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Datasheets:
A4985: DMOS Microstepping Driver with Translator and Overcurrent Protection (PDF)
Selection Guides:
Power Integrated Circuits,
Power Motor Drivers,
Power Motor Drivers - Full-Bridge
Press Releases:
A4982, A4984, A4985, A4988: Allegro MicroSystems, Inc. Announces New DMOS Microstepping Motor Drivers With Overcurrent Protection,
A4982, A4984, A4985 und A4988: Mikroschritt-Motortreiberserie mit DMOS-Ausgangsstufen und Überstromschutz,
A4982, A4984, A4985, A4988: Circuit de commande de moteurs pas à pas DMOS intégrant les protections en sur-courant
Design Support Tools:
APEK4985SLP-01-T Demo Board
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A4985
DMOS Microstepping Driver with Translator and Overcurrent Protection
Features and Benefits
- 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)
Description
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.
Typical Applications
Functional Block Diagram
| Part Number | Package Type | RoHS Compliant |
Part Composition/ RoHS Data |
Temperature | Comments | Samples | Distributor Stock |
|---|---|---|---|---|---|---|---|
| A4985SESTR-T | 24-lead QFN | Yes | view data | -20 °C to 85 °C | new |
Contact Local Sales Representative or check distributor stock |
|
| A4985SETTR-T | 32-lead QFN | Yes | view data | -20 °C to 85 °C | new |
Contact Local Sales Representative or check distributor stock |
|
| A4985SLPTR-T | 24-lead TSSOP | Yes | view data | -20 °C to 85 °C | new |
Contact Local Sales Representative or check distributor stock |
|
| APEK4985SES-01-T | 1-lead n/a | -- | -- | -20 °C to 85 °C |
Contact Local Sales Representative or check distributor stock |
||
| APEK4985SLP-01-T | 1-lead n/a | -- | -- | -20 °C to 85 °C |
Contact Local Sales Representative or check distributor stock |
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.