Analog Devices Inc./Maxim Integrated DS56S

Overview

DS56S from Dallas Semiconductor (now Maxim Integrated) is a dual-temperature comparator IC with integrated bandgap voltage reference and analog temperature sensor output. It features two independent open-drain thermostat outputs (TOUT1/TOUT2), ±2.0°C thermometer accuracy over 0°C–85°C, +6.2 mV/°C sensor sensitivity, and operates from 2.7V to 5.5V in an 8-pin SOIC (150-mil) package - used for thermal monitoring and control in disk drives and HVAC systems.

For engineers reviewing the DS56S datasheet, DS56S pinout, DS56S application, or DS56S equivalent, key selection considerations include its dual trip-point architecture, factory-calibrated sensor accuracy, VTEMP analog output for measurement, open-drain logic outputs requiring external pull-ups, and compatibility with LM56xIM-based designs.

Technical Context

The DS56S integrates three core functional blocks: a precision 1.25V bandgap voltage reference (VREF), a linear temperature sensor with transfer function VTEMP = 6.2·T + 395 mV, and two independent comparators comparing VTEMP against externally set trip voltages on VT1 and VT2. Each comparator drives an open-drain output (TOUT1/TOUT2) with 5°C hysteresis.

Tripping thresholds are set by resistive dividers from VREF (1.25V nominal), enabling flexible, user-defined temperature setpoints. The device supports full-range operation from –40°C to +125°C, with supply regulation of ±0.3 mV/V and VREF load regulation of 0.15 mV/µA across 3–50 µA loading.

Key Specifications

Pinout & Package

DS56S is housed in a narrow-body 8-pin SOIC package with 150-mil width (JEDEC MS-012), 1.27 mm pitch, and standard gull-wing lead form factor suitable for reflow soldering per IPC standards.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-temperature comparator applications.

Compared with LM56CMX/NOPB and MAX6502ESA+, the DS56S uniquely combines dual open-drain outputs, factory-calibrated ±2°C accuracy, analog VTEMP readout, and integrated 1.25 V reference - making it the only option supporting both precise thermal measurement and dual-point control in one SOIC-8 package.

Availability

DS56S is available at Aetrix Electronics and suitable for disk drive thermal protection, laser printer fuser control, HVAC zone monitoring, and smart appliance temperature management requiring stable component supply and long-term industrial availability.

Supply support for DS56S 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

Dallas Semiconductor, now part of Maxim Integrated (analog and mixed-signal division of Analog Devices), designs high-reliability temperature and timing ICs for industrial, computing, and embedded applications.

The DS56S belongs to Dallas' precision thermal monitoring product line, engineered specifically for applications needing both analog temperature measurement and dual independent thermostat outputs in a single compact IC.

FAQ

What is the primary function of the DS56S?

The DS56S is a dual-temperature comparator IC that provides two independent open-drain thermostat outputs (TOUT1 and TOUT2) and an analog temperature sensor output (VTEMP). Its core function is to monitor junction temperature and assert logic outputs when predefined thresholds - set via external resistors on VT1 and VT2 - are crossed. The DS56S also delivers calibrated temperature data through its VTEMP pin, supporting both control and measurement roles in one device.

How accurate is the DS56S temperature measurement over its full operating range?

The DS56S offers ±2.0°C thermometer accuracy over 0°C to +85°C and ±3.0°C over –40°C to +125°C. This accuracy includes contributions from sensor gain, DC offset, amplifier nonlinearity, and internal reference variation - but excludes external resistor tolerance and temperature coefficient effects. For highest accuracy, use 0.1% metal-film resistors and calibrate at system level if required for critical applications.

Can the DS56S operate from a 3.3 V supply?

Yes, the DS56S fully supports 3.3 V operation within its specified 2.7 V to 5.5 V supply range. At 3.3 V, VREF remains stable at 1.25 V (±12 mV), VTEMP retains its 6.2 mV/°C slope and 395 mV offset, and both TOUT1/TOUT2 deliver valid open-drain logic levels. Power supply regulation is ±0.3 mV/V, ensuring minimal impact on trip-point stability across the 3.3 V rail.

What is the purpose of the VREF pin on the DS56S?

The VREF pin on the DS56S provides a stable 1.25 V (nominal) bandgap voltage reference used to set external trip-point voltages on VT1 and VT2 via resistor dividers. This eliminates the need for an external precision reference IC. For optimum performance, VREF should be loaded with 50 µA - typically achieved using a resistor network that draws this current while establishing the desired trip voltage.

Does the DS56S require external pull-up resistors on its TOUT1 and TOUT2 outputs?

Yes, the DS56S TOUT1 and TOUT2 outputs are open-drain FETs and require external pull-up resistors to a positive supply (e.g., VDD or another logic rail). Typical values range from 4.7 kΩ to 10 kΩ depending on rise time and bus loading requirements. Without pull-ups, the outputs cannot drive a logic-high state, rendering thermostat functionality inoperative.