原标题：Allegromicro SI-7321M单极2相微步进马达驱动方案

　　Allegromicro公司的SI-7321M是单极2相微步进马达驱动器, 采用恒流模式工作,有满步进,半步进和1/4,1/8和1/16微步进几种选择.电源电压VBB最大46V,正常工作范围10V-44V,逻辑电源VDD 为3.3V到5.5V,最大输出电流1.5A,具有四个NMOS输出MOSFET,典型R DS(on) = 0.25 Ω,自激励的PWM电流控制.本文介绍了SI-7321M特性和优势,方框图和典型应用电路.

　　The SI-7321M constant-current mode motor driver IC features efficient unipolar driver design for full- and half-step operation, and 1/4 , 1/8 , and 1/16 microstepping. The clock-in type input interface allows simplified control logic, with the flexibility of sequencer timing using either rising Clock edge only or both rising and falling edges. Additional flexibility is provided by user-configurable blanking time, and load circuit short or open protection (patent pending). Along with inputs for built-in sense current detection, these features minimize power losses.

　　The device has a multi-chip internal structure for lower thermal resistance. The control IC (MIC) and the four power elements (MOSFET) are all separate ICs. The package (HSOP) provides wide output terminals at each corner, further enhancing device thermal dissipation.

　　The built-in excitation distribution circuit (sequencer) allows motor control using only the Clock signal for simple operations (forward, reverse, hold), with motor speed control by frequency input into Clock pin, and rotation direction control by a dedicated logic input. This eliminates logic signal lines required for conventional phase-input methods, and reduces demand on heavily-used CPUs.

　　Low-power sleep mode, as well as reduced power during PWM off-time maximize energy savings.

　　SI-7321M特性和优势:

　　▪ Power supply voltage, VBB , 46 V maximum, 10 to 44 V normal operating range

　　▪ 18.6 × 9.9 mm package footprint

　　▪ Logic supply voltage, VDD , 3.3 to 5.5 V

　　▪ Maximum output current: 1.5 A

　　▪ Four NMOS output MOSFETs, R DS(on) = 0.25 Ω typical

　　▪ Built-in sequencer

　　▪ Simplified clock-in stepping control

　　▪ Full- and half-stepping and 1/4 , 1/8 , and 1/16 microstepping

　　▪ Surface mount type 44-pin molded package for automatic assembly and low profile

　　▪ Self-excitation PWM current control with fixed off-time

　　▪ Microstepping off-time adjusted automatically by step reference current ratio

　　▪ Built-in synchronous rectifying circuit reduces losses at PWM switch-off

　　▪ Synchronous PWM chopping function prevents motor noise in Hold mode

　　▪ Built-in current sensing for each phase, set externally

　　▪ Dual sleep modes reduce IC input current in stand-by state

　　▪ Built-in protection against motor coil opens and shorts

　　• User-configurable operation options, set by external logic input:

　　▫ Blanking time: 1.8 μs or 3.6 μs

　　▫ Sequencer timing on Clock input rising (POS) edge or both rising and falling (POS/NEG) edges

　　▫ Protection features enable or disable

　　图1. SI-7321M方框图

　　图2. SI-7321M典型应用电路图