Analog Devices Inc./Maxim Integrated DS1481S

Overview

DS1481S from Maxim Integrated is a dedicated 1-Wire® bus master timing generator for parallel-port-based host interfaces, supporting standard and overdrive-speed communication (tSIO = 8 μs / 2 μs), reset generation (≥480 μs low pulse), and cascaded multi-device configurations via ENO→ENI daisy-chaining. It operates from 2.7–5.5 V and targets short-distance 1-Wire networks (<3 inches) in legacy PC peripheral adapters.

For engineers reviewing the DS1481S datasheet, DS1481S pinout, DS1481S application, or DS1481S equivalent, key selection considerations include its dual busy-signal interface (O1/BSY1 & O2/BSY2), transparent/EPP/ECP mode toggle sequence, printer coexistence logic, and explicit support for cascading with identical DS1481S units - all critical for parallel-port 1-Wire bridge designs.

Technical Context

The DS1481S implements a synchronous, host-controlled 1-Wire timing engine that offloads time-slot generation (read/write/reset) from the CPU using D/CLK and RES input states, with ENI-triggered execution and O1/BSY1/O2/BSY2 busy signaling to enable concurrent spooler operation. Its internal OD flip-flop supports overdrive mode toggling without I/O line disturbance.

It features weak internal pullups (50 kΩ) on I1, I2, ENI, D/CLK, RES, and ENO; open-drain I/O and ENO outputs; and automatic last-device detection via absence of upstream busy signals - enabling stackable topology where each DS1481S propagates printer BUSY/SELECT OUT states unless it is the final unit.

Key Specifications

Pinout & Package

DS1481S is housed in a space-saving 14-pin SOIC package (150 mil width), with exposed pad omitted and NC pins unused. Pin functions are validated per Maxim's official DS1481 datasheet Rev. 0, pages 2–3 and 8.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 1-Wire bus master applications.

Compared with DS2480B and DS9490R, the DS1481S uniquely preserves legacy parallel-port hardware investment, offers deterministic low-latency timing control via direct GPIO, and enables compact, cost-optimized PCB integration - but requires parallel-port controller access and is limited to short cable runs.

Availability

DS1481S is available at Aetrix Electronics and suitable for legacy industrial PC upgrades, microcontroller-based sensor bridges, multi-device 1-Wire stacks, and printer-shared authentication interfaces requiring stable component supply and long-term obsolescence management.

Supply support for DS1481S 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 precision analog, mixed-signal, and power management ICs for industrial, communications, and computing applications.

The DS1481S belongs to Maxim's 1-Wire interface product line, designed specifically to simplify host-side 1-Wire protocol implementation in resource-constrained or legacy-platform environments.

FAQ

What is the primary function of the DS1481S in a 1-Wire system?

The DS1481S serves as a dedicated 1-Wire bus master timing generator that converts parallel-port or microcontroller GPIO signals into electrically and temporally compliant 1-Wire time slots and reset pulses. It handles all critical timing (e.g., 8 μs sampling, 480 μs reset low) and busy signaling, allowing the host processor to offload 1-Wire communication while running other tasks like print spooling. The DS1481S does not interpret 1-Wire data packets - it only generates physical-layer waveforms.

How does the DS1481S support cascading with other DS1481S units?

The DS1481S supports cascading via its ENO (Enable Out) and ENI (Enable In) pins: ENO of one device connects to ENI of the next, forming a daisy chain. Each unit monitors upstream busy signals to detect whether it is the last device in the chain; only the final DS1481S ignores its I1/I2 inputs during ENI assertion to prevent printer interference. This architecture enables up to eight DS1481S units on a single parallel port without external arbitration logic.

What is the significance of the "Not Recommended for New Design" status for the DS1481S?

The "Not Recommended for New Design" designation reflects Maxim's strategic shift toward USB-based 1-Wire solutions (e.g., DS2480B, DS9490R) and discontinuation of parallel-port interface development. While the DS1481S remains fully functional and supported for existing legacy systems, new designs should consider modern alternatives offering longer reach, USB compatibility, and ongoing technical updates. Aetrix Electronics maintains inventory and lifecycle coordination for DS1481S to support installed base maintenance.

Can the DS1481S operate with 3.3 V microcontrollers, and what are the voltage interface considerations?

Yes, the DS1481S operates from 2.7 V to 5.5 V, making it compatible with 3.3 V microcontrollers. All digital inputs (ENI, D/CLK, RES, I1, I2) meet 3.3 V logic thresholds (VIH ≥ 2.4 V, VIL ≤ 0.8 V), and internal 50 kΩ pullups ensure robust signal detection even with weak MCU drive strength. However, the I/O pin requires an external pullup resistor (typically 4.7 kΩ to VCC), and VCC must match the target 1-Wire bus voltage to avoid level-shifting complications.

What happens if a DS1481S is connected to a powered-off parallel-port printer?

If the attached printer is powered off, both BUSY (I1) and SELECT OUT (I2) lines go low, preventing the DS1481S from de-asserting its busy signals (O1/BSY1 and O2/BSY2 remain low) and blocking valid I/O sampling. The DS1481S detects this condition via absence of upstream busy signals and enters last-device mode - ignoring I1/I2 during ENI assertion and holding ENO high to avoid unintended line-feed commands. This ensures basic 1-Wire operation remains possible despite printer power loss.