What is meant by EOS?

 

EOS is a current term, because overmuch electron tries to enter circuit through corresponding method,express, bring about a system to had borne great pressure. A bit need to notice, this is a function that changes along with power and time.

 

If will complex circuit regards a simple component that consumes power, for example, regard it as a resistor. 1.1 V voltage brings to bear on on the 1 Ω resistor that is 1 W in rated power, the formula of computational power comsumption is as follows:

 

 

Computation reachs, the power that consume is 1.21 W. Although the rated power of resistor is 1 W, but the likelihood is put in a few surplus, need not worry about this temporarily so. But not can such from beginning to end.

 

Increase tension 2 V, can you appear what circumstance? If power comsumption is achieved before 4 times of give typical examples, so resistor may resemble heater of a space raising environmental temperature inside very limited time, but remember this formula please:

 

 

If increase tension 10 V, but last only 10 millisecond? Interesting place is here: If do not understand a part, and the purpose that designs processing unit, you cannot understand truly can produce what effect to this component. Now, will view whole component system.

 

What part suffers EOS effect easily?

 

Generally speaking, any shares that include electronic component are affected easily by EOS. Particularly weak part is the interface of those and outside, because they are probable,be most first bring into contact with is electrostatic discharge (ESD) , be struck by lightning the part that wait. The component that we are interested in includes the imitate front of USB port, oscillograph, and of blender of newest net of couplet of high-powered other people charge port.

 

Graph 1. The ideal when 8 KV contacts weaveform of discharge electric current.

 

How to know to want to be on guard what problem?

 

Although we want protection system to avoid,suffer electric overload, but this technical terms is too broad extensive, to the decision how protection system does not have any helps. For this, IEC (and a lot of other organizations) the EOS kind that made a large number of jobs clear up in actual life to may be encountered. Discuss the key IEC standard then, because they cover wide market application, and the troubled condition related to this standard also shows need the article comes li is clear. Watch 1 indicated 3 standards, they defined the EOS state kind that the system may encounter. Do development to discuss to ESD only in the article, also can let everybody be familiar with report at the same time fast twinkling changes (EFT) and surge.

 

Graph 2. The report that accords with IEC61000-4-4 standard is fast twinkling changes 4 class are undee.

 

Express 1. IEC standard

 

How does integrated circuit manufacturer answer chip ESD?

 

The protection in chip basically is used at answering to make the ESD in the process, is not the ESD below systematic electrify condition. This one difference is very significant, when because join in amplifier power source is mixed,doing not have join power source, its are being sufferred electrostatic the reaction when is disparate. For example, protective diode can eliminate interior to be pounded to the electrostatic discharge of the component when having power source power supply. But, when having power source power supply, the electric current that to the electrostatic discharge of the component concussion may make internal composition is conducted exceeds its design to bear level, this may bring about this component to mar, specific decide by component and power source voltage.

 

This is the problem that solves urgently inside global limits! How to protect IC to avoid suffer this kind of potential menace?

 

Hope you can realize, this challenge involves a lot of elements, a simple solution cannot apply at all circumstances. Lower part is one involves element list, listed decision part whether bear the element of EOS incident. These element cent are two groups: It is OK that uncontrollable element is mixed pilot element.

 

Uncontrollable element:

 

● IEC is undee: The curve of ESD, EFT and surge has each different, they can atttack the certain weak point of parts of an apparatus with different kind.

 

● considers the engineering technology of parts of an apparatus: Some engineering technology are more incidental than other technology latch. For example, CMOS craft is incidental latch, but in a lot of modern technology, can reduce this kind of harm through elaborate design and groove segregation.

 

● considers the internal composition of parts of an apparatus: The design method of integrated circuit is very much, so effective to a kind of circuit protection program disables possibly to another kind. For example, a lot of parts of an apparatus have sequential circuit, detect undee and enough fast when, can start protective construction. This may be meant, if you increase more electric capacity in the position of electrostatic discharge, can bear so parts of an apparatus of electrostatic discharge percussive cannot bear possibly concussion of this kind of capacitance. Unexpected of this kind of result, but realise the following this are very important: Common circuit protects a method, namely RC filter, may allow a condition more flooey.

 

Graph 3. IEC61000-4-5 surge turns in position of weaveform of electric current of 8 μs/20 μs for whack.

 

Can pilot element:

 

● PCB layout: The component is closer from percussive position, weaveform of its electric energy is taller. Because,this is, when bow wave form travels along some method, the electromagnetic wave that from transmission method radiate goes out can have energy loss, this is the quantity of heat that produces as a result of method resistor and the parasitism capacitance with circumjacent conductor coupling and inductance place bring about.

