When does Hardware Engineer gets clueless?

 

In the previous blog post we read what frequencies trouble the hardware engineer. While that is one aspect which hardware should take care of, there are several other aspects of design which trouble a lot. One of the important aspect is EMI/EMC. Every experienced design engineer in some time of the career has been hit by the EMI/EMC issues which led to longer development times and costs. If you cannot pass EMI/EMC you cannot sell your product in any market. Every market has their own compliance requirements and product has to pass all such compliance to enter into that market. The major problem is that design engineers don't invest time reading the compliance documents. It is important that design engineers have to purchase these standards and read them thoroughly. One major point is that after reading what is required for the product is to be extracted from the standard. All the conditions in the standard may not be required at all times. Design Engineer has to take a call and apply whatever are applicable. Let us try to list some of the precautions hardware engineer has to take in order to avoid EMI/EMC issues while designing an electrical circuit.

• The design engineer has to be clear of what kind of compliance product has to pass. 
• During the initial product analysis, it is important that compliance engineer need to be made part of if available so that design engineer shall have that knowledge of what are all the considerations and standards applicable before starting the product
• In the circuit design, take necessary precautions near the connectors, take considerations to eliminate reflections there by improving signal integrity. Example, scenario could be having series resistors on the clock to control edge rates.Especially, the clocks and high speed interfaces are the trouble creators. 
• PCB Layout is the most critical stage and if the board pass or fail this is the stage where the engineers have to put special focus on. Starting from the floor planning, PCB Material selection, stack up, constraints setting in the tool everything matters.
• One more important aspect are the external interfaces which can give sleepless nights to engineers. The external cables need to be properly shielded, the connectors to which these cables mate need to be properly earthed to enclosure, ESD considerations near the connectors help to avoid ESD failures, EMI chokes on the interfaces like USB, Ethernet help pass EMI issues.
• Pre and Post PCB Layout simulation is important criteria. Performing Signal and Power Integrity on the PCB Layout to check if all the interfaces are fine gives confidence to engineer.
• Some engineers due to non-availability of Signal Integrity tools like HyperLynx, Sigrity use free simulations to perform transient and steady state analysis to check if the circuit output is proper at different frequencies.
• Most of the component vendors have lot of technical data, PCB guidelines, test scenarios which need to be understood and applied to PCB wisely.
• If one has a spectrum analyzer, it is a shot in the arm as engineer in the lab itself can check to see if there any radiations out of the unit.
• Some design engineers design an environment by themselves where they can test their unit under various radiations. This helps to test the immunity.
• The firmware component in helping the EMI/EMC is always under looked and team has to sit through and see what can be done there to improve EMI of the circuit.
• Multiple reviews on the design are very important to help eliminate any issues during the design stage itself

Design engineer has to use all the weapons in his armory to verify various aspects of design at bench and system level before moving it to external labs for compliance tests. Even if engineers follow this there is lot of time being wasted and costs involved and issues have been caught post the design. The only relief is that before spending lot of money by sending to labs and finding out that there is an issue, it is found out at the bench level only. If the designer engineer has to save time, costs, it is important that focus also to be put on Compliance requriements.