Marvell International Limited

Stmicroelectronics Asia Pacific Pte Limited

Sakti Pada Rana

Siew Yong Chui

Yayue Zhang

Kuong Hoo, Legal Representative

Foo Leng Leong

Ying Tian Li

Cheng Yong Teoh

Vishnu Kumar

A linear regulator and methods of regulation are provided. In one implementation, a linear regulator is provided. The linear regulator can receive an input voltage, generate an internal bias voltage in response to the received input voltage. The linear regulator can determine if the input voltage meets one or more first criteria and second criteria, and adjust an output voltage based on the internal bias voltage if the input voltage meets the one or more first criteria. The linear regulator also can supply the input voltage directly to the load if the input voltage meets the one or more second criteria. In some implementations, the linear regulator can generate an internal bias voltage that is clamped within a desired operating range if the input voltage meets the one or more first criteria, and adjusts one or more electronic circuits using the internal bias voltage to provide the adjusted output voltage.

Linear regulation for use with electronic circuits

A driver for a motor in a device includes a reference generator to generate a reference value. A clock management module receives a plurality of clock signals. Each clock signal has a corresponding frequency that is different relative to the corresponding frequency of another clock signal. A clock management module selects a different clock signal of the plurality of clock signals for output from the clock management module at different times during operation of the device. A ramp generating module generates a ramp signal in accordance with the corresponding frequency associated with the selected clock signal. A first pulse width modulation module receives the reference signal and the ramp signal. The first pulse width modulation module outputs a first pulse width modulation driver signal for driving the motor based on the reference signal and the ramp signal.

Adjustable frequency PWM driver

A circuit system and process utilizes back electromotive force (BEMF) voltage to assist in safe power down of devices, such as the read/write head in from low factor disk drives or similar devices. The BEMF voltage from a motor device, such as a spindle motor utilized in a circuit using negative voltage to drive some switches, such as positive channel metal oxide semiconductor ('PMOS') driver transistors, to reduce and/or effectively minimize the on-resistance of the switches while delivering the current from BEMF voltage of the motor to another device, such as a motor that retracts controls a read/write head.

System and process for utilizing back electromotive force in disk drives

A linear regulator is described that includes a mode selection circuit. In one implementation, the mode selection circuit is operable to receive an input voltage and to set an operation mode to one of a first mode or a second mode (e.g., based on a voltage level of the input voltage) so as to generate an output voltage. For example, when the voltage level of the input voltage is within a voltage range, the mode selection circuit can set the first mode as the operation mode to supply the input voltage as the output voltage to a load without voltage regulation. Similarly, when the voltage level of the input voltage is outside the voltage range, the mode selection circuit can set the second mode as the operation mode to regulate the output voltage to the load.

Linear regulator for use with electronic circuits

A charging system includes a current source, a voltage pump, and a comparator that compares a charging level of a capacitor to each of a first threshold and a second threshold. A controller turns on the voltage pump and turns off the current source after the charging level exceeds the first threshold, and turns off the voltage pump and turns on the current source when the charging level falls below the second threshold. The first threshold is greater than the second threshold.

Circuit and method for protecting emergency head-retract capacitor in a hard disk drive

A spindle/voice coil motor (VCM) driver includes a clock management module that receives a system clock signal and a second clock signal, and that selects one of the system clock signal or the second clock signal as a selected clock signal. A reference generating module generates a reference signal. A ramp generating module receives the selected clock signal and generates a ramp signal. A pulse width modulation (PWM) module receives the reference signal and the ramp signal and outputs a first PWM driver signal based thereon.

A protection circuit for a capacitor comprises a voltage pump that selectively charges the capacitor. A current source selectively charges the capacitor. A controller compares a charging voltage to a threshold charging voltage and selects at least one of the voltage pump and the current source based on the comparison.

A protection circuit for a capacitor comprises a voltage pump that selectively charges the capacitor. A current source selectively charges the capacitor. A controller selectively activates the current source while deactivating the voltage pump when a charging voltage is less than a threshold charging voltage level and selectively deactivates the current source while activating the voltage pump when the charging voltage is greater than the threshold charging voltage level.

A circuit and method protects an emergency head-retract capacitor that regulates initial charge current using a constant current source. The initial charge current is applied at power-up to the capacitor until a charging voltage having a desired threshold level is attained in the capacitor. The charging voltage is monitored through an analog-to-digital converter by an overall controller that, upon detecting the presence of the desired threshold level in the capacitor, deenergizes the constant current source. A voltage pump, which includes a voltage multiplier (doubler), is then activated to selectively apply regulated charging voltage to thereafter maintain the desired threshold level. The pump includes a voltage pump controller that is controlled by a voltage comparator having a reference voltage set to a desired threshold level. That voltage comparator is also in communication with the capacitor to measure its present input charging voltage. When the desired threshold level is met or exceeded at the capacitor, the comparator signals the controller to deactivate the pump. When the capacitor's charging voltage is less than the reference voltage, the comparator signals the controller to activate the voltage pump and, thus, pump the capacitor with regulated voltage.

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