodes It has been suggested that it is not necessarily the diode design type that determines if the diode is more or less susceptible to ESD stress, but instead a result of quality control of the manufacturing.
What causes a TVS diode to fail?
Another common way for the diodes to fail is for a 24v supply to be connected instead of a 12v. Without the TVS diode, this just causes the regulator to run hot, but WITH the TVS diode, the board is fried instantly due to it going into conduction and subsequently failing shorted. Are there any solid ways to protect the TVS diode?
What is a local defect in a diode?
The local defect will concentrate the current during ESD into a very small area and cause the diode locally to melt. Thus, the robustness of such a diode is much worse than a diode that passes the 100V reverse voltage, which may indicate that it does have few, and less severe local defects.