Electronic Design Process

Requirements and Specifications

The first step in the design process is to understand (and document) the functions the electronics device must perform and the constraints under which it operates. Designing any electronics should start with creating the specification, and not with jumping into the design process. The act of documenting the requirements has some useful effects that actually can save you time in the long run:

• The design team thinks through the issues and reaches agreement. Some issues are well understood at a high level, but raise additional questions when working at the hardware level.
• Interfaces to other areas (software, other hardware) are defined and available for review by all affected parties.
• Non-engineers can understand what the device is supposed to do.
• If the trade-offs and rationales are documented, as well as the requirements, future design changes will require less impact assessment.
• The requirements can be reviewed to assure that they provide measurable, testable criteria.

Design Entry and PCB Layout

Once the specifications have been understood, the next step in creating a design involves entering the design. Schematic capture (also called schematic entry) creates the electronic diagram, or schematic, of the electronic circuit. This is usually done interactively with the help of a schematic capture tool also known as schematic editor.

 

With the schematic capture complete the electronic design of the circuit is contained within the file and can be converted to what is termed a "netlist". The netlist is the interconnectivity information and it essentially the component pins and the circuit nodes, or nets, to which each pin connects.

 

Before proceeding with the detailed PCB design and layout, it is necessary to gain a rough idea of where components will be located and whether there is sufficient space on the board to contain all the required circuitry. This will enable decisions about the number of layers needed in the board, and also whether there is sufficient space to contain all the circuitry may need to be made.

 

Once the basic placement has been completed and component footprints have been created, the next stage of the PCB design is to route the connections between all the components. The PCB software then routes the physical connections on the board according to the netlist from the schematic.

 

Once complete, the information for the PCB will be used in many areas of the manufacturing process. Not only will it be used for the manufacture of the actual PCB itself, but the files will also be used in other areas of the manufacturing process (such as creating solder paste screen or pick-and-place programs for automated board stuffing)

Building Prototype Boards

The schematic capture also results in bill of materials. It is used to identify individual electronic components (such as resistors, capacitors and integrated circuits) that are part of the actual board. All the components need to be purchased and soldered to the actual PCB.

 

The PCB manufacturing and PCB aassembly is typically performed by a board stuffing company.

Firmware Design and Programming

Almost every electronic design, now includes a microcontroller or some programmable logic. A programmer would design and implement program to run in the product.

 

In-circuit debugging tools are used to load and test the program.

Simulation and Verification

After design entry, parts of the the design are simulated to verify that the design meets the requirements. We may want to prototype critical parts of the design to further verify the functionality.

The goal of functional simulation is to ensure that the logic of the design does what you want it to do, per the specification, and that it produces the correct results. This type of simulation is very important to get as many bugs out of the device as possible. If any errors are discovered, then the design entry step is re-visited and necessary required changes are made, leading to a successful simulation.

 

Verification is a parallel set of activities to design and development. Various tasks are performed at each phase of the development. The specific verification activities, performed by either the electronic design engineer or quality assurance.

Functional Testing and Validation

Once the prototype has been built, a set of functional tests are performed to verify the device operation meets the requirements. Signals are applied to the inputs and the response of the circuit is examined with electronic measuring tools such as oscilloscopes, logic analyzers and multi meters.

 

We typically ask the clients to perform the validation. They are in the best position to confirm that the product meets their needs.

Regulatory Agency Testing

Typically a product will require regulatory testing. This may include safety testing to confirm that it meets some specific standard. Other tests may include electromagnetic emission testing to confirm that the device does not interfere with other electronic devices.

 

The tests are performed by specialized labs. These tests need to be ordered separately from the design work.

Environmental/Field Testing

Many products operate in extreme environmental testing. It is important to subject the product conditions that the product is likely to encounter during the service life. Environmental testing may include temperature cycling or vibration.

 

The tests are performed by specialized labs. These tests need to be ordered separately from the design work.

Initial Production Run

We recommend that the first production run be small. The full-scale production should not start until you have field-tested a reasonable number of units over a significant period of time.

Once the product is manufactured it is important to monitor its performance in the field.

 

Not only the performance of the design needs to be confirmed but also the initial requirements.