Allegro MicroSystems A8431EEHTR-T

Overview

A8431EEHTR-T from Allegro MicroSystems is a constant-current, noninverting boost DC-DC converter IC designed to drive white LEDs in series or parallel configurations. It delivers up to 32 V output with programmable current up to 20 mA per string, operates from 2.5–10 V input, features 1.2 MHz switching frequency, integrated 300 mA power switch, and built-in overvoltage protection (OVP) with 32 V typical rising threshold.

For engineers reviewing the A8431EEHTR-T datasheet, A8431EEHTR-T pinout, A8431EEHTR-T application, or A8431EEHTR-T equivalent, key selection criteria include its 6-pin MLP/DFN package, 95 mV feedback reference, shutdown current of 1 μA, OVP functionality eliminating external Zener diodes, and suitability for space-constrained portable LED backlighting designs requiring stable current regulation.

Technical Context

The A8431EEHTR-T employs a constant-frequency, current-mode control architecture with internal ramp generation and error amplification to regulate LED current via feedback at the FB pin referenced to 95 mV. Its low-side N-channel MOSFET switch integrates 350 mV saturation voltage and 300 mA current limit, enabling efficient step-up conversion without external sense FETs.

Overvoltage protection is implemented through dedicated OVP pin monitoring SW node voltage; when exceeding 28–35 V (rising), the switch disables until voltage falls below 27.5–34.5 V (falling), providing hysteresis of 0.5 V. Dimming is supported via analog voltage injection at FB or PWM on EN pin, with full brightness at 0% duty cycle when filtered PWM is applied.

Key Specifications

Pinout & Package

The A8431EEHTR-T is housed in a 2 mm × 3 mm, 0.75 mm nominal height, 6-pin MLP/DFN package (suffix EH) with exposed thermal pad for enhanced heat dissipation. Lead-free with 100% matte tin plating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX8630YETA+ and TPS61160DRVR, the A8431EEHTR-T offers unique OVP pin flexibility (enabling/disabling via grounding), wider 2.5 V minimum input for aging batteries, and proven integration in legacy portable designs - though newer alternatives provide higher integration or better thermal metrics.

Availability

A8431EEHTR-T is available at Aetrix Electronics and suitable for LED backlighting, portable battery-powered equipment, and mobile GPS systems requiring stable component supply despite end-of-life status.

Supply support for A8431EEHTR-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 A8431 belongs to Allegro's white LED driver product line, engineered specifically for compact, high-efficiency constant-current boost conversion in battery-powered portable electronics with stringent size and thermal constraints.

FAQ

What is the minimum input voltage required for A8431EEHTR-T to drive four white LEDs?

The A8431EEHTR-T can drive up to four white LEDs at 20 mA from a 2.5 V supply, as confirmed in the official datasheet. At this input voltage, the device maintains regulation by boosting to ~12–14 V (depending on LED forward voltage), leveraging its 32 V OVP headroom and 300 mA switch current limit. Operation below 2.5 V is outside specification and may result in dropout or unstable regulation.

Does A8431EEHTR-T support PWM dimming, and how is it implemented?

Yes, A8431EEHTR-T supports PWM dimming via its EN pin: applying a 1–10 kHz PWM signal directly toggles the IC between full-on and shutdown states, scaling average LED current linearly with duty cycle. Full brightness occurs at 100% duty cycle; 0% duty cycle turns off the LEDs. This method avoids color shift and preserves current accuracy, unlike analog dimming which modulates the FB reference.

Can A8431EEHTR-T drive more than one string of LEDs, and what are the layout requirements?

Yes, A8431EEHTR-T can drive up to two parallel strings of LEDs (e.g., two strings of eight LEDs each at 20 mA), provided each string has identical LED count and forward voltage. Layout requires matched trace lengths and separate Kelvin connections from each string's sense resistor to the FB and GND pins to ensure current balance; mismatched impedances cause unequal current sharing and brightness variation.

What is the purpose of the OVP pin on A8431EEHTR-T, and how should it be connected?

The OVP pin on A8431EEHTR-T monitors the SW node voltage to detect overvoltage conditions caused by LED open-circuit failure. It must be connected directly to the output capacitor (C2) to enable protection; if left floating, behavior is undefined. To disable OVP, tie the pin to GND. The internal hysteresis (0.5 V) prevents oscillation during recovery, eliminating need for external Zener clamping components.

Is A8431EEHTR-T still in production, and what does "Last Time Buy" mean for design use?

No, A8431EEHTR-T is classified as Last Time Buy with final order deadline April 30, 2010. It is obsolete and no longer in production. Aetrix Electronics supplies remaining inventory for existing customer applications only; new designs should select active alternatives like TPS61160DRVR or MAX20446, as samples and long-term supply cannot be guaranteed for A8431EEHTR-T.