Overview

Features and Benefits

A2B BUS FEATURES
  • Line topology
    • Single main node, multiple subordinate nodes
    • Up to 15 m between nodes and up to 40 m overall cable length
  • Communication over distance
    • Synchronous data
      • Multichannel I2S/TDM to I2S/TDM
      • Synchronous clock, phase aligned in all nodes
      • Low latency node to node communication
    • Control and status information I2C to I2C
    • GPIO and interrupt
  • Bus power or local power subordinate nodes
  • Configurable with SigmaStudio/SigmaStudio+ graphical software tool
  • AEC-Q100 qualified for automotive applications
A2B TRANSCEIVER FEATURES
  • Configurable A2B bus main node or subordinate node
  • Programmable via I2C interface
  • 8-bit to 32-bit multichannel I2S/TDM interface
    • Programmable I2S/TDM data rate
    • Up to 32 upstream and 32 downstream channels
  • PDM interface
    • Programmable PDM clock rate
    • Up to 4 high dynamic range microphone inputs
  • Simultaneous reception of I2S data with up to 4 PDM microphones
  • Unique ID register for each transceiver
  • Crossover or straight-through cabling
  • Programmable settings to optimize EMC performance

Product Details

The Automotive Audio Bus (A2B®) provides a multichannel, I2S/TDM link over distances of up to 15 m between nodes. It embeds bidirectional synchronous pulse-code modulation (PCM) data (for example, digital audio), clock, and synchronization signals onto a single differential wire pair. A2B supports a direct point to point connection and allows multiple, daisy-chained nodes at different locations to contribute and/or consume time division multiplexed (TDM) channel content.

A2B is a single main node, multiple subordinate node system where the transceiver at the host controller is the main node. The main node generates clock, synchronization, and framing for all subordinate nodes. The main A2B transceiver is programmable over a control port (I2C) for configuration and read back. An extension of the control port protocol is embedded in the A2B data stream, which allows direct access of registers and status information on subordinate transceivers, as well as I2C to I2C communication over distance.

The transceiver can connect directly to general-purpose digital signal processors (DSPs), field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), microphones, analog-to-digital converters (ADCs), digital-to-analog converters (DACs), and codecs through a multichannel I2S/TDM interface. It also provides a pulse density modulation (PDM) interface for direct connection of up to four PDM digital microphones.

Finally, the transceiver also supports an A2B bus powering feature, where the main node supplies voltage and current to the subordinate nodes over the same daisy-chained, twisted pair wire cable as used for the communication link.

Table 1. Product Comparison Guide
Feature AD2420 AD2426 AD2427 AD2428 AD2429
Main node capable No No No Yes Yes
Number of subordinate nodes discoverable1 N/A N/A N/A Up to 10 Up to 2
Functional TRX blocks A only A only A + B A + B B only
I2S/TDM support No No No Yes Yes
PDM microphone inputs 2 mics2 4 mics 4 mics 4 mics 4 mics
Max node to node cable length 5 m 15 m 15 m 15 m 5 m

1 N/A means not applicable.
2 PDM microphones must be connected to the DRX0/IO5 pin.

Applications

  • Audio communication link
  • Microphone arrays
    • Beamforming
    • Hands free and in car communication
  • Active and road noise cancellation
  • Audio/video conferencing systems

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