Analog Devices Inc./Maxim Integrated DS56U

Overview

DS56U from Dallas Semiconductor (now Maxim Integrated) is a dual-temperature comparator IC with integrated bandgap voltage reference and analog temperature sensor output. It delivers ±2.0°C accuracy from 0°C to 85°C, supports two independent open-drain thermostat outputs with 5°C hysteresis, operates from 2.7V to 5.5V, and is housed in a narrow-body SO8 (150-mil) package - used for thermal monitoring and overtemperature protection in disk drives and HVAC systems.

For engineers reviewing the DS56U datasheet, DS56U pinout, DS56U application, or DS56U equivalent, key selection considerations include its dual trip-point configuration, VTEMP transfer function (6.2 mV/°C + 395 mV), factory-calibrated thermometer accuracy, open-drain TOUT1/TOUT2 outputs requiring external pull-ups, and functional compatibility with LM56xIM-series devices.

Technical Context

The DS56U integrates three core subsystems: a precision 1.25V bandgap voltage reference (±1.45 mV regulation error), a linear temperature sensor with DC offset of 395 mV at 0°C and gain of 6.25 mV/°C, and two independent comparators comparing VTEMP against externally set VT1/VT2 thresholds derived from VREF.

Each comparator drives an open-drain digital output (TOUT1/TOUT2) with typical 5.0°C hysteresis and logic-low active state; both outputs share the same VTEMP input but respond independently to their respective trip points, enabling high/low temperature window detection without external logic.

Key Specifications

Pinout & Package

Packaged in narrow-body 8-pin SOIC (150-mil width), the DS56U uses a standard SO8 footprint with gull-wing leads and 1.27 mm pitch. Pin 1 is VREF, located at top-left corner when notch faces up.

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 DS56U uniquely provides both dual independent trip points and a buffered analog temperature output (VTEMP) in one SO8 package - making it optimal for designs needing simultaneous thermal measurement and windowed control without added components.

Availability

DS56U is available at Aetrix Electronics and suitable for hard disk drive thermal protection, laser printer fuser monitoring, office equipment ambient sensing, industrial HVAC fan control, and any power/cost/temperature-sensitive environments requiring stable component supply and long-term lifecycle support.

Supply support for DS56U 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 (acquired 2001), specialized in precision analog, mixed-signal, and thermal management ICs for industrial, computing, and communications markets.

The DS56U belongs to Dallas' thermal monitoring product line, designed specifically for cost-sensitive, space-constrained applications requiring both analog temperature measurement and dual-point digital thermal control in a single SO8 package.

FAQ

What is the operating temperature range of the DS56U?

The DS56U operates across -40°C to +125°C. Its thermometer accuracy is specified as ±2.0°C from 0°C to 85°C and ±3.0°C over the full -40°C to +125°C range. This extended range supports deployment in harsh environments such as industrial enclosures and automotive under-hood proximity zones - though the DS56U itself is not AEC-Q100 qualified.

How do I set the trip points VT1 and VT2 on the DS56U?

VT1 and VT2 are set using external resistor dividers from VREF (1.25 V) to GND. For example, a 10 kΩ resistor from VREF to VT1 and 20 kΩ from VT1 to GND yields VT1 = 1.25 V × (20/(10+20)) ≈ 0.833 V, corresponding to ~70.6°C using VTEMP = 6.25×T + 395 mV. The DS56U datasheet provides full calculation guidance and tolerance analysis.

Does the DS56U require external pull-up resistors on TOUT1 and TOUT2?

Yes - TOUT1 and TOUT2 are open-drain outputs and require external pull-up resistors to a valid logic-high voltage (e.g., VDD or another system rail). Typical values range from 4.7 kΩ to 10 kΩ. Without pull-ups, the outputs remain floating and cannot drive downstream logic reliably - this is a mandatory design requirement for DS56U operation.

Can the DS56U replace the LM56xIM series directly?

Yes - the DS56U is functionally compatible with LM56xIM devices, sharing identical pinout, electrical characteristics, and transfer functions. Dallas Semiconductor documented this compatibility explicitly in the DS56U datasheet. No PCB changes are required when substituting DS56U for LM56CMX/NOPB in existing designs.

What is the output impedance of the VTEMP pin on the DS56U?

The VTEMP pin has a typical output impedance of 1.5 kΩ, as confirmed in the DS56U DC Electrical Characteristics table. This value impacts ADC sampling accuracy: high-impedance ADC inputs may require an op-amp buffer or longer acquisition time to avoid measurement error - a key layout consideration when using DS56U for precision temperature reading.