Motion Control

Cirrus Logic Expands Family Of PWM ICs For Driving Mid-Range Brushless & Brush DC Motors

Cirrus Logic Inc. has added the SA303-IHZ and SA53-IHZ to its Apex Precision Power™ product family of what it describes as industry first high current pulse width modulated (PWM) ICs for driving three-phase brush and brushless dc motors. As follow-on products to the 2008 launch of its SA3XX and SA5X series of single-packaged units, these new ICs are said to offer a lower per unit cost of up to 40% for industrial motor applications such as fans, pumps and robotics operating on supplies up to 60V and requiring output current in the 3A range (10A PEAK).

The SA303-IHZ and SA53-IHZ make use of the same 64-pin Power Quad package used in the SA3XX and SA5X series. With a footprint of less than two centimeters square, Cirrus claims that the ICs require up to 70% less board space compared to alternate discrete solutions with comparable power requirements. Cost savings can be realized through a reduction in the size, weight and overall system layout, while increasing the thermal efficiency of the motor control circuitry. The company claims that the power dissipation capabilities of the package can be increased by up to 3X versus a standard on-board mounting configuration by using a patent-pending approach that involves mounting the device upside down through a cutout in the uniquely designed printed circuit board.

The use of pulse width modulation (PWM), or switching technology, further minimize power dissipation issues by allowing the overall operating system to run cooler and thus increase long-term reliability. The SA303-IHZ and the SA53-IHZ also use smaller filter components because they are able to switch at frequencies of up to 100 KHz.

Inside the package, these ICs deliver cycle-by-cycle current limit to precisely control motor current in real time for each motor phase, as well as the ability to soft start the motor by allowing the driver to handle the inrush of start-up current. This functionality negates the necessity to de-rate the driver’s current rating even at 3A continuous or greater.

All models in the SA3XX and SA5X series are designed to provide customers with a seamless interface to either a digital microcontroller (MCU) or a DSP. The top side and bottom side output FETs on these PWM drivers can be individually controlled via direct signals from the processor. This communication includes current sensing for each phase. Each current path is supplied as an individual input to the ADC of the processor.

Additional protection features such as under voltage and over temperature can generate performance gains in the overall motor control circuitry by eliminating motor shutdown and re-starts. For example, should an over-temperature or short circuit occur, these ICs will not shutdown the outputs, but instead, allow the system to continue running while it signals the external controller to take corrective action. In most cases, the processor can correct the condition by utilizing software to remedy the external interrupt.

The SA303-IHZ and SA53-IHZ are available in sample quantities for evaluation and prototyping, as well as volume production. Evaluation kits with a fully populated demo board, including the IC, are available.

Cirrus Logic Inc.
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