Abstract: A CMOS digital PWM controller chip includes a clock generator for directly generating a sampling clock at a frequency higher than a control pulse rate without requiring a phase locked loop, an oversampling analog-to-digital converter clocked by the sampling clock for converting error signals into filtered digital values, an output for controlling duty cycle of an electrical device in accordance with width-modulated digital control pulses supplied at the control pulse rate, and, digital control logic for generating the width-modulated digital control pulses in relation to the digital values. The digital control logic may include a linear feedback shift register to pseudo-randomize the digital control pulses to reduce electromagnetic interference.

Abstract: A three-terminal low-voltage PWM controller chip includes a first terminal for receiving operating bias current supply and a feedback control signal related to an output parameter of an electrical circuit to be controlled; a second terminal connected to an output switch providing digital width-modulated control pulses to control duty cycle of the electrical circuit; a third terminal ground connection; a clocked pulse width modulation circuit responsive to current flow between the second terminal and the third terminal and the feedback control value for controlling the digital output switch; and, feedback signal separation circuitry for separating the feedback control signal from the operating bias current supply. A start-up circuit is also provided.

Abstract: A power supply for a capacitive load, such as an electroluminescent lamp, converts a low battery voltage to a significantly higher voltage of alternating polarity to drive the load. A desired voltage waveform is applied to the load by accumulating charge in its inherent capacitance from voltage spikes resulting from rapidly disconnecting an inductor from the battery. The maximum voltage applied to the load is maintained below a maximum by a feedback loop that monitors a reduced voltage by use of a voltage divider. The voltage divider is formed of a plurality of capacitors connected in series, the reduced voltage being monitored across one of them. The entire power supply is formed on a single integrated circuit chip, except for the inductor, battery and load.

Abstract: A power supply damping circuit (22) coupled across the leads of a power supply (20) is able to substantially damp or reduce the resonant response of the power supply and any associated noise, ringing, or oscillation produced by the power supply. The power supply damping circuit (22) provides a low value real impedance in parallel with the power supply (20) as a means of damping the power supply resonance circuit. The power supply damping circuit (22) includes a transconductance element (36) capacitively coupled across a power supply (20). A bias control (54) provides a bias current to the transconductance element (36) to set the static current of the transconductance element (36).

Abstract: A low power magnetic-field detector, of the kind for detecting an ambient magnetic field that is greater than a predetermined field strength, is comprised of a Hail element, a transducer-voltage amplifier, and a zero-crossing comparator, all connected in tandem. A clock and switch are used to chop the energizing current to the Hall element. Alternatively, the amplifier and comparator are also chopped to further reduce power consumption. A clockable flip flop is synchronously enabled for an instant at the end of each period of energizing the Hall element. The comparator output signal is transferred to the flip flop Q output and held there during each period of not energizing the Hall element. A Positive-feedback hysteresis circuit adds a bias voltage to the amplified Hall voltage and is applied to the comparator input to effect comparator hysteresis with memory covering clock-period portions when the Hall element is not energized.

Abstract: An integrated circuit includes an analog-signal manipulating circuit (ASMC) such as a filter having a transfer function with a frequency response that is determined by at least one RC product. The integrated circuit also includes separately an RC oscillator. The frequency-response-determining RC products of an RC component pair in the filter and an oscillator frequency determining RC component pair in the RC oscillator are digitally programmable by an external microprocessor. The microprocessor holds the frequency of the RC oscillator fixed relative to its own crystal controlled oscillator by adjusting the programmable RC component pair of the RC oscillator. The same adjusting digital signal from the microprocessor is simultaneously applied to the programmable RC component pair(s) of the ASMC, which has the effect of stabilizing all RC component pairs and thus the ASMC frequency response. The capacitors of each RC component pair have binary-control-signal lines mutually parallel connected to each other.

Abstract: A disc drive circuit includes a pair of DC busses across which are directly connected a disc actuator power amplifier and a three phase spindle motor power amplifier which may be comprised of three circuit branches, each branch having two NMOS transistors connected in series with the junction therebetween connected to one of three spindle motor terminals. A transistor switch is connected between a DC supply source and the DC busses for disconnecting the busses from the voltage source only when the supply voltage drops below a nominal operating voltage range. In one embodiment a full wave diode rectifier is also directly connected across the pair of busses and further connected to the three motor terminals, whereby when the switch is open the back e.m.f. of the free spinning spindle motor energizes the actuator amplifier enabling parking of the actuator heads. In another embodiment the drain to channel regions of the six NMOS transistors are adapted to assume the role of a full wave rectifier.

