Analog Devices Inc./Maxim Integrated MAX155AEWI+

Overview

The MAX155AEWI+ from Maxim Integrated is an 8-channel, 8-bit simultaneous-sampling analog-to-digital converter (ADC) with integrated track-and-hold amplifiers, 2.5V internal reference, and 3.6µs per-channel conversion time. It operates from single +5V or dual ±5V supplies, supports unipolar/bipolar and single-ended/differential input configurations, and stores results in an internal 8×8 RAM-enabling phase-coherent data acquisition for vibration analysis and power metering.

For engineers reviewing the MAX155AEWI+ datasheet, MAX155AEWI+ pinout, MAX155AEWI+ application, or MAX155AEWI+ equivalent, this page delivers verified technical context, real-world interface timing constraints, channel-matching accuracy (±½ LSB), aperture delay matching (4 ns), and hard-wired vs. I/O mode selection guidance critical for deterministic multi-channel sampling systems.

Technical Context

The MAX155AEWI+ implements a successive-approximation ADC core with eight independent track-and-hold amplifiers that sample all analog inputs simultaneously on the falling edge of WR. Conversion sequencing is controlled via an internal configuration register updated on WR's rising edge, supporting mixed-mode input setups (e.g., some channels unipolar single-ended, others bipolar differential) without reconfiguration overhead between conversions.

It features dual operational modes: I/O mode (MODE = open circuit) enables full programmability of channel selection, polarity, and input type through shared D0–D7/data-address pins; hard-wired mode (MODE tied high/low with VSS) bypasses register programming to execute fixed 8-channel single-ended or 4-channel differential conversions directly. Internal 2.5V reference output (REFOUT) requires 4.7µF + 0.1µF bypassing for stability.

Key Specifications

Pinout & Package

MAX155AEWI+ is supplied in a 28-pin wide SO (Small Outline) package with 300 mil body width, gull-wing leads, and RoHS-compliant matte tin plating. Pin 1 is marked by a beveled corner; pin numbering follows standard counter-clockwise convention from top view.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar multichannel simultaneous-sampling ADC applications.

Compared with AD7864ASTZ-1 and ADS8588SIPM, the MAX155AEWI+ uniquely combines 8-channel simultaneous sampling, parallel 8-bit interface, internal 2.5 V reference, and mixed-mode configurability in a single 28-pin SO package-making it optimal for cost-sensitive, space-constrained systems requiring deterministic multi-channel timing without external support components.

Availability

MAX155AEWI+ is available at Aetrix Electronics and suitable for vibration monitoring systems, power quality analyzers, portable data loggers, and motor control feedback loops requiring stable component supply across industrial temperature ranges (-40°C to +85°C).

Supply support for MAX155AEWI+ 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, automotive, and communications applications-with emphasis on signal integrity and system-level integration.

The MAX155AEWI+ belongs to Maxim's high-speed data acquisition product line, engineered specifically for applications demanding phase-coherent multi-channel sampling, such as power metering, structural health monitoring, and real-time DSP front-ends.

FAQ

What is the maximum sampling rate achievable with the MAX155AEWI+ in 8-channel simultaneous mode?

The MAX155AEWI+ completes conversion of one channel in 3.6 µs. In full 8-channel simultaneous mode, all channels are sampled at once and converted sequentially, resulting in a total conversion time of approximately 28.8 µs (8 × 3.6 µs). This yields an effective aggregate sampling rate of ~220 kSPS. The MAX155AEWI+ achieves this without external timing control-only WR and RD pulses are required to initiate and retrieve data.

Does the MAX155AEWI+ support true differential input measurements across all eight channels?

No-the MAX155AEWI+ supports differential input per channel pair (e.g., AIN0–AIN1, AIN2–AIN3), not across all eight as a single 4-channel differential set. Its pinout and configuration register allow selecting differential mode for individual pairs, but only four differential channels can be active simultaneously due to internal routing. The MAX155AEWI+ documentation confirms differential operation is implemented per pair, with Table 2 and Figure 9 explicitly defining AIN0/AIN1, AIN2/AIN3, etc., as matched differential inputs.

How does the MAX155AEWI+ handle power-down mode, and what is the wake-up time?

The MAX155AEWI+ enters power-down mode when PD = 1 is written to its configuration register. Supply current drops to ≤100 µA, and the internal 2.5 V reference is disabled. Upon exiting (PD = 0), the internal reference requires up to 5 ms to recharge its 4.7 µF bypass capacitor before valid conversions resume. If an external reference remains active, wake-up time reduces to ≤50 µs-verified in Electrical Characteristics under "Power Requirements" section.

Can the MAX155AEWI+ operate with an external reference while retaining its internal reference functionality?

No-the MAX155AEWI+ cannot use both internal and external references concurrently. When REFIN is driven with an external voltage (2.375–2.625 V), REFOUT must be either bypassed to AGND or tied to VDD to prevent oscillation and noise coupling. Tying REFOUT to VDD disables the internal reference but increases power-down current by ~250 µA. The MAX155AEWI+ datasheet explicitly states REFOUT must be "bypassed or disabled" when using an external reference.

What is the significance of aperture delay matching being specified as 4 ns for the MAX155AEWI+?

The 4 ns aperture delay matching specification means the timing variation between when each of the eight track-and-hold amplifiers actually samples its respective analog input is ≤4 ns. This ensures sub-degree phase alignment at 100 kHz (where 4 ns = 0.14°), which is critical for accurate FFT-based analysis in vibration monitoring and power quality applications. This parameter is measured and guaranteed-not just designed-and appears in the "Dynamic Performance" table of the MAX155AEWI+ datasheet.