Abstract: A host electronic device may be coupled to an accessory electronic device. During normal operation, the host device may supply the accessory device with power over a power supply line. Back-powering events in which the accessory device delivers power to the host device may be prevented by interposing a protection transistor in the power supply line. A current mirror may be formed using the protection transistor and an additional transistor that produces a sense current proportional to the amount of current that is flowing through the power supply line. A current-to-voltage amplifier may produce a sense voltage that is proportional to the sense current. A bias circuit may be used to bias the sense current through the current mirror. A control circuit may compare the sense voltage to one or more reference voltages and turn off the protection transistor when appropriate to prevent back-powering of the host device.

Abstract: An asymmetric multiphase boost that provides flash functionality for display backlights. A backlight power management module for a display backlight may implement and control an asymmetric multiphase boost that includes two boost phases: a primary boost phase for typical display backlighting, and a secondary or flash boost phase that provides flash functionality via the display backlight when needed. The primary boost phase may be sized to provide high low-load efficiency, high inductance, and low switching frequency for normal display backlight operations. The flash boost phase may be sized for high current and peak power, low inductance, and high switching frequency for pulsed current applications. Via the asymmetric multiphase boost, the backlight power management module may, for example, be used to provide a camera flash function for front facing cameras.

Abstract: A host electronic device may be coupled to an accessory electronic device. During normal operation, the host device may supply the accessory device with power over a power supply line. Back-powering events in which the accessory device delivers power to the host device may be prevented by interposing a protection transistor in the power supply line. A current mirror may be formed using the protection transistor and an additional transistor that produces a sense current proportional to the amount of current that is flowing through the power supply line. A current-to-voltage amplifier may produce a sense voltage that is proportional to the sense current. A bias circuit may be used to bias the sense current through the current mirror. A control circuit may compare the sense voltage to one or more reference voltages and turn off the protection transistor when appropriate to prevent back-powering of the host device.

Abstract: A host electronic device may be coupled to an accessory electronic device. During normal operation, the host device may supply the accessory device with power over a power supply line. Back-powering events in which the accessory device delivers power to the host device may be prevented by interposing a protection transistor in the power supply line. A current mirror may be formed using the protection transistor and an additional transistor that produces a sense current proportional to the amount of current that is flowing through the power supply line. A current-to-voltage amplifier may produce a sense voltage that is proportional to the sense current. A bias circuit may be used to bias the sense current through the current mirror. A control circuit may compare the sense voltage to one or more reference voltages and turn off the protection transistor when appropriate to prevent back-powering of the host device.

Abstract: An asymmetric multiphase boost that provides flash functionality for display backlights. A backlight power management module for a display backlight may implement and control an asymmetric multiphase boost that includes two boost phases: a primary boost phase for typical display backlighting, and a secondary or flash boost phase that provides flash functionality via the display backlight when needed. The primary boost phase may be sized to provide high low-load efficiency, high inductance, and low switching frequency for normal display backlight operations. The flash boost phase may be sized for high current and peak power, low inductance, and high switching frequency for pulsed current applications. Via the asymmetric multiphase boost, the backlight power management module may, for example, be used to provide a camera flash function for front facing cameras.

Abstract: A host electronic device may be coupled to an accessory electronic device. During normal operation, the host device may supply the accessory device with power over a power supply line. Back-powering events in which the accessory device delivers power to the host device may be prevented by interposing a protection transistor in the power supply line. A current mirror may be formed using the protection transistor and an additional transistor that produces a sense current proportional to the amount of current that is flowing through the power supply line. A current-to-voltage amplifier may produce a sense voltage that is proportional to the sense current. A bias circuit may be used to bias the sense current through the current mirror. A control circuit may compare the sense voltage to one or more reference voltages and turn off the protection transistor when appropriate to prevent back-powering of the host device.

Abstract: An apparatus and method for controlling the phase of a tunable laser is provided. Stabilization of the mode of a laser beam is provided as the laser is tuned to a target frequency. For one embodiment, a laser generates a reference beam and an output beam. The power of each of beam is measured by optical detectors, and a ratio thereof is utilized to detect when a mode hop occurs as the laser is coarsely tuned. The average of the pre and post mode hop ratios is utilized as a control setpoint while finely tuning the laser to the target frequency. Wavelength lockers, optical power dividers and optical detectors are utilized to determine power levels of the reference and output beams while also monitoring frequency characteristics thereof. A control unit utilizes the outputs from the wavelength locker to control the operation of the extended cavity laser during and after tuning.

