Allegro MicroSystems A3935KJP

Overview

A3935KJP from Allegro MicroSystems is a 48-pin LQFP three-phase power MOSFET controller designed for automotive high-power motor drives. It integrates six TTL-compatible gate drivers, a PFM boost converter (VBOOST ≈ 16 V), internal LDO-regulated VREG (12.7–14 V), bootstrap circuits for n-channel high-side FETs, and a differential current-sense amplifier (gain = 19.2 V/V) - enabling precise phase-current monitoring in electric power steering and HVAC blower systems.

For engineers reviewing the A3935KJP datasheet, A3935KJP pinout, A3935KJP application, or A3935KJP equivalent, this page delivers verified technical context, validated pin functions, real-world automotive use cases, and two confirmed alternative controllers with documented functional differences and selection guidance.

Technical Context

The A3935KJP implements a dedicated 3-phase gate driver architecture with independent high-side (GHA/GHB/GHC) and low-side (GLA/GLB/GLC) outputs, each supporting pulsed source/sink currents up to 800 mA at 25°C. Its integrated PFM boost converter maintains stable VBOOST (~16 V) across 7–40 V battery input, feeding an internal LDO that regulates VREG to 12.7–14 V for gate-drive supply - eliminating need for external high-voltage bias rails.

Fault protection includes real-time motor-lead diagnostics: short-to-battery detection via VDSTH-referenced VSX monitoring during low-side conduction, short-to-ground detection during high-side conduction, bridge-open (VDRAIN-based) faulting, and programmable VBAT overvoltage (19.4–40 V range via OVSET) with 9–15% hysteresis. All logic inputs are TTL-compatible with 2.0 V VI(1) min and 0.8 V VI(0) max.

Key Specifications

Pinout & Package

Package: 48-pin LQFP (exposed thermal pad), JEDEC MS-026 variant, body size 7 mm × 7 mm × 1.4 mm, pitch 0.5 mm. Thermal pad soldered to PCB ground plane for enhanced power dissipation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar three-phase gate driver applications.

Compared with MP6532DJ-LF-Z and TLE9201SG, the A3935KJP uniquely combines integrated PFM boost, analog-programmable VBAT overvoltage, and differential current sense in a single 48-pin LQFP - reducing external components and simplifying compliance with automotive transient immunity standards.

Availability

A3935KJP is available at Aetrix Electronics and suitable for electric power steering, HVAC blower motor control, engine cooling fan drives, and turbocharger actuator systems requiring stable component supply across extended temperature and voltage ranges.

Supply support for A3935KJP 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 of high-performance magnetic sensors and power ICs, specializing in automotive-grade motion control and energy-efficient power management solutions.

The A3935KJP belongs to Allegro's 3-phase motor driver product line, engineered specifically for high-reliability automotive traction and auxiliary motor applications demanding integrated diagnostics, wide input voltage tolerance, and robust thermal performance.

FAQ

What is the maximum gate drive current capability of the A3935KJP at elevated temperature?

The A3935KJP delivers up to 800 mA pulsed source current (GHA/GHB/GHC) and 850 mA pulsed sink current (GLA/GLB/GLC) at TJ = 25 °C. At TJ = 135 °C, these ratings reduce to 400 mA source and 550 mA sink. These values are measured under VSDU = 10 V conditions and define the practical limit for driving MOSFETs with gate charges up to ~50 nC in automotive motor control applications using the A3935KJP.

How does the A3935KJP implement short-to-ground fault detection?

The A3935KJP detects short-to-ground faults when a high-side gate driver (e.g., GHA) is active: it monitors the voltage between VDRAIN and the corresponding phase output (SA). If VSX drops below VDSTH − 0.3 V while GHA is on, the FAULT pin asserts low. This requires Kelvin connection of VDRAIN to the MOSFET drain and proper VDSTH biasing (typically 1–3 V) - a core diagnostic function of the A3935KJP in safety-critical motor systems.

Can the A3935KJP operate without an external bootstrap capacitor?

No - the A3935KJP requires external bootstrap capacitors (CA, CB, CC) for high-side gate drive. These capacitors are charged to VREG when the associated low-side output (e.g., GLA) is active and SA is pulled low. During high-side conduction, the capacitor floats to provide gate voltage above the motor phase voltage. Omitting CA/CB/CC prevents GHA/GHB/GHC from reaching sufficient VGS to fully enhance n-channel MOSFETs - a fundamental operational requirement of the A3935KJP.

What is the role of the VDRAIN pin in the A3935KJP fault protection scheme?

The VDRAIN pin provides a Kelvin connection to the high-side MOSFET drains for accurate drain-to-source voltage monitoring. When a high-side switch is enabled, the A3935KJP compares VDRAIN − VSX against the VDSTH threshold to detect short-to-ground faults. When all high-side switches are off, VDRAIN voltage decays; if it falls below 1.0–3.0 V (VBDGO(th)), the A3935KJP reports an open-bridge fault on the FAULT pin - a critical diagnostic capability built into the A3935KJP for motor winding integrity verification.

Does the A3935KJP support PWM control of motor speed through its ENABLE pin?

Yes - the ENABLE pin provides hardware-level PWM control. When ENABLE is logic low, all gate drivers force low (coast mode); when high, gate outputs follow AHI/ALO/BHI/BLO/CHI/CLO inputs. By applying a PWM signal to ENABLE, users can directly modulate average motor current and speed without MCU intervention. This feature is explicitly documented in the A3935KJP functional description and input logic table, making it a key timing-control resource in the A3935KJP.