Driver chip controls stepper motors at full current

September 24, 2013 // By Christoph Hammerschmidt
The A4990 from Allegro MicroSystems Europe is a new dual full-bridge driver IC designed to operate one bipolar stepper or two brush DC motors in automotive and harsh environment industrial applications.

Each full bridge in the new device uses DMOS power devices with integrated freewheeling diodes. Peak motor current can be limited to provide higher efficiency and reduce motor heating.

The IC is targeted at both the automotive and the industrial markets. Key automotive applications include HVAC actuators, EGR (exhaust gas recirculation) valves, and idle speed control. It is also designed for harsh environments where stepper or DC actuators are needed: for example, in satellite dish or solar panel positioning systems.

The A4990 enables stepper motors to be driven with full current in either direction in each phase, allowing two-phase “on” full-step operation. DC motors can be driven both clockwise and anticlockwise, and in brake mode. A single input turns all bridges off, allowing all motors to coast. All control modes can easily be achieved using three, four or five outputs from a standard parallel interface of a microcontroller.

The device is designed for typical applications requiring up to 800 mA and 28 V, and has 3.3 V and 5 V compatible inputs. The peak motor current can be limited by sense resistor selection to provide higher efficiency, reduced motor heating and longer motor life.

The outputs are protected from short circuits to supply and ground, and low-load current detection is included. Chip-level protection includes overtemperature shutdown and overvoltage and undervoltage lockout.

The A4990KLPTR-T is supplied in a 20-lead TSSOP power package with an exposed thermal pad (package type LP). This package is lead (Pb) free with 100% matt-tin leadframe plating.

For more information visit www.allegromicro.com