PDM Protocolos compatibles

Audio

Pulse Density Modulation

¿Qué es PDM?

PDM (Pulse Density Modulation) is a single-bit digital audio encoding used primarily as the output format for MEMS digital microphones. A PDM stream consists of a clock signal (CLK) driven by the host and a data signal (DATA) driven by the microphone, where the density of logic-high pulses represents the instantaneous amplitude of the audio signal. PDM microphones are found in smartphones, laptops, smart speakers, hearing aids, and IoT devices due to their small size and simple two-wire interface. Engineers debugging PDM interfaces need to verify clock frequency accuracy, confirm left/right channel selection via clock edge assignment, and validate that the pulse density pattern corresponds to the expected audio input.

PDM Referencia rápida

type Serial, synchronous
signals CLK, DATA
max Speed Up to 4.8 MHz
voltage Range 1.8V – 3.3V
features Digital microphone interface

Instrumentos Acute compatibles con PDM

Soluciones recomendadas

Recomendado para decodificación

TB3016F

TB3016F

Con canales analógicos

MSO2116E

MSO2116E

Con validación eléctrica

MSO3124V

MSO3124V

Todos los productos compatibles

Decodificación de protocolo
Disparo por hardware
Validación eléctrica
Emulador de protocolo

Serie MSO3000

Familias de productos compatibles

Decodificación de protocolo
Disparo por hardware

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¿Cómo analizar PDM con instrumentos Acute

1

Conecte su analizador lógico Acute a las lineas PDM CLK y DATA en el microfono o codec.

2

Conecte un cable de tierra a la referencia de tierra de la placa objetivo.

3

En el software Acute, seleccione el PDM protocol decoder y asigne CLK y DATA a los canales de entrada correspondientes.

4

Configure los parametros esperados de clock frequency and channel mapping (left on rising edge, right on falling edge, or vice versa).

5

Capture el trafico y visualice el PDM bitstream, verifying clock timing and data alignment for each audio channel.

Preguntas frecuentes

Que tasa de muestreo necesito para el análisis PDM ?
PDM clocks typically run between 1 MHz and 4.8 MHz. Use a sample rate of at least 4x the PDM clock frequency — for a 3.072 MHz clock, sample at 12 MHz or higher. Higher sample rates improve timing accuracy when measuring clock duty cycle and data setup/hold times.
Por que la salida de mi microfono PDM no muestra transiciones de datos?
The most common cause is a missing or incorrect clock signal — PDM microphones are passive and only output data when clocked by the host. Verify the CLK signal is present and at the correct frequency. Also check power supply to the microphone, confirm the correct channel select pin state (some mics use a separate L/R select), and ensure the logic analyzer threshold matches the PDM signal voltage (typically 1.8V or 3.3V).
Cuantos canales necesito para el análisis de PDM ?
PDM requires 2 channels — one for CLK and one for DATA. A single DATA line can carry two channels of audio (left and right on opposite clock edges). If your design has multiple PDM microphone arrays with separate data lines, add one channel per additional DATA line.

Protocolos relacionados

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