基于A4982設計的DMOS微型步進馬達驅動技術

Allegro公司的A4982是集成了電平轉換和過流保護的微型步進馬達驅動器,適用于雙極步進馬達驅動,工作在全步進,半步進,1/4步進和1/6步進模式,輸出驅動能力高達35V和±2 A. A4982包括固定的離線電流調節器,兼容3.3V和5V邏輯,睡眠模式電流小于10 μA.本文介紹了A4982主要特性和優勢, 功能方框圖, 典型應用框圖以及LP和ET封裝的應用電路和PCB布局框圖.

DMOS Microstepping Driver with Translator and Overcurrent Protection

The A4982 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 sixteenth-step modes, with an output drive capacity of up to 35 V and ±2 A.

The A4982 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 A4982. 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 A4982 interface is an ideal fit for applications where a complex microprocessor is unavailable or is overburdened. During stepping operation, the chopping control in the A4982 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 A4982 is supplied in two surface mount package, the ET, a 5 mm × 5 mm, 0.90 mm nominal overall package height QFN package, and the LP package, a 24-pin TSSOP. Both packages have exposed pads for enhanced thermal dissipation, and are lead (Pb) free (suffix –T), with 100% matte tin plated leadframes.

A4982主要特性和優勢:

? 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)


圖1.A4982功能方框圖

圖2.A4982典型應用框圖

圖3.A4982 LP封裝應用電路和PCB布局框圖

圖4.A4982 ET封裝應用電路和PCB布局框圖