Analog Devices Inc./Maxim Integrated DS2409P

Overview

DS2409P from Maxim Integrated is a 1-Wire MicroLAN coupler IC designed to enable hierarchical, multi-level 1-Wire networks with common-ground topology. It features dual 1-Wire outputs (Main and Auxiliary), a programmable open-drain control output, factory-lasered 64-bit ROM (family code 1FH), and operates at 16.3 kbps over a single bidirectional line. It is used in access control systems to isolate and activate branches containing iButton devices while preserving parasitic power integrity.

For engineers reviewing the DS2409P datasheet, DS2409P pinout, DS2409P application, or DS2409P equivalent, this page delivers verified technical context, validated pin functions, confirmed 1-Wire protocol behavior, real-world topology management use cases, and traceable alternative options for MicroLAN branching architectures.

Technical Context

The DS2409P implements a bidirectional, low-impedance electronic switch between its 1-Wire input and either Main or Auxiliary output, with on-resistances of 10–20 Ω (Main) and 15–30 Ω (Auxiliary). Its internal logic supports five ROM function commands (e.g., Conditional Search ROM, Match ROM) and six device-specific control commands (e.g., Smart-On Main, Discharge Lines), all executed via strict 1-Wire timing compliant with tSLOT = 60–120 µs and reset pulse windows of 480–960 µs.

It integrates no user memory but provides event flag detection on both outputs, status read/write via 0x5A command, and auto-control/manual modes for the N-channel MOSFET control output. The device maintains inactive branches at VDD (5V) and supports conditional search for fast-event signaling-critical for detecting iButton arrivals in dynamic access control deployments.

Key Specifications

Pinout & Package

DS2409P is housed in a compact 6-pin TSOC surface-mount package (3.7 mm × 4.0 mm × 1.5 mm), optimized for space-constrained MicroLAN node designs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS2406P and DS2413P, the DS2409P uniquely delivers hierarchical branch activation, conditional event detection, and ROM-based topology navigation-making it irreplaceable for scalable, event-driven 1-Wire systems requiring deterministic branch isolation and labeling.

Availability

DS2409P is available at Aetrix Electronics and suitable for access control systems, warehouse inventory tracking, dual-master coordination, and building automation networks requiring stable component supply and long-term MicroLAN infrastructure support.

Supply support for DS2409P 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 high-reliability interface solutions for industrial, communications, and embedded systems.

The DS2409P belongs to Maxim's 1-Wire MicroLAN product line, engineered specifically to solve hierarchical network scalability, parasitic power preservation, and event-driven topology management in distributed sensor and identification systems.

FAQ

What is the primary function of the DS2409P in a 1-Wire network?

The DS2409P acts as a hierarchical coupler that enables multi-level branching while maintaining a common ground. It electrically isolates inactive branches, keeps them powered at 5V, and allows selective activation of Main or Auxiliary 1-Wire outputs via Smart-On or Direct-On commands. This preserves parasitic power states and accelerates topology analysis-core functionality confirmed in the DS2409P datasheet sections on "MicroLAN Coupler" and "Smart-On Main".

Does the DS2409P include user-programmable memory?

No, the DS2409P does not contain any user-programmable memory. As explicitly stated in the DESCRIPTION section: "The coupler does not contain any user-programmable memory." It relies solely on its factory-lasered 64-bit ROM for identification and uses external 1-Wire memory (e.g., DS2430A) connected to the Auxiliary output for branch labeling-verified on page 1 of the DS2409P datasheet.

How does the DS2409P handle event detection on inactive branches?

The DS2409P sets dedicated event flags (EVNT MAIN / EVNT AUX) when a negative edge is detected on an inactive 1-Wire output. These flags persist until cleared by the All Lines Off command (0x66) and are used exclusively by the Conditional Search ROM (0xEC) command to identify arriving iButtons. This behavior is fully documented in Status Info Byte Table 2 and the "Conditional Search ROM" section on page 11 of the DS2409P datasheet.

What is the purpose of the Control Output (Pin 5) on the DS2409P?

The Control Output is a programmable open-drain N-channel MOSFET used for status indication (e.g., driving an LED) or handshaking in dual-master systems. It operates in auto-control mode (default, tied to Main/Aux selection) or manual mode (bit 5 = 1), where bit 7 directly controls conduction. Its design value is confirmed in the STATUS READ/WRITE command description and Pin Assignment table on pages 4–5 and 1 of the DS2409P datasheet.

Is the DS2409P suitable for new designs?

No-the DS2409P is marked "Not Recommended for New Design" on every page of its official datasheet (pages 1–18). While fully functional and supported for legacy MicroLAN systems, Maxim/Analog Devices advises against its use in new projects due to obsolescence planning. Engineers should evaluate modern alternatives like DS2406P or DS2413P for simpler switching needs-or redesign with newer 1-Wire infrastructure where applicable.