Abstract: A method and apparatus for calibrating a Gm cell using a Gm replica cell. A digital to analog converter receives a Gm setting code and generates a reference current. The Gm replica cell adjusts the tuning voltage until the difference between a pair of drain currents is substantially equal to the reference current. Where this condition is satisfied, the proper tuning voltage has been acquired. This results in proper calibration for the tuning voltage, which then may be utilized by a Gm cell connected with the Gm replica cell.

Abstract: A method and apparatus for calibrating a Gm cell using a Gm replica cell. A digital to analog converter receives a Gm setting code and generates a reference current. The Gm replica cell adjusts the tuning voltage until the difference between a pair of drain currents is substantially equal to the reference current. Where this condition is satisfied, the proper tuning voltage has been acquired. This results in proper calibration for the tuning voltage, which then may be utilized by a Gm cell connected with the Gm replica cell.

Abstract: A high speed zero phase restart for a multiphase clock for a PRML read/write channel design. The zero phase restart includes an input for receiving a plurality of clock pulse waves, each having substantially equal period and each being out of phase with respect to other clock pulse waves; an output including at least one output terminal corresponding to one of the clock pulse waves; and a zero phase circuit configured to sequentially couple the plurality of clock pulse waves to the corresponding output terminals.

Abstract: A method and apparatus for operating a continuous time filter (CTF) (128) of a read/write channel (108) for a hard disk drive (100). The apparatus includes an input multiplexer (220) that receives an analog signal (215) and transmits the analog signal (215) to a read filter circuit (254) when the CTF (128) is in read mode and to a servo filter circuit (256) when the CTF (128) is in servo mode. The apparatus also includes an output multiplexer (222) that receives a read filter output signal (225) from the read filter circuit (254) when the CTF (128) is in read mode and a servo filter output signal (227) from the servo filter circuit (256) when the CTF (128) is in servo mode. The method includes receiving the analog signal (215) by the input multiplexer (220) and routing the analog signal (215) to the read filter circuit (254) when the CTF (128) is in read mode and routing the analog signal (215) to the servo filter circuit (256) when the CTF (128) is in servo mode.

Abstract: A write output driver with internal programmable pull-up resistive devices is disclosed. The write output driver provides an integrated output driver circuit configurable to provide near end transmission line termination. The output driver is configured to provide transmission of a high-speed signal with increased frequencies over prior output drivers. The output impedance of the output driver is programmable and maintained substantially constant, despite ambient fluctuations. An internal bias signal generator is provided to control the impedance of the output driver.

Abstract: Improved systems and methods of phase detecting are described. In one aspect, a phase detector includes a latch having an input stage and an output stage. The input stage couples to the output stage through a dynamic storage node and includes a discharge circuit. The discharge circuit has a first input and a second input and defines a discharge path for discharging the dynamic storage node that is substantially symmetric with respect to the first and second inputs. In another aspect, the dynamic storage node is discharged with a characteristic discharge time in response to a transition of the first input from a low logic level to a high logic level when the second input is at a high logic level. The dynamic storage node also is discharged with substantially the same characteristic discharge time in response to a transition of the second input from a low logic level to a high logic level when the first input is at a high logic level.

Abstract: A high-speed programmable synchronous counter is disclosed. The high speed counter includes a most-significant-bit counter synchronized with a least-significant bit counter. The least-significant-bit counter is programmed to an initial state and configured to decrement a state with each pulse of a clock wave. The least-significant-bit counter provides an output signal when the least-significant-bit counter has a zero-count state. The most-significant-bit counter decrements when the least-significant-bit counter has a zero-count state and provides an output signal when the least-significant-bit counter has a zero-count state. A counter output pulse is generated and the high-speed counter is reset to the initial state when both the least-significant bit counter and the most-significant bit counter have a zero-count state.

Abstract: A clock generation device includes a delay-locked loop and a plurality of programmable counters. The plurality of programmable counters are coupled to delay-locked loop. Each of the programmable counters has a separate output. The delay-locked loop is configured to generate a plurality of phase delay line outputs. A hard drive includes the delay-locked loop and the programmable counters, which generate multiple timing signals such as read, write, servo, and system timing signals. The method of generating timing signals includes delaying an input signal by a programmable delay and generating a plurality of timing pulses through the programmable counters.

Abstract: A method and apparatus for running an analog portion (162) of a read/write channel (108) from a highly regulated power supply (260). The apparatus includes an analog portion (162), a clock synthesizer (154), and a highly regulated power supply (260) connected to the analog portion (162) and the clock synthesizer (154). The analog portion (162) and the clock synthesizer (154) both comprise high voltage transistors which operate in a first voltage range and low voltage transistors which operate in a second voltage range, wherein the first voltage range is within the second voltage range. The highly regulated power supply (260) supplies power that is within the first voltage range to the analog portion (162) and the clock synthesizer (154). The method includes generating power that is within the first voltage range using the highly regulated power supply (260), and supplying the power to the analog portion (162) and the clock synthesizer (154).

Abstract: An improved write precompensation circuit. Eight phases from a PLL phase oscillator are received as inputs into a bank of four phase blenders (104). The phase blenders (104) output a 0%, 25%, 50%, or 75% interpolation to the adjacent phases. A multiplexer (110) is then used to select which of the phase outputs is used for the write precompensation.

