Allegro MicroSystems APM80905KNBATR

Overview

The APM80905KNBATR from Allegro MicroSystems is a 36 V, 4 A, ASIL B–qualified synchronous buck LED driver module with integrated high- and low-side N-channel MOSFETs, programmable PWM monitoring, analog dimming (ADIM), and an open-drain fault flag (FFn). It delivers regulated current to drive infrared or standard LED strings in automotive driver monitoring systems, with ultra-low EMI via spread-spectrum switching and internal EMI-mitigation capacitors.

For engineers reviewing the APM80905KNBATR datasheet, APM80905KNBATR pinout, APM80905KNBATR application, or APM80905KNBATR equivalent, key selection considerations include its 24-pin wettable-flank QFN package, 400 kHz–2.2 MHz programmable switching frequency, 195 mV typical current sense voltage (VCSREG), safety diagnostics for ASIL B compliance, and dual PWM on-time/duty cycle fault monitoring for eye-safe operation.

Technical Context

The APM80905KNBATR employs fixed adaptive on-time control architecture with external resistor-programmable t_ON (via TON pin), enabling input- and load-dependent switching frequency tuning. Its integrated current-mode regulation maintains precise LED current using differential sensing across CSH/CSL pins with 195 mV nominal reference voltage.

Safety-critical operation is enforced by independent, resistor-configurable PWM monitors: TMAX sets maximum safe on-time (0.25–5.0 ms range), while DMAX enforces minimum off-time (0.82–19 ms) to limit duty cycle. Fault detection triggers active-low FFn assertion and disables LED current within 60 µs (typical deglitch timer).

Key Specifications

Pinout & Package

APM80905KNBATR is housed in a compact, thermally optimized 24-pin QFN package (4 mm × 4 mm × 2 mm) with wettable flank and dual exposed pads: PAD1 soldered to VIN for power delivery, PAD2 soldered to PGND for thermal dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM3409QMH/NOPB and TPS92692QPWPRQ1, the APM80905KNBATR delivers higher integration (full power stage + safety monitors), lower EMI (integrated capacitors + spread spectrum), and smaller footprint (4 mm × 4 mm QFN), making it optimal for space-constrained, safety-critical automotive LED drivers.

Availability

APM80905KNBATR is available at Aetrix Electronics and suitable for driver monitoring systems, advanced driver assistance systems, and instrument clusters requiring stable component supply, automotive-grade reliability, and ASIL B compliance.

Supply support for APM80905KNBATR 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, specializing in automotive and industrial motion control solutions.

The APM80905KNBATR belongs to Allegro's ASIL B–qualified LED driver product line, engineered specifically for eye-safe, fault-monitored infrared illumination in driver monitoring and ADAS applications.

FAQ

What is the maximum input voltage rating for the APM80905KNBATR?

The APM80905KNBATR has an absolute maximum input voltage rating of 42 V for transient conditions (e.g., automotive load dump), with continuous operation supported from 4.5 V to 36 V. This range accommodates cold-crank events and standard 12 V/24 V vehicle electrical systems. Exceeding 42 V may cause permanent damage, as specified in the Absolute Maximum Ratings table.

How does the APM80905KNBATR implement eye-safety protection for infrared LED drivers?

The APM80905KNBATR implements eye-safety protection via two independent, resistor-programmable PWM monitors: TMAX limits maximum on-time (0.25–5.0 ms), and DMAX enforces minimum off-time (0.82–19 ms) to cap duty cycle. When either limit is exceeded, the device asserts the FFn pin low and disables LED current within 60 µs, ensuring compliance with IEC 62471 and automotive functional safety requirements.

Can the APM80905KNBATR drive multiple LEDs in series, and how is output voltage managed?

Yes, the APM80905KNBATR automatically adjusts output voltage to drive one or multiple LEDs in series by regulating current through the CSH/CSL sense resistor. The buck converter's duty cycle adapts to maintain 195 mV across R_SENSE, allowing output voltage to scale up to VIN – V_SW(LS) × I_LED, supporting strings requiring up to ~32 V at 4 A. Minimum/maximum output voltage is constrained by t_ON(MIN) and t_OFF(MIN).

What thermal performance can be expected from the APM80905KNBATR in a standard 4-layer PCB layout?

In a JEDEC-standard 4-layer PCB layout, the APM80905KNBATR achieves a junction-to-ambient thermal resistance (R_θJA) of 43°C/W. With its exposed VIN and PGND pads soldered to internal copper planes, the device sustains 4 A output current at ambient temperatures up to +85°C without forced airflow. Thermal shutdown activates at 165°C (typ), with 25°C hysteresis for automatic recovery.

Does the APM80905KNBATR support both analog and PWM dimming simultaneously?

Yes, the APM80905KNBATR supports simultaneous analog and PWM dimming: ADIM sets baseline current level (20–100%), while PWM modulates that level at high frequency. For example, setting ADIM to 0.925 V yields 50% current, then applying 50% duty-cycle PWM results in 25% average LED output. This dual-mode capability enables fine-grained brightness control and thermal foldback without sacrificing dimming resolution.