Allegro MicroSystems A8518KLPTR-T-1

Overview

A8518KLPTR-T-1 from Allegro MicroSystems is a discontinued automotive-grade LED driver IC designed for dual-string LCD backlighting in infotainment and instrument clusters. It integrates a 2.15 MHz current-mode boost converter with internal 42 V MOSFET, two matched 200 mA LED current sinks, and fault-tolerant protection including OVP, OTP, LED short/open detection, and input overcurrent shutdown. It operates from 4.5–40 V input and supports PWM+analog dimming for 100,000:1 contrast ratio.

For engineers reviewing the A8518KLPTR-T-1 datasheet, A8518KLPTR-T-1 pinout, A8518KLPTR-T-1 application, or A8518KLPTR-T-1 equivalent, key selection considerations include its fixed 2.15 MHz switching frequency (no dithering), –40°C to +125°C AEC-Q100 qualified operation, 16-pin TSSOP package with exposed thermal pad, and absence of frequency dithering compared to A8518KLPTR-T.

Technical Context

The A8518KLPTR-T-1 implements a current-mode boost topology with cycle-by-cycle current limiting and soft-start ramp control. Its dual LED current sinks are trimmed to 0.7% accuracy per channel and 0.8% matching, enabling precise brightness control across strings without external sensing resistors per channel.

It features integrated protection logic for VOUT-to-GND short detection via optional P-channel MOSFET gate drive, overvoltage protection triggered at 8.3 V on the OVP pin (±5% accuracy), and thermal shutdown at 170°C with 20°C hysteresis. The device latches off during input overcurrent faults but retries autonomously after undervoltage protection (UVP) faults clear.

Key Specifications

Pinout & Package

Package: 16-pin TSSOP with exposed thermal pad (suffix LP); thermal pad must be connected to PCB ground plane using ≥8 vias for reliable power dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with A8518KLPTR-T-1, AL8863T-13 offers lower integration and no automotive qualification, while LM3409QMY/NOPB provides greater frequency flexibility but requires full external power stage design and lacks built-in dual-string current regulation.

Availability

A8518KLPTR-T-1 is available at Aetrix Electronics and suitable for automotive infotainment backlighting, instrument cluster illumination, and center stack display applications requiring stable component supply despite end-of-life status.

Supply support for A8518KLPTR-T-1 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 sensors and power ICs, specializing in automotive and industrial motion control and power management solutions.

The A8518 product line was developed specifically for fault-tolerant, high-brightness LCD backlighting in automotive cockpits, emphasizing AEC-Q100 compliance, wide-input operation, and integrated protection against real-world electrical faults.

FAQ

What is the key functional difference between A8518KLPTR-T-1 and A8518KLPTR-T?

The A8518KLPTR-T-1 lacks the boost switching frequency dithering feature present in A8518KLPTR-T. This means A8518KLPTR-T-1 operates at a strict 2.15 MHz fixed frequency without modulation, resulting in higher peak EMI but simpler EMI filter design. All other electrical specifications, pinout, package, and protection features are identical between the two variants.

Is A8518KLPTR-T-1 still available for new designs?

No - A8518KLPTR-T-1 is a discontinued product. Allegro MicroSystems explicitly states it "should not be purchased for new design applications" and that samples are no longer available. Aetrix Electronics supports legacy procurement and last-time buy programs, but design-in for new projects is not recommended.

How does the A8518KLPTR-T-1 achieve 100,000:1 LED dimming ratio?

The A8518KLPTR-T-1 achieves 100,000:1 dimming only when combining PWM dimming (e.g., 100 Hz) with analog current scaling via the APWM pin. PWM alone delivers 10,000:1. The APWM pin accepts a digital signal (40–1000 kHz) whose duty cycle inversely controls ISET current - e.g., 25% APWM duty cycle reduces full-scale LED current by 25%, extending effective dimming range beyond PWM limits.

What protection features does A8518KLPTR-T-1 provide against LED string faults?

A8518KLPTR-T-1 detects and responds to LED open circuits, LED short-to-GND, and LED short-to-VOUT conditions. During startup, it checks LEDx pin voltages: <70 mV indicates short-to-GND (halts startup); ~150 mV indicates unused pin (removes from regulation); >325 mV confirms active string. Faults trigger FAULT pin assertion and may cause latch-off (e.g., input OCP) or auto-retry (e.g., OVP).

Can A8518KLPTR-T-1 drive more than 200 mA per LED string?

Yes - A8518KLPTR-T-1 supports paralleling LED1 and LED2 current sinks to deliver up to 400 mA total LED current. This requires connecting both LEDx pins to the same cathode net and configuring the ISET resistor for 400 mA (e.g., RISET ≈ 3.57 kΩ). Thermal design must accommodate doubled power dissipation in the IC's exposed pad and PCB layout.