Allegro MicroSystems A8435EESTR-T

Overview

A8435EESTR-T from Allegro MicroSystems is a high-efficiency fractional charge pump white LED driver IC designed for portable display backlighting. It delivers up to 30 mA per channel across four regulated current sinks, supports 1×/1.5× adaptive voltage conversion, achieves >92% peak efficiency, and operates from 2.7–5.5 V input-optimized for Li-ion battery-powered handheld devices.

For engineers reviewing the A8435EESTR-T datasheet, A8435EESTR-T pinout, A8435EESTR-T application, or A8435EESTR-T equivalent, key selection criteria include its 0.5% LED current matching, 1 MHz switching frequency, flexible dimming (serial 11-level, 2-bit parallel, PWM), thermal shutdown at 165°C, and QFN/MLP-16 (3 × 3 mm, 0.75 mm height) package compatibility with space-constrained PCB layouts.

Technical Context

The A8435EESTR-T implements a proprietary adaptive control scheme that dynamically selects between 1× (bypass) and 1.5× charge pump modes based on LED forward voltage and input supply, maximizing efficiency across the full Li-ion discharge curve (2.7–4.2 V). Its internal current mirrors maintain tight regulation without external feedback loops.

It integrates soft-start (2 ms), overvoltage protection (5.74 V), short-circuit protection, and thermal shutdown (165°C with 20°C hysteresis). Dimming is implemented via three independent methods-serial single-wire (11 levels), 2-bit parallel (4 states), or external PWM-each mapped to distinct pin configurations (CTRL, EN1, EN2) with defined logic thresholds and timing constraints.

Key Specifications

Pinout & Package

The A8435EESTR-T is housed in a lead-free 3 × 3 mm QFN/MLP-16 package (suffix ES) with 0.75 mm nominal height and exposed thermal pad (EP) for enhanced heat dissipation. The package complies with JEDEC MO-220WEED and IPC-7351 land pattern standards.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AL8862T-13 and TPS61165DRVR, the A8435EESTR-T offers superior integration (capacitor-only solution), thinner profile (0.75 mm), and tighter current matching (±0.5% vs. ±1.5–2%), making it optimal for space-constrained portable backlighting-but lacks the higher output voltage headroom of inductive boost alternatives.

Availability

A8435EESTR-T is available at Aetrix Electronics and suitable for cellular phone backlighting, digital camera displays, portable audio UI illumination, and WLED flash/torch applications requiring stable component supply during transition from legacy designs.

Supply support for A8435EESTR-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 power ICs, magnetic sensors, and motor driver solutions for automotive, industrial, and consumer markets.

The A8435EESTR-T belongs to Allegro's white LED driver product line, engineered specifically for energy-efficient, space-optimized backlighting in battery-powered portable electronics with stringent thickness and thermal constraints.

FAQ

What is the recommended capacitor type and value for C1 and C2 in the A8435EESTR-T circuit?

X5R or X7R ceramic capacitors rated at 1 µF are recommended for C1 and C2 in the A8435EESTR-T circuit. These dielectrics provide stable capacitance over temperature and DC bias, ensuring reliable 1.5× charge pump operation. The datasheet specifies 1 µF as the standard value for both capacitors in typical applications, and using lower values may degrade efficiency or cause instability under load.

Can the A8435EESTR-T drive fewer than four LEDs, and how should unused LED pins be handled?

Yes, the A8435EESTR-T can drive 1–4 LEDs, but LED3 must always be connected. Unused LED pins (e.g., LED1, LED2, or LED4) must be tied to either VIN or VOUT-not left floating-to prevent leakage current or undefined behavior. When tied to VIN or VOUT, each unused pin sinks ~30 µA in enabled state, ensuring predictable shutdown and dimming behavior across all configurations.

What is the function of the CTRL pin on the A8435EESTR-T, and how does it affect dimming mode selection?

The CTRL pin on the A8435EESTR-T selects the dimming interface: when open or pulled HIGH, it enables 2-bit parallel or PWM dimming via EN1/EN2; when grounded, it activates single-wire serial dimming on EN1 (11 brightness levels). Leaving CTRL unconnected risks undefined operation, so it must be explicitly tied to VIN, GND, or left open with proper noise immunity-never floating.

Does the A8435EESTR-T support analog dimming via the ISET pin, or is dimming exclusively digital?

The A8435EESTR-T does not support analog dimming via the ISET pin; ISET sets only the full-scale current reference (e.g., 30 mA per LED) using an external resistor. All dimming is digital-via 2-bit parallel inputs (EN1/EN2), external PWM applied to EN1, or serial pulses on EN1 (when CTRL = GND). No analog voltage or current modulation is supported on ISET for brightness control.

What is the thermal performance of the A8435EESTR-T, and how does the exposed pad (EP) impact junction temperature?

The A8435EESTR-T has a junction-to-ambient thermal resistance (θ_JA) of 47 °C/W on a 4-layer JEDEC-standard PCB when the exposed pad (EP) is soldered to a solid ground plane. Without proper EP connection, thermal performance degrades significantly-potentially exceeding the 150°C maximum junction limit under 120 mA load. Thermal vias under EP are strongly recommended to maintain safe operation in continuous flash/torch mode.