Texas Instruments DP83840AVCE

Overview

DP83840AVCE from National Semiconductor is a 10/100 Mb/s Ethernet Physical Layer (PHY) transceiver IC supporting IEEE 802.3 10BASE-T and IEEE 802.3u 100BASE-X standards. It integrates dual-speed ENDEC, clock recovery, PCS, auto-negotiation, and MII interface, operating with category 5 UTP, type 1 STP, or fiber optic media. It serves as the physical layer bridge between MAC and PMD in embedded LAN controllers and industrial Ethernet nodes.

For engineers reviewing the DP83840AVCE datasheet, DP83840AVCE pinout, DP83840AVCE application, or DP83840AVCE equivalent, key selection considerations include its 100-pin PQFP package, IEEE 802.3u-compliant MII and serial management interface, full-duplex support at both speeds, integrated 100 Mb/s clock recovery, and IEEE 1149.1 boundary-scan capability.

Technical Context

The DP83840AVCE implements a dual-speed architecture with separate 10BASE-T transceiver and 100BASE-X PCS modules sharing a unified MII interface and auto-negotiation engine. Its clock recovery module operates without external filters, and its scrambler/descrambler supports multi-PHY applications via individualized seed configuration.

It supports configurable node/repeater modes, programmable loopback (local 100BASE-TX, encoder/alignment/scrambler bypass), and flexible LED control with monostable timing for visibility. The device uses National's BiCMOS process and integrates FDDI-derived clock generation and stream cipher logic.

Key Specifications

Pinout & Package

DP83840AVCE is housed in a 100-pin JEDEC metric PQFP package (14 mm × 20 mm, 0.65 mm pitch), optimized for high-density Ethernet PHY placement with thermal and signal integrity considerations.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DP83840A and LAN83C185, the DP83840AVCE offers identical core functionality with verified VCE-grade reliability, full JTAG testability, and seamless register compatibility-making it the preferred choice for new designs requiring long-term supply stability and production test coverage.

Availability

DP83840AVCE is available at Aetrix Electronics and suitable for industrial control network nodes, legacy equipment Ethernet retrofit, multi-port switch modules, and 100BASE-TX repeater hubs requiring stable component supply and long-lifecycle support.

Supply support for DP83840AVCE 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

National Semiconductor was a pioneering analog and mixed-signal semiconductor company, acquired by Texas Instruments in 2011. It developed foundational Ethernet PHY, data converter, and power management technologies widely adopted in industrial and communications systems.

The DP83840AVCE belongs to National's early-generation 10/100 Mb/s Ethernet PHY product line, engineered specifically for cost-sensitive, high-reliability embedded LAN applications requiring IEEE 802.3u compliance and minimal external component count.

FAQ

What is the primary function of the DP83840AVCE in an Ethernet system?

The DP83840AVCE serves as a dual-speed Physical Layer (PHY) transceiver, converting digital MAC-layer data from the MII interface into analog 10BASE-T or 100BASE-X signals for transmission over copper or fiber media. It handles encoding/decoding, clock recovery, auto-negotiation, and signal conditioning-enabling interoperable, standards-compliant Ethernet connectivity. Its role is strictly physical layer translation, not packet processing or switching logic.

Does the DP83840AVCE support both half-duplex and full-duplex operation at 10 Mb/s and 100 Mb/s?

Yes, the DP83840AVCE supports full-duplex and half-duplex operation at both 10 Mb/s and 100 Mb/s, as defined by IEEE 802.3u. Full-duplex mode disables collision detection (COL remains low), while half-duplex enables it. Duplex mode is determined during auto-negotiation or via forced configuration using AN0/AN1 pins. The DP83840AVCE implements all required timing, carrier sense, and collision logic per standard.

Can the DP83840AVCE operate without an external crystal or oscillator?

No-the DP83840AVCE requires either a 50 MHz TTL oscillator on OSCIN (pin 2) or a 20 MHz crystal across X1/X2 (pins 33/34) to generate internal clocks. The 50 MHz input feeds the PLL for 100 Mb/s operation; the 20 MHz crystal supports 10 Mb/s timing and auto-negotiation. REF IN (pin 86) may accept a 25 MHz external clock as alternative, but no clock source can be omitted without functional failure.

How does the DP83840AVCE handle PHY addressing in multi-device MII configurations?

The DP83840AVCE uses five dedicated PHY address pins (PHYAD[4:0], mapped to pins RX_ER, SPEED_100, CRS, ENCSEL, LBEN) to configure a unique 5-bit address. Pull-up/down resistors set each bit at power-up, latching the value into the PHY Address Register (address 19h). This allows up to 31 distinct PHYs on a shared MII bus-critical for multi-port switches or modular systems-without software address conflicts or MDIO arbitration overhead.

Is the DP83840AVCE pin-compatible with newer National Semiconductor or TI Ethernet PHYs?

No-the DP83840AVCE is not pin-compatible with later-generation PHYs such as the DP83865 or TLK100 series. Its 100-pin PQFP footprint, ECL-level PMD signals (TD+/RD+/SD+), and dedicated 10 Mb/s analog interfaces differ fundamentally from modern 48-pin QFN devices with integrated magnetics drivers and digital SGMII/RMII interfaces. Migration requires PCB redesign and firmware register mapping updates.