Analog Devices Inc./Maxim Integrated MAX7359ETG+

Overview

The MAX7359ETG+ from Maxim Integrated is a 2-wire (I²C) interfaced key switch controller that manages up to 64 mechanical or resistive keys with static matrix scanning, 16-entry FIFO buffering, and configurable autosleep (1µA typ) for portable consumer electronics. It supports +1.62V to +3.6V supply, delivers 20–35µA key-switch source current, and integrates seven open-drain column drivers (COL2–COL7/PORT2–PORT7) usable as GPOs.

For engineers reviewing the MAX7359ETG+ datasheet, MAX7359ETG+ pinout, MAX7359ETG+ application, or MAX7359ETG+ equivalent, this page provides verified technical context on low-EMI key-scan architecture, I²C timeout control, interrupt configuration options, and GPO reconfiguration trade-offs between key count and output flexibility.

Technical Context

The MAX7359ETG+ implements static key-matrix monitoring-no dynamic row/column toggling-reducing EMI and enabling routing near noise-sensitive circuits. Its internal 64kHz oscillator drives key-scan timing, and all key events (press/release, autorepeat) are debounced and queued in a 16-byte FIFO with user-configurable 9–40ms debounce intervals.

Autosleep triggers after programmable idle time (up to 8192ms), maintaining FIFO contents during sleep; autowake resumes full operation within 2ms + debounce time upon key press. The INT pin operates as either hardware interrupt (FIFO-level or time-based) or configurable open-drain GPO, and up to six column outputs can be repurposed as LED-driving GPOs at the cost of −8 keys per GPO enabled.

Key Specifications

Pinout & Package

MAX7359ETG+ uses a 24-pin TQFN package (3.5mm × 3.5mm, exposed pad) optimized for space-constrained handheld designs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX7348ETG+ and TCA8418RTWR, the MAX7359ETG+ uniquely combines 64-key scalability, sub-1µA sleep, configurable GPOs, and robust I²C timeout-making it optimal for premium portable devices demanding both power efficiency and interface flexibility.

Availability

MAX7359ETG+ is available at Aetrix Electronics and suitable for smartphone keypad interfaces, handheld gaming console controls, industrial handheld terminals, portable medical device keypads, and ruggedized consumer electronics requiring stable component supply across extended temperature ranges.

Supply support for MAX7359ETG+ 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 high-reliability applications.

The MAX7359ETG+ belongs to Maxim's human-interface peripheral product line, engineered specifically for low-EMI, battery-optimized key scanning in space- and power-constrained portable electronics.

FAQ

What is the minimum debounce time supported by the MAX7359ETG+?

The MAX7359ETG+ supports a minimum debounce time of 9ms, configurable via the Debounce Register (0x02) using bits D0–D4. This value is factory-programmable and applies uniformly across all 64 keys. The MAX7359ETG+ does not support shorter debounce intervals, and values below 9ms are not functional per the datasheet specification.

Can the MAX7359ETG+ operate with a 5V I²C master?

Yes, the MAX7359ETG+ supports 5.5V-tolerant SDA and SCL pins, allowing direct interface with 5V I²C masters without level-shifting circuitry. Its VCC supply remains limited to +1.62V to +3.6V, but the I²C bus signals tolerate up to 5.5V, ensuring compatibility with legacy or mixed-voltage system designs using the MAX7359ETG+.

How many keys can be monitored if all six configurable column drivers are used as GPOs?

When all six column drivers (COL2/PORT2 through COL7/PORT7) are configured as general-purpose outputs, the MAX7359ETG+ supports 16 keys (64 − 6 × 8 = 16). Each GPO-enabled column reduces the maximum key count by eight, as the underlying 8×8 matrix structure allocates one column per eight keys. COL0 and COL1 remain fixed as key drivers and cannot be repurposed.

Does the MAX7359ETG+ retain FIFO contents during autosleep mode?

Yes, the MAX7359ETG+ maintains all FIFO contents-including pending key-press and key-release events-while in autosleep mode. The FIFO remains readable over I²C, and no data is lost or overwritten. This behavior enables host processors to poll the FIFO on wake-up without missing events that occurred during sleep, a critical capability for responsive user interfaces relying on the MAX7359ETG+.

What is the purpose of the I.C. pin on the MAX7359ETG+?

The I.C. pin on the MAX7359ETG+ is an internally connected node that must be tied to GND for normal operation. It is not a functional signal pin but a required connection to ensure proper internal biasing and device stability. Leaving the I.C. pin floating or connecting it to any voltage other than GND may cause undefined behavior or failure to initialize correctly in the MAX7359ETG+.