The A4985 is a complete microstep motor driver with a built-in converter for easy operation. The driver can operate bipolar stepper motors in full, 1/2, 1/4, and 1/8 stepper modes. The step mode is selectable via the MSx logic input. It has a drive capacity of up to 35 V and ±1 A. The A4985 includes a fixed downtime current regulator that operates in slow or mixed attenuation mode.
The ET package adds a non-connection pin between the key output, induction, and power pins to meet customer requirements for smoke-free and flame-free (NSNF) designs. Therefore, even if a short circuit occurs between the pin and the adjacent pin, the device will not smoke or catch fire. In addition, the device will not smoke or catch fire even if any pin is shorted or open to ground.
The converter is key to the ease of implementation of the A4985. A pulse is simply entered into the "stepper" input to drive the motor to produce microsteps. No phase sequence tables, high-frequency control lines, or complex interface programming are required. The A4985 interface is ideal for applications where complex microprocessors are unavailable or overloaded.
The chopper control within the A4985 automatically selects the current decay mode (slow or mixed) when microstep operation. In hybrid attenuation mode, the device is initially set to degrade rapidly for partial fixed downtime and then slowly decay for the remainder of downtime. The hybrid attenuation current control solution reduces the audible motor noise, increases step accuracy, and reduces power consumption.
An internal synchronous rectification control circuit is provided to improve power consumption during pulse-width modulation (PWM) operation. Internal circuit protection includes thermal shutdown with hysteresis, undervoltage lockout (UVLO), and cross-current protection. No special power-up sequencing is required.
The A4985 is available in three surface-mount packages: two QFN packages: 4 mm × 4 mm, 0.75 mm nominal overall height ES package, and 5 mm × 5 mm × 0.90 mm ET package. The LP package is a 24-pin TSSOP. All three packages have exposed pads for improved heat dissipation and are lead-free (suffix: –T) with 100% matte tin plating on the pin frame.
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低 RDS (On) 输出
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自动电流衰减模式检测/选择
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混合与慢电流衰减模式
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对低功率耗散同步整流
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内部 UVLO
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交叉电流保护
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3.3 及 5 V 兼容逻辑电源
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超薄 QFN 和 TSSOP 封装
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过热关机电路
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接地短路保护
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加载短路保护
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低电流休眠模式，
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符合无烟无火(NSNF) 规范 （ET 封装）