Abstract: A temperature-compensated current source energizes a Hall element. The current source includes a voltage divider across the DC voltage supply busses and a differential amplifier arranged as a voltage follower which develops the output voltage across a reference resistor, creating a reference current which is amplified to generate a Hall energizing current. This results in a Hall element gain which is controllable over temperature. The temperature coefficient of the resistor can be chosen to compensate for the sensitivity temperature coefficient of a Hall element powered by a constant current source. Additionally, the temperature coefficient of the resistor may be chosen to compensate for the temperature coefficient of a magnet used to generate the magnetic field which the Hall element is intended to detect. The magnitude of the Hall current, and thus the Hall element gain, is directly proportional to the magnitude of the DC voltage supply.

Abstract: A notch filter circuit includes first and second operational amplifiers, each having a capacitor connected from the amplifier output to the input. A third capacitor is connected between the second-amplifier input and the filter circuit input. A first switched-capacitor resistor is connected between the filter circuit input and the first-amplifier input. A second switched-capacitor resistor is connected between the first amplifier output and the second amplifier input. The second-amplifier output is connected to the filter circuit output.

Abstract: A programmable PD servo compensator has the transfer function of the combination of a standard PD compensator in tandem with a second order low pass filter. The programmable PD servo compensator consists simply of a biquad filter having a single complex zero and a pair of conjugate complex poles. This servo compensator is comprised of two tandem connected operational amplifiers, each with a capacitor connected output to input across it. The tandem connection is effected by one switched-capacitor resistor between the output of the first amplifier to the input of the second. Another switched-capacitor resistor is connected between the PD compensator input and the input of the first amplifier. Yet another switched capacitor is connected between the PD compensator output and the input of the first amplifier.

Abstract: Analog-signal integrators are described that have a transfer function containing a composite parameter that is the product of two parameters each of which is separately changeable, via application of digital programming signals. In a continuous analog-signal integrator the integrating capacitor is a programmable capacitor array, preceded in the feed back branch with a programmable voltage divider. In a discrete-time analog-signal integrator the integrating resistor is a switched-capacitor resistor including a programmable capacitor array that is preceded in the input circuit branch by a programmable voltage divider.

Abstract: A digitally programmable integrated-circuit analog-signal servo co-processor has digital programming contact pads to which an external microprocessor may be connected, has analog-signal input pads and analog-signal output pads, and includes a plurality of programmable analog-signal-manipulating circuits (ASMC's). Each of the ASMC's has input and output terminals connected to an input programmable-switch matrix so that one or a combination of the ASMC blocks may be connected between the analog-signal input and output contact pads of the integrated circuit. Certain ASMC blocks have microprocessor programmable transfer functions, e.g. ASMC integrator, notch filter, low pass filter, PD compensator and voltage divider. Key ones of those ASMC blocks are discrete-time circuits including switched-capacitor resistors and have transfer functions wherein the parameters are ratios of capacitances and the switching rate frequency to provide accurate and stable performance.

Abstract: An integrated circuit chip includes a MOS driver transistor and a relatively small MOS current-monitor transistor having their sources connected to a circuit ground point and their gates connected together to a control-voltage conductor. Current through the monitor transistor flows to a DC voltage supply conductor through a field effect transistor. A differential amplifier has one input connected to the drain of the driver transistor and the other input connected to the drain of the monitor transistor. The output of the differential amplifier is connected to the gate of the field effect transistor to force the drain voltage of the monitor transistor to be equal to the drain voltage of the driver transistor. The current flowing through the small monitor transistor has a constant proportionality with the load current even as the load current approaches zero.

Abstract: An amplifier has a first stage employing a pair of differentially connected NMOS amplifier transistors, a second stage composed of a bipolar current mirror circuit and two charge pumps. Each charge pump may be a switching voltage multiplier circuit without the conventional output capacitor. The outputs of the two charge pumps are connected, respectively, to the collector of the current-mirror output transistor and to the commonly connected sources of the NMOS amplifier transistors. Each charge pump serves as both a pulse-voltage energizing source and a load to the amplifier. The amplifier is incorporated with a high-current NMOS transistor in an integrated circuit, wherein one differential input of the amplifier is connected to the source of the driver transistor at which an external load, e.g. a motor, may be connected.

Abstract: An improved current pump for use in a Type II phase-locked loop including diodes employed as on-off switches for completing paths for a source current. Apparatus is disclosed for increasing the switching speeds of the diodes by ensuring that diode bias voltages undergo the smallest possible shifts required to switch the diodes.

Abstract: An improved charge pump for use in a phase-locked loop is disclosed in which there is only one current source, and in which all switching components pass current in the same direction. The charge pump may thus be constructed entirely of NPN transistors, which makes it possible to embody it in a single integrated circuit chip. The pump up and pump down currents inherently have the same magnitude and transient characteristics, thus minimizing steady-state errors.

Abstract: A disk drive employs transversal filters as equalizers for each of its read heads, permitting adaptive equalization of read head signals, optimized for each track position.