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Related Links:

Datasheets:
A3979: Microstepping DMOS Driver with Translator (PDF)

Selection Guides:
Power Integrated Circuits,

Power Motor Drivers,

Power Motor Drivers - Full-Bridge

when this product is updated

Press Releases:
A3979: Allegro MicroSystems, Inc. Announces Microstepping Motor Driver with Built-In Translator

A3979
Microstepping DMOS Driver with Translator

Features

• ±2.5 A, 35 V output rating
• Low R_DS(On) outputs: 0.28 Ω source, 0.22 Ω sink, typical
• Automatic current decay mode detection/selection
• 3.0 to 5.5 V logic supply voltage range
• Slow, Fast or Mixed current decay modes
• Home output
• Synchronous rectification for low power dissipation
• Internal UVLO and thermal shutdown circuitry
• Crossover-current protection

Description

The A3979 is a complete microstepping motor driver with built-in translator, designed as a pin-compatible replacement for the successful A3977, with enhanced microstepping (1/16 step) precision. It is designed to operate bipolar stepper motors in full-, half-, quarter-, and sixteenth-step modes, with an output drive capacity of up to 35 V and ±2.5 A. The A3979 includes a fixed off-time current regulator that has the ability to operate in Slow, Fast, or Mixed decay modes. This current-decay control scheme results in reduced audible motor noise, increased step accuracy, and reduced power dissipation.

The translator is the key to the easy implementation of the A3979. It allows the simple input of one pulse on the STEP pin to drive the motor one microstep, which can be either a full step, half, quarter, or sixteenth, depending on the setting of the MS1 and MS2 logic inputs. There are no phase-sequence tables, high-frequency control lines, or complex interfaces to program. The A3979 interface is an ideal fit for applications where a complex microprocessor is unavailable or is overburdened.

Internal synchronous-rectification control circuitry is provided to improve power dissipation during PWM operation. Internal circuit protection includes: thermal shutdown with hysteresis, UVLO (undervoltage lockout), and crossover-current protection. Special power-on sequencing is not required.

The A3979 is supplied in a low-profile (maximum height ≤1.20 mm), 28-pin TSSOP with exposed thermal pad. The package is available in a lead (Pb) free version, with 100% matte tin leadframe plating.

Functional Block Diagram

Complete Part Numbers

Part Number	Package Type	RoHS Compliant	Part Composition/ RoHS Data	Temperature	Comments	Samples	Distributor Stock
A3979SLP-T	28-lead TSSOP	Yes	view data	-20 °C to  85 °C	new	Due to warehouse relocation, samples will be unavailable until July 21, 2008. Contact your sales rep or purchase from distributor.
A3979SLPTR-T	28-lead TSSOP	Yes	view data	-20 °C to  85 °C	new	Due to warehouse relocation, samples will be unavailable until July 21, 2008. Contact your sales rep or purchase from distributor.

Allegro's products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the failure of that life support device or system, or to affect the safety or effectiveness of that device or system.