AD2420 datasheet(17/38 Pages) AD

17 / 38 page

AD2420/AD2426/AD2427/AD2428/AD2429

Rev. D

Page 17 of 38

May 2022

A2B BUS SYSTEM SPECIFICATION

Table 9. A2B System Specifications

Parameter

System Specification

Cable

Unshielded, single, twisted pair wire (UTP) with 100 Ω differential impedance. EMC performance

and full functionality under worst-case environmental conditions is confirmed with Leoni Dacar

545 cable (76D00305).

Maximum Cable Length

AD2428 Main Transceiver System

40 m total, 15 m between nodes.

AD2429 Main Transceiver System

10 m total, 5 m between nodes.

Maximum Number of Nodes

AD2428 Main Transceiver System

11 nodes (1 main node and 10 subordinate nodes).

AD2429 Main Transceiver System

Three nodes (1 main node and 2 subordinate nodes).

Maximum Number of Audio Slots

AD2426/AD2427/AD2428

64 total, up to 32 upstream and 32 downstream slots, depending upon system design.

AD2420/AD24291

AD2429: 4 upstream and 2 downstream slots, depending upon system design.



AD2420: 2 upstream slots, depending upon system design.

Number of Audio Channels per



Subordinate Node

Individually programmable 0 to 32 upstream channels and 0 to 32 downstream channels.

Synchronous A

2B Data Slot Size

8, 12, 16, 20, 24, 28, or 32 bits to match I

2S/TDM data-word lengths. Same slot size for all nodes.

Upstream and downstream can choose different slot sizes. 12-, 16-, or 20-bit slot sizes can carry

compressed data over the A2B bus for 16-, 20-, or 24-bit I2S/TDM word lengths.

Audio Sampling Frequency

44.1 kHz to 48 kHz. All nodes sample synchronously. Subordinate node transceivers support sample

rates (fS) of 1× (48 kHz), 2× (96 kHz) or 4× (192 kHz), individually configured per subordinate.

To support 2× and 4× sampling rates in subordinates, the main transceiver uses two and four times

the number of I2S/TDM data channels as the 1× sampling frequency (fSYNCM) interface to the host.

Transceivers also support reduced rate sampling for 24 kHz, 12 kHz, 6 kHz, 4 kHz, 3 kHz, 2.4 kHz,



2 kHz, 1.71 kHz, or 1.5 kHz at a low latency 48 kHz superframe rate.

Discovery Time

Less than 35 ms per node. Much less than 350 ms for total system startup in a system with 10 nodes.

Includes register initialization.

Maximum Bus Current per Node



Prior to Discovery Completion (IBUSDISC)

60 mA. Measured at the negative bias switch.

Maximum Total Bus Capacitance (CBUSDISC) 70 μF. Capacitance measured between the N and P pins in the CON1-B connector terminal.

Bit Error Detection

Robust error detection for control data and status data with 16-bit cyclic redundancy check (CRC).

Error Correction

Parity and line code error detection on synchronous data slots with audio error correction (repeat

of last known good data).

For 24-bit and 32-bit data channels, single error correction and double error detection (SECDED) of

synchronous data slots is possible.

Line Fault Diagnostics

Location and cause of cable fault can be detected for A

2B wires shorted to a high voltage (for

example, positive terminal of car battery), shorted to ground (for example, car chassis), wires

shorted to each other, wires reversed or open connection.

System EMI/EMC

Meets or exceeds industry specifications for robustness (ISO 11452-2, ISO 11452-4, ISO 7637-3) and

emissions (CISPR25).

System ESD Rating

Meets ISO 10605 severity levels.

1 See the AD2420/6/7/8/9 Automotive Audio Bus (A2B) Transceiver Technical Reference for more information.

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