特点：

• ±2.5A，35V额定输出
• 低导通电阻RDS（ON）输出
• 自动电流衰减模式检测/选择
• 3V~5.5V逻辑输入电压范围
• 慢速、快速及混合衰减模式
• 同步整流减少功耗
• 内置UVLO几热关断保护电路
• 交叉电流保护

   A3977是一种带微步控制的步进电机驱动器，内置译码器。它能控制双极型步进电机工作在整步、半步、四分之一步、八分之一步及十六分之一步（仅A3977）状态，额定输出电压35V，电流±2.5A。有一个固定关断的电流调节器，可以控制慢速、快速或混合衰减模式。

   译码器是易于控制的关键。每次给步进电机一个脉冲信号，电机就会动作一步（整步、半步、四分之一步、八分之一步及十六分之一步取决于两个逻辑输入）。不需要相序表，高频控制线，及复杂的编程。

   同步整流电路可减少PWM控制中的功耗。内部保护电路包括带滞的热关断、欠电压锁定（UVLO）和交叉电流保护。不需要专门的电源时序。

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A3977
Microstepping DMOS Driver with Translator

Features

• ±2.5 A, 35 V output rating
• Low rDS(ON) outputs, 0.45 Ω source, 0.36 Ω sink typical
• Automatic current decay mode detection/selection
• 3.0 to 5.5 V logic supply voltage range
• Mixed, fast, and slow current decay modes
• Home output
• Synchronous rectification for low power dissipation
• Internal UVLO and thermal-shutdown circuitry
• Crossover-current protection

Description

The A3977 is a complete microstepping motor driver, with builtin translator. It is designed to operate bipolar stepper motors in full-, half-, quarter-, and eighth-step modes, with output drive capability of 35 V and ±2.5 A. The A3977 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 A3977. Simply inputting one pulse on the STEP input drives the motor one step (two logic inputs determine if it is a full-, half-, quarter-, or eighth-step). There are no phase-sequence tables, high-frequency control lines, or complex interfaces to program. The A3977 interface is an ideal fit for applications where a complex microprocessor is unavailable or over-burdened.

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-up sequencing is not required.

The A3977 is supplied in a choice of two power packages, a 44-pin plastic PLCC with 3 internally-fused pins on each of four sides (suffix ED), and a thin (<1.2 mm), 28-pin TSSOP with an exposed thermal pad (suffix LP). Both packages are lead (Pb) free, with 100% matte tin leadframe plating.

A3977KLPTR-T is in production but has been determined to be LAST TIME BUY. This classification indicates that the variant is obsolete and notice has been given. Sale of the variant is currently restricted to existing customer applications. The variant should not be purchased for new design applications because of obsolescence in the near future. Samples are no longer available. Status date change May 3, 2010. Deadline for receipt of LAST TIME BUY orders is October 29, 2010. Recommended alternative: A3977SLPTR-T.

Functional Block Diagram