VOICE-COIL MOTOR DRIVER

Providing control and drive of the voice-coil motor used for head positioning in 5 V disk drive applications, the second-generation A8932CLWA is a full-bridge driver that can be configured so that its output current is a direct function of an externally applied control voltage or current. This linear current control function is supplemented by additional circuitry to protect the heads and the data disk during system failure or normal system shutdown.
The two ±500 mA MOS driver outputs provide very low saturation voltage and minimal power dissipation. Additional headroom is achieved by the sense-FET structure eliminating the need for an external current-sense resistor. Internal circuitry can be configured to provide closed-loop velocity control of the actuator by utilizing the generated back-EMF of the voice-coil motor. Thermal protection and under-voltage lockout disables the system in a controlled sequence if a fault condition occurs.

FEATURES
■ Class-B, 2 Ω rDS(on) at 500 mA Output
■ Lossless Current Sensing
■ Zero Current-Loop Deadband
■ High Transconductance Bandwidth
■ User-Adjustable Transconductance Gain
■ Digital Transconductance Gain Switch (4:1 Ratio)
■ 5 Volt Monitor with Selectable UV Trip Point
■ Retract Circuitry Functional to 0 Volts
■ Sleep Mode Function
■ Internal Back-EMF Velocity Loop Option
■ Internal Thermal Shutdown Circuitry