TJA1085GHN/0Z - FlexRay Active Star Coupler 4-Branch | NXP
MPN: TJA1085GHN/0Z β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $6.79 | $6.79 |
| 10 | $6.45 | $64.50 |
| 100 | $5.98 | $598.00 |
| 500 | $5.55 | $2,775.00 |
| 1,000 | $5.12 | $5,120.00 |
TJA1085GHN/0Z Overview
An active star coupler is a network topology device that receives signals on one branch, regenerates them, and retransmits them on the remaining branches. Unlike passive coupling, active star topology means a short circuit or fault on one branch does not disable the entire FlexRay bus, because the coupler electrically decouples each branch. In the automotive in-vehicle networking hierarchy, the TJA1085G sits at the physical-layer level above simple linear bus transceivers, serving as the backbone node of safety-critical, time-triggered communication systems.
Key features include support for 4 FlexRay branches with TRXD0/TRXD1 receive interfaces that allow several TJA1085G devices to be cascaded for networks requiring more branches, a dedicated Communication Controller (CC) interface for direct attachment to the FlexRay communication controller, and full compliance with FlexRay V3.0.1/ISO 17458-4 timing and electrical requirements. The HVQFN-44 package with its exposed pad provides low inductance and good thermal performance for the sustained drive currents needed to power four actively driven branches.
Architecturally, the device integrates receiver, driver, and supervision logic per branch, detecting branch faults and isolating defective stubs so the healthy portion of the network keeps operating. Because FlexRay is a time-triggered protocol with deterministic 10 Mbit/s communication, the coupler's loop-through delay and signal symmetry directly affect the network's static segment timing budget, which the TJA1085G meets within the V3.0.1 specification limits.
Typical applications include chassis-domain FlexRay backbones in premium vehicles, x-by-wire systems (steer-by-wire, brake-by-wire), advanced driver assistance sensor fusion rings, and gateway modules that aggregate multiple FlexRay branches.
Design consideration: provide a low-impedance ground path via the exposed die pad and observe branch-wiring stub length limits per ISO 17458-4 to preserve signal integrity at 10 Mbit/s.
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Drop-in alternatives for TJA1085GHN/0Z β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
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TJA1085GHN
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TJA1085GHN/0Z Specifications
| Product Type | FlexRay active star coupler |
| Number of Branches | 4 |
| Protocol Compliance | FlexRay electrical physical layer V3.0.1 / ISO 17458-4 |
| Transceiver Configuration | 4/4 |
| Package | 44-HVQFN, 9x9 mm |
| Mounting Type | Surface Mount |
| Moisture Sensitivity Level (MSL) | 1 |
| Peak Reflow Temperature | 260 C |
| Maximum Time at Peak Reflow | 30 s |
| Terminal Finish | Nickel Palladium Gold Silver (JESD-609 e4) |
| Cascade Interface | TRXD0/TRXD1 for multi-device expansion |
| Controller Interface | Dedicated CC (Communication Controller) interface |
| RoHS Status | unknown |
TJA1085GHN/0Z 44-hvqfn, 9x9 mm Pin Configuration Guide
Pin configuration for TJA1085GHN/0Z (44-hvqfn, 9x9 mm package). Pin numbering, functions, and connection diagrams are defined in the manufacturer datasheet. Refer to it for the exact footprint and soldering guidelines.
No detailed pinout data available for TJA1085GHN/0Z.
Refer to the datasheet for full pin configuration.
Typical Applications
TJA1085GHN/0Z is suitable for 6 applications: Chassis-Domain FlexRay Backbone, X-by-Wire Systems, ADAS Sensor Fusion Ring, Gateway Modules, Test and Validation Equipment, Body and Comfort Domain Networks.
Chassis-Domain FlexRay Backbone
The TJA1085GHN/0Z serves as the physical star point of a chassis-domain FlexRay backbone, connecting up to 4 branches of chassis control units (suspension, steering, braking modules) that require deterministic 10 Mbit/s time-triggered communication. Because FlexRay V3.0.1/ISO 17458-4 compliance governs loop-through delay and signal symmetry, the coupler preserves the static-segment timing budget across all four branches. In a star topology, a wiring short on one branch is isolated by the coupler, so the remaining branches continue communication - a mandatory property for chassis systems. The device's TRXD0/TRXD1 interfaces allow a second TJA1085G to be cascaded when more than four chassis nodes must be served.
Recommended
X-by-Wire Systems
Steer-by-wire and brake-by-wire architectures demand a communication physical layer that survives single-point wiring faults. The TJA1085GHN/0Z meets this requirement with four independently driven and supervised FlexRay branches: the coupler detects a faulted stub and electrically decouples it while regenerating signals onto healthy branches. Its dedicated Communication Controller (CC) interface attaches directly to the FlexRay CC in the by-wire ECU, and ISO 17458-4 compliance guarantees the deterministic latency the by-wire control loop depends on. Designers should budget the coupler's loop-through delay into the network schedule and ground the exposed die pad solidly to support the current of four active drivers.
