Analog Devices Inc./Maxim Integrated MAX1281BEUP+

Overview

The MAX1281BEUP+ from Maxim Integrated is a 12-bit, 300ksps successive-approximation analog-to-digital converter (ADC) with integrated 8-channel analog multiplexer, track/hold, and SPI/QSPI/MICROWIRE-compatible 4-wire serial interface. It operates from a single +2.7V to +3.6V supply, features an internal +2.5V reference with ±1.5% adjustability, and supports software-configurable unipolar/bipolar and single-ended/pseudo-differential input modes. It is used in battery-powered medical instruments and portable data loggers requiring low power and high channel density.

For engineers reviewing the MAX1281BEUP+ datasheet, MAX1281BEUP+ pinout, MAX1281BEUP+ application, or MAX1281BEUP+ equivalent, this page delivers verified electrical specs, thermal operating range (–40°C to +85°C), TSSOP-20 package mapping, real-world timing constraints (e.g., 4.8MHz max SCLK, 625ns acquisition time), and validated alternative parts for design continuity.

Technical Context

The MAX1281BEUP+ implements a switched-capacitor SAR architecture with a dedicated track/hold stage that acquires input signals within 625ns and completes conversion in 3.3µs using a 4.8MHz serial clock. Its pseudo-differential input structure allows four differential channel pairs (CH0/CH1 through CH6/CH7), while maintaining single-ended sampling on IN+ and stable COM or IN– reference.

Power management includes four software-selectable modes-normal (2.5mA), reduced-power (1.3mA), fast power-down (0.9mA), and full power-down (2µA)-with automatic wake-on-CS assertion and sub-100µA average current at low sampling rates. The internal reference buffer provides 2.500V ±10mV output with ±15ppm/°C TC and supports external reference injection via REF pin.

Key Specifications

Pinout & Package

MAX1281BEUP+ is housed in a 20-pin TSSOP package (4.4mm × 6.5mm, 0.65mm pitch) with exposed pad for thermal enhancement. Pin functions are electrically validated per Maxim's Rev 2 datasheet (19-1684).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 12-bit SAR ADC applications.

Compared with ADS7822U and AD7490BRUZ, the MAX1281BEUP+ uniquely balances ultra-low power (2.5mA @ 300ksps), integrated reference, and compact 20-pin TSSOP-making it optimal for space-constrained, battery-operated systems needing guaranteed –40°C to +85°C performance without external support components.

Availability

MAX1281BEUP+ is available at Aetrix Electronics and suitable for portable medical instruments, battery-powered data loggers, and industrial process controllers requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX1281BEUP+ 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 high-performance analog, mixed-signal, and power management ICs for industrial, medical, and communications applications.

The MAX1280/MAX1281 product line was designed for low-power, multi-channel data acquisition in portable and battery-operated systems-emphasizing integrated functionality, wide supply range, and robust operation across industrial temperatures.

FAQ

What is the maximum serial clock frequency supported by the MAX1281BEUP+?

The MAX1281BEUP+ supports a maximum serial clock (SCLK) frequency of 4.8MHz, as specified in its electrical characteristics table for the –40°C to +85°C temperature range. This clock rate enables the full 300ksps sampling capability. Exceeding 4.8MHz may cause timing violations in setup/hold windows and lead to incorrect control byte latching or corrupted conversion results. Always maintain 40–60% duty cycle and terminate SCLK with appropriate impedance matching for noise immunity.

Does the MAX1281BEUP+ require an external reference voltage?

No, the MAX1281BEUP+ does not require an external reference voltage-it includes an internal +2.500V reference with ±10mV initial accuracy and ±15ppm/°C temperature coefficient. The REFADJ pin allows ±1.5% fine adjustment of the output. An external reference (1.0V to VDD1) may be used by disabling the internal buffer (tie REFADJ to VDD1), but this is optional-not mandatory-for standard operation.

How does the pseudo-differential input mode work on the MAX1281BEUP+?

The MAX1281BEUP+ pseudo-differential mode uses four fixed channel pairs (CH0/CH1, CH2/CH3, CH4/CH5, CH6/CH7), where only the positive input (IN+) is actively sampled and held; the negative input (IN–) remains stable during conversion. Unlike true differential ADCs, it does not reject common-mode noise on IN–-so COM or IN– must be held within ±0.5LSB of GND. This architecture reduces pin count while supporting differential signal acquisition in space-constrained designs.

What is the minimum acquisition time required for accurate conversions with the MAX1281BEUP+?

The MAX1281BEUP+ requires a minimum track/hold acquisition time (tACQ) of 625ns, as guaranteed across the full –40°C to +85°C operating range. This value assumes ≤2kΩ source impedance driving the analog input. Longer acquisition times are needed for higher source impedances, calculated as tACQ = 9 × (RS + 800Ω) × 12pF. Failure to meet this minimum results in missing codes or degraded INL/DNL performance.

Can the MAX1281BEUP+ operate with separate analog and digital supplies?

Yes, the MAX1281BEUP+ has two independent supply pins: VDD1 (analog core, mux, T/H) and VDD2 (digital interface). Both must be connected to the same nominal voltage (+2.7V to +3.6V), and their difference must not exceed ±0.3V. This separation allows localized decoupling-4.7µF + 0.1µF on VDD1, and 0.1µF on VDD2-to minimize digital switching noise coupling into the analog path, preserving SNR and THD performance.