Allegro MicroSystems A8509GLPTR-T

Overview

A8509GLPTR-T from Allegro MicroSystems is a 4-channel fault-tolerant white LED driver IC for LCD backlighting, integrating a current-mode boost controller and four independent high-accuracy current sinks. It operates from 9–40 V input, delivers up to 300 mA per channel, supports PWM/analog dimming, and features active current sharing (0.7% accuracy, 0.8% matching) and comprehensive protection including open/short LED detection, overvoltage, and thermal shutdown. It targets automotive and industrial LCD displays requiring robust, scalable backlight power.

For engineers reviewing the A8509GLPTR-T datasheet, A8509GLPTR-T pinout, A8509GLPTR-T application, or A8509GLPTR-T equivalent, this page provides verified technical context, validated pin functions, confirmed thermal and electrical specifications, real-world dimming timing data (tdPWM(on) ≤ 1.1 µs), and two documented alternative parts with precise functional and application differences.

Technical Context

The A8509GLPTR-T implements a fixed-frequency current-mode boost architecture with an integrated gate driver capable of driving external N-channel MOSFETs, enabling scalable LED string voltage via adjustable switching frequency (300–800 kHz) set by RFSET or synchronized externally. Its four current sinks operate independently or in parallel, with active current sharing enabled via MODE pin configuration.

It incorporates dual-level pulse-by-pulse current limiting (VSWSS(LIM) = 39 mV during soft-start; ISW(LIM) in normal operation), LED pin short-to-GND detection (<100 mV threshold), and programmable overvoltage protection (VOVP(th) = 1.25 V typical, set via ROVP). The IC uses separate AGND and PGND pins, includes internal LDO (VDD = regulated output), and supports single-supply operation at VIN = 12 V or 24 V.

Key Specifications

Pinout & Package

Package: 24-pin TSSOP with exposed thermal pad (LP package); RoHS-compliant, 100% matte tin leadframe plating; requires minimum 8 vias connecting PAD to ground plane for thermal integrity.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 4-channel LED driver applications.

Compared with A80604KESJSR, the A8509GLPTR-T offers identical pinout and core functionality but lacks AEC-Q100 qualification and has higher sleep current; versus LM3409QMYX/NOPB, it delivers integrated 4-channel regulation and fault diagnostics at the cost of topology flexibility and external component count.

Availability

A8509GLPTR-T is available at Aetrix Electronics and suitable for automotive instrument clusters, industrial HMI displays, medical diagnostic monitors, and avionics display systems requiring stable component supply despite its discontinued status for new designs.

Supply support for A8509GLPTR-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 semiconductor company specializing in high-performance magnetic sensing, power ICs, and motor driver solutions for automotive, industrial, and consumer markets.

The A8509 product line was designed specifically for fault-tolerant, multi-string LCD backlighting in harsh environments - emphasizing thermal resilience, channel-matching precision, and integrated protection for mission-critical displays.

FAQ

Is the A8509GLPTR-T still available for purchase, and what is its production status?

Yes, A8509GLPTR-T is available through Aetrix Electronics for legacy support and repair applications. However, Allegro MicroSystems officially discontinued the A8509GLPTR-T for new design-in as of September 30, 2024. It is no longer in production, and samples are unavailable. Customers developing new products should consider the recommended substitution A80604KESJSR.

What is the maximum LED current per channel supported by the A8509GLPTR-T?

The A8509GLPTR-T supports up to 300 mA per LED channel, set precisely via the external RISET resistor. At this level, the device maintains ±0.7% current accuracy and 0.8% matching between all four channels. The actual achievable current depends on thermal design - with proper PCB layout using the exposed thermal pad, full 300 mA per channel is sustainable at 105°C ambient.

How does the A8509GLPTR-T handle LED string faults such as open or short circuits?

The A8509GLPTR-T actively monitors each LEDx pin for open or short conditions. An LED pin voltage below 100 mV indicates a short-to-GND, halting startup until resolved. An open LED is detected via VLEDSC = 4.6 V threshold. Upon fault detection, the FAULT pin pulls low, and the affected channel exits regulation without disrupting other strings - preserving partial backlight functionality.

Can the A8509GLPTR-T be synchronized to an external clock, and what are the timing requirements?

Yes, the A8509GLPTR-T supports external synchronization via the FSET/SYNC pin. The clock must be push-pull type, 1.5–3.3 V amplitude, with minimum on-time (tPWSYNCON) and off-time (tPWSYNCOFF) of 150 ns each. At 800 kHz, this corresponds to 19–85% duty cycle compatibility. If the clock is lost, the IC automatically reverts to its RFSET-set frequency within ~5 µs.

What thermal design considerations are critical for reliable operation of the A8509GLPTR-T?

Reliable operation of the A8509GLPTR-T requires strict adherence to thermal guidelines for its 24-pin TSSOP (LP) package: the exposed PAD must be soldered to the PCB ground plane using ≥8 thermal vias directly under the pad. This achieves the specified RθJA = 28 °C/W. Failure to implement this results in junction temperature exceeding 150°C at moderate load, triggering thermal shutdown (TSD = 165°C) and system instability.