 

● protects circuit: This is the most significant to the viability of parts of an apparatus portion. Afore-mentioned uncontrollable elements will affect the design that protects program.

 

Had had now press protection (OVP) and pass limit (OTT) is characteristic. Can you use these character to protect circuit not to suffer high-pressured twinkling to change affect?

 

The input that OVP and OTT character allow a part is in bear when the voltage that exceeds power source voltage, itself won’t be damaged. Rely on these character to protect circuit not to suffer high-pressured twinkling to change influence, resembling is support rain boots like answer high pressure to develop water aircraft. The shallow water Hang that pluvial boots does not exceed its height to depth of water only is effective, apply to lower than its rating voltage only like OVP and OTT. The rated report pressure ratio of OVP and OTT is given voltage of power supply course is tall a few bend over. It is overpowering the high pressure of 8000V.

 

How to know whether protective circuit is effective?

 

Through combining knowledge of parts of an apparatus, experience and test, can know roughly, what part should be used in the system the most advantageous. To make sure parts of an apparatus can accuse, each manufacturer offerred multifarious protective package, the article discusses two kinds of classics to confirm the circuit that can protect imitate front effectively protects program only. The operation amplifier that uses an amortize configuration suppose with lower part case. This is considered as the strictest protection test, can bear because of inphase input all concussion, divide this beyond, nowhere can go to electric energy (before installation protects circuit) .

 

Graph 4. The circuit that uses in IEC-61000-4-2 test.

 

The design thinks:

 

● R1 should be one prevents pulse (thick film) resistor, when it is enduring high-pressured twinkling to change, won’t destroy easily so.

The square root of noise of ● R1 voltage and resistance becomes direct ratio, if the system needs low noise, this is a main consideration factor.

● C1 should be capacitance of a pottery and porcelain, its enclose dimension to be at least 0805, with reducing enclosed exterior electric arc.

The capacitance that ● C1 should be X5R type temperature coefficient at least (ideal is C0G/NP0 type) , the electric capacity that can calculate in order to maintain is worth.

The inductance of equivalent series connection of ● C1 interior and resistor should as far as possible low, so that absorb concussion effectively.

● is aimed at given enclose dimension, the rated voltage of C1 should as far as possible tall (lowermost 100 V) .

● is in this exemple, the position of C1 is before R1, because its compose built voltage divider of a capacitance, among them 150 PF capacitance (if the graph is shown 5 times) ESD weaveform discharge arrives in the system, endure weaveform in amplifier so before, energy already first billabong.

 

Graph 5. Configure through end is being inputted in imitate low a protection of filter implementation input.

 

RC network protects program

 

RC network protects program

 

Attention: Although this is planted,approbate without what get capacitance manufacturer, but proving in hundreds test that is aimed at amplifier is effective. ESD checks a curve (following place are narrated) it is only on the capacitance product of narrow range had had a test, accordingly, if use different capacitance product, need first its answer token percussive is characteristic, the method of the capacitance after before enduring ESD to pound through measuring for example, be being mixed and resistor of equivalent series connection, this are very important. This capacitance parts of an apparatus should maintain the stability that hold a cost, after and be in be being pounded, hold open circuit position below dc from beginning to end.

 

The design thinks:

 

● and RC network are same: R1 should bear pulse, but the likelihood needs to consider noise.

● should the standard that demonstrate D1 needs to satisfy. Cover ESD a little possibly only, other cover EFT and surge standard.

● D1 should be two-way, such it can answer to be pounded to be being lost at the same time.

Voltage of ● D1 retrorse job should as far as possible tall, still need to pass necessary test at the same time. If pass low, likelihood occurrence leakage current falls in normal systematic voltage n. If exorbitant, likely cannot ● response is made before the system damages.

 

The influence of TVS diode leak to function

 

 

In imitate electron domain, everybody knows TVS diode is incidental leak, because this cannot be used at accurate imitate front. But sometimes the circumstance is not such, the discharge leakage current in a lot of data manual<100µA, it is quite tall that to most imitate product this is worth. Numeric to this, the problem depends on, it is in highest temperature (150°C) and depressive of report of the biggest job take a cost. Below this kind of circumstance, diode is extremely easy leak. Exceed 85°C, the discharge leakage current of all diode will be taller. Want to choose the TVS diode with retrorse job taller voltage only, and do not expect to realize extremely small leakage current in 85°C above, criterion hopeful obtains smaller discharge leakage current.

