Micrel, Incorporated

Koninklijke Philips Corporation N.V.

Ramesh Selvaraj

Bruce Lee Inn

Sanjay Manohar Bhandari

Charles Vinn

Patrick Leclerc

Eric Pieraerts

Wendy Ng

Joao Nuno V L Ramalho

One embodiment of the invention is a hybrid boost regulator that includes a conventional boost regulator chip that operates when its input voltage is above 2.5 volts and a pre-boost circuit that operates when its input voltage is above 1 volt. A single 1.5 volt battery may be used to power the hybrid boost regulator. The pre-boost circuit is connected to the voltage input terminal of the boost regulator chip. The pre-boost circuit boosts the battery voltage (e.g., 1.5v) at an output terminal of the hybrid boost regulator to approximately the minimum operating voltage (e.g., 2.5v) of the boost regulator chip. Since this pre-boosted voltage is applied to the voltage input terminal of the boost regulator chip, the boost regulator chip will become operational when the ramping output voltage of the hybrid boost regulator exceeds about 2.5 volts. Once the boost regulator chip is operational, the pre-boost circuit is then turned off, and the boost regulator chip runs off the 1.5 volt power supply to ramp up the output voltage to the full regulated voltage.

Extending the voltage operating range of boost regulators

A method for starting up a voltage-mode switching power supply into a biased load includes computing a ratio of the load voltage at the biased load to an input voltage of the switching power supply, generating a first signal indicative of the duty cycle of the voltage-mode switching power supply, comparing the first signal indicative of the duty cycle to the ratio, and turning on an output stage of the voltage-mode switching power supply only when the first signal indicative of the duty cycle is equal to the ratio. In this manner, the voltage-mode switching power supply can be started up to supply power to a biased load without dragging down the load voltage of the biased load.

Method for starting a voltage-mode switching power supply into a biased load

In master-slave current-tracking load-share systems using switching power supplies, a method and apparatus for preventing current recirculation at light-load and no-load operational conditions. The slave power supply is run in a discontinuous mode when load current falls to light-load or no-load state, preventing the slave from sinking current, therefore preventing recirculation from the master to the slave. The slave power supply is run at a lower current level than the master, preventing recirculation from the slave to the master.

Elimination of recirculation current loss in load-shared switching mode power supplies

A magnetic head reader circuit comprises a gain stage that is configured to effect multiple functions. In a preferred embodiment, the gain stage is a single stage circuit that includes programmable gain, programmable bandwidth and high-frequency boost, and squelch control. The single stage circuit also includes a folded cascode current drive that provides an increased dynamic range of the gain stage. To provide a low DC offset, the reader also includes an integrator that is operated in closed loop to appropriately attenuate the currents from the cascode current drive. By employing a multi-function single stage reader, a substantial reduction in circuit area, and a substantial increase in bandwidth, is achieved.

Optimized stage reader for low cost implementation of preamplifiers

A preamplifier for a multi-head disk drive includes a circuit that tests the connectivity of each magnetic head in the disk drive by driving each head with a small current, and detecting the flow of this current. By driving and sensing the current flowing through the magnetic heads, both open-circuit faults and bridging faults can be detected. In a preferred embodiment, each head is tested sequentially. The result of each test is stored as a bit value in a register, for subsequent access. The circuit may be activated by a test device, or by a microcontroller in an assembled disk drive. To minimize costs, the circuit is integral to the circuitry that is conventionally used to read and write information via the magnetic heads. The oscillator that is conventionally used to characterize the read heads of a disk drive is used in a preferred embodiment to control the sequencing of tests through each head. A very low common mode voltage is provided during the testing of each write head, to minimize ESD (electro-static discharge) related problems. In a test mode, each write head is selected after a read head is selected, thereby minimizing the possibility of an accidental corruption of the data when the write head is tested. To avoid a degradation of performance, and in particular a degradation of rise/fall times in the write driver, the circuitry that controls the test voltages and currents is provided substantially up-stream of the write driver.

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Santa Clara, CA, United States of America

Ramesh Selvaraj