AD2437 datasheet(3/42 Pages) AD

3 / 42 page

AD2437

Rev. 0

Page 3 of 42

July 2023

GENERAL DESCRIPTION

The AD2437 A2B

® transceiver provides a multichannel,

I2S/TDM link over distances of up to 30 m between nodes. It

embeds bidirectional synchronous pulse-code modulation

(PCM) data (for example, digital audio), clock, and synchroni-

zation signals onto a single-pair differential cable. A2B supports

a direct point to point connection and allows multiple, daisy-

chained nodes at different locations to contribute and/or con-

sume time division multiplexed 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 program-

mable over a control port (I2C/SPI) for configuration and read

back. An extension of the control port protocol is embedded in

the A2B data stream. This allows direct access to registers and

status information on subordinate transceivers, as well as I2C to

I2C, SPI to I2C, or SPI to SPI communication from the host to a

peripheral in a subordinate node. SPI to SPI communication

between subordinate nodes can be performed directly and does

not need to involve the main node.

The transceiver can connect directly to general-purpose digital

signal processors (DSPs), field-programmable gate arrays

(FPGAs), application specific integrated circuits (ASICs), digital

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.

The transceiver supports a bus power feature, where the main

node supplies voltage and current to the subordinate nodes over

the same daisy-chained, single-pair wire or XLR/DMX cable as

used for the communication link.

The transceiver also supports a broad spectrum of Ethernet

cables in which the A2B occupies only one pair of a category

(CAT) cable. This frees up the remaining CAT cable pairs for

power delivery.

A2B BUS DETAILS

Figure 2 shows a single main node, multiple subordinate node

A2B communications system with the main transceiver con-

trolled by the host. The host generates a periodic

synchronization signal on the I2S/TDM interface at a fixed fre-

quency (typically 48 kHz) to which all A2B nodes synchronize.

Communications along the A2B bus occur in periodic super-

frames. The superframe frequency is the same as the

synchronization signal frequency, and data is transferred at a bit

rate that is 1024 times faster (typically 49.152 MHz). Each

superframe is divided into periods of downstream transmission,

upstream transmission, and no transmission (where the bus is

not driven). Data is exchanged over the A2B bus in equal width

slots for both upstream and downstream transmissions. Up to

32 bidirectional slots can be configured at 24 bits, while up to 51

slots can be configured at 16 bits.

The A2B bus also communicates the following control and

status information between nodes:

•I2C to I2C or SPI to I2C/SPI communication

• General-purpose input/output (GPIO)

•Interrupts

In Figure 3, a superframe is shown with an initial period of

downstream transmission and a later period of upstream

transmission.

All signals on the A2B bus are line coded, and the main node

forwards the synchronization signal downstream from the main

transceiver to the last subordinate node transceiver in the form

Table 1. Product Features

Feature

AD2437

Main node capable

Yes

Functional TRX blocks

A + B

I2S/TDM support

Yes

PDM microphone inputs

4 mics

A2B bus power

Up to 50 W

Nominal bus bias voltage (VBUS)

24 V

SPI over distance

Yes

Power configuration

CFG-4

Figure 2. Communication System Block Diagram

HOST

DSP

I2C/SPI

MAIN

A2B

TRANSCEIVER

SUBORDINATE

A2B

TRANSCEIVER

I2S/TDM/PDM

I2S/TDM

I2C/SPI

I2S/TDM/PDM

SUBORDINATE

A2B

TRANSCEIVER

SUBORDINATE

A2B

TRANSCEIVER

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