AMI Semiconductor (AMIS) announced two new single-chip stepper motor driver ICs. They will greatly reduce component count and material cost (BOM) in dynamic motion applications. The AMIS-30521 and AMIS-30522 eliminate the need for switches, Hall sensors, flyback diodes and many passive components in some applications, ranging from automotive headlamp positioning systems to surveillance cameras to automatic pick and place. "Systems, vending machines, textile machinery, stage lighting and many other products.

Each new mixed-signal IC contains two built-in H-bridges that can drive two-phase stepper motors with currents up to 1600mA. The speed and load angle outputs allow the main microcontroller to detect the stall rotor and end of operation without the need for additional switches, Hall sensors or optical encoders. In addition to stall detection, these features allow the designer to program the microcontroller to calculate rotor position and dynamically adjust current or speed as required to prevent out-of-step. This eliminates the noise and vibration of the end stop and improves the accuracy and reliability of the motion control without the need to add components.

The new devices are designed as co-chips for use with the main microcontroller or DSP. The device has an SPI interface that fully controls the NXT “next” input pulse conversion to provide the appropriate PWM output for the motor coil. In addition, the AMIS-30522 includes a 50mA regulator and a watchdog for an external microcontroller. Both devices offer full-step to 1/32 microstep capability, including compensated and uncompensated half-stepping. Built-in current sensing eliminates the need for external current sense resistors, further reducing component count.

One option for this new device is to use an NQFP package with an exposed pad that has a cross-section of less than 1mm and a footprint of only 7mm x 7mm. In addition to their small size, these devices offer a range of additional features, including overcurrent, undervoltage and overvoltage, coil open or short, and thermal and diagnostics. In addition to saving board space, the small size of the components allows for direct mounting on stepper motors, further saving space and reducing circuit complexity. In addition, the improved SOIC's exposed under pad design greatly enhances thermal resistance and ensures efficient heat dissipation from the IC to the PCB. If the purchase amount exceeds 1,000, the unit price of the AMIS-3052x unit is $4.65. (limited to the US market)