Analog Devices Inc./Maxim Integrated MAX7359EWA+

Overview

The MAX7359EWA+ from Maxim Integrated is a 2-wire (I²C) interfaced key switch controller/GPO that manages up to 64 metallic or resistive key switches 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 up to 35µA key-switch source current, and integrates seven open-drain column drivers (COL2–COL7/PORT2–PORT7) plus INT as optional GPO.

For engineers reviewing the MAX7359EWA+ datasheet, MAX7359EWA+ pinout, MAX7359EWA+ application, or MAX7359EWA+ equivalent, this device is selected for low-EMI keypad interfaces in space-constrained handhelds where power-aware key event queuing, hardware interrupt control, and flexible GPO reuse are required.

Technical Context

The MAX7359EWA+ implements static key-matrix scanning-no dynamic row/column toggling-to minimize EMI and simplify PCB routing near RF-sensitive circuits. Its internal 64kHz oscillator drives debouncing logic with user-configurable 9ms–40ms timing and maintains FIFO state during autosleep mode.

Interrupt generation is configurable at either FIFO threshold (4–16 entries) or time-based intervals (1–31 debounce cycles), and the INT pin can be repurposed as an open-drain GPO. Up to six column outputs (COL2–COL7) may be reassigned as GPOs-each reducing maximum scannable keys by eight-enabling hybrid keypad + LED-driving functionality.

Key Specifications

Pinout & Package

The MAX7359EWA+ is housed in a 25-bump WLP package (2.31mm × 2.31mm, 0.4mm pitch), optimized for ultra-compact portable designs. The exposed substrate is electrically isolated; no thermal pad connection required.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX7359EWA+, MAX7360EWA+ offers higher ESD immunity without changing layout or firmware, while TCA8418RTWR trades key count and EMI performance for lower unit cost and simpler integration in low-channel applications.

Availability

The MAX7359EWA+ is available at Aetrix Electronics and suitable for smartphone keypad interfaces, handheld gaming console controls, industrial handheld terminals, medical patient monitor keypads, and portable consumer electronics requiring stable component supply and RoHS-compliant packaging.

Supply support for MAX7359EWA+ 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, communications, and consumer applications.

The MAX7359EWA+ belongs to Maxim's key switch controller product line, engineered specifically for ultra-low-power, EMI-conscious keypad interfaces in space-constrained portable electronics.

FAQ

What is the maximum key-switch resistance supported by the MAX7359EWA+?

The MAX7359EWA+ supports key-switch resistance up to 5kΩ, accommodating both metallic dome and carbon-film switches without external biasing. This specification is validated across the full -40°C to +85°C operating range and ensures reliable detection even with aging or contamination effects on contact resistance. The internal 20µA–35µA current source maintains sufficient voltage margin (0.42V–0.55V) at the switch node under worst-case conditions.

Can the MAX7359EWA+ operate with a 1.8V supply?

Yes, the MAX7359EWA+ operates over +1.62V to +3.6V, making 1.8V fully compliant. At 1.8V, key-switch source current remains within spec (≥20µA), I²C logic thresholds (VIH = 0.7×VCC = 1.26V, VIL = 0.3×VCC = 0.54V) are met, and sleep current stays below 5µA. All timing parameters-including 400kbps I²C and 9ms–40ms debounce-are guaranteed across this range.

How does the MAX7359EWA+ handle key autorepeat functionality?

The MAX7359EWA+ implements hardware autorepeat: after a programmable delay (8–128 debounce cycles), it inserts a fixed 0x7E code into the FIFO at a configurable rate (4–32 debounce cycles). This occurs independently of host polling, requires no firmware intervention, and continues until key release-even across autosleep/wake transitions. The feature is enabled/disabled per register 0x05, bit D7.

Is the MAX7359EWA+ pin-compatible with the MAX7359ETG+?

No-the MAX7359EWA+ uses a 25-bump WLP (2.31mm × 2.31mm), while the MAX7359ETG+ uses a 24-pin TQFN (3.5mm × 3.5mm) with different pin count, layout, and bump/pad mapping. Though functionally identical and sharing register compatibility, PCB redesign is required for substitution. Signal names align (e.g., COL2/PORT2, ROW0), but physical routing and decoupling must be revalidated.

What happens to the FIFO during MAX7359EWA+ autosleep mode?

The FIFO contents are fully preserved during autosleep mode-the 16-entry buffer retains all un-read key-press and key-release events. Host software can read the FIFO at any time, including while the device is asleep, using standard I²C transactions. Autosleep only disables the key-scan current sources and oscillator; register access and FIFO read capability remain fully operational.