Analog Devices Inc./Maxim Integrated DS2409P/T&R

Overview

DS2409P/T&R from Maxim Integrated is a 1-Wire MicroLAN coupler in a 6-pin TSOC package, enabling multi-level branching with common-ground topology, 16.3kbit/s communication rate, and factory-lasered 64-bit ROM (family code 1FH). It provides two independently switchable 1-Wire outputs (main and auxiliary), a programmable open-drain control output, and conditional search support for dynamic network event detection in access control systems.

For engineers reviewing the DS2409P/T&R datasheet, DS2409P/T&R pinout, DS2409P/T&R application, or DS2409P/T&R equivalent, this page delivers verified technical context, validated pin functions, real-world use cases in hierarchical 1-Wire networks, and confirmed alternative couplers for topology expansion and dual-master coordination.

Technical Context

The DS2409P/T&R implements a bidirectional, low-impedance electronic switch architecture with separate main and auxiliary 1-Wire outputs, each featuring ON-resistance of 10–20 Ω (main) and 15–30 Ω (auxiliary). Its internal 64-bit ROM includes an 8-bit family code (1FH), 48-bit unique serial number, and 8-bit CRC, enabling absolute device identification and ROM-based addressing.

It supports five 1-Wire ROM commands (Read/Match/Skip/Search/Conditional Search) and six control function commands (e.g., Smart-On Main/Auxiliary, Direct-On Main, All Lines Off, Discharge Lines), all executed over a single bi-directional line using strict timing slots (tSLOT = 60–120 µs) and reset/presence signaling compliant with Dallas Semiconductor 1-Wire protocol.

Key Specifications

Pinout & Package

DS2409P/T&R is housed in a compact 3.7 mm × 4.0 mm × 1.5 mm 6-pin TSOC surface-mount package, optimized for space-constrained embedded nodes in distributed sensing and access control hardware.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 1-Wire network coupler applications.

Compared with DS2406P and DS2413P, the DS2409P/T&R uniquely combines branch-switching intelligence, conditional event detection, and reset-pulse generation-making it the only option capable of enabling scalable, self-reporting 1-Wire networks with zero-latency arrival detection and deterministic topology analysis.

Availability

DS2409P/T&R is available at Aetrix Electronics and suitable for access control systems, industrial inventory tracking, dual-master coordination, and scalable sensor network infrastructure requiring stable component supply and long-term obsolescence planning.

Supply support for DS2409P/T&R 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

Maxim Integrated (now part of Analog Devices) is a semiconductor company specializing in analog, mixed-signal, and digital ICs for industrial, communications, computing, and consumer applications.

The DS2409P/T&R belongs to Maxim's 1-Wire interface product line, designed specifically to enable robust, low-wire-count, multi-drop networks for distributed identification, sensing, and control in harsh or space-constrained environments.

FAQ

What is the primary function of the DS2409P/T&R in a 1-Wire network?

The DS2409P/T&R functions as a hierarchical MicroLAN coupler that enables multi-level branching while maintaining a common ground. It provides two independently switchable 1-Wire outputs (main and auxiliary), a programmable control output, and supports conditional search for real-time event detection. Its Smart-On command generates reset/presence sequences before activation, allowing precise device enumeration on selected branches without disrupting the rest of the network - a capability essential for scalable access control and inventory systems using the DS2409P/T&R.

Does the DS2409P/T&R include user-programmable memory?

No, the DS2409P/T&R does not contain any user-programmable memory. It features only a factory-lasered 64-bit ROM (8-bit family code 1FH, 48-bit serial number, 8-bit CRC) used exclusively for device identification and ROM command execution. All control functionality - including branch switching, status reporting, and event flagging - is implemented in hardwired logic and accessed via 1-Wire commands such as Status Read/Write (5Ah), Smart-On Main (CCh), and Conditional Search ROM (ECh). This design ensures deterministic behavior and eliminates firmware update requirements for the DS2409P/T&R.

How does the DS2409P/T&R handle parasitically powered devices during branch switching?

The DS2409P/T&R maintains inactive branches at a pulled-high 5V level while keeping a common ground, which preserves the charge state of parasitically powered devices (e.g., iButtons, DS1990A) on deselected segments. Unlike ground-switching approaches, this architecture prevents loss of device status and avoids communication disruption caused by parasitic power collapse. When a branch is activated via Smart-On or Direct-On commands, the DS2409P/T&R first issues a reset/presence pulse - ensuring parasitic devices are properly initialized before data exchange begins. This behavior is explicitly guaranteed in the DS2409P/T&R datasheet and validated across its -40°C to +85°C operating range.

What is the purpose of the auxiliary 1-Wire output on the DS2409P/T&R?

The auxiliary 1-Wire output on the DS2409P/T&R serves two confirmed purposes: (1) connecting a programmed 1-Wire memory chip (e.g., DS2430A) to label the physical location or identity of the branch, and (2) acting as a digital input for event detection via the Conditional Search ROM command. When an iButton arrives on the main output, the DS2409P/T&R sets the main event flag; similarly, activity on the auxiliary line triggers its own event flag. This dual-event capability allows the bus master to distinguish between branch-level events and peripheral-level interactions - a feature directly documented in the DS2409P/T&R's Status Info Byte (Table 2) and usage examples.

Is the DS2409P/T&R compatible with the DS2480 1-Wire line driver?

Yes, the DS2409P/T&R is explicitly designed to work with the DS2480 line driver, as stated in the datasheet: "The network size can be maximized by using a DS2480 line driver at the bus master's serial interface. The DS2480 compensates for the rising ground level caused by the non-zero on-resistance of couplers in multi-level networks." The DS2480 provides active pull-up and timing compensation necessary to maintain signal integrity across cascaded DS2409P/T&R stages, supporting longer cable runs and higher node counts than passive pull-up solutions. This interoperability is integral to the DS2409P/T&R's system-level design and validated under AC electrical specifications (tSLOT, tRSTL, tPDL).