Reduce those who keep apart type CAN system to blast off to raise immunity to interference

As at present more and more systems move below different voltage, arrive from elevator electric car, maritime even system, segregation type CAN is sent and receive implement had made indispensable one part.

These sending and receive implement network of CAN(controller area) of the standard preferential close with arbitral function 2 for one, the advantage that offers segregation (disconnect road of ground connection annulus, compression resistance difference, in all modular very short time changes the) such as immunity to interference, conduce to the reliable communication between region of two voltage in maintaining a system.

Like be not system of segregation type CAN together, the main problem of system of CAN of use segregation type depends on keeping apart type CAN to send and receive implement electromagnetism compatibility (EMC) function. EMC function measures through two parameter:

1. equipment arises blast off

The immunity to interference of generation is disturbed in 2. system

Blast off

Blasting off is electromagnetism energy is needless release. Below good case, low blast off ensure subsystem can move reliable, do not affect the performance of photograph adjacent subsystem at the same time.

According to the market (industry or car) with application, the system must accord with different emissive level. Although launch a test,undertake in systematic level, but the component that design personnel can choose to satisfy package class to ask normally. This conduces to those who ensure single facility does not exceed its itself be restricted to be worth. In addition, the system is designed and circuit board layout also launchs function to having main effect to systematic whole. In numerous emissive test, zwickau standard is the strict test that is aimed at car application, emphasize particularly on CAN is sent and receive implement emissive function.

Graph 1 it is the give a demonstration that EMC test uses circuit board. Circuit board has 3 to join to the segregation of same bus line type CAN is sent and receive implement. Nod in the test (graph the CP1) of 1 undertakes emissive metrical, among them one is sent and receive implement transmit the 50% square wave signal that take sky comparing, 250 KHz.

Reduce those who keep apart type CAN system to blast off to raise immunity to interference

Graph 1: The circuit of heart state apparatus that EMC test uses board

In send and receive implement and place between bus line in all modular choke (CMC) meeting filter is divided a few blast off. In car and industrial application, use generally in all modular choke.

The emissive data that through EMC the ISO1042 of test board carries out with rate of traditional CAN data sees a picture 2.

Reduce those who keep apart type CAN system to blast off to raise immunity to interference

Graph 2: ISO1042 (500 Kbps carries out blast off)

Certain attestation orgnaization asks to data is collected below the case that using CMC, this also benefit blasts off at keeping low. Below same condition, ISO1042 is launching device of respect excel competition.

Immunity to interference

The circumstance that immunity to interference points to to equipment is disturbed in existence leaves the capacity that moves correctly. Fight ability of a confusion of voices to prove those who keep apart type CAN parts of an apparatus, the identical circuit that we show 1 times to the graph carried out direct power infuse (DPI) checks, but use different coupling network. Undertake scanning to the noise frequency of the infuse on bus line, check the difference that blast off and receives mode through test of film of attack by surprise. The noise signal that checks an infuse includes successive wave (CW) noise signal and amplitude modulation (AM) noise signal. AM signal is the 1-kHz signal of 80% . Constant tension exceeds to be restricted to be worth on perpendicular direction (time exceeds to be restricted to be worth on ±0.9 V) or horizontal way (the change of ±0.2μs) treats failure.

We carried out a test below two kinds of different conditions:

1. is not had in all the noise of 36 DBm infuse of modular choke

2. is taken in all the signal of 39 DBm noise of modular choke

Graph 3 with the graph the 4 ISO1042 that showed traditional CAN to fall in two kinds of conditions pursue. Below two kinds of circumstances, prep above of function of segregation type CAN is restricted to be worth a line, make clear passed DPI test. Through these immunity to interference the test can ensure communication is reliable, reduce systematic error and breakdown.

Reduce those who keep apart type CAN system to blast off to raise immunity to interference

Graph 3: Without in all the ISO1042 DPI of modular choke checks
Reduce those who keep apart type CAN system to blast off to raise immunity to interference

Graph 4: Belt in all the ISO1042 DPI of modular choke checks

Like predicting parts of an apparatus of CAN of compositive segregation type is not parts of an apparatus of segregation type CAN together, can satisfy blast off identically and standard of immunity to interference. Considering small-sized those who enclose is low blast off to be spent with Gao Kang faze, ISO1042 and ISO1042-Q1 satisfy industry and the strict requirement that the car uses.

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