By Neil Miller | Nov 21, 2013
The worst fear of any electronic product company is that serious design issues will be uncovered after the product has shipped in volume. In 2010 the world experienced “Antennagate” when Apple customers reported dropped calls and poor reception with the iPhone 4. A class-action lawsuit was filed, and the settlement resulted in over 21 million people in the US being eligible for $15 or a free case from Apple. These scenarios are embarrassing for an electronic product company at best, and at worst can have irreparable financial repercussions.
The surest way to prevent a debacle like this is with thorough design validation testing (DVT). DVT is a method of testing products to verify that a product satisfies all of its design specifications. After production begins, DVT is required again if there are component substitutions due to second-sourcing or component obsolescence, to ensure that none of the design specifications has been compromised.
Design validation covers various aspects of a product design and can be categorized as follows:
- Electronic DVT
- Electromagnetic Compatibility DVT
- Environmental DVT
- Mechanical DVT
- Reliability DVT
- Transportation DVT
With Electronic DVT the product design is broken into various subsystems, and tests are created to validate each one. Subsystems in a typical electronic product design could include power supplies, clock and reset, memory, Video, USB, Ethernet, Bluetooth and Wi-Fi.
The power supply tests, for example, would check that all the power rails are within specification, they meet ripple and noise requirements, and the correct power-on sequencing order is followed. Tests for the clock subsystem would ensure that clock frequencies, rise and fall times, duty cycles, jitter, noise, reflections, and stability all satisfy the product requirement specification.
Electronic DVT is the first step in design validation and usually consists of a combination of manual and automated test procedures. These tests can be reused to qualify component changes.
Electromagnetic Compatibility (EMC) DVT
In most cases EMC DVT follows Electronic DVT. EMC DVT is required to ensure that a product complies with EMC regulations for country where it will be sold. Although there are some harmonized standards, like in the European Union (EU), EMC requirements usually vary between countries. The EMC requirements also vary depending on the type of product and its end use. The US, Canada, and EU regulatory standards for a product with an intentional radiator used in a residential environment, such as Wi-Fi or Bluetooth, are shown in the table below:
|US||FCC15 Class B||Radiated and AC/DC Conducted Emissions|
|EU/Generic||EN 55022 Class B|
|US||FCC 15 Class C||Conducted RF power (TX), Transmitter E-field measurements|
|EU||ETSI 300 328|
|EU||ETSI 301-489||Radiated & Conducted Immunity, ESD, EFT|
|EU||EN60251||Electrical Safety for RF device|
Some level of EMC DVT is necessary to re-qualify a product that has undergone component substitutions or design changes. This is to ensure EMC integrity of the design has been maintained. EMC retesting is recommended for a product when there are any changes to:
- Component values
- Schematic connections hence PCB layout
- Type of ferrites used
- Connector types
- The enclosure design that might affect shielding effectiveness
- Decoupling capacitors quantity or package type
- Crystal frequencies
- Crystal oscillator substitutions with different timing characteristics, such as rise time
In our next post we take a look at Environmental DVT and what tests are performed to ensure that an electronic product will survive the elements.
Nuvation Engineering can provide design validation testing support through our New Product Introduction service. As part of this service we prepare test plans and test procedures tailored to customer requirements. We can also develop supporting test software to monitoring the behavior of the product under test during DVT. We work with local test houses to determine an overall DVT program tailored specifically for the product’s end application. Contact us to discuss your electronic design services needs.