Allegro MicroSystems A3948SLBTR

Overview

A3948SLBTR from Allegro MicroSystems is a discontinued 24-lead SOIC DMOS full-bridge PWM motor driver IC designed for bidirectional DC motor control with ±1.5 A continuous output current, 50 V load supply rating, and programmable mixed/fast/slow current-decay modes via 3-wire serial interface. It integrates synchronous rectification, thermal shutdown (165°C), UVLO (4.2 V), and internal charge pump for high-side gate drive - used in precision industrial actuators and embedded motion control systems.

For engineers reviewing the A3948SLBTR datasheet, A3948SLBTR pinout, A3948SLBTR application, or A3948SLBTR equivalent, key selection considerations include its fixed-off-time PWM architecture, VREF/RS-based current regulation (ITRIP = VREF/5RS or VREF/10RS), batwing SOIC thermal package (RθJA = 77°C/W), and serial-programmable blank time (4–24/fOSC) and decay timing.

Technical Context

The A3948SLBTR implements a fixed-off-time PWM current-control engine with programmable blank time (D0–D1), off-time (D2–D6), and fast-decay duration (D7–D10), all referenced to an external oscillator (1.8–6.1 MHz). Its serial port configures synchronous rectification mode (active/passive), enable logic (D14), phase logic (D15), and RANGE-selectable reference division (÷5 or ÷10).

Internal protection includes thermal shutdown with 15°C hysteresis, crossover-current prevention, and independent monitoring of CP and VREG rails. The device operates without special power-up sequencing and supports external PWM via PHASE/ENABLE inputs while retaining full serial configurability for internal PWM timing and decay behavior.

Key Specifications

Pinout & Package

Package: 24-lead plastic SOIC with copper batwing tab (exposed ground pad); thermal resistance RθJA = 77°C/W, RθJT = 6°C/W; power tab is at ground potential and requires no electrical isolation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar full-bridge PWM motor driver applications.

Compared with A3948SLBTR, TB6612FNG offers simpler implementation but sacrifices programmability and thermal headroom, while DRV8876N provides higher current and diagnostics at the cost of increased complexity and non-pin-compatible packaging.

Availability

A3948SLBTR is available at Aetrix Electronics and suitable for industrial actuators, embedded motion control, DC motor braking systems, and lab equipment positioning requiring stable component supply despite end-of-life status.

Supply support for A3948SLBTR 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 sensors and power ICs, specializing in motion control, current sensing, and motor driver solutions.

The A3948 product line was engineered for precision PWM-controlled DC motor applications demanding programmable current decay, integrated gate drive, and robust thermal protection in industrial and instrumentation environments.

FAQ

What is the maximum continuous output current rating for the A3948SLBTR?

The A3948SLBTR has a ±1.5 A continuous output current rating per channel under specified thermal conditions (TA = 25°C, adequate PCB copper). This rating assumes proper heat sinking via the exposed batwing ground tab and adherence to RθJA = 77°C/W. Exceeding this current may trigger thermal shutdown at 165°C junction temperature, and actual achievable current depends on ambient temperature, duty cycle, and PCB layout.

Does the A3948SLBTR support external PWM speed control?

Yes, the A3948SLBTR supports external PWM speed control using the PHASE and ENABLE inputs. When configured via serial bit D13, ENABLE can be used to chop the bridge in fast or slow decay mode independently of the internal PWM timer. PHASE controls direction, allowing full bidirectional speed modulation without reprogramming the serial interface during operation.

How does the A3948SLBTR implement current regulation?

The A3948SLBTR regulates motor current using an internal fixed-off-time PWM controller that compares the voltage across an external sense resistor (RS) to a divided VREF. Depending on RANGE and serial bit D16, ITRIP equals VREF/5RS or VREF/10RS. At the trip point, the source driver turns off and current recirculates for a programmable off-time - enabling precise, adjustable current limiting without external op-amps or comparators.

What is the purpose of the CP, CP1, and CP2 pins on the A3948SLBTR?

The CP, CP1, and CP2 pins form the charge pump network that generates a gate drive voltage higher than VBB for the high-side (source) DMOS transistors. CP connects to VBB through a 0.22 µF reservoir capacitor, while CP1 and CP2 connect to a 0.22 µF flying capacitor. This circuit enables full enhancement of the N-channel high-side FETs without requiring a bootstrap capacitor or external high-voltage supply - critical for reliable 50 V operation.

Is the A3948SLBTR still recommended for new designs?

No, the A3948SLBTR is a discontinued product and should not be purchased for new design applications. Allegro MicroSystems declared it obsolete as of April 28, 2007, with no samples available. While Aetrix Electronics maintains legacy supply for existing production, engineers are advised to evaluate alternatives like the DRV8876N or TB6612FNG for new projects requiring similar functionality and reliability.