Analog Devices Inc./Maxim Integrated DS2484Q+T

DS2484Q+T Single-Channel 1-Wire Master Product Summary

Analog Devices Inc./Maxim Integrated’s DS2484Q+T is a specialized single-channel bridge device that converts I2C signals to the 1-Wire® protocol, enabling seamless communication between I2C masters and downstream 1-Wire slave devices. Offered in a compact 8-TDFN package, it is designed to integrate robustly into modern electronics where reliability, timing control, and protocol flexibility are essential—e.g., in medical instrumentation, industrial sensors, printers, and mobile devices. As the 1-Wire master relative to connected slave devices, DS2484Q+T streamlines protocol conversion, optimizes timing requirements, and reduces the burden on system hosts.

DS2484Q+T Main Features

The DS2484Q+T distinguishes itself with advanced functional capabilities targeted at engineering teams requiring high flexibility and robust 1-Wire communications. Key features include:

Support for both 100kHz (standard) and 400kHz (fast) I2C communication, facilitating integration with a wide range of controllers.

Dual-speed 1-Wire operation, with selectable standard and overdrive speeds for compatibility and performance optimization.

Adjustable timing parameters for critical 1-Wire phases: reset low time (t_RSTL), presence detect (t_MSP), write-zero (t_W0L), and recovery (t_REC0).

Software-controlled power-down of the 1-Wire port, allowing efficient energy management and slave device resets.

Integrated sleep mode (via SLPZ pin) for low-power standby, with the 1-Wire port entering a high-impedance state.

Wide voltage operation: I2C side accepts 1.8V, 3.3V, or 5.0V supplies; 1-Wire side is independently configurable for 1.8V–5.0V operation.

Built-in level translation for seamless voltage domain bridging.

Strong and active pullup circuitry to enable reliable 1-Wire bus power delivery, critical for EEPROMs and sensors.

ESD protection up to ±8kV Human Body Model (HBM) on the IO pin, supporting resilience in harsh environments.

Extended operating temperature range (-40°C to +85°C), positioning the DS2484Q+T for wide-ranging industrial applications.

DS2484Q+T Internal Design and Operation Overview

The DS2484Q+T operates as a self-timed 1-Wire master, offloading time-critical waveform generation from the host processor. Once a command sequence is supplied via I2C, it autonomously handles reset/presence detection, read/write operations, and bit-level R/W cycles. Advanced timing management ensures both reliability and compatibility with standard and overdrive 1-Wire devices. The integrated status feedback mechanism via dedicated registers allows the host processor to monitor execution status, presence pulses, detection of shorts, and the direction of search algorithms.

DS2484Q+T Configuration and Control Register Details

Control of the DS2484Q+T is anchored around four primary registers:

Device Configuration Register: Enables or modifies key features such as active pullup (APU), strong pullup (SPU), 1-Wire power-down (PDN), and communication speed selection (1WS). Each feature is represented by a control bit. Configuration changes require adherence to a specific write protocol (upper nibble must be the one’s complement of the lower nibble), ensuring robust settings management.

Status Register: Provides real-time feedback, including 1-Wire busy status, presence pulse detection, short detection, logic level monitoring, reset status, single bit results, triplet command outputs, and search direction indicators.

Read Data Register: Used to retrieve bytes read from the 1-Wire slave devices.

Port Configuration Register: Allows verification and adjustment of timing and electrical characteristics for optimal operation on the 1-Wire bus. Eight bytes convey configuration parameters covering timing and pullup resistor values.

DS2484Q+T 1-Wire Timing Mechanisms and Power Supply Modes

Fine timing control is a central capability of the DS2484Q+T. Four adjustable parameters (t_RSTL, t_MSP, t_W0L, t_REC0) ensure compatibility and communication integrity across diverse 1-Wire devices. Power delivery is highly flexible, featuring:

Active Pullup (APU): When enabled, a low-impedance transistor assists the bus in returning to logic-high state, supporting faster communication and improved signal integrity, particularly with heavy capacitive loads.

Strong Pullup (SPU): Designed for power-intensive operations, such as scratchpad copying or SHA computations in EEPROMs and sensors that utilize parasitic power. The strong pullup is activated before specific commands and remains engaged until communication sequence completion.

Power-Down (PDN): Software-controlled removal of power from the 1-Wire port, supporting scenarios requiring device reset or energy conservation.

