OM5193H

1.1 Servo control

` 10-bit VCM Digital-to-Analog Converter (DAC)
` 7-channel 10-bit Analog-to-Digital Converter (ADC)
` Programmable spindle commutation control logic
` 3-wire serial interface
` Two stand-alone operational amplifiers (op-amps) with outputs connected to the ADC
` Analog multiplexer with two inputs used to select VCM seek mode or track-following mode.

1.2 Motor control

1.2.1 SPINDLE MOTOR DRIVER

` 3-phase output motor driver
` 1.9 A maximum available start-up current
` Total Rds(on) = 0.6 (typical) at 25 °C
` Back ElectroMotive Force (BEMF) processing for sensorless motor commutation
` Linear current control
` External current sense resistor
` External current control loop compensation
` Adjustable slew rate control
` Short-circuit brake
` Adjustable brake-after-park delay time.

1.2.2 VOICE COIL MOTOR DRIVER

` 1.5 A maximum current capability
` Total Rds(on) = 0.8 (typical) at 25 °C
` Linear class AB output with low cross-over distortion delay
` Precision current control loop with external current sense resistor
` Programmable seek and track-following mode with adjustable current loop gain
` External current control loop compensation
` Precharge during brake mode
` 20 kHz current control loop bandwidth
` Parking function
` Adjustable park voltage with limiter.

1.3 Miscellaneous items

` Precision low voltage 5 and 12 V power monitor with hysteresis
` Precision internal voltage reference for servo and power control circuits
` Thermal sense circuit with over-temperature shutdown sensor
` Internal charge pump voltage generator
` Automatic brake-after-park at power-down, thermal shutdown or sleep mode
` Sleep mode: low power consumption mode.

3.1 Overview

The OM5193H is a combination of a voice coil motor and a spindle motor driver with embedded servo controller designed for use in disk drives. Configuration and control registers are set via a 3-wire serial port running up to 30 MHz to interface commonly to a microcontroller or a digital signal processor.

The OM5193H operates at 5 and 12 V power supplies and integrates safety functions such as power stages overvoltage protection, power and temperature monitor, over-temperature shutdown and dynamic brake-after-park.

The OM5193H is contained in a QFP80 package with 18 pins connected to the leadframe thus providing low thermal resistance.

3.2 Servo controller

The servo controller includes the following circuits:
` 3-wire serial interface
` Spindle commutation logic
` A 10-bit ADC with 7 inputs selected by an internal multiplexer
` A 10-bit VCM DAC with 1.5, 2.5 and 3.5 V voltage references
` Two low-offset stand-alone op-amps
` Analog multiplexer with 2 inputs.

The serial interface of OM5193H is used:
` To adjust the timing parameters for proper spindle commutation sequence
` To accurately adjust head positioning via the 10-bit VCM DAC
` To set VCM seek or track-following mode via the low-impedance switch
` To select and process analog signals via a 7-channel multiplexer connected to the 10-bit ADC.

The spindle commutation logic circuit ensures proper spindle start-up (no reverse rotation) and commutation sequence for the spindle driver by processing BEMF sensing circuit output signals.

The two stand-alone op-amps, with the inputs connected to the read channel IC, provide servo track signals processed by the microcontroller to perform accurate track-following mode.

3.3 Spindle and voice coil motor

The OM5193H drives a 3-phase brushless, sensorless DC spindle motor and a voice coil motor.

Spindle and voice coil motor power stages with low Rds(on) and high current capability are suitable for mid-end and low-end 12 V disk drives. Power stages are designed in such a way that external Schottky diodes are not needed.

Spindle current is sensed by an external resistor and monitored by the external signal SPCC (SPindle Current Control). Spindle speed is regulated by the microcontroller via the ZCROSS signal (Zero CROSSing detection frequency output). BEMF comparators provide the digital zero crossing signals. These are processed by the commutation logic circuit to properly switch-on and switch-off spindle power drivers thus ensuring the rotation of the motor.

The control of the heads positioning is accomplished by the internal 10-bit VCM DAC. Seek and track-following VCM current loop gain is set by external resistors. VCM zero current is referenced to the 2.5 V internal voltage reference.

An internal precharge of the actuator (magnetic latch) during brake mode guarantees total control of the current when VCM starts running without current spikes.

3.4 Safety functions

The OM5193H is protected against transient voltage spikes that are generated by the inductive loads of spindle and VCM.

Power supplies and temperature are monitored in order to guarantee data reliability and self-protection of the OM5193H in case of power loss or temperatures beyond maximum rating.

Park and brake functions secure heads and disk media in case of power-down or high temperature failure. This function is also activated by the sleep mode.

An internal temperature monitor is available to monitor the chip temperature and thus prevents over-temperature shutdown. Internally connected to the ADC channel 4, OM5193H can be used by the microcontroller as an early 'temperature-too-high' warning during a long VCM seek sequence.