Allegro MicroSystems A3903EEETR-T

Overview

A3903EEETR-T from Allegro MicroSystems is a discontinued low-voltage bidirectional DC motor driver IC in an 8-lead DFN package, delivering up to 500 mA output current with adjustable constant-voltage regulation across the motor coil. It operates from 3–5.5 V supply, supports forward/reverse/brake/standby modes via dual logic inputs, and integrates thermal shutdown, UVLO, and shoot-through protection. Used in portable printers, robotic actuators, and camera lens control.

For engineers reviewing the A3903EEETR-T datasheet, A3903EEETR-T pinout, A3903EEETR-T application, or A3903EEETR-T equivalent, key selection considerations include its regulated source-side linear operation, <500 nA standby current, 2 mm × 2 mm footprint, –40°C to +85°C operating range, and discontinuation status requiring transition planning.

Technical Context

The A3903EEETR-T implements a full-bridge output stage with source-side linear regulation to maintain precise motor coil voltage (VOUT = 4 × VREF × R2/(R1+R2)), where VREF is a 1.285 V bandgap reference. This architecture eliminates I×RDS(on) and battery voltage variation effects on motor voltage.

Control logic interprets IN1/IN2 states for four functional modes: standby (both low), forward (IN1 high, IN2 low), reverse (IN1 low, IN2 high), and high-side brake (both high). Thermal shutdown activates at 165°C with 15°C hysteresis, and undervoltage lockout triggers below 2.6 V with 120 mV hysteresis.

Key Specifications

Pinout & Package

The A3903EEETR-T is housed in an 8-lead, 2 mm × 2 mm, 0.55 mm nominal height DFN package with exposed thermal pad (suffix EE), RoHS-compliant and lead-free.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-voltage DC motor driver applications.

Compared with A3903EEETR-T, the A3906SESTR-T offers direct replacement capability with broader voltage support and lower thermal resistance, while the TB6612FNG provides higher current capacity at the cost of regulation precision and standby efficiency-making the choice dependent on whether voltage stability or peak drive strength is the primary design constraint.

Availability

A3903EEETR-T is available at Aetrix Electronics and suitable for robotic actuators, portable printers, and camera lens control requiring stable component supply despite its discontinued status-inventory is limited and intended for legacy system support and repair.

Supply support for A3903EEETR-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 designer and manufacturer of high-performance Hall-effect sensors, motor drivers, and power ICs, founded in 1989 and headquartered in Manchester, NH.

The A3903 belongs to Allegro's low-voltage motor driver product line, engineered specifically for precision motion control in space- and power-constrained portable electronics where regulated coil voltage and nanoscale standby current are critical.

FAQ

Is the A3903EEETR-T still in production?

No, the A3903EEETR-T is a discontinued product. Allegro MicroSystems declared it End-of-Life in July 2020, and it is no longer manufactured. Aetrix Electronics holds remaining inventory for legacy support, but new designs should migrate to the recommended substitute A3906SESTR-T. The A3903EEETR-T datasheet remains publicly accessible on Allegro's website for reference and repair use.

What is the function of the VSET and VREF pins on the A3903EEETR-T?

The VREF pin outputs a stable 1.285 V bandgap reference used internally for voltage regulation. The VSET pin accepts an external voltage (typically derived from VREF via a resistor divider) to set the regulated motor coil voltage: VOUT = 4 × VREF × R2/(R1+R2). For the A3903EEETR-T, adjusting VSET between 500 mV and 1.2 V configures motor output from 2 V to 4.8 V, enabling precise speed control without closed-loop feedback.

Can the A3903EEETR-T be used in PWM motor control applications?

Yes, the A3903EEETR-T supports PWM operation in two ways: (1) external PWM applied to IN1/IN2 inputs for enable chopping (current control via duty cycle), and (2) internal voltage regulation with optional PWM override by connecting VREF directly to VSET. In enable chopping mode, the A3903EEETR-T alternates between forward/reverse and brake states to regulate average winding current-ideal for torque-controlled micro-actuators.

What thermal design considerations apply to the A3903EEETR-T?

The A3903EEETR-T requires careful thermal management due to its 49°C/W junction-to-ambient thermal resistance. Its exposed thermal pad must be soldered to a large PCB ground plane with multiple thermal vias. Layout must follow Allegro's recommended land pattern (IPC-7351 SON50P200X200X100-9M), and bulk capacitance (10 µF) plus local 0.1 µF ceramic must be placed near VDD. Without proper thermal design, the A3903EEETR-T will trigger thermal shutdown above 165°C junction temperature.

How does the A3903EEETR-T implement brake mode, and what precautions are needed?

The A3903EEETR-T enters high-side brake mode when both IN1 and IN2 are driven high, turning on both source drivers (OUTA and OUTB high) to short the motor coil through the upper switches. Unlike low-side braking, this mode lacks current limiting-peak current is only constrained by motor inductance and total RDS(on) (~1.2 Ω). To prevent damage, users must ensure motor back-EMF and supply voltage do not cause instantaneous current to exceed the A3903EEETR-T's 500 mA absolute maximum rating.