A4985: DMOS Microstepping Driver with Translator and Overcurrent Protection

The A4985 is a complete microstepping motor driver with built-in translator for easy operation. It is designed to operate bipolar stepper motors in full-, half-, quarter-, and eighth-step modes. Step modes are selectable by MSx logic inputs. It has an output drive capacity of up to 35 V and ±1 A. The A4985 includes a fixed off-time current regulator which has the ability to operate in slow or mixed decay modes.

The ET package meets customer requirements for no smoke no fire (NSNF) designs by adding no-connect pins between critical output, sense, and supply pins. So, in the case of a pin-to-adjacent-pin short, the device does not cause smoke or fire. Additionally, the device does not cause smoke or fire when any pin is shorted to ground or left open.

The translator is the key to the easy implementation of the A4985. Simply inputting one pulse on the STEP input drives the motor one microstep. There are no phase sequence tables, high frequency control lines, or complex interfaces to program. The A4985 interface is an ideal fit for applications where a complex microprocessor is unavailable or is overburdened.

During stepping operation, the chopping control in the A4985 automatically selects the current decay mode, Slow or Mixed. In Mixed decay mode, the device is set initially to a fast decay for a proportion of the fixed off-time, then to a slow decay for the remainder of the off-time. Mixed decay current control results in reduced audible motor noise, increased step accuracy, and reduced power dissipation.

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

The A4985 is supplied in three surface mount packages: two QFN packages, the 4 mm × 4 mm, 0.75 mm nominal overall height ES package, and the 5 mm × 5 mm × 0.90 mm ET package. The LP package is a 24-pin TSSOP. All three packages have exposed pads for enhanced thermal dissipation, and are lead (Pb) free (suffix –T), with 100% matte tin plated leadframes.

DATASHEETS
SAMPLE & BUY

Astrorep Inc. (Allegro and Sanken Semiconductors, Sanken Power Supplies)
141 John Street, Suite 300
Babylon, NY 11702
Phone: (631)422-2500
Fax: (631)422-2504
Web: www.astrorepinc.com
Email: donna.tweedy@astrorepinc.com

If this is not your local representative, find your local sales rep here.

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  • Features and BenefitsFeatures and Benefits
  • PackagingPackaging
  • Technical DocsTechnical Docs
  • NewsNews
  • Low RDS(ON) outputs
  • Automatic current decay mode detection/selection
  • Mixed and Slow current decay modes
  • Synchronous rectification for low power dissipation
  • Internal UVLO
  • Crossover-current protection
  • 3.3 and 5 V compatible logic supply
  • Thin profile QFN and TSSOP packages
  • Thermal shutdown circuitry
  • Short-to-ground protection
  • Shorted load protection
  • Low current Sleep mode, <10 µA
  • No smoke no fire (NSNF) compliance (ET package)

The A4985 is supplied in three surface mount packages: two QFN packages, the 4 mm × 4 mm, 0.75 mm nominal overall height ES package, and the 5 mm × 5 mm × 0.90 mm ET package. The LP package is a 24-pin TSSOP. All three packages have exposed pads for enhanced thermal dissipation, and are lead (Pb) free (suffix –T), with 100% matte tin plated leadframes.

ES-QFN, ET-QFN, and LP-TSSOP Combined

Typical Application

Typical Application

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Product Image Functional Block Diagram Typical Application

Part Number Specifications and Availability

Part Number Package Type Temperature RoHS
Compliant
Part Composition /
RoHS Data
Comments Samples Check
Distributor Stock
A4985SESTR-T 24-lead QFN -20°C to 85°C Yes View Data Contact your
local sales rep
Check Stock
A4985SETTR-T 32-lead QFN -20°C to 85°C Yes View Data Contact your
local sales rep
Check Stock
A4985SLPTR-T 24-lead TSSOP -20°C to 85°C Yes View Data Contact your
local sales rep
Check Stock
APEK4985SES-01-T DEMO BOARD -20°C to 85°C No -- Contact your
local sales rep
Check Stock
APEK4985SLP-01-T DEMO BOARD -20°C to 85°C No -- Contact your
local sales rep
Check Stock

Allegro’s products are not to be used in any devices or systems, including but not limited to life support devices or systems, in which a failure of Allegro’s product can reasonably be expected to cause bodily harm.

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