New Industry Products

TI Intros TLS2254 Servo/Spindle Driver ICs

November 16, 2000 by Jeff Shepard

Texas Instruments (TI, Dallas, TX) has introduced the TLS2254 5V servo/spindle driver ICs. TI claims that these new mixed-signal devices combine best-in-class control solutions to drive a voice coil servo for head positioning and a three-phase brushless dc spindle motor for spinning the recording media with a range of advanced utilities on a single substrate.

The voice coil motor positioning control section of the TLS2254 combo servo/spindle driver is controlled by the combination of a 10-bit current control DAC and 6-bit offset

control DAC. The spindle driver subsystem provides zero-crossing detection for six state commutation. Current slew rate limiting on the upper and lower FETs is used to minimize the acoustic noise generation during spin-up and run. On-chip speed control is supported using both an FLL and PLL to give good stability and eliminate the dc error terms associated with FLL-only speed control. Active synchronous rectification is also employed, allowing the designer to utilize the back electromotive force (emf) generated by the motor to retract and safely park the heads during a power failure, as well as a temperature or voltage fault or a shock event. A VCM back emf monitor circuit and auto-calibration feature are added to allow this device to implement a stand-alone ramp load solution.

On-chip utilities include a fixed 3.3-V regulator, a programmable voltage regulator for setting event thresholds, a charge pump style -3.3V regulator for use by differential preamplifiers, low voltage detection and power-on reset signaling, and a shock detector interface circuit. This latter circuit notifies the drive's processor of shock events, allowing it to take appropriate action to protect the media from accidental overwrites. A 10-bit ADC and analog multiplexer are implemented to enable the processor to monitor any of 16 signals important to operation of the drive. Several low-power sleep modes are also provided to meet power consumption specifications used in mobile drives.

The new TLS2254 combo controller IC can be programmed using an industry standard serial port. Variables such as spindle slew rate and commutation delay, head retract/brake delay, as well as other spindle motor and VCM control parameters can be input and used by the device for more efficient control.

"Our goal was to integrate every function that a servo/spindle system designer for portable drives could want in a single control device optimized for battery-powered environments," said Mike Arkin, marketing manager for servo products at TI Storage Products. "The new TLS2254 device is powered from a single 5-V supply, with many internal systems actually operating at 3.3V and 2.5V from internal on-chip regulators. Such an approach accommodates the 5V motors in use today, while providing compatibility with 3.3V and 2.5V logic levels found in most advanced digital systems."

The new TLS2254 combo controller IC is available in a 56-pin TSSOP package, with suggested resale pricing starting at $6.25 in quantities of 100. Samples are now available.