Littelfuse® SPA™ Family of TVS Diode Arrays
Littelfuse SPA family of TVS diode array devices are designed to protect electronics from very fast and often damaging voltage transients, such as lightning and electrostatic discharge (ESD). They offer an ideal protection solution for analog and digital I/O interfaces for markets including consumer, telecommunications, industrial, medical, computing, etc.
Electrostatic Discharge (ESD) is an electrical transient that poses a serious threat to electronic circuits. The most common cause is friction between two dissimilar materials, causing a buildup of electric charges on their surfaces. Typically, one of the surfaces is the human body, and it is not uncommon for this static charge to reach a potential as high as 15,000 volts. At 6,000 static volts, an ESD event will be painful to a person. Lower voltage discharges may go unnoticed, but can still cause catastrophic damage to electronic components and circuits. These robust diodes can safely absorb repetitive ESD strikes at the maximum level (Level 4) specified in the IEC 61000-4-2 international standard, without performance degradation.
High Performance Transient Voltage Protection With Devices That Meet the Latest High Bandwidth Requirements
How Do They Work?
Littelfuse TVS diode arrays, provide high level protection against ESDs, Electromagnetic Interferences (EMI), Electrical Fast Transients (EFT) and Lightning, mainly for sensitive digital and analogue input circuits, on data, signal, or control lines operating on power supplies.
SPA's work in two ways, first, they absorb transients with diodes, to steer the current, and then, an avalanching or zener diode, clamps the voltage levels. This prevents the device from exceeding its voltage rating. During over-voltage fault conditions, the device must have a low clamp voltage at the specified current wave form to protect sensitive IC's and ports.
In normal operation, the reverse stand off voltage must be higher than the equipment supply/working voltage, with low leakage current to prevent power supply loading. The device capacitance must be low enough to reduce input signal distortion. The device package must have a small footprint and low height to enable a high density Printed Circuit Board (PCB) layout.
The device must withstand multiple ESD/EFT pulses as specified in the IEC 61000-4-2.
What Is A Transient Voltage Event And Why Should I Be Concerned?
Voltage Transients are defined as short duration surges of electrical energy and are the result of the sudden release of energy previously stored or induced by other means, such as heavy inductive loads or lightning. In electrical or electronic circuits, this energy can be released in a predictable manner via controlled switching actions, or randomly induced into a circuit from external sources.
Repeatable transients are frequently caused by the operation of motors, generators, or the switching of reactive circuit components. Random transients, on the other hand, are often caused by Lightning and Electrostatic Discharge (ESD). Lightning and ESD generally occur unpredictably, and may require elaborate monitoring to be accurately measured, especially if induced at the circuit board level. Numerous electronics standards groups have analyzed transient voltage occurrences using accepted monitoring or testing methods. The key characteristics of several transients are shown in the table below.
Why are Transients of Increasing Concern?
Component miniaturization has resulted in increased sensitivity to electrical stresses. Microprocessors for example, have structures and conductive paths which are unable to handle high currents from ESD transients. Such components operate at very low voltages, so voltage disturbances must be controlled to prevent device interruption and latent or catastrophic failures.
Sensitive microprocessors are prevelant today in a wide range of devices. Everything from home appliances, such as dishwashers, to industrial controls and even toys use microprocessors to improve functionality and efficiency.
Most vehicles now also employ multiple electronic systems to control the engine, climate, braking and, in some cases, steering, traction and safety systems.
Many of the sub- or supporting components (such as electric motors or accessories) within appliances and automobiles present transient threats to the entire system.
Careful circuit design should not only factor environmental scenarios but also the potential effects of these related components. Table 2 below shows the vulnerability of various component technologies.
To view a datasheet click here to visit our part search and choose the appropriate series.
Littelfuse SPA Devices are designed to protect electronics from very fast and often damaging voltage transients, such as lightning and electrostatic discharge (ESD). They offer an ideal protection solution for I/O interfaces and digital and analog signal lines, in computer and consumer portable electronics markets.
Littelfuse SPA Devices are available in a range of packaging configurations including DIP, SOIC, MSOP, SOT23, SOT143, SC70, SOT5x3, SOT953, μDFN, SOD723, and flipchip. View catalog.
Designers of today's electronic devices have demanded more functionality with greater flexibility and higher levels of user interaction. These circumstances have helped in driving the development of nanometer chipsets along with a multitude of user interfaces or ports. The confluence of these two has made electronic devices more susceptible to ESD and required the need for a more robust solution. View guide.
Board designers today are confronted with a multitude of choices for ESD protection. Often the designer is constrained by certain limits such as the amount of parasitic capacitance his/her application can withstand or the required ESD level the board must pass without fail. More often than not, the constraints do not narrow down the available number of ESD devices to a manageable list. This white paper will provide guidance to the designer that will help him/her in choosing an ESD device that will give the best chance of a successful first pass design. View application note.
In this white paper we'll address various techniques a board designer can employ to help him/her attain the ESD level required for their design should the chosen ESD protection devices fail in-system ESD testing. View application note.
This article explains the issues in greater detail and shows USB3.0 eye diagram test results to prove why the right kind of silicon protection array is the best technology for protecting USB 3.0 applications against ESD. View application note.
Understanding the nature and "directionality" of the events listed above will help guide the designer in how to best protect an Ethernet port, and more importantly, how the device's pin connections will affect system performance. View application note.