FlexRay Active Star Coupler – 4 Branch

TJA1085

The TJA1085 is a FlexRay active star coupler that can connect up to 4 branches of a FlexRay network. The TJA1085 is compliant with the FlexRay electrical physical layer specification V3.0.1/ISO17458-4

Several TJA1085 devices can be connected via their TRXD0/1 interfaces to increase the number of branches in the network. A dedicated Communication Controller (CC) interface allows for integration into an ECU. The TJA1085 supports low-power management by offering bus wake-up capability along with battery supply and voltage regulator control. The TJA1085 meets industry standards for EMC/ESD performance and provides enhanced bus error detection, low current consumption and unmatched asymmetric delay performance.

The TJA1085 also fulfills the JASPAR requirements as defined by the Japanese car industry.

Product Details

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Block Diagram

TJA1085 Block Diagram

TJA1085 Block Diagram
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Features

General

  • Fulfills JASPAR requirements
  • Automotive product qualification in accordance with AEC-Q100
  • Data transfer rates from 2.5 Mbit/s to 10 Mbit/s
  • Supports 60 ns minimum bit time at 400 mV differential voltage
  • Low-power management for battery-supplied ECUs
  • Very low current consumption in AS_Sleep mode
  • Leadless HVQFN44 package with improved Automated Optical Inspection (AOI) capability

Functional

  • Supports autonomous active star operation independent of the host ensuring the TJA1085 remains active even if the host fails or is switched off
  • Branches can be independently configured
  • Branch extension via TRXD0/1 inner star interface
  • 16-bit bidirectional SPI interface up to 2 Mbit/s for host communication
  • Full host control over branch status
  • Enhanced wake-up capability:
    • Remote wake-up via wake-up pattern and dedicated FlexRay data frames
    • Local wake-up via pin LWU
    • Wake-up source recognition
    • Configurable per branch
  • Enhanced supply voltage monitoring on VIO, VCC, VBUF and VBAT
  • Auto I/O level adaptation to host controller supply voltage VIO
  • Can be used in 14 V, 24 V and 48 V powered systems
  • Enhanced bus error detection - detects short-circuit conditions on the bus
  • Instant transmitter shut-down interface (BGE pin)
  • Selective branch shut-down (partial networking)

Robustness

  • Bus pins protected against ±8 kV ESD pulses according to HBM and ±6 kV ESD pulses according to IEC61000-4-2
  • All pins protected against ±1000 V ESD according to CDM
  • All pins protected against ±200 V ESD according to MM
  • No reverse currents from the digital input pins to VIO or VCC when the TJA1085 is not powered up
  • Bus pins short-circuit proof to battery voltage (14 V, 24 V or 48 V) and ground
  • Overtemperature detection and protection
  • Bus pins protected against transients in automotive environment (according to ISO 7637 class C)

Active star functional classes

  • Active star - communication controller interface
  • Active star - bus guardian interface
  • Active star - voltage regulator control
  • Active star - logic level adaptation
  • Active star - host interface
  • Active star - increased voltage amplitude transmitter

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