onsemi NCN26000XMNTBG

Overview

NCN26000XMNTBG from onsemi is an IEEE 802.3cg-compliant 10BASE-T1S Ethernet PHY transceiver for industrial multi-drop networks. It operates at 10 Mb/s half-duplex over a single unshielded twisted-pair, interfaces via standard MII to CSMA/CD MACs, and integrates Physical Layer Collision Avoidance (PLCA) for deterministic communication in noise-prone environments such as factory floor sensor networks.

For engineers reviewing the NCN26000XMNTBG datasheet, pinout, applications, or equivalent options, this device delivers collision-free operation across ≥8 nodes on >25 m UTP cable, supports 3.3 V supply with 2.5 V I/O option, enables boot-time mode selection (NORMAL/ISOLATED), and provides MDIO-based configuration of PLCA, ENI, and diagnostic registers.

Technical Context

The NCN26000XMNTBG implements a full 10BASE-T1S PHY stack including PMA, PCS, and PLCA Reconciliation Sublayer (RS), enabling deterministic medium access without MAC-level modifications. Its MII interface runs at 2.5 MHz and exposes CRS/COL pins required for CSMA/CD compatibility, while supporting Clause 22 and Clause 45 MIIM register access for both standard and 10BASE-T1S-specific control.

It features dual boot modes selected via strap pins: NORMAL mode activates all MII and line drivers immediately; ISOLATED mode holds MII and LINEx pins in high-impedance until cleared via MDIO register 0.10, facilitating safe system power sequencing. Enhanced Noise Immunity (ENI) mode extends operation beyond IEEE 802.3cg noise limits.

Key Specifications

Pinout & Package

NCN26000XMNTBG is housed in a 5 mm × 5 mm QFN32 package (Case 484AB) with exposed thermal pad (EP) connected to GND. Pin assignments follow JEDEC MO-220 standard; all analog and digital supplies are decoupled externally using 2.2 µF capacitors on VDRVN and DVDD.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 10BASE-T1S PHY applications.

Compared with MAX22503EASA+ and DP83TC811RQWR, NCN26000XMNTBG uniquely combines PLCA Reconciliation Sublayer, Enhanced Noise Immunity, and hardware-strapped ISOLATED boot mode - making it the only choice for deterministic, noise-resilient, and power-sequencing-safe 10BASE-T1S deployments in harsh industrial environments.

Availability

NCN26000XMNTBG is available at Aetrix Electronics and suitable for industrial automation, sensor interfacing, and building control systems requiring stable component supply, long-term lifecycle assurance, and automotive-grade reliability under extended temperature operation.

Supply support for NCN26000XMNTBG includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

onsemi is a global semiconductor supplier focused on energy-efficient innovation, serving automotive, industrial, cloud, medical, and IoT markets with silicon solutions for sensing, power, and connectivity.

The NCN26000XMNTBG belongs to onsemi's Industrial Ethernet PHY product line, designed specifically to enable robust, deterministic, and cost-effective 10BASE-T1S networking in multi-drop industrial environments where traditional Ethernet is impractical.

FAQ

What is the primary compliance standard for NCN26000XMNTBG?

The NCN26000XMNTBG is fully compliant with IEEE 802.3cg-2019, specifically implementing the 10BASE-T1S physical layer specification for multi-drop industrial Ethernet. It meets all mandatory requirements for differential signaling, timing, noise immunity, and PLCA operation defined in Clauses 147–149 of the standard. Compliance is verified through onsemi's internal characterization and third-party lab testing per IEEE test procedures.

Does NCN26000XMNTBG support full-duplex operation?

No, NCN26000XMNTBG supports only half-duplex 10 Mb/s operation as mandated by IEEE 802.3cg for 10BASE-T1S. The Control Register (Address 0, Bit 8) always reads as 0 and has no effect when written, confirming fixed half-duplex mode. This design enables shared-medium multi-drop topology and deterministic PLCA arbitration - full-duplex is not defined or supported in the 10BASE-T1S standard.

How is PLCA configured on NCN26000XMNTBG?

PLCA is configured via Clause 45 MIIM registers (MMD 31, addresses 51712–51715) accessible through the standard MDIO interface. Key settings include coordinator selection, node ID assignment, beacon interval, and precedence mode - all programmable at runtime. Configuration can also be partially set at boot via strap pins (RXER, RXD[3:0]) to assign PHY address and isolate mode, but full PLCA parameters require MDIO writes post-initialization.

What clock sources are supported by NCN26000XMNTBG?

NCN26000XMNTBG supports three clock source options: (1) 25 MHz quartz crystal connected between XO and XI pins; (2) 25 MHz LVCMOS clock applied to XI with XO left floating; or (3) external CMOS oscillator at XI. The device's internal oscillator circuitry accepts ±100 ppm frequency tolerance and automatically conditions the signal for PHY timing - no external PLL or clock buffer is required.

Can NCN26000XMNTBG operate with a 2.5 V I/O supply?

Yes, NCN26000XMNTBG supports VDDIO = 2.5 V ±10% for its digital I/O pins (MII, MDIO, DIOx), while maintaining VDD = 3.3 V for core analog functions. This dual-supply flexibility allows direct interfacing with 2.5 V MACs or FPGAs without level shifters. Electrical characteristics including VIH/VIL thresholds, drive strength, and slew rate are validated across both 2.5 V and 3.3 V VDDIO conditions per Table 5 in the datasheet.