Analog Devices Inc./Maxim Integrated MAX135CWI+T

Overview

MAX135CWI+T from Maxim Integrated is a 16-bit, dual-slope analog-to-digital converter (ADC) with serial interface, ±0.003% integral nonlinearity (INL), 100µV offset error, and 2.5V internal reference. It operates from a single +5V supply and is used in precision digital multimeters and benchtop test equipment.

For engineers reviewing the MAX135CWI+T datasheet, MAX135CWI+T pinout, MAX135CWI+T application, or MAX135CWI+T equivalent, key selection factors include dual-slope architecture for noise rejection, integrated reference stability, serial output timing, and guaranteed monotonicity over temperature.

Technical Context

The MAX135CWI+T implements a dual-slope integration architecture with auto-zeroing and internal clock generation. It supports programmable conversion rates of 2.5, 5, or 10 readings per second and includes an on-chip 2.5V reference with ±10ppm/°C drift.

Its serial interface uses a 3-wire SPI-compatible protocol (CLK, DIN, DOUT) with no external timing components required. The device performs automatic zero and reference calibration at power-up and supports continuous or single-conversion modes.

Key Specifications

Pinout & Package

MAX135CWI+T is housed in a 28-pin SOIC wide-body package (SO28W) with 0.3-inch body width and standard 0.050-inch lead pitch.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar precision dual-slope ADC applications.

Compared with AD7730BRUZ and LTC2400CGN#PBF, the MAX135CWI+T offers deterministic dual-slope timing, guaranteed monotonicity, and self-contained calibration-making it optimal for portable metrology tools where reliability, simplicity, and AC-line immunity are prioritized over raw bit depth.

Availability

MAX135CWI+T is available at Aetrix Electronics and suitable for digital multimeters, benchtop test equipment, and industrial calibration systems requiring stable component supply and long-term manufacturability.

Supply support for MAX135CWI+T 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 test equipment applications.

The MAX135CWI+T belongs to Maxim's high-accuracy metrology ADC product line, engineered specifically for applications demanding guaranteed linearity, low drift, and minimal external component count in portable and benchtop instrumentation.

FAQ

What is the maximum conversion rate of the MAX135CWI+T?

The MAX135CWI+T supports three programmable conversion rates: 2.5, 5, or 10 readings per second. The selected rate is configured via control bits written to its internal register through the serial interface. At 10 rps, the MAX135CWI+T maintains full 16-bit accuracy and ±0.003% INL performance without degradation.

Does the MAX135CWI+T require an external reference voltage?

No, the MAX135CWI+T includes a precision 2.5V internal reference with ±10ppm/°C temperature drift. External reference use is optional and only needed if a different reference voltage or tighter drift specification is required. When REFIN/REFOUT is left unconnected, the MAX135CWI+T automatically enables its internal reference.

Is the MAX135CWI+T pin-compatible with other Maxim dual-slope ADCs?

No, the MAX135CWI+T has a unique 28-pin SOIC pinout optimized for its dual-slope architecture and serial interface. It is not pin-compatible with MAX134 or MAX136 variants, which differ in pin count, signal assignment, and internal register mapping. Board redesign is required when substituting between these families.

What serial interface protocol does the MAX135CWI+T use?

The MAX135CWI+T uses a 3-wire SPI-compatible serial interface with CLK, DIN, and DOUT lines. It does not require CS or frame synchronization signals. Data is clocked out MSB-first after conversion completion, and commands are written synchronously on the rising edge of CLK. The MAX135CWI+T generates its own internal timing for integration cycles independent of the serial clock.

How does the MAX135CWI+T handle offset and gain errors over temperature?

The MAX135CWI+T performs automatic zero calibration at power-up and supports periodic user-initiated calibration. Its ±100µV offset error and ±0.003% INL are specified over –40°C to +85°C. Gain error remains within ±0.01% FS across temperature due to matched on-chip resistor networks and the stable 2.5V reference, eliminating need for external trimming in most applications.