Integration Associates Incorporated

Intergration Associates Inc.

Matthijs D Pardoen

Wayne Thomas Holcombe

Attila Zólomy

János Erdélyi

Ferenc Mernyei

Hendricus De Ruijter

Péter Onódy

András Hegyi

Gábor Tóth

Disclosed is a circuit and method for automatic tuning of a resonant circuit in a transceiver having a receiver and a transmitter that includes a power amplifier for driving the resonant circuit. During a transmit mode of the transceiver, a resonance voltage of the resonant circuit is compared to an input voltage signal to the power amplifier to determine an error signal that is converted into a control word. The control word drives an adjustable capacitance bank that is part of the resonant circuit. During a receive mode of the transceiver, the control word value is held constant to substantially maintain resonance of the resonant circuit during operation of the receiver.

Method and apparatus for automatic tuning of a resonant loop antenna in a transceiver circuit

A hook switch circuit is shown wherein two high-voltage bipolar transistors, a PNP transistor Qand a NPN transistor Q. that are connected in a regenerative feedback manner to form a bi-stable latch. The regenerative structure permits the use of low beta transistors that may be turned on with a low control current, but still conduct a sufficient off-hook current. Also shown is a polarity steering regenerative switch (MP, MP) that provides a power supply voltage from a telephone line pair and may be adapted for a polarity signal and can be combined with a current mirror (MP) to produce a current signal proportional to the line voltage (LV).

DAA hook switch

Disclosed is a circuit and method for continuous automatic tuning of a resonant circuit. A resonance voltage of the resonant circuit is phase shifted by a predetermined phase shift &#x3a6; degrees and an input voltage signal to a power amplifier driving the resonant circuit is phase shifted by &#x3a6;&#xb1;90 degrees to place the signals in quadrature. The phase shifted signals are mixed to obtain a error signal. The error signal is compared to a predetermined voltage range in order to generate control signals for a control word generator, such as an up-down counter. The control word generator produces a control word that drives a capacitance bank that is part of the resonant circuit. The present invention continuously automatically adjusts the capacitance of the capacitance bank to tune the resonant circuit.

Method and apparatus for automatic tuning of a resonant loop antenna

The present invention is directed toward a method and apparatus for transferring data across an isolation barrier using high speed analog encoded signals. A line side circuit interfaces with tip and ring contacts on one side of a capacitive isolation barrier that isolates the line side circuit from a modem side circuit. During an on-hook state, the line side circuit converts an analog line side voltage signal to a frequency signal and then encodes the frequency signal into a high frequency pulse-width-modulated (PWM) signal. The high frequency PWM signal is transmitted across the capacitive isolation barrier to the modem side circuit. During an off-hook state, the analog line side voltage is again encoded into a high frequency pulse-width-modulated (PWM) signal for transmission across the isolation barrier. The modem side circuit recovers the transmitted PWM signal and converts it into a digital count value that represents the amplitude of the analog voltage observed at the tip and ring. The digital count value may be directly processed by a processor on the modem side or may be converted back to an analog signal.

Method and apparatus for isolation in a data access arrangement using analog encoded pulse signaling

A circuit and method are shown for battery reversal protection. The circuit includes a first transistor that buffers a bulk terminal of a protected transistor from an input terminal for receiving a power supply voltage. A second transistor is coupled to both the input terminal of the circuit and an output terminal of the circuit and detects when the power supply voltage falls below an output voltage at the output terminal and, responsive thereto, switches off the first transistor to isolate the bulk terminal of the protected transistor from the input terminal. Another aspect of the invention provides current reversal protection using a third transistor that also detects when the power supply voltage falls below an output voltage at the output terminal and, responsive thereto, conducts current from the output terminal to the gate terminal of the protected transistor. In yet another aspect of the invention, a bulk of the third transistor is coupled to a low current circuit to provide current to the low current circuit from the output terminal when power at the input terminal is interrupted. Because of low current demands on the transistors of the protection circuit, small area transistors may be used to implement the protection circuit using reduced die area.

Battery and current reversal protect circuit

One aspect of the present invention detects an equivalent series resistance (ESR) of an external capacitor and adjusts a transfer function of a feedback loop of the voltage regulator to compensate for the ESR. The ESR is detected by measuring a phase shift in a ripple voltage signal of an output voltage of the voltage regulator. Based upon the measured phase shift, an adjustable capacitance is introduced to the feedback loop to compensate for the ESR by introducing a zero to the transfer function to stabilize the voltage regulator circuit. Another aspect of the present invention is to adjust the transfer function of the feedback loop to improve transient response. By measuring both the phase shift and the amplitude of the ripple voltage signal, a gain and the position of a pole in the transfer function of the feedback loop may be adjusted to improve the transient response.

Automatic bandwidth and stability control for switched pulse width modulation voltage regulator

A method and circuit are shown for controlling an in-rush current to a voltage regulator circuit. A sense transistor is coupled in parallel with a pass transistor of the voltage regulator circuit and used to monitor the current through the pass transistor. A sense current through the sense transistor is converted to a voltage signal and input to an amplifier along with a ramping voltage signal generated in response to a circuit activation signal. An output of the amplifier drives a control gate of a current source that sources current to gate terminals of both the pass transistor and the sense transistor. A limiting circuit also monitors the sense current and sinks current from the control terminal of the current source in order to limit a maximum current through the pass transistor.

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Sunnyvale, CA, United States of America

Matthijs D Pardoen