 

Graph 6. Configure TVS diode to realize input protection through end is being inputted in imitate.

 

TVS network protects program

 

If you chose appropriate TVS, cost of leak electric current may be low to make you open-eyed. The graph shows the leak data that when be the TVS diode that measures model of 12 same products, obtains 7 times.

 

Graph 7. The leak of Bournes T36SC of diode of 36 V two-way TVS is worth, ADA4530 is used to evaluate in TIA board, take screen, 10 G resistor is used when 25°C.

 

In metrical 12 TVS diode, when dc bias voltage is 5 V, the most serious leakage rate is 7 PA. The value that this expresses than the data below worst circumstance is close friends 1 billion times. Of course, the TVS diode of different batch exists in leak respect difference, but this can show expectant leak extent at least. If the system is endured temperature won’t exceed 85°C, TVS diode may be a right choice. Want to remember only, if the product of your choice is not the test product that article place narrates, ask token its leak is characteristic. The conclusion with to a component or manufacturer right word, may incorrect to other part or manufacturer.

 

Test result:

 

Used IEC ESD standard to have a test to a series of operation amplifier. Express the 2 component that show different protection program suits to protect respectively. Although ESD standard regulation wants to assure to endure concussion 3 times in ±8 KV, but all these plan were passed percussive test is undergone 100 times when ±9 KV, offer enough protective surplus in order to ensure.
 

Express 2. The list of parts of an apparatus that checks through IEC-61000-4-2 and its respective protection are configured

 

EC standard asks, pass paralell connection of resistor of two 470 KΩ and 30 PF capacitance, make the ground connection of the ground connection end of ESD source and amplifier carries join to be together. The setting of this test is more strict, the ground connection end of its ground connection end ESD source and amplifier is linked together directly. These results also got test and verify in plan of coupling of IEC ground connection, what this can enhance a product further is calculable degree. Remember please, because the internal composition presence of amplifier is very large different, applicable to the parts of an apparatus in this list data may be applicable, do not apply to other parts of an apparatus possibly also. If use other parts of an apparatus or other protection cell, the proposal has full-scale test to its.

 

Use protective cell:

 

● resistor: Series of Panasonic 0805 ERJ-P6

● capacitance: Yageo 0805 100 V C0G/NPO

● TVS diode: Bourns CDSOD323-T36SC (two-way, 36 V, extremely small leakage current, accord with ESD, EFT and surge standard)

● ESD presses quick resistor: Bourns MLA series, 0603 26 V

 

BBonus component: ESD is pressed quick resistor

 

TVS diode performance is good, can endure concussion countless times. This is very pretty good to EFT and surge protection, but, if you need ESD protection only, might as well see ESD press quick resistor, before achieving a certain voltage to be worth, they use as high-pressured resistor, after achieving this voltage to be worth, their change is low-pressure resistor, can divide run off to press quick the electric energy in resistor.

 

Can use as identical as TVS diode configuration. Their leak is fewer, cost is less than the half of TVS diode. Ask an attention, its are designed and do not ask to endure concussion hundreds times, and its resistor is met as pound every time drop. ESD is pressed quick resistor also had a test on afore-mentioned products, be TVS diode place to require a cost about when series connection resistance double when, this pressing quick the function of resistor is optimal.

 

These products had had a test below ESD standard only. The unique part of EFT depends on, although voltage is not tall (4 KV and the following) , its are pounded is to erupt however type (5 KHz or above) , rise time is slower (5 Ns) . Surge every time 1000 times percussive energy is EFT about, but speed has undee 1/1000 only. If return need to cover these standards, ensure to make clear on the data manual that protects component in these please, they can answer this question.

 

Circuit protects an overview

 

It is not difficult that although look,after the event adds RC filter or TVS diode in circuit, but ask an attention, all and other factor that mentions in the article can affect systematic performance and protective level. This includes the parts of an apparatus or appliance that layout, front uses, and the IEC standard with contented need. If you from begin to write down this sincerely, the emergency that likelihood occurrence need redesigns the final phase that can avoid to be designed in the system.

 

Article far from is summed up in the round. Sensitivity topic will undertake more thorough discussion in follow-up article. In addition, base the other challenge that station receiver designs includes automatic gain control (channel estimation and AGC) algorithm, balanced algorithm. Sequel still will roll out a series of technology articles, the purpose is to simplify to design circuit and promote everybody the understanding to receiver system.