Quality assurance

AN4428

8/18

DocID025706 Rev 1

1.2

Final test information

After production the microphone must be screened to avoid shipping failing parts to the final

customer. Both electrical and acoustic parameters are tested. First of all the microphones

are tested in terms of electrical behavior. The ASIC, on each pin, is rigorously analyzed to

find any occurrence of open circuit or shorts. Additionally the device is analyzed to check for

any evidence of current leakage. Finally, reference voltages and current consumption are

checked. Once the entire electrical parameters have been verified, the microphones are

screened in terms of acoustic performance. It is sufficient to test the sensitivity and the

frequency response in order to determine whether the microphone works properly or not.

The sensitivity can be used to determine if the membrane is damaged in which case the

THD, as well as the noise floor, is out of specification. Finally the sensitivity is checked

across the audio band.

Each microphone is tested according to the previously mentioned criteria to avoid shipping

failing parts.

Figure 2. Final test checklist