Allegro MicroSystems ALT80802KEJJTR

Overview

ALT80802KEJJTR from Allegro MicroSystems is a high-frequency, AEC-Q100-qualified LED driver IC supporting buck or buck-boost topology with integrated 150 mΩ N-channel MOSFET, 2 A output current capability, 3.8–50 V input range, and programmable switching frequency up to 2.5 MHz - designed for automotive lighting including daytime running lights and fog lamps.

For engineers reviewing the ALT80802KEJJTR datasheet, ALT80802KEJJTR pinout, ALT80802KEJJTR application, or ALT80802KEJJTR equivalent, key selection considerations include its buck-boost operation with ground-referenced EN/FFn, PWM dimming down to 15 µs on-time, dithered switching for AM-band EMI suppression, and integrated open-LED clamping in buck-boost mode.

Technical Context

The ALT80802KEJJTR employs current-mode control with internal slope compensation (3.1 A/µs at 2 MHz) to stabilize duty cycles above 50%, supports dual-mode operation via VSS pin configuration (buck: VSS = GND; buck-boost: VSS = LED−), and integrates level-shifting circuitry enabling ground-referenced enable and fault flag even in inverting topologies.

Its protection architecture includes pulse-by-pulse current limit (5.5 A typ), hiccup-mode short-circuit response with 6 ms retry timer, BOOT open/short detection, VIN UVLO (3.3 V start), thermal shutdown (170 °C), and internal clamp limiting output voltage to 18 V in buck-boost mode during open-LED faults.

Key Specifications

Pinout & Package

ALT80802KEJJTR is housed in a 10-pin DFN package with exposed thermal pad and wettable flank (suffix EJ), optimized for automotive PCB assembly and thermal performance (R_θJA = 45 °C/W on 4-layer JEDEC board).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM3409QMYX/NOPB and MAX20050ATP/V+T, ALT80802KEJJTR uniquely combines buck-boost topology flexibility, ground-referenced control in inverting mode, and integrated open-LED clamping - making it the only option among the three qualified for automotive interior lighting where output polarity and fault safety are co-constrained.

Availability

ALT80802KEJJTR is available at Aetrix Electronics and suitable for automotive lighting, industrial LED signage, and transportation display systems requiring stable component supply, AEC-Q100 compliance, and long-term production continuity.

Supply support for ALT80802KEJJTR 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 power ICs, magnetic sensors, and motor driver solutions for automotive and industrial markets.

The ALT80802KEJJTR belongs to Allegro's automotive-grade LED driver product line, engineered specifically for robust, EMI-compliant, and thermally efficient constant-current LED control in harsh vehicular environments.

FAQ

What topology modes does the ALT80802KEJJTR support, and how is mode selection implemented?

The ALT80802KEJJTR supports both buck and buck-boost topologies. Mode selection is determined solely by the connection of the VSS pin: in buck mode, VSS is tied to GND; in buck-boost mode, VSS serves as the negative output terminal (LED−). This pin-strapping method eliminates external configuration pins or registers, ensuring deterministic operation across temperature and voltage. The ALT80802KEJJTR's internal level shifter enables ground-referenced EN and FFn signals in either configuration - a key differentiator for automotive system integration.

How does the ALT80802KEJJTR handle open-LED faults in buck-boost configuration?

In buck-boost mode, the ALT80802KEJJTR incorporates an internal voltage clamp that limits output voltage to 18 V (typical) if the LED string opens. This prevents destructive overvoltage on downstream components such as freewheel diodes or output capacitors. The fault is detected when the CS pin voltage drops below 150 mV for more than 50 µs, triggering the FFn pin to assert low after the delay. Unlike buck-only drivers, this clamping action is active and specified - a critical safety feature for automotive lighting where open-circuit failures must be fail-safe.

What is the minimum PWM dimming on-time supported by the ALT80802KEJJTR, and how is it achieved?

The ALT80802KEJJTR supports a minimum PWM dimming on-time of 15 µs, enabled by its high-speed PWM comparator with 80 ns typical minimum on-time (t_ON(MIN)). This is achieved through optimized internal timing circuits and fast current-sense path propagation. During dimming, the COMP pin voltage is held steady during EN low periods, allowing immediate recovery to regulation upon re-enable - eliminating startup delays. This capability makes the ALT80802KEJJTR suitable for high-resolution dimming in adaptive front-lighting systems (AFS) and dynamic interior lighting.

Does the ALT80802KEJJTR require external components for bootstrap operation, and what are the requirements?

Yes, the ALT80802KEJJTR requires an external bootstrap capacitor between BST and SW pins. Allegro specifies a minimum capacitance of 0.22 µF, ceramic, placed as close as possible to the BST and SW pins. The capacitor must withstand ≥10 V rating due to charge pump operation. The internal bootstrap UVLO (1.8 V rising) monitors BST-to-SW voltage and disables the MOSFET if insufficient - preventing shoot-through. Failure to meet these requirements results in erratic switching or hiccup-mode faults, as documented in the Fault Table for "Boot capacitor open/short" conditions.

What protection features are integrated into the ALT80802KEJJTR, and how do they respond to a shorted freewheel diode?

The ALT80802KEJJTR integrates 12+ protection features including pulse-by-pulse current limit, hiccup-mode short-circuit response, BOOT fault detection, and freewheel diode open/short protection. For a shorted freewheel diode, the device detects excessive switch current, trips the secondary current limit (7.1 A typ) after two consecutive cycles, and enters hiccup mode with a 6 ms retry timer. This prevents thermal runaway and allows automatic recovery once the fault clears - a behavior explicitly confirmed in the Fault Table and validated per AEC-Q100 stress testing.