A customer of Presto Engineering had a problem: The conventional way of testing a crystal oscillator used as a frequency reference in a mobile phone took 25 seconds to run through its entire operational range for each unit. A 25 second (s) test per unit was expensive and so the oscillators were going into the phone PCB without testing. Any assembled PCB with a defective oscillator would be detected in the final testing and rejected.
“Mathematically, it was going to be more cost effective to scrap the occasional final PCB compared to the cost of 25 seconds of test time per oscillator,” explained Edouard de Lédinghen, the Presto test manager. “The conventional test protocol took 25 seconds as it would require 16.25 million samples over 25 steps to fully test it to ensure that it did not stick between step changes in frequency. Our challenge was to devise a new test protocol that only took a fraction of a second per unit to make testing cost effective for the customer.”
Presto’s solution was to upscale the oscillator’s frequency, which makes any faults much easier to detect. According to the company, test time was reduced with an innovative algorithm that directly processes the resulting time data. Now, only 20,800 samples over the 25 steps are needed to ensure that the part is working properly, and that takes only 150 ms instead of 25 s. As a result, Presto’s test methodology can cost-effectively detect any faulty components so that they can be rejected before they enter the assembly process.
Martin Kingdon, Presto’s VP of sales, added, “The customer was delighted with our solution. When we implemented the testing for them, we found out the typical percentage of faulty oscillators. Running the mathematics, it showed that the tiny cost of testing all the oscillators was now outweighed by the greater cost that would have resulted from having to scrap populated PCBs with faulty oscillators. This is just one example of how we have created novel testing solutions to save customers money. We have highly skilled teams of test engineers around the world who can draw on many years of experience to devise innovative ways to solve problems.”
For more information, visit Presto.
Source: Presto Engineering