Abstract: An input signal is received having a period and an input pulse width. The input pulse width of an input signal is adjusted to an output pulse width of an output signal based upon a recording control signal for control of recording on a storage medium. The output signal and the output pulse width is derived from a triggering edge of a first selected signal of a first selected phase and a triggering edge of a second selected signal of a second selected phase in succession. The first selected signal and the second selected signal are selected from an assortment of reference signals that have distinct relative phases to provide the output pulse width of a desired duration. The number of distinct relative phases available for formation of the output pulse width is increased by one or more of the following: delaying, dividing, inverting, and interpolating one or more reference signals.

Abstract: This invention provides a read/write channel with a multiplex input/output system for a disk drive, which may have one or more magnetic disks, one or more read/write heads, and a read/write channel. The read/write channel may comprise a multiplex input/output (I/O) terminal, a write output driver, and a digital to analog converter. The read/write channel may be implemented on an integrated circuit. The multiplex input/output system may send different signals or voltages through the same input/output terminal at essentially at the same time or different periods of time.

Abstract: An ultra high-speed clocked analog latch is revealed for use at clock speeds from 100 MHz to several GHz. The analog latch is used as a latching comparator for comparing a time-varying analog signal with an analog reference voltage. The latch uses CMOS manufacturing technology and a minimal amount of space for a two-stage amplifying and signal-generating device. The latch is useful in analog to digital converters (ADCs) in which high speed and high reliability are required, but only a small amount of space is available. The device is so small and economical that several may be used in series to avoid any meta-stability problems in high-speed read/write operations.

Abstract: An active offset cancellation circuit for an open loop differential amplifier is disclosed. The amplifier is operated on a two-phase clock where the normal operation occurs on the first phase and offset detection and cancellation occurs on the second phase. On the second phase, the offset cancellation circuit measures the offset created by the amplifier when both differential inputs are connected to a common source. The circuit then adjusts a bias current and stores this adjustment to cancel offset during the operational phase of the amplifier. During the operational phase, the first phase of the clock, the stored adjustment is used to bias the current in one of the two input stages of the amplifier, canceling any offset imparted by the amplifier circuitry. One each clock cycle, any additional offset is similarly detected and canceled.

Abstract: A voltage buffer and follower includes a single ended output, a source follower, and a current feedback loop. The current feedback loop is coupled to the source follower and to the single ended output. When two voltage followers are used in a differential configuration, the voltage followers can become part of a high bandwidth gain cell. The high bandwidth gain cell includes a first and a second source follower circuit that are coupled to the first and the second current feedback loops, respectively. The first and the second source follower circuits are further coupled to a first and a second current mirror circuit, respectively. The first and second current mirror circuits are coupled to a load, which is coupled to a common-mode feedback circuit. The common-mode feedback circuit controls a constant current source that sinks mirrored direct currents that flow through the first and the second current mirror circuits.

Abstract: Transconductance-based variable gain amplifiers amplify an input voltage by converting the voltage difference to a current and then amplifying the result. At least one resistor network is adjusted depending on the magnitude of the input voltage difference and the output desired. A network of MOS transistor switches with a small footprint adjusts the resistance of the input voltage circuit in a way to insure consistent resistance and low stray capacitance.

Abstract: An active offset cancellation circuit for an open loop differential amplifier having programmable gain is disclosed. The amplifier is operated on a two-phase clock where the normal operation occurs on the first phase and offset detection and cancellation occurs on the second phase. On the first phase, the programmable gain of the amplifier is set according to the application of the amplifier. On the second phase, the programmable gain of the amplifier is set to the maximum value and the offset cancellation circuit measures the offset created by the amplifier when both differential inputs are connected to a common source. The circuit then adjusts a bias current and stores this adjustment to cancel offset during the operational phase of the amplifier.

Abstract: The invention provides a read/write channel with a diagnostic system for a disk drive. The diagnostic system may process internal and external signals. The read/write channel may have one or more clock generators, a digital to analog converter, an analog comparator, and a successive approximation register. The read/write channel may be implemented on an integrated circuit or a complementary metal oxide semiconductor. The read/write channel may have partial response maximum likelihood (PRML) encoding and decoding. The diagnostic system uses bit-weighing or successive approximation to convert analog signals into digital diagnostic signals.

Abstract: An efficient current feedback buffer is revealed. The buffer is useful in power supplies for a number of analog and digital devices, including CMOS voltage controlled ring oscillators, frequency synthesizers, delay locked loops, phase accumulators, and phase locked loops. The power supply and buffer maintains a low impedance output to the load, regulates the voltage output of the supply, and rejects power line noise.

Abstract: A view DAC feedback inside an analog front circuit for a partial response, maximum likelihood based read/write channel is disclosed. The view DAC feedback circuit may be configured to apply an analog signal associated with an operation level of the PRML based read/write channel to the analog front circuit of the read channel. The view DAC analog signal may be used to calibrate operating parameters for a continuous time filter component of the analog front circuit. The view DAC feedback circuit may be configured to add digitally-controlled noise to the PRMIL read/write channel to optimize performance of the channel in a low signal-to-noise (SNR) environment.