Abstract: An apparatus comprising a first reference element having an output power that varies monotonically with input frequency over an operating frequency range and receiving at least a portion of an output beam of light from an optical source. A second reference element having an output power that is frequency dependent receives at least a portion of the output beam of light. A first optical detector measures the power of a first reference beam of light from the first reference element. A second optical detector measures the power of a second reference beam of light from the second reference element. Electronic circuitry is coupled to the first and second optical detectors for receiving first and second reference signals therefrom and producing a coarse error signal for permitting coarse adjustment and a fine error signal for permitting fine adjustment of the frequency of the output beam of light.

Abstract: A patterned recording media is comprised of a combination of raised features and depressed features in or on the surface of the recording disk. A depressed feature is known as a pit, while a raised feature is known as an island. The islands form areas where one or more data bits can be written. The recording head is synchronized to the discrete bit pattern by determining the correct clock cycle (phase) and clock count within the clock cycle.

Abstract: An apparatus and method for controlling the phase of a tunable laser is provided. Stabilization of the mode of a laser beam is provided as the laser is tuned to a target frequency. For one embodiment, a laser generates a reference beam and an output beam. The power of each of beam is measured by optical detectors, and a ratio thereof is utilized to detect when a mode hop occurs as the laser is coarsely tuned. The average of the pre and post mode hop ratios is utilized as a control setpoint while finely tuning the laser to the target frequency. Wavelength lockers, optical power dividers and optical detectors are utilized to determine power levels of the reference and output beams while also monitoring frequency characteristics thereof. A control unit utilizes the outputs from the wavelength locker to control the operation of the extended cavity laser during and after tuning.

Abstract: An apparatus comprising a first reference element having an output power that varies monotonically with input frequency over an operating frequency range and receiving at least a portion of an output beam of light from an optical source. A second reference element having an output power that is frequency dependent receives at least a portion of the output beam of light. A first optical detector measures the power of a first reference beam of light from the first reference element. A second optical detector measures the power of a second reference beam of light from the second reference element. Electronic circuitry is coupled to the first and second optical detectors for receiving first and second reference signals therefrom and producing a coarse error signal for permitting coarse adjustment and a fine error signal for permitting fine adjustment of the frequency of the output beam of light.

Abstract: A system and method is disclosed for correcting gain and offset errors in a signal amplifier for a position sensitive detector. The present invention eliminates the need to perform division for normalization by holding constant a signal proportional to the sum of the two signals generated by the position sensitive detector. First the two signals generated by the position sensitive detector are pulse-width modulated with a common variable duty cycle clock, and then the resulting modulated signals are low-pass filtered to extract the DC component. The duty cycle is varied so that the sum of the two DC components is held constant. In the preferred embodiment, the means for varying the duty cycle are closed-loop feedback and open-loop feed forward. The closed-loop feedback gives long term accuracy and the open-loop feed forward gives rapid settling time.

Abstract: In a magneto-optical storage device, a digitally adjustable preamplifier stage balances polarization signal levels through use of a digital compensation value. A separate digital compensation value is stored for the signals corresponding to each detector head. Each time a different detector head is activated, the digital compensation value for the polarization signals corresponding to that head is accessed. The accessed digital compensation value is input to a digital to analog converter (DAC), which produces a voltage for setting the gain of the adjustable amplifier.

Abstract: An actuator assembly directs a first beam of light towards an optical assembly. A particular angular displacement of the beam of light relative to the optical assembly by the actuator assembly directs the beam of light to exit the optical assembly at a particular output port.

Abstract: Optical switching of light is effected between an input and an output utilizing a low-bandwidth actuator and a hi-bandwidth actuator.

Abstract: Curvilinear servo sector patterns are produced on a master media by determining a series of offsets between a radially aligned reference and the desired curvilinear servo sector and expressing each offset as a delay that can be expressed in settings for controlling a master writer. Incorporation of the delay into the master writer allows a curvilinear servo sector pattern to be produced using data mapping that is ordinarily used for the radially aligned servo sector pattern. Thus, curvilinear servo sector patterns with a desired resolution are produced without increasing computational overhead or memory requirements, or decreasing throughput. The delay can be converted into control settings such as sector delay, clock cycle delay and residual fractional delay settings that each represent a portion of the delay.

Abstract: An optical disk recorder employs laser drive signals having diverse current or power levels. A scaling digital-analog-converter (DAC) supplies a scaled reference signal to a plurality of scaled DACs. The scaled DACs supply the diverse laser drive signals. Calibrating the scaling DAC calibrates the scaled DACs. A base array of DACs include not only the scaling DAC but a plurality of base array DACs. Such base array DACs control reading operations as well as supplying a threshold current. The threshold current is that laser drive signal current level below which laser 25 does not emit a laser beam. During writing, the CUT current is added to the laser drive currents supplied by the scaled DACs. A desired CUT current is determined by calculating a slope of the laser drive current to emission of radiation. Then the slope is extrapolated to a zero emission point below which no coherent emission of radiation occurs.