Fairchild Semiconductor Corporation

National Semiconductor Corporation

Oscar W Freitas

James B Boomer

Steven M Macaluso

Tyler Daigle

Seth M Prentice

Nickole Gagne

John R Turner

Trenor F Goodell

Christian Klein

Derek Richardson

Wonsoo Moon

Apparatus and methods for reducing crosstalk in personal audio equipment are provided. In an example, a method to reduce headset audio crosstalk can include applying a first signal to a first speaker channel of a headset, coupling a second speaker channel to a first input of a comparator of a crosstalk compensation circuit using a first switch of the crosstalk compensation circuit, the switch and detect circuit including the crosstalk compensation circuit, coupling a first resistor divider to a second input of the comparator using a second switch of the crosstalk compensation circuit, and adjusting a resistance setting of the first resistor divider from an initial setting using an output of the comparator.

Remote ground sensing for reduced crosstalk of headset and microphone audio signals

Method and apparatus, among other things, are provided for detecting a charger type. In an example, a method to classify a potential charger coupled to a port of an electronic device can include detecting the potential charger coupled to a USB-compatible port of the electronic device, applying a pull-down current to first and second data lines of the USB-compatible port to provide a first test voltage on each of the first and second data lines, and executing a primary detection process of a USB Battery Charging 1.2 Compliance Plan if the first test voltage on each of the first and second data lines is not between a first threshold and a second threshold using the pull-down current.

Charger detection with proprietary charger support

This document discusses, among other things, an audio jack detection circuit configured to be coupled to an audio jack receptacle of an external device. The audio jack detection circuit configured to receive to receive audio jack receptacle information, to disable an oscillator when the audio jack receptacle information indicates that the audio jack receptacle is empty, and to enable the oscillator when the audio jack receptacle information indicates that the audio jack receptacle includes an audio jack.

Audio jack detection and configuration

An MIPI interface is connected to two sensor sources that each may be transferring both high and low speed information, typically video information in the high speed state. The clock signals are monitored and when one of the clock signals exceed a threshold, an analog switch between the MIPI interface and the sensors, may connect the other source to the MIPI interface.

MIPI analog switch for automatic selection of multiple image sensors

A serializer/deserializer interfacing a keypad or keyboard to a processing system is illustrated. However, to minimize wires on intervening cables, a serializer and deserializer is inserted between the processor system and the keypad forming a virtual keypad. The processor scans the deserializer as if it were the keypad and the keypad is scanned by the serializer as if it were the processor. The serializer converts the scanning of the keypad into a serial bit stream and clock that is sent to the deserializer. The deserializer accepts the serial bit stream and reconfigures the data into a response that mimics the response of the physical keypad. In one embodiment an actual second keypad is formed in the deserializer and activated as the first keypad is activated.

Method and circuit for capturing keypad data serializing/deserializing and regenerating the keypad interface

MIPI analog switch for automatic selection of multiple inputs based on clock voltages

A system for interleaving high speed data and slower data that is serialized and delivered to a microprocessor. The typical source of the high speed data is a camera and the source of the slower data is a keyboard. The high speed data and the slower data, illustratively, are interfaced with a micro-processor in a parallel fashion. The present invention mirrors the parallel interface to the microprocessor, and mirrors the parallel interface to the sources of the high speed (camera) and slower (keypad) data. The present system formats parallel data from the sources and passes that data in serial form, typically with a clock, on a flexible cable that joins two sections of many cell phones or other hand held devices.

Method and circuit for interleaving, serializing and deserializing camera and keypad data

A system and process for eliminating a control wire between logic systems that communicate with each other. In one embodiment, a system sends to a receiver a frequency that indicates a first mode. In the first mode a first data type may be sent. When the frequency is changed a second mode is indicated wherein a second data type may be sent. The receiver detects the frequency change and assumes the first or second mode as indicated.

Method and circuit for changing modes without dedicated control pin

A transceiver driver for shaping an output signal includes one or more capacitive elements designed to manipulate the current applied to the control node of the driver's output transistor. The capacitive elements may be one or more capacitors coupled to an inverter branch that provides turn-on and turn-off potential to the gate of the output transistor. The capacitive elements act to charge or discharge the transistor's gate gradual in a highly programmable way so as to make the driver substantially independent of fabrication, supply voltage, and operating temperature vagaries.

Transceiver driver with programmable edge rate control independent of fabrication process, supply voltage, and temperature

A CMOS-based circuit for translating a differential-input into a single-ended output capable of driving large loads with little or no compromise in speed. This translator provides a symmetric single-ended output signal capable of driving a wide range of loads with minimal distortion. In contrast to earlier such translators, the circuit of the present invention ensures that the output signal is coupled directly to the high-voltage rail after being switched to logic HIGH and that that coupling remains in effect until an input signal causing the output to switch to logic LOW is received. Similarly, when the output signal is switched to logic LOW, it is coupled directly to the low-voltage rail of the circuit and left so coupled until it is affirmatively switched to logic HIGH. This feature ensures that regardless of load, the output signal completely switches to the proper logic stage.

