Microchip Technology KSZ8081RNDIA-TR

Overview

KSZ8081RNDIA-TR from Microchip Technology is a single-chip, IEEE 802.3-compliant 10BASE-T/100BASE-TX Ethernet PHY transceiver with RMII v1.2 interface, 50 MHz reference clock input (power-up default), on-chip 1.2V regulator, and integrated termination resistors for differential pairs. It supports HP Auto MDI/MDI-X, LinkMD® TDR-based cable diagnostics, and operates from a single 3.3V supply with configurable 1.8V/2.5V/3.3V I/O.

For engineers reviewing the KSZ8081RNDIA-TR datasheet, KSZ8081RNDIA-TR pinout, KSZ8081RNDIA-TR application, or KSZ8081RNDIA-TR equivalent, key selection considerations include RMII 50 MHz input mode vs. 25 MHz crystal mode, PHY address strapping (PHYAD[2:0]), LinkMD® diagnostic capability, and 24-pin QFN package compatibility with board-level magnetics and MAC timing constraints.

Technical Context

The KSZ8081RNDIA-TR implements full 10/100 Mbps physical layer functions including adaptive equalization, baseline wander correction, MLT3 encoding/decoding, and 4B/5B scrambling for EMI reduction. Its RMII interface uses synchronous 50 MHz timing for TXD[1:0], RXD[1:0], TXEN, CRS_DV, and RXER signals, with REF_CLK pin unused in 50 MHz mode.

It features hardware-configurable PHY addressing via strap-in pins (PHYAD[2:0] latched at reset de-assertion), programmable interrupt output (INTRP), LED0 with link/activity modes, and MDC/MDIO management interface supporting IEEE 802.3 Clause 22 register access. Power-down and auto-negotiation are software-controllable via PHY registers.

Key Specifications

Pinout & Package

KSZ8081RNDIA-TR is housed in a 24-pin, 4 mm × 4 mm QFN package with exposed thermal paddle (GND). Pin assignment follows standard KSZ8081RND layout per DS00002199F.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar Ethernet PHY applications.

Compared with KSZ8081RNA-TR and LAN8720AI-TR, the KSZ8081RNDIA-TR uniquely supports 50 MHz reference clock input as power-up default-enabling direct integration with SoCs that provide clean 50 MHz clocks-while retaining LinkMD® diagnostics and identical QFN packaging for drop-in layout reuse.

Availability

KSZ8081RNDIA-TR is available at Aetrix Electronics and suitable for IP phones, networked printers, and IP set-top boxes requiring stable component supply, industrial temperature operation, and production-ready Ethernet PHY functionality.

Supply support for KSZ8081RNDIA-TR 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

Microchip Technology Inc. is a leading provider of microcontrollers, analog, FPGA, and connectivity solutions, serving automotive, industrial, communications, and consumer markets with high-reliability silicon and development tools.

The KSZ8081RNDIA-TR belongs to Microchip's KSZ80xx family of single-chip Ethernet PHYs designed for cost-sensitive, space-constrained embedded systems requiring IEEE 802.3 compliance, RMII interface, and built-in diagnostics.

FAQ

What is the default clocking mode for KSZ8081RNDIA-TR at power-up?

The KSZ8081RNDIA-TR powers up in RMII 50 MHz input mode: it expects a 50 MHz ±50 ppm clock signal on the XI pin and leaves REF_CLK (Pin 16) as no-connect. Unlike the KSZ8081RNA variant, it does not support crystal oscillators on XI/XO. This behavior is fixed at power-on and can only be changed via software register programming if a driven 25 MHz clock is applied.

Does KSZ8081RNDIA-TR support auto-negotiation and how is it configured?

Yes, KSZ8081RNDIA-TR fully supports IEEE 802.3 Clause 28 auto-negotiation. It is enabled by default at power-up via hardware strapping on the ANEN_SPEED pin (Pin 23, pulled up). Auto-negotiation can also be controlled via Register 0h Bit [12]. When disabled, speed (10/100 Mbps) and duplex (half/full) are set by Register 0h Bits [13] and [8], respectively.

What are the key differences between KSZ8081RNDIA-TR and KSZ8081RNA-TR?

The KSZ8081RNDIA-TR defaults to 50 MHz clock input on XI and disables the crystal oscillator circuit, while the KSZ8081RNA-TR defaults to 25 MHz crystal input on XI/XO and outputs 50 MHz on REF_CLK. Both share identical pinout, package, LinkMD®, and RMII functionality-but clock source architecture and strap-in behavior differ. Software register control allows mode switching only under specific clock-source conditions.

How does LinkMD® cable diagnostics work in KSZ8081RNDIA-TR?

LinkMD® in KSZ8081RNDIA-TR uses time-domain reflectometry (TDR) to inject calibrated pulses onto the TXP/TXM pair and analyze reflected waveforms. It identifies open circuits, shorts, impedance mismatches, and cable length (up to 150 m) without external test gear. Results are accessible via PHY registers 1Eh–1Fh and require no host CPU intervention beyond command initiation and result polling.

Can KSZ8081RNDIA-TR operate with 1.8V I/O voltage?

Yes, KSZ8081RNDIA-TR supports 1.8V, 2.5V, or 3.3V digital I/O levels via the VDDIO pin (Pin 14). The I/O voltage is independent of the 3.3V analog supply (VDDA_3.3) and 1.2V core supply (VDD_1.2). When using 1.8V I/O, ensure RMII interface signals (TXD[1:0], RXD[1:0], TXEN, CRS_DV, RXER) meet timing and voltage thresholds specified in Section 6.0 of the datasheet.