Created on 2013-12-17 00:18:00
APx PDM Line Driver
The AP PDM Line Driver solves a key problem encountered when testing PDM MEMS (Micro Electro-Mechanical Systems) microphones: the distance between the DUT and the analyzer itself.
PDM data is one-bit oversampled audio, most commonly employing a oversampling factor of 64. This means that in order to represent the performance of a PCM audio system with a 48kHz sample rate, many digital MEMS microphones employ a sample rate of 48kHz x 64 = 3.072MHz. The low-power, current-limited design of MEMS devices means that this high-frequency signal can suffer severe degradation due to cable capacitance in many test bench configurations, especially where the DUT must be a substantial distance – 1 meter or more – from the analyzer.
Testing microphones in an anechoic chamber is just such a scenario. All noise-generating equipment (PCs, analyzers) must remain outside the chamber, requiring substantial cable runs from the inside.
AP PDM Line Driver with cables
The Audio Precision PDM Line Driver provides a buffer for the PDM audio data, allowing cable lengths of up to 45ft (13.7m) to be used between DUT and analyzer with no loss or alteration of the digital signal.
Maximum cable length vs. PDM clock frequency
Contact your AP Partner for ordering information.