Analog Devices Inc./Maxim Integrated MAX156ACWI+

Overview

The MAX156ACWI+ from Maxim Integrated is a high-speed, 4-channel, 8-bit analog-to-digital converter (ADC) with simultaneous track-and-hold (T/H) inputs for phase-coherent sampling across all channels. It delivers 3.6µs per-channel conversion time, supports unipolar/bipolar and single-ended/differential input configurations, and integrates a 2.5V internal reference. It is used in vibration analysis systems where synchronized multi-channel acquisition preserves waveform timing integrity.

For engineers reviewing the MAX156ACWI+ datasheet, MAX156ACWI+ pinout, MAX156ACWI+ application, or MAX156ACWI+ equivalent, this page provides verified technical context, real-world interface timing constraints, channel configuration behavior, supply voltage dependencies (±5V vs. +5V only), and validated alternatives for data-acquisition system design.

Technical Context

The MAX156ACWI+ implements a successive-approximation ADC core with eight independent T/H amplifiers-four active and four unused-enabling true simultaneous sampling of all four analog inputs on the WR falling edge. Its I/O mode uses shared D0–D7 pins for both configuration register loading and data readout, requiring careful sequencing of INH, BIP, DIFF, and ALL bits to avoid unintended conversions.

Hard-wired mode (MODE tied high/low with VSS grounded or at –5V) bypasses register programming and directly selects fixed configurations: e.g., MODE = 1 and VSS = AGND initiates a 4-channel differential unipolar conversion. Internal reference stability requires 4.7µF + 0.1µF bypassing at REFOUT; external reference use mandates REFOUT disable or bypass to prevent oscillation.

Key Specifications

Pinout & Package

MAX156ACWI+ is housed in a 24-pin narrow plastic DIP (PDIP) package with 0.3-inch body width and 0.1-inch lead pitch. Pin 1 is marked with a notch or dot; leads are tin-lead plated. Thermal resistance θ_JA = 115°C/W; max continuous power dissipation at +70°C is 696mW.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 4-channel, 8-bit, simultaneous-sampling ADC applications.

Compared with ADS8325IPW and AD7864ASRZ-1, the MAX156ACWI+ uniquely balances 8-bit resolution, 3.6µs speed, integrated T/H, and simple parallel interface - making it optimal for cost-sensitive, phase-coherent, medium-bandwidth acquisition where 12+ bit resolution is unnecessary.

Availability

MAX156ACWI+ is available at Aetrix Electronics and suitable for vibration analysis systems, AC power meters, portable data loggers, and DSP front-ends requiring stable component supply, long-term obsolescence management, and traceable sourcing.

Supply support for MAX156ACWI+ 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 power-management ICs for industrial, medical, and communications applications.

The MAX155/MAX156 family was engineered specifically for high-fidelity, multi-channel data acquisition where timing coherence across inputs is essential - targeting test equipment, power quality analyzers, and condition-monitoring systems.

FAQ

What is the maximum clock frequency supported by the MAX156ACWI+?

The MAX156ACWI+ operates with an external clock frequency ranging from 0.5MHz to 5.0MHz. At 5MHz, the device achieves its specified 3.6µs conversion time per channel. Clock frequencies below 0.5MHz increase conversion time linearly; exceeding 5MHz violates timing specifications and may cause data corruption or BUSY timing violations.

Does the MAX156ACWI+ require separate analog and digital ground planes?

Yes - the MAX156ACWI+ has dedicated AGND and DGND pins that must be connected to separate ground planes, joined at a single point near the device. This separation prevents digital switching noise from coupling into analog sampling paths, preserving the 47dB SINAD performance and ±1 LSB linearity. Mixing AGND and DGND on a common plane degrades accuracy.

Can the MAX156ACWI+ perform differential conversions on arbitrary channel pairs?

No - differential conversions are limited to predefined pairs: AIN0–AIN1, AIN2–AIN3, AIN4–AIN5, and AIN6–AIN7. Since the MAX156ACWI+ only exposes AIN0–AIN3, only AIN0–AIN1 and AIN2–AIN3 are usable. The configuration register's DIFF bit applies globally per selected channel address; cross-pair combinations (e.g., AIN0–AIN2) are not supported.

How does power-down mode affect the configuration register and RAM contents in the MAX156ACWI+?

In power-down mode (PD = 1), the MAX156ACWI+ retains all configuration register contents and RAM data, allowing immediate resumption of prior acquisition sequences upon wake-up. However, no conversions can be initiated and no RAM reads are possible until PD is cleared. The internal 2.5V reference is disabled, reducing current draw to ≤100µA.

Is the MAX156ACWI+ pin-compatible with the MAX155 series?

No - the MAX156ACWI+ uses a 24-pin narrow PDIP package, while the MAX155 uses 28-pin packages (PDIP or wide SO). Pin functions differ significantly: the MAX156ACWI+ lacks A2 address pin and AIN4–AIN7 inputs present on MAX155, and its MODE/VSS hard-wired logic maps differently. PCB layout and firmware must be redesigned for substitution.