Allegro MicroSystems A6278ELP-T

Overview

A6278ELP-T from Allegro MicroSystems is an 8-channel serial-input constant-current latched LED driver with open-LED detection, designed for multiplexed LED display systems. It features Schmitt-trigger inputs, 3.0–5.5 V logic supply, up to 90 mA per output, and 20 ns output staggering delay. Used in industrial panel meters and signage where reliable current sinking and fault reporting are required.

For engineers reviewing the A6278ELP-T datasheet, A6278ELP-T pinout, A6278ELP-T application, or A6278ELP-T equivalent, this page provides verified technical context, real-world design meaning of key specs, validated package and pin mapping, confirmed alternatives, and production-ready supply support - all grounded in Allegro's official documentation (Rev. 10).

Technical Context

The A6278ELP-T integrates a CMOS shift register, parallel latches, and eight NPN constant-current sink drivers in a single TSSOP-16 LP package with exposed thermal pad. Its open-LED detection operates via V_CE threshold comparison (0.30 V typical) and reports faults serially through the SERIAL DATA OUT pin during dedicated test mode.

Internal UVLO (2.15–2.85 V range) and thermal shutdown (165 °C typical) ensure robust operation under supply transients and overtemperature conditions. Output current is set externally via R_EXT, enabling precise per-bit current control independent of V_LED or V_DD variation.

Key Specifications

Pinout & Package

TSSOP-16 package with exposed thermal pad (LP suffix), 4.4 mm × 5.0 mm footprint, 1.2 mm max height, matte tin-plated leads, Pb-free.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLC59282DBQR and MAX7219CWG+, the A6278ELP-T delivers superior fault visibility, tighter current matching (±6%), and integrated thermal/UVLO protection - making it the preferred choice for industrial and medical LED systems demanding operational integrity.

Availability

A6278ELP-T is available at Aetrix Electronics and suitable for industrial panel meters, LED signage modules, automated test equipment displays, and medical device status indicators requiring stable component supply across multi-year production cycles.

Supply support for A6278ELP-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 and manufacturer of high-performance magnetic sensors and power ICs, headquartered in Worcester, Massachusetts.

The A6278 product line targets LED display systems requiring robust current regulation, fault diagnostics, and thermal resilience - specifically engineered for industrial HMI, instrumentation, and safety-critical visual indicators.

FAQ

What is the maximum output current per channel for the A6278ELP-T?

The A6278ELP-T supports up to 90 mA per output channel when configured with appropriate R_EXT (e.g., 225 Ω). This value is specified under V_CE = 0.7 V and TA = 25 °C. Derating applies at higher ambient temperatures or duty cycles - see Figure 11 in the A6278-DS Rev. 10 datasheet for allowable current vs. DC curves. The A6278ELP-T maintains tight matching (±6%) across all eight outputs at any given R_EXT.

Does the A6278ELP-T support open-LED detection, and how is it implemented?

Yes, the A6278ELP-T implements open-LED detection by monitoring V_CE on each output. When an enabled output exhibits V_CE < 0.30 V (typical), it flags an open-circuit condition. Error bits are stored in the shift register and read back via SERIAL DATA OUT during dedicated test mode - requiring specific OE/LE/CLOCK sequencing per page 7 of the A6278-DS Rev. 10. This eliminates need for external sensing components.

What package type does the A6278ELP-T use, and what are its thermal characteristics?

The A6278ELP-T uses a 16-pin TSSOP package with exposed thermal pad (LP suffix). Its thermal resistance R_θJA is 34 °C/W on a 4-layer JEDEC board. The exposed pad (EP) must be soldered to a copper plane with thermal vias for optimal heat dissipation. At 85 °C ambient, maximum continuous output current is ~45 mA per channel at 100% duty cycle - consult Figure 11 in A6278-DS Rev. 10 for full derating curves.

Can the A6278ELP-T be cascaded with other devices, and how is that achieved?

Yes, the A6278ELP-T supports daisy-chaining via its CMOS SERIAL DATA OUT pin, which connects directly to the SERIAL DATA IN of the next device. Cascading preserves full 8-bit resolution per device and enables synchronized latching across multiple A6278ELP-T units using shared CLOCK and LATCH ENABLE signals. Up to 16 devices can be cascaded without signal degradation, provided trace lengths are impedance-controlled and terminated per Allegro's layout guidelines.

What is the purpose of the REXT pin on the A6278ELP-T, and how is current set?

The REXT pin on the A6278ELP-T connects to an external resistor that sets the constant-current magnitude for all eight outputs simultaneously. Current per channel follows IO ≈ 17.5 V / REXT (e.g., 75.5 mA typ. at REXT = 225 Ω). This single-resistor method ensures matched output currents without per-channel calibration. REXT must be connected to GND; floating or incorrect values cause undefined current levels or thermal shutdown.