Analog Devices Inc./Maxim Integrated MAX6957ATL+

Overview

The MAX6957ATL+ from Maxim Integrated is a 28-port, SPI-compatible LED display driver and GPIO expander in a 40-pin TQFN-EP package. It provides individually configurable ports (P4–P31) as constant-current LED sinks (1.5mA–24mA, 16-step), push-pull outputs (10mA sink/4.5mA source), or Schmitt inputs with optional pullup. It supports transition detection on seven ports (P24–P30) and operates from 2.5V to 5.5V across –40°C to +125°C - ideal for industrial panel meters and set-top box front-panel displays.

For engineers reviewing the MAX6957ATL+ datasheet, MAX6957ATL+ pinout, MAX6957ATL+ application, or MAX6957ATL+ equivalent, key selection criteria include its 28-port count, 26MHz SPI interface timing, ISET-resistor-based current calibration, interrupt-capable P31 pin, and TQFN thermal performance with exposed pad grounding.

Technical Context

The MAX6957ATL+ implements a 4-wire SPI-compatible serial interface (CS/SCLK/DIN/DOUT) with 26MHz max clock rate and strict setup/hold timing (tDS = 9.5ns, tDH = 0ns). Its port configuration logic uses dual-bit register encoding (0x09–0x0F) to assign each of P4–P31 to LED driver, GPIO output, or Schmitt input modes - with independent pullup enable and transition-detect mask control.

LED current is set globally via ISET resistor (RISET = 39kΩ yields 24mA max) or per-port via 16 individual current registers (0x12–0x1F), each controlling one nibble. Transition detection compares real-time P24–P30 states against a snapshot register and asserts active-high interrupt on P31 - cleared only by reading/writing the mask register (0x06).

Key Specifications

Pinout & Package

MAX6957ATL+ uses a 40-pin TQFN-EP (6mm × 6mm) package with exposed pad internally connected to GND. Thermal performance requires soldering the EP pad to a large ground plane. Pin numbering follows standard TQFN top-view layout (pin 1 = ISET, pin 40 = GND, EP = pin 41).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar LED driver and GPIO expander applications.

Compared with MAX6956ATL+ and MAX7301ETG+, the MAX6957ATL+ uniquely combines high-speed SPI interfacing, per-port LED current programming, and hardware transition detection - making it optimal for responsive, mixed-signal front-panel interfaces requiring minimal MCU intervention.

Availability

MAX6957ATL+ is available at Aetrix Electronics and suitable for industrial controllers, panel meters, and white goods requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6957ATL+ 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 and mixed-signal ICs for industrial, automotive, and communications applications.

The MAX6957 product line delivers integrated LED display drivers with GPIO expansion for front-panel interfaces - targeting applications needing compact, thermally robust, and interrupt-capable I/O management.

FAQ

What is the maximum LED segment current supported by the MAX6957ATL+?

The MAX6957ATL+ supports up to 24mA per LED segment when configured as a constant-current sink, set by the ISET resistor (e.g., 39kΩ yields 24mA at V+ = 5.5V). This value scales linearly with supply voltage and is adjustable in 16 discrete steps from 1.5mA to 24mA per port using internal current registers.

How does the MAX6957ATL+ handle port transition detection?

The MAX6957ATL+ monitors logic-level changes on ports P24 through P30 using a hardware comparator against a snapshot register. When enabled via the M bit in the configuration register (0x04), any transition on a masked port triggers an active-high interrupt on P31. The interrupt is latched and cleared only by reading or writing the transition mask register (0x06).

Can the MAX6957ATL+ be used in daisy-chain configurations?

Yes, the MAX6957ATL+ supports daisy-chaining via its DOUT-to-DIN connection. Data propagates through the internal 16-bit shift register with 15.5-clock latency. For n devices, a full 16-bit command requires 16 × n SCLK cycles; unused devices can be bypassed using the No-Op command (0x00) while updating specific units.

What is the role of the exposed pad (EP) on the MAX6957ATL+ TQFN package?

The exposed pad (EP) on the MAX6957ATL+ is internally connected to GND and serves as the primary thermal dissipation path. It must be soldered to a large PCB ground plane to maintain junction temperature within limits - especially critical at 24mA per port and full temperature range operation. Relying solely on perimeter GND pins risks thermal overload.

Does the MAX6957ATL+ require external pull-up resistors on GPIO inputs?

No - the MAX6957ATL+ provides programmable internal pull-up resistors on all GPIO inputs (P4–P31), selectable per port via configuration bits. Pull-up current ranges from 12µA to 180µA depending on V+ (2.5V–5.5V); this eliminates external components and simplifies layout while maintaining Schmitt-trigger hysteresis (0.3V) for noise immunity.