Analog Devices Inc./Maxim Integrated MAX7349ATG+T

Overview

The MAX7349ATG+T from Maxim Integrated is a 24-pin TQFN-packaged I²C key-switch and sounder controller IC that monitors up to 64 metallic or resistive (≤1kΩ) keys using static matrix scanning, debounces events into an 8-deep FIFO, and drives piezo transducers with 14 programmable musical tones (523Hz–2637Hz) for key-click or alarm feedback in industrial control panels.

For engineers reviewing the MAX7349ATG+T datasheet, MAX7349ATG+T pinout, MAX7349ATG+T application, or MAX7349ATG+T equivalent, this device is selected for low-EMI human-interface designs requiring integrated key-scan logic, interrupt-driven event reporting, tone generation, and up to six configurable open-drain GPOs - all operating from 2.4V–3.6V across –40°C to +125°C.

Technical Context

The MAX7349ATG+T implements static (non-scanned) key monitoring to minimize EMI emissions and supports I²C communication at up to 400kbps with 5.5V-tolerant SDA/SCL pins and four selectable slave addresses via AD0. Its dual-address architecture separates key-scan (0x48–0x4F) and sounder (0x50–0x57) register spaces.

It integrates a tone generator with double-buffered command queueing for glitch-free transitions between tones, programmable duration (15.625ms–1s), and autoloop capability. The ALERT input (exclusive to MAX7349) enables edge-triggered interrupt + tone generation independent of key events.

Key Specifications

Pinout & Package

MAX7349ATG+T uses a 24-pin TQFN-EP package (5mm × 5mm, 0.5mm pitch) with exposed paddle thermally connected to GND. Pin functions are validated per Maxim's official datasheet revision 5 (May 2007).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar key-switch and sounder controller applications.

Compared with MAX7349ATG+T, MAX7348AEP+ offers reduced key count and no ALERT input but shares identical I²C protocol and tone engine; TCA9554PWR provides basic GPIO expansion only and cannot replace MAX7349ATG+T's integrated key-scan and sounder functions without significant firmware and hardware redesign.

Availability

MAX7349ATG+T is available at Aetrix Electronics and suitable for medical instrument keypads, industrial control panels, security access terminals, and test equipment requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX7349ATG+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 demanding industrial, medical, and automotive applications.

The MAX7349 belongs to Maxim's human-interface controller product line, engineered specifically for EMI-sensitive, high-reliability key-scan and audible feedback applications in harsh environments.

FAQ

What is the maximum number of keys supported by the MAX7349ATG+T?

The MAX7349ATG+T supports up to 64 keys arranged in an 8×8 matrix using ROW0–ROW7 and COL0–COL7/PORT7 pins. This capacity is fixed for the MAX7349 variant and confirmed in the device's ordering information and feature table. Each GPO configuration reduces the total key count by eight, so using all six PORT pins as GPOs limits key monitoring to 16 switches.

Does the MAX7349ATG+T require external components for basic key-scan operation?

No, the MAX7349ATG+T operates autonomously for key-scan: internal current sources drive key switches, and debounce/FIFO logic runs independently. Only two external 4.7kΩ pull-up resistors on SDA and SCL, plus a 0.047µF ceramic capacitor from V+ to GND, are required for reliable I²C communication and power supply decoupling - no external RC networks or amplifiers needed.

Can the SOUNDER output of the MAX7349ATG+T drive a standard 8Ω speaker?

No, the SOUNDER output is optimized for piezoelectric transducers (capacitive load) and electronic sounders, not low-impedance speakers. It delivers ±25mA into resistive loads but lacks the current drive and voltage swing needed for 8Ω voice coils. For 8Ω speakers, an external audio amplifier stage is required - the MAX7349ATG+T's SOUNDER pin should connect only to piezo elements, relays, or logic-level indicators.

How does the ALERT input function on the MAX7349ATG+T?

The ALERT input on the MAX7349ATG+T is a dedicated edge-triggered logic input that generates both an interrupt and optional tone on each falling edge. It is read via register 0x07 and can be enabled/disabled independently of key-scan interrupts. This feature is exclusive to MAX7349 and absent in MAX7347/MAX7348, enabling external event response (e.g., door-open detection) without consuming key matrix resources.

Is the MAX7349ATG+T pin-compatible with other devices in the MAX7347/MAX7348/MAX7349 family?

No, the MAX7349ATG+T is not pin-compatible with MAX7347 or MAX7348 due to differing pin counts (24 vs. 16 or 20) and unique signals: COL7/PORT7 and ALERT exist only on MAX7349. While all three share functional similarity, direct replacement requires PCB redesign. The MAX7349ATG+T's 24-pin TQFN footprint matches only the MAX7349AEG+ (QSOP), not other variants.