Differential-input/single-ended-output translator

A multiplexer for selecting a single output signal from a plurality of input signals. For a plurality of complementary input signal pairs in particular, the multiplexer includes for each pair of complementary input signals a control sub-circuit having a selection switch and a common resistance in parallel. The switch and the common resistance have a common low-potential node that is tied to a pair of resistances that are in parallel, wherein each of the parallel resistances is coupled to the respective high-potential nodes of a differential amplifier. A particular pair of incoming complementary input signal pairs controls the differential amplifier. An off-circuit selection signal selects which switch of a plurality of control sub-circuits is activated. When a switch is on, it creates a bypassing of the common resistance, thereby enabling the turn-on of output drivers coupled to the differential amplifier. When a switch is off, the potential drops across the common resistance and the parallel resistances reduce the potential at the output drivers' control nodes enough to block their turn-on. As a result, the only output drivers providing signal output are those associated with the one selected control sub-circuit having its switch turned on.

Low voltage, high speed multiplexer

A pointer processor circuit substantially eliminates the pointer gap during justification of an outgoing SONET/SDH frame relative to an incoming SONET/SDH frame. The pointer interpreter circuit PI is constructed to receive an incoming frame, interpret the pointer H1H2, and write data payload bytes of the incoming frame into a FIFO memory. An input clock CLK1 controls the writing of data payload bytes into the FIFO. The FIFO stores only data bytes. A pointer generator circuit PG is coupled to the FIFO and is constructed to read out data payload bytes from the FIFO, create an outgoing frame, and calculate a new pointer. An output clock CLK2 controls reading of data from the FIFO to form an outgoing frame. The PI, FIFO and PG cooperate for justification of the outgoing frame relative to the incoming frame. The PG is constructed to determine the time X between justifications, to count justifications, and to determine the occurrence of N justifications corresponding to a row N data payload bytes of the SONET/SDH frame in the time (N-1)X adjacent to a pointer gap time interval (R+1)X of no justifications corresponding to R transport overhead bytes of the row. The PG is also constructed to average approximately and spread out the justifications over the interval X (N+R) by spacing the justifications to occur at intervals of approximately X (1+R/N), thereby substantially eliminating the pointer gap. Whole integer approximations are typically used for spacing the justifications during justification steps along a row of the SONET/SDH frame.

SONET/SDH pointer justification gap elimination circuit

A pointer processing circuit processes SONET/SDH frames and calculates a new pointer value. A pointer interpreter circuit (PI) is constructed to receive an incoming frame, identify the pointer in transport overhead bytes of the frame, interpret the pointer, and send the pointer value directly to a pointer generator circuit (PG). The pointer value indicates the position of the first byte of the data payload bytes of the incoming frame starting at the trace byte J1. The PI is constructed to tag the next data byte after the pointer H1 H2 and negative justification data holding byte location H3 and send the tagged data byte directly to a FIFO without the delay of counting down to the trace byte J1 of the incoming frame. A first in first out memory FIFO is coupled to the PI for writing data payload bytes from the incoming frame into the FIFO. A pointer generator circuit (PG) is coupled to the FIFO for changing the pointer on the outgoing frame. The PG is constructed to determine the position of the tagged data byte relative to the outgoing frame and receive the value of the pointer for the previous incoming frame directly from the PI. The pointer generator is also constructed to calculate a new pointer value for the outgoing frame based upon the position of the tagged data byte relative to the outgoing frame and the pointer value for the previous incoming frame.

Sonet/SDH pointer calculation circuit

A temperature compensated ECL output driver circuit incorporates an ECL output gate (Q4,Q3) coupled between high (V.sub.CC) and low (V.sub.EE) potential power rails with output voltage swing resistors (R2, R1). The ECL output gate provides an output node (N1) at the collector node of one of the ECL output gate transistors (Q4). A first current sink (Q5,R4) is coupled between the common emitter node coupling (N3) of the ECL output gate (Q4,Q3) and low potential power rail (V.sub.EE). A compensating current source (Q11,R5) is coupled to the ECL output gate output node (N1) for generating a supplementary compensating current during operation of the ECL output driver circuit in intermediate and high temperature operating ranges. A compensating current switch (Q9,Q10) is coupled in the compensating current path and is constructed for switching off the supplementary compensating current in a specified low temperature operating range to maintain the logic high output signal V.sub.OH within specifications. The compensating current switch is an ECL compensating current switch (CCS) gate (Q9,Q10) and the compensating current source is a second current sink (Q11,R5) coupled to the ECL CCS gate.

Low power low temperature ECL output driver circuit

An ECL cutoff driver circuit for an ECL gate coupled between ECL high and low potential power rails includes a cutoff clamp circuit. The ECL gate with differential signal inputs and at least one output node is coupled for delivering ECL logic output signals of high and low potential levels during operation of the ECL gate in a switching mode. The cutoff driver circuit includes cutoff transistor elements for shifting down the ECL output at least to a maximum specified cutoff potential level below the ECL logic low potential level in a cutoff state. The cutoff clamp circuit is coupled between the ECL high potential power rail and the output node or output nodes for clamping the ECL output at a minimum or lower bound voltage level substantially at the specified cutoff voltage level V.sub.OLZ. This prevents output buffer transistor elements from being completely turned off for faster return of the ECL gate from the cutoff state to operation in the switching mode. The clamp circuit references the clamp voltage level to the ECL high potential power rail and is substantially independent of the current level in the cutoff clamp circuit.

Growing community of inventors

Cape Elizabeth, ME, United States of America

Oscar W Freitas