Recommended
ADAS Sensor Fusion Ring
Advanced driver assistance systems aggregate radar, camera, and lidar data over a low-latency, deterministic backbone; FlexRay remains in use in premium platforms for this role. The TJA1085GHN/0Z forms the star center of such a ring, actively regenerating FlexRay frames to each of 4 sensor clusters so propagation delay and jitter stay within V3.0.1 limits. Active star coupling prevents one damaged sensor harness from silencing the fusion ECU. With MSL 1 and 260 C reflow tolerance, the HVQFN-44 package fits standard automotive SMT assembly, and the cascade interfaces allow additional branches as the sensor suite grows across vehicle generations.
Recommended
Gateway Modules
Central gateways that bridge FlexRay domains to CAN, LIN, or Ethernet backbones need a physical star to concentrate multiple FlexRay branches in one ECU. The TJA1085GHN/0Z provides exactly this: four actively driven branches plus a CC interface to the gateway's communication controller, all within a 9x9 mm HVQFN-44 footprint that saves board area in dense gateway designs. Compliance with FlexRay V3.0.1/ISO 17458-4 means the gateway can rely on the coupler to maintain frame symmetry and timing. Per-branch fault supervision also feeds gateway diagnostics, enabling the vehicle to log a degraded branch without losing the whole FlexRay segment.
Recommended
Test and Validation Equipment
FlexRay network testers, bus analyzers, and hardware-in-the-loop rigs must emulate a complete star topology with multiple branches. The TJA1085GHN/0Z lets test equipment present four compliant V3.0.1/ISO 17458-4 branches from a single device, with TRXD0/TRXD1 cascading to build 8- or 12-branch emulators for fault-injection testing. Because the coupler is a production-grade automotive part, the test rig reproduces the same loop-through delay and signal characteristics as the target vehicle network, making timing validation meaningful. MSL 1 handling simplifies bench assembly of custom adapter boards around the 44-HVQFN (9x9 mm) package.
Recommended
Body and Comfort Domain Networks
Premium vehicles extend FlexRay beyond chassis into body and comfort domains where multiple ECUs (doors, seats, lighting modules) communicate over a star backbone. The TJA1085GHN/0Z concentrates up to four such branches, isolating a harness fault in one zone so lighting or seat control in other zones remains functional. ISO 17458-4 compliance ensures deterministic delivery for synchronized body functions such as adaptive lighting. The e4 Ni-Pd-Au-Ag terminal finish and MSL 1 rating support high-volume body-ECU assembly lines, and the 9x9 mm HVQFN-44 footprint fits compact body control modules with limited board space.
Recommended
Recommended Products Summary
Engineering reference data for TJA1085GHN/0Z β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | TJA1085GHN |
|---|---|---|
| Package | 44-HVQFN (9x9 mm) | 44-HVQFN (9x9 mm) - same |
| Brand | NXP Semiconductors | NXP Semiconductors |
| Number of Branches | 4 | 4 |
| Protocol Compliance | FlexRay V3.0.1 / ISO 17458-4 | FlexRay V3.0.1 / ISO 17458-4 |
| Cascade Interface | TRXD0/TRXD1 | TRXD0/TRXD1 |
| Transceiver Configuration | 4/4 | 4/4 |
| MSL | 1 | 1 |
Key Differentiators
- Four actively driven FlexRay branches in one package (vs TJA1080T)
- Cascade expansion via TRXD0/TRXD1 (vs TJA1080T)
- Dedicated Communication Controller interface (vs TJA1080T)
Design Notes
The 44-HVQFN (9x9 mm) package exposes a central die pad that must be soldered to a solid ground plane with an array of thermal vias. This pad carries the return current of four actively driven FlexRay branches and dissipates device heat; a poorly soldered pad causes both signal-integrity and thermal problems. Follow NXP's HVQFN application hints for stencil design - use a segmented paste pattern (approximately 70% coverage) to avoid voiding under the pad during reflow, and verify with X-ray on first articles.
FlexRay branch wiring must meet ISO 17458-4 impedance and stub-length requirements to preserve the deterministic 10 Mbit/s signal. Keep each of the four branch differential pairs length-matched within the pair, route them on a single layer with a continuous reference plane, and avoid stubs at branch connectors. The coupler's loop-through delay consumes part of the network timing budget, so account for it in the cluster schedule when cascading multiple TJA1085G devices via TRXD0/TRXD1.
Do not treat the TJA1085G like a simple two-node FlexRay bus transceiver: it is a star coupler with per-branch supervision and a dedicated CC interface, so firmware must handle branch fault detection and the CC handshake correctly. During reflow, respect the 260 C peak with a maximum of 30 s (MSL 1 still requires dry storage if the bag has been opened). Verify that the branch supply sequencing matches the datasheet requirements before powering all four branches simultaneously.
Compliance Information
Terminal finish JESD-609 code e4 (Nickel Palladium Gold Silver) indicates lead-free plating. RoHS/REACH/AEC-Q100 status not stated in the retrieved web data - verify on the NXP product page.
