Allegro MicroSystems A3907ECGTR

Overview

A3907ECGTR from Allegro MicroSystems is a low-voltage, I²C-controlled voice coil motor (VCM) driver IC designed for linear current control in compact autofocus actuators. It delivers peak output current up to 102.3 mA, operates from 2.3 V to 5.5 V, integrates a 10-bit DAC with 100 µA LSB resolution, and features thermal shutdown, UVLO, and internal flyback clamping. It is used in smartphone camera focus modules requiring precise, low-power actuator control.

For engineers reviewing the A3907ECGTR datasheet, A3907ECGTR pinout, A3907ECGTR application, or A3907ECGTR equivalent, key selection criteria include its WLCSP-6 package footprint, fixed-threshold I²C interface (VIH = 1.26 V, VIL = 0.84 V), ramp-controlled slew rate programming, sleep-mode current <500 nA, and guaranteed monotonic 10-bit DAC performance across –40°C to +85°C.

Technical Context

The A3907ECGTR implements a digitally programmable current sink using an integrated 10-bit DAC and precision current-output stage, where output current is calculated as I_OUT = DAC code × 100 µA (code 1–1023). Its I²C slave address supports four options (0x18/0x1A/0x1C/0x1E), and logic thresholds are voltage-independent-fixed at ~1 V-enabling interoperability with host controllers operating at different supply voltages.

Internal protection includes undervoltage lockout (UVLOth = 2.295 V, hysteresis = 100 mV), thermal shutdown at 165°C with 15°C recovery hysteresis, and a clamp diode from IOUT to VDD. Slew rate is configurable via four timing bits (T3–T0), enabling single-step, two-step, or ramped transitions between DAC codes with step delays from 781 ns to 200 µs.

Key Specifications

Pinout & Package

Package: 6-bump Wafer-Level Chip Scale Package (WLCSP), 0.8 mm × 0.8 mm, 0.4 mm pitch, bottom-side solder bumps.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar voice coil motor driver applications.

Compared with DRV2605L and BU21022KV, the A3907ECGTR delivers superior linearity (±4 LSB INL vs. typical ±12 LSB), finer current resolution (100 µA vs. 312 µA), and dedicated VCM ramp control-making it the optimal choice for optical autofocus demanding micron-level repeatability and minimal mechanical noise.

Availability

A3907ECGTR is available at Aetrix Electronics and suitable for smartphone camera modules, medical endoscopes, and AR/VR micro-display systems requiring stable component supply, long-term manufacturability, and automotive-grade reliability screening.

Supply support for A3907ECGTR 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 sensing and power IC solutions, headquartered in Worcester, Massachusetts.

The A3907 product line targets compact, battery-powered optical actuation-specifically engineered for linear voice coil motor control in mobile imaging with emphasis on low quiescent current, small footprint, and robust protection.

FAQ

What is the absolute maximum supply voltage for the A3907ECGTR?

The A3907ECGTR has an absolute maximum supply voltage (VDD) of 6 V. Operation above this rating risks permanent damage. The recommended operating range is 2.3 V to 5.5 V, and UVLO activates at 2.295 V (rising) with 100 mV hysteresis. Exceeding 6 V-even momentarily-may degrade the internal clamp diode or oxide layers. Always verify input rail stability and transient suppression in the host system before deploying the A3907ECGTR.

Does the A3907ECGTR support multiple I²C addresses, and how are they selected?

Yes, the A3907ECGTR supports four fixed I²C slave addresses: 0x18, 0x1A, 0x1C, and 0x1E. Address selection is determined by the state of two external pins (ADDR0 and ADDR1) tied to VDD or GND-though these pins are not exposed in the WLCSP-6 package of the A3907ECGTR. Instead, Allegro assigns address variants at wafer sort; the A3907ECGTR is factory-configured to one of these four addresses. Users must confirm the assigned address via device readback or datasheet revision notes prior to firmware integration.

How does the slew rate control work in the A3907ECGTR, and what timing options are available?

The A3907ECGTR uses four dedicated bits (T3–T0) in its I²C control register to configure slew rate timing. These bits define step delay intervals ranging from 781 ns to 200 µs and select between single-step, two-step, or multi-step ramp methods. For example, T3–T0 = 1100 yields 50 µs between steps in a two-step transition. This feature prevents mechanical ringing in voice coil motors by limiting di/dt-critical for silent, jitter-free autofocus. All timing values are process- and temperature-compensated per Allegro characterization.

What is the minimum output voltage headroom required for linear operation of the A3907ECGTR?

The A3907ECGTR requires ≥350 mV headroom between VDD and the IOUT node voltage to maintain linear DAC accuracy and monotonicity. This is expressed as VDD − (IOUT × RLOAD) ≥ 0.35 V. If violated, the output enters saturation, causing current droop and nonlinearity. Designers must size the VCM coil resistance and select VDD accordingly-for instance, at 102.3 mA output, RLOAD must be ≤ (VDD − 0.35 V)/0.1023 A. This constraint is explicitly verified in the A3907ECGTR's electrical characteristics table.

Can the A3907ECGTR drive bidirectional voice coil motors, or is it limited to unidirectional current sinking?

The A3907ECGTR is a unidirectional current sink only-it drives current from VDD through the VCM coil into the IOUT pin, which then sinks to GND. It cannot reverse polarity or source current. Bidirectional control requires either an H-bridge driver (e.g., A4950) or dual A3907ECGTR units with complementary coil connections. For autofocus applications-which rely on linear displacement proportional to current magnitude, not direction-the single-sink architecture is sufficient and reduces component count, PCB area, and power loss versus full-bridge solutions.