UMW DS18B20Z

Overview

DS18B20Z from Maxim Integrated is a programmable-resolution 1-Wire digital thermometer with ±0.5°C accuracy from −10°C to +85°C, −55°C to +125°C operating range, and parasite-power capability requiring only DQ and GND pins. It delivers 9–12-bit temperature data over a single-wire bus and supports distributed sensing in HVAC control systems.

For engineers reviewing the DS18B20Z datasheet, DS18B20Z pinout, DS18B20Z application, or DS18B20Z equivalent, key selection considerations include parasitic vs. VDD-powered operation, 1-Wire multidrop topology support, alarm threshold programming via EEPROM, and resolution–conversion time tradeoffs (750 ms at 12-bit).

Technical Context

The DS18B20Z implements a 1-Wire interface using open-drain DQ signaling with weak pullup (4.7 kΩ) and optional strong pullup for parasite-power temperature conversions. Its internal architecture integrates a bandgap temperature sensor, 2-byte sign-extended two's complement temperature register, and 64-bit laser-programmed ROM containing family code 28h.

It features nonvolatile TH/TL alarm registers and configuration register (R0/R1 bits) stored in EEPROM, enabling user-defined trip points and resolution settings retained across power cycles. Alarm status is verified via ECh command, and CRC-8 validation (X⁸+X⁵+X⁴+1) ensures data integrity for both ROM reads and scratchpad access.

Key Specifications

Pinout & Package

DS18B20Z is supplied in an 8-pin SO (150 mils) surface-mount package. Pin 1 is NC; Pin 2 is NC; Pin 3 is VDD (must be grounded in parasite-power mode); Pin 4 is DQ (open-drain 1-Wire I/O and parasite power input); Pin 5 is GND; Pins 6–8 are NC.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar digital thermometer applications.

Compared with DS18B20Z, DS18S20 offers lower cost but sacrifices resolution, accuracy, and alarm functionality; MAX31820 maintains full compatibility while enhancing robustness in electrically noisy industrial settings - making it a drop-in upgrade where signal integrity is critical.

Availability

DS18B20Z is available at Aetrix Electronics and suitable for HVAC environmental controls, industrial machinery monitoring, and consumer appliance thermal management requiring stable component supply and long-term lifecycle support.

Supply support for DS18B20Z 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) designs precision analog, mixed-signal, and digital ICs for industrial, communications, and computing applications.

The DS18B20Z belongs to Maxim's 1-Wire sensor family, engineered specifically for distributed, low-wiring-count temperature measurement in harsh or space-constrained environments.

FAQ

What is the maximum number of DS18B20Z sensors supported on a single 1-Wire bus?

The DS18B20Z uses a unique 64-bit ROM address, allowing theoretically unlimited devices on one bus. In practice, signal integrity limits reliable operation to ~50–100 units depending on bus length, pullup strength, and noise. For DS18B20Z deployments beyond 30 units, a 1-Wire repeater or active pullup is recommended to maintain timing margins.

Does DS18B20Z require external components for basic operation?

No - DS18B20Z operates with only a 4.7 kΩ pullup resistor on the DQ line and GND connection. In parasite-power mode, VDD is grounded; in VDD-powered mode, a clean 3.0–5.5 V supply is connected to Pin 3. No decoupling capacitor or additional passive components are needed for standard use cases.

How does DS18B20Z handle temperature conversion during parasite power operation?

During parasite-power temperature conversion, DS18B20Z requires a strong pullup (e.g., MOSFET-switched VDD) applied to DQ within 10 µs of issuing Convert T [44h]. This ensures sufficient current (up to 1.5 mA) for accurate conversion. Without strong pullup, measurements may fail or report invalid data - especially above +85°C.

Can DS18B20Z alarm thresholds be updated in the field without reprogramming firmware?

Yes - DS18B20Z stores TH and TL alarm values in nonvolatile EEPROM. Host firmware can issue Write Scratchpad [4Eh] followed by Copy Scratchpad [48h] commands to update thresholds dynamically. These values persist across power cycles, enabling remote recalibration of thermal limits in deployed systems.

What is the significance of the DS18B20Z family code 28h in the 64-bit ROM?

The 8-bit family code 28h identifies the device as a DS18B20-series 1-Wire thermometer. It allows the bus master to distinguish DS18B20Z from other 1-Wire devices (e.g., DS2401 = 01h, DS2438 = 26h) during ROM search operations - ensuring correct command dispatch and preventing protocol conflicts on shared buses.