Speed Selection (1WS): Allows dynamic toggling between standard and overdrive speeds, synchronized across master and slaves.

DS2484Q+T Status and Port Configuration Register Overview

The status register in DS2484Q+T gives actionable information to the host processor. Unique bits indicate real-time events on the 1-Wire bus (busy, short detected, presence pulses, logic levels), and register state is consistently updated with communication commands. The port configuration register, accessed by the “Adjust 1-Wire Port” command, reports timing parameters and pullup resistor status to facilitate real-time adjustment and verification, valuable in systems requiring fine-tuned electrical and timing performance.

DS2484Q+T Supported Core Commands

DS2484Q+T provides nine function commands, zone-specific for device control, I2C interface management, 1-Wire port setup, and communication:

Device Reset

Set Read Pointer

Write Device Configuration

Adjust 1-Wire Port

1-Wire Reset

1-Wire Single Bit

1-Wire Write Byte

1-Wire Read Byte

1-Wire Triplet (for ROM search algorithms)

These commands allow engineers to efficiently initialize, configure, and monitor the device and its network communication, with minimal protocol overhead and robust feedback mechanisms for error handling, polling, and synchronization.

DS2484Q+T I2C Communication Implementation

The DS2484Q+T’s I2C bus implementation (SDA and SCL) supports up to 400kbps data rates. Key I2C protocol elements—slave address, data direction (read/write), acknowledge cycles, START/STOP conditions, and repeated STARTs—are supported per the I2C bus specification. Write and read operations are mediated through the direction bit in the slave address/control byte. The I2C interface does not obstruct SDA/SCL lines during sleep or when V_CC is off, aiding multi-device bus sharing.

DS2484Q+T Electrical Specifications and Environmental Conditions

Operating parameters for DS2484Q+T are engineered for robust system integration:

Voltage range: All pins tolerate -0.5V to +6V relative to ground; operating I2C voltages are tightly specified for 1.8V ±5%, 3.3V ±10%, or 5.0V +5/-10%.

Current: Maximum allowed into any pin is 20mA.

Power dissipation: TDFN allows up to 1333.3mW (derated above +70°C).

Temperature: Operating range -40°C to +85°C, junction up to +150°C, storage -55°C to +125°C.

ESD robustness: ±8kV HBM on I/O pins ensures high reliability in industrial and mobile contexts.

Packages: Available in 8-pin TDFN and 6-pin SOT23, supporting flexible PCB integration.

DS2484Q+T Circuitry Recommendations for Pull-up Resistor Selection

SDA (open-drain on DS2484Q+T) and SCL require pullup resistors sized per the I2C bus specification and actual system conditions. Key considerations:

Minimum resistor value (Rp): Derived from supply voltage, e.g., at 5.5V, Rp(min) = (5.5V-0.4V)/3mA = 1.7kΩ.

Maximum allowable bus capacitance: 400pF for standard mode, 200pF for fast mode.

Rise time limits: Should not exceed 300ns; for 400pF, maximum Rp is 885Ω.

Optimal design: Balance is needed between resistor value, voltage, and bus capacitance to ensure correct timing and avoid excessive loading, especially at higher voltages or capacitance.

DS2484Q+T Alternative or Substitute Product Options

When considering alternatives to DS2484Q+T, engineers may evaluate:

DS2483: Offers similar functionality but may differ in device configuration and port control logic.

DS2482 series: Provides multi-channel 1-Wire masters with I2C interfaces for systems needing greater bus coverage.

Custom 1-Wire I2C bridge implementations: In some applications, microcontrollers with dedicated 1-Wire/I2C peripherals can substitute, but may lack the integrated timing and power delivery features of DS2484Q+T.

Careful review of timing flexibility, strong pullup support, voltage domains, and register interface is recommended to maintain compatibility and performance.

Conclusion

The DS2484Q+T single-channel 1-Wire master from Analog Devices Inc./Maxim Integrated offers a powerful and flexible solution for bridging I2C masters to the 1-Wire network, with advanced timing controls, integrated power delivery, and robust status and configuration mechanisms. Engineers and procurement specialists evaluating sensor, EEPROM, and memory integrations will benefit from its wide voltage support, selectable communication speed, and enhanced power features. The device’s architecture facilitates efficient development and operational reliability, making DS2484Q+T a preferred choice for modern industrial, medical, and mobile platforms requiring dependable 1-Wire connectivity.