How to prevent device destruction due to overvoltage! ?

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Design Analog Devices

The main cause of destroying a device is applying a voltage outside the device's specified range.
From the point of view of the reliability of systems shipped to the market, it is important to take measures such as using protective devices on circuits to prevent device destruction due to overvoltage.

To prevent damage caused by static electricity

ESD destruction due to static electricity is considered to be one type of overvoltage destruction.

In the case of static electricity, an extremely high voltage is applied in a short period of time (1ns or less), so an ESD suppressor/TVS diode is required as a protection element for ESD countermeasures. For example, you can use Würth Electronics ESD protection devices (available here).

For interfaces, ESD countermeasures are particularly important because they are exposed with metal outside the housing.

Analog Devices has developed interface products with enhanced ESD countermeasures, some of which comply with the IEC 61000-4-2 Level 3 standard. For more information, please refer to the ESD enhanced RS485 device ADM3065E.

Overvoltage breakdown due to noise

Confirmation of Zener characteristics by LTspice

Overvoltage destruction due to noise is caused by noise from the power supply source and noise generated between devices and boards that propagate through power lines and communication lines, destroying devices.

Overvoltage noise may be generated by turning on/off the switch or plugging/unplugging the board/cable in a hot state.

As a countermeasure against these overvoltage noises, the breakdown voltage of the Zener diode is used to clamp the overvoltage. Click here for Zener Diodes from ON Semiconductor.

The figure on the right is a simulation result using LTspice of the clamp characteristics when 48V overvoltage noise is applied to ON Semiconductor's Zener diode (BZX84C12L).

The figure below shows that the input is an overvoltage of 48V. The figure above is a simulation result where the 48V overvoltage noise is clamped to 12.5V by the Zener.

Overvoltage generation due to inductive loads and inductance

In systems where the power supply must be connected with a long cable, an overvoltage of 1msec or more may occur when the power is turned on due to the inductance of the cable.

Under these conditions, the power consumption of the Zener diode, which is included as a noise countermeasure, may exceed the expected power consumption and may exceed the allowable power.

In such cases, it is necessary to stably supply power to the circuit by inserting a high-voltage power supply IC or module between the power supply and the circuit.

However, since power supply ICs and modules require a regulation function that outputs a stable voltage, there is a limit to the operating voltage range that they can support.

Applications that meet these conditions include cameras and sensor modules made for industrial equipment, and in-vehicle equipment.

Overvoltage Protection Solution "Surge Stopper"

A surge stopper product developed by Analog Devices, Inc. can be used as a countermeasure against an overvoltage of 1msec or more, which is difficult to protect with a TVS or Zener diode.

Before getting into the content of the "Surge Stopper" product, I did some research on the word "Surge". Then I found out that it means "swell" or "big wave".

Somehow, I had an image that surge = static electricity and noise, and I was wondering why the overvoltage was over 1msec, but I was convinced that it was a solution to stop overvoltage over 1msec if it meant "swell".

The MIL Standard specification (MIL-STD-1275D) stipulates: As a surge, we can see that it is required to support overvoltage of 500msec.

specification	Normal operating mode	Generator only mode
steady state	25V < VIN < 30V	23V < VIN < 33V
spike	up to 250V Energy = 15mJ	Same as normal operating mode
surge	Maximum 40V, about 500ms, RSOURCE = 20mΩ	Max 100V, about 500ms, RSOURCE = 500mΩ
ripple	Magnitude ±2V	magnitude ±7V

MIL-STANDARD PROVISIONS (MIL-STD-1275D)

The figure on the right shows the circuit diagram of the LTC4364 surge stopper product and the waveform when a 92V surge is applied.

When a surge voltage is input to the 12V line, the LTC4364 controls the FET (FDB33N25) to clamp it to the voltage set by the voltage divider resistor.

In the waveform on the right, a surge voltage of 92V is clamped to 27V. When the input drops below the clamp setting voltage of 27V, the output also drops to match the input.

Now, let's take a look at the detailed explanation and demo video about our surge stopper products.