Simple SPICE ESD Generator Circuit based on IEC61000-4-2 Standard

Università Politecnica delle Marche, Ancona, Italy.

by

Ing. Luca Buccolini

A SIMPLE SPICE ESD GENERATOR CIRCUIT BASED ON IEC61000-4-2 STANDARD

 

WHAT IS ESD?

Static charge is an unbalanced electrical charge at rest. Typically, it is created by insulator surfaces rubbing together or pulling apart. One surface gains electrons, while the other surface loses electrons. This results in an unbalanced electrical condition known as static charge.

When a static charge moves from one surface to another, it becomes ESD. ESD is a miniature lightning bolt of charge that moves between two surfaces that have different potentials. It can occur only when the voltage differential between the two surfaces is sufficiently high to break down the dielectric strength of the medium separating the two surfaces.

When a static charge moves, it becomes a current that damages or destroys gate oxide, metallization, and junctions. ESD can occur in any one of four different ways: a charged body can touch an IC, a charged IC can touch a grounded surface, a charged machine can touch an IC, or an electrostatic field can induce a voltage across a dielectric sufficient to break it down

 

ESD STRESS MODELS

ESD can have serious detrimental effects on all semiconductor ICs and the system that contains them. Standards are developed to enhance the quality and reliability of ICs by ensuring all devices employed have undergone proper ESD design and testing, thereby, minimizing the detrimental effects of ESD. Three major stress methods are widely used in the industry today to describe uniform methods for establishing ESD withstand thresholds (highest passing level).

 

HUMAN BODY MODEL (HBM)

The HBM is a component level stress developed to simulate the action of a human body discharging accumulated static charge through a device to ground, and employs a series RC network consisting of a 100 pF capacitor and a 1500 Ohm resistor.

 

CHARGED DEVICE MODEL (CDM)

The CDM is a component level stress that simulates charging and discharging events that occur in production equipment and processes. Potential for CDM ESD events occur when there is metal-to-metal contact in manufacturing.

 

SYSTEM LEVEL ESD (IEC 61000-4-2)

The IEC system level ESD is a widely accepted European standard that defines an ESD event that is meant to be tested on actual end equipment to simulate a charged person or object discharging into electronic systems. The IEC standard defines an ESD stress that is much stronger than the component level ESD stresses defined by HBM and CDM.

The engineer must design following IEC 61000-4-2 standard to be able to declare the conformity CE (“Conformité Européenne”).

The ESD generator circuit realized in this work is compliant with ESD generator used in EMC laboratories to perform CE-conformity tests, thus a SPICE simulation can be used to test ESD-immunity solutions before circuit production.

 

 

IEC 61000-4-2 WAVEFORM CHARACTERISTICS

The standard accurately describe the characteristics and performances of the ESD generator as well as the current waveform parameters.

The ESD phenomenon is a very short but very strong current transient and is represented in Figure 1.

 

idealcontactESDwaveform

Figure 1. 61000-4-2 ideal contact ESD waveform at 4kV

This pulse is divided into two parts: The first peak, known as the “Initial Peak”, is caused by the discharge of the arm, and generates the maximum current. The second peak is caused by the discharge of the body. The rise time of the initial peak is between 0.6 ns and 1 ns, and its amplitude depends on the charging voltage of the ESD simulator.

The standard describe a formula and the mains current level of the waveform for different test level.

dischargeESDwaceform

Table 1 contact discharge current waveform parameters

Even though the IEC 61000-4-2 [2] include a simplified circuit of ESD generator, it is incompatible with the discharge current equation descripted in the standard and the waveform shown in Figure 1. A PSpice software simulation can prove this.

THE BASIC ESD GENERATOR MODEL

In order to run ESD stress simulation, an ESD-generator model was built. This can help engineers to test different solutions in a SPICE simulator to overcome strength over-voltages before realizing PCB circuit and test it against ESD.

The objective is to generate an ESD pulse that accurately corresponds to the current stress waveforms at various stress levels in accordance with the IEC 61000-4-2 specification.

The ESD can be simulated by two parallel R, L, C circuits with charged capacitors. The generator equivalent circuit is shown in Figure 2.

Here the standardized network elements of the ESD-generator are represented by R1 (330ohm) and C1 (150pF). The inductor L1 is considered to be the obligatory ground strap with the length of about 2 m. Physically the first peak of the pulse is shaped by additional lumped and parasitic elements around and in the tip of the ESD-generator [5].

Note that the values of R, L, and C for both branches are tweaked to correctly represent standard IEC stress waveform; “.ic V(c1)=4kV V(c2)=4kV” refers to the initial condition of the voltage on the capacitors for a 4kV zap.

 

Figure 2  The general equivalent circuit of basic IEC61000-4-2 generator model

Designing and Simulation of LNA using LTspice and Matlab

Ventspils University College

Faculty of Information

by

Marcis Bleider

LOW NOISE PREAMPLIFIER FOR SATELLITE BASE STATION

 

In this article low noise preamplifiers (LNA) for satellite ground station (GS) of Ventspils University College (VUC) are designed creating possibility to repair and replace these commercially expensive, extremely sensitive and easily damageable units.

One of main purposes of GS of VUC is for communication with soon to be launched satellite Venta-1. GS will provide uplink/downlink communication channels for satellite telecommands and telemetry in 2m and 70cm amateur frequency bands as well as main data downlink channel in s-band. GS also will (and are) communicate with other student satellites orbiting in low earth orbits (LEO), like Estonian Estcube-1 and Danish AAUSat cubesat series.

Because it is not always possible to receive and decode all data packets in particular satellite pass, skipped packets should be retransmitted in next pass – there are only few passes with acceptable elevation per day. Even though we are located very close to Estonia and Denmark and we are receiving same data as their ground station, our received data may contain packets that main station failed to receive, so data could be forwarded to main mission control center resulting in higher throughput. In any case, our station could be used as remote backup station, increasing redundancy of communication system.

 

Signals from satellites can be exquisitely weak, which means they need as much amplification as possible to be readable. The way to ensure that you have a useable received signal is to install a receive LNA at the antenna [1]. This is a high gain, low-noise amplifier with a frequency response tailored for one band only. Even though equipment of GS  includes a few such preamplifiers, these units are very expensive, for example 2m/70cm band Kuhne Electronic LNAs costs 224 EUR per unit  [6].

Because  LNA  is  very  sensitive device  it  is  very  prone  to  damage  by lightening induced voltage spikes, static electricity and even by strong nearby radio transmission  signals.  Of  course  by  correct  system  setup,  like  switchover  relays, damage risk is greatly reduced, but LNA is still one of weakest link of the system in respect to failing. If device fails, it would be very non-economical to by new one each time, not to mention that it would not be possible to repair or replace it right away to reestablish operation of communication system as fast as possible.

 

In this work, theory of operation and typical design methods of LNAs are researched, and example design and testing procedure is described. For reference, two 70cm band LNAs are designed, built, tested and performance-price compared. In this particular paper, one 70cm LNA is designed and simulated with MATLAB using scattering parameter (s-parameter) and Smith chart method and LTSPICE software. It should be noted that preceding description is very superficial and only presentative.

The RF amplifier which is at the input stage of the receiver is usually designed to give the best gain parameter and the least noise. It is done so for the reason that the noise and distortion parameters would get depressed in the later stages of the receiver system [3]. Friis’s formula is used to calculate the total noise factor of a cascade of stages, each with its own noise factor and gain (assuming that the impedances are matched at each stage) [7]. The total noise factor can then be used to calculate the total noise figure is given in equation 1.

 

Ftotal

(1)

 Where

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