Allegro MicroSystems A6280EESTR-T

Overview

A6280EESTR-T from Allegro MicroSystems is a 3-channel constant-current LED driver IC designed for RGB pixel control in large-character signage and architectural lighting. It delivers programmable 10-bit PWM brightness per channel (0–1023 levels), 7-bit dot correction per output, and supports 10–150 mA output current per channel via external R_EXT. The device operates from 5–17 V and enables daisy-chained control of hundreds of LEDs using only four logic signals.

For engineers reviewing the A6280EESTR-T datasheet, A6280EESTR-T pinout, A6280EESTR-T application, or A6280EESTR-T equivalent, key selection considerations include its QFN-16 package, shared serial/PWM clock pin architecture, thermal shutdown (165°C), undervoltage lockout (3.0–4.5 V), and compatibility with high-speed daisy-chain topologies requiring precise CI-to-LI setup timing.

Technical Context

The A6280EESTR-T integrates three independent linear current regulators with matched output characteristics (±7% matching error) and embeds a 31-bit shift register that loads brightness, dot correction, and clock divider data via SDI/CI. Its dual-function CI pin concurrently serves as serial clock input and PWM timing source, reducing pin count while enabling synchronized daisy chaining.

Each channel features a dedicated 10-bit PWM counter and 7-bit scalar register; brightness data determines duty cycle (DC = [(PWM_n + 1)/1024] × 100%), while dot correction scales maximum current from 36.5% to 100% to compensate for LED binning and aging. Internal thermal shutdown and UVLO protect against overtemperature and supply brownout.

Key Specifications

Pinout & Package

Package: 16-contact QFN (ES suffix), lead-free with 100% matte-tin plating; exposed thermal pad (PAD) must be externally connected to LGND and PGND for thermal performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 3-channel constant-current LED driver applications.

Compared with TLC59284PWR and MAX6967AUG+T, the A6280EESTR-T uniquely balances daisy-chain scalability, per-channel dot correction, and shared-clock efficiency - making it optimal for large-format RGB signage where uniformity and wiring simplicity are critical.

Availability

A6280EESTR-T is available at Aetrix Electronics and suitable for colored large-character LED signs, architectural lighting, and scrolling marquees requiring stable component supply during legacy design support and end-of-life transition phases.

Supply support for A6280EESTR-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

Allegro MicroSystems is a U.S.-based designer of high-performance magnetic sensing and power IC solutions, headquartered in Worcester, Massachusetts.

The A6280 product line was developed specifically for high-reliability, large-pixel-count LED display systems requiring precise current matching, thermal robustness, and scalable serial control - targeting outdoor signage and architectural applications.

FAQ

What is the function of the REXT pin on the A6280EESTR-T?

The REXT pin on the A6280EESTR-T accepts an external resistor that sets the global maximum output current for all three channels using the formula I_OUT(max) = 753.12 / R_EXT. For example, a 5 kΩ resistor yields ~150 mA per channel. This resistor establishes a stable current reference independent of supply voltage, temperature, or LED V_F variation - ensuring consistent brightness across operating conditions. The A6280EESTR-T uses this value as the baseline for all dot correction and PWM scaling operations.

How does the A6280EESTR-T support daisy-chaining of multiple devices?

The A6280EESTR-T supports daisy-chaining through buffered outputs: CO (Clock Out), LO (Latch Out), OEO (Output Enable Out), and SDO (Serial Data Out) replicate their respective inputs (CI, LI, OEI, SDI) with TTL-level drive strength. These outputs drive the next device's inputs directly, enabling chains of up to 250+ units over Cat5 UTP. The internal 100 ns one-shot on CO ensures clock edge consistency across the chain, while the 31-bit shift register and address-bit protocol prevent data corruption during long serial transfers - a core capability of the A6280EESTR-T.

What is the purpose of the dual-mode shift register in the A6280EESTR-T?

The A6280EESTR-T's 31-bit shift register uses bit 30 as an address selector: when '0', subsequent bits load into the three 10-bit PWM brightness registers; when '1', they load into dot correction and clock divider configuration fields. This dual-mode architecture allows full control of both intensity and current scaling using a single serial interface - eliminating the need for separate command protocols or additional control lines. This design directly enables the A6280EESTR-T's compact 16-pin QFN footprint while retaining full functional flexibility.

Does the A6280EESTR-T require an external voltage regulator?

No, the A6280EESTR-T integrates an internal linear regulator that derives logic power from the VIN supply (5–17 V), eliminating the need for an external 5 V regulator. The VREG pin is solely for decoupling - a 1.0 μF ceramic capacitor must connect between VREG and LGND. When VIN is 5 V, it must be externally tied to VREG to ensure proper regulation; however, VIN must never exceed the VREG absolute maximum rating of 6 V. This integrated regulation is a defining feature of the A6280EESTR-T, simplifying power architecture in LED pixel boards.

What happens to the A6280EESTR-T outputs during thermal shutdown?

When the A6280EESTR-T junction temperature reaches 165°C (typical), thermal shutdown disables all three output drivers (OUT0/OUT1/OUT2) until the die cools by ~15°C. Crucially, the shift register, latch registers, and logic circuitry remain fully operational - preserving all loaded brightness, dot correction, and clock divider settings. Once temperature falls below the recovery threshold (~150°C), outputs resume normal operation using the retained configuration. This behavior ensures display state integrity during transient overtemperature events - a critical reliability feature of the A6280EESTR-T in enclosed or high-power-density signage.