Analog Devices Inc./Maxim Integrated DS2490Y

Overview

DS2490Y from Maxim Integrated is a USB-to-1-Wire bridge IC that enables full-speed USB 2.0 host systems to interface with 1-Wire networks at regular, overdrive, and programmable flexible speeds. It integrates a USB-compliant transceiver, crystal-based 12MHz oscillator, active 5V pullup, and slew-rate-controlled 1-Wire I/O for reliable operation on long bus lines up to 300m. Used in iButton readers, sensor hubs, and secure authentication peripherals.

For engineers reviewing the DS2490Y datasheet, DS2490Y pinout, DS2490Y application, or DS2490Y equivalent, key selection criteria include USB remote wake-up support, programmable 1-Wire timing (tLOW1, tDSO, slew rate), stiff 5V pullup capability, crystal-referenced waveform accuracy, and compatibility with Dallas/Maxim 1-Wire devices including EEPROMs, temperature sensors, and crypto iButtons.

Technical Context

The DS2490Y implements a dedicated USB device controller with vendor-specific command handling over EP0, plus three additional endpoints: EP1 (interrupt pipe, 1ms or 10ms polling) for status and attach detection, EP2 (bulk OUT) for host-to-1-Wire data, and EP3 (bulk IN) for 1-Wire-to-host data. Its 1-Wire interface controller actively shapes rising edges using dual-current pullup (IWEAKPU/IACTPU) and supports configurable falling-edge slew rates (1V/µs typical for 300m lines).

Timing is crystal-locked via 12.0MHz fundamental-mode parallel-resonant crystal on XI/XO pins. All 1-Wire waveforms - reset/presence detect, Write-0/Write-1 time slots, and strong pullup pulses - are generated autonomously with precise control over tRSTL (512µs regular), tLOW1 (4–11µs flexible), tDSO (10–24µs), and STRONG PULLUP DURATION (predefined or infinite).

Key Specifications

Pinout & Package

DS2490Y is housed in a 24-pin SOIC (300-mil) package with exposed pad not internally connected. Power domains are segregated: VD/VD2 supply digital and 1-Wire circuitry; VB supplies USB transceiver; GND serves as common reference and 1-Wire return path.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar USB-to-1-Wire bridge applications.

Compared with DS2490Y, DS2480B adds external component overhead and timing uncertainty, while DS2490Z+ offers identical functionality in a smaller package - making DS2490Y optimal for industrial USB adapters requiring robust SOIC mounting and thermal stability.

Availability

DS2490Y is available at Aetrix Electronics and suitable for industrial sensor hubs, iButton authentication terminals, secure firmware programming adapters, and legacy system modernization interfaces requiring stable component supply and long-term lifecycle support.

Supply support for DS2490Y 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, and computing applications.

The DS2490Y belongs to Maxim's 1-Wire interface product line, designed specifically to simplify USB host connectivity to 1-Wire networks while maintaining strict timing compliance and electromagnetic compatibility on extended bus lengths.

FAQ

What is the primary function of the DS2490Y in a USB-to-1-Wire system?

The DS2490Y serves as a dedicated bridge IC that translates USB host commands into precisely timed 1-Wire transactions. It handles all physical layer responsibilities - including crystal-referenced waveform generation, active 5V pullup, slew-rate-controlled edges, and USB enumeration - allowing host software to interact with 1-Wire devices via vendor-specific USB commands without real-time timing constraints. This makes DS2490Y essential for reliable, standards-compliant 1-Wire communication over USB.

Does the DS2490Y require an external crystal, and why is it critical?

Yes, the DS2490Y requires a 12.0MHz fundamental-mode parallel-resonant crystal connected between XI and XO pins. This crystal establishes the timing reference for all 1-Wire waveforms - including reset pulses, read/write slots, and strong pullup durations - ensuring compliance with Dallas/Maxim 1-Wire timing specifications across voltage and temperature. Without this crystal, DS2490Y cannot generate accurate 1-Wire signals, and communication will fail. A CMOS clock source may substitute, but crystal remains the recommended solution for stability.

How does the DS2490Y support long 1-Wire bus lengths up to 300 meters?

The DS2490Y supports long 1-Wire buses through three integrated features: (1) slew-rate-controlled falling edges (configurable via PULLDOWN SLEW RATE mode command to target ~1V/µs), (2) active dual-current 5V pullup that accelerates bus rise time, and (3) non-TTL input threshold sensing that improves noise margin. These features collectively reduce ringing, improve signal integrity, and maintain timing margins on high-capacitance lines - validated for reliable operation on 300m networks when configured per DS2490Y datasheet guidelines.

Can the DS2490Y wake up a suspended USB host system, and how is this enabled?

Yes, the DS2490Y supports USB remote wake-up: when enabled via the DEVICE_REMOTE_WAKEUP feature selector, it detects 1-Wire device attachment (e.g., iButton insertion) and initiates USB resume signaling to awaken a suspended host. This function is disabled by default and must be explicitly enabled by host software using a SET_FEATURE USB core command. The SUSO pin provides local indication of USB suspend state, aiding in low-power system design. DS2490Y thus enables energy-efficient, event-driven host interaction without continuous polling.

What are the power supply requirements for the DS2490Y, and how are they segregated?

The DS2490Y requires three distinct power domains: VD (5.0V ±10%) powers digital logic and the 1-Wire interface; VD2 is a second 5V pin that must be externally tied to VD (not internally connected); VB (3.3V ±10%) supplies the USB transceiver and is typically derived from USB VBUS via an LDO. This segregation isolates noise-sensitive USB signaling from 1-Wire switching transients, ensuring robust communication. All supplies require local ceramic decoupling per the DS2490Y layout guidelines.