Fairchild Semiconductor Corporation

Other

Myron J Miske

Gregory A Maher

John R Turner

Jeffrey B Davis

Trenor F Goodell

Christian Klein

Lei Huang

Julie Lynn Stultz

Danyang Zhu

Robert A Card

David P Morrill

Peter Chadbourne

Michael Smith

Jefferson Hopkins

Jaeyoung Yoo

Stephen B Lombard

This document discusses, among other things, systems and methods to provide an internal supply rail with over voltage protection using a host power source, an external power source, and a switch configured to receive indications of host and external power source validity. In an example, the switch can be configured to provide the internal supply rail using the host power source when the indication of host power source validity indicates a valid host power source and the external power source when the indication of host power source validity indicates an invalid host power source and the indication of external power source validity indicates a valid external power source.

Power management with over voltage protection

This document discusses, among other things, circuits and methods for providing an indication of an impedance between a detecting pin and a first signal pin of an audio socket using first and second comparators to, among other things, determine if moisture is present in the audio socket. If moisture is present in the audio socket, communication between an audio processing unit and the audio socket can be disabled.

Audio jack insertion/removal fault detection

This document discusses, among other things, an attack detection module configured to permanently shut down a slave device after a number of consecutive attacks.

Permanent lockout attack detection

An ESD protection circuit is described that protects the output transistors of a target circuit, usually an integrated circuit, that has an output enable, OE, or similar control input. An OE signal turns off the output transistors allowing the target circuit output, or outputs, to electrically float. Such a condition is commonly called a three state condition. The inventive protection circuit is not connected to the output directly, it senses an ESD voltage spike at the +Vdd contact to the circuit and produces a timed signal. The timed signal is converted to logic levels and gated with the OE signal (that the system previously provided to the OE control input). The output of gate forms a new OE control input signal that forces the target circuit into its three state condition during the period of the timed signal.

ESD protection for outputs

An embodiment of a bidirectional signal interface includes first and second nodes and first and second translating circuits. The first and second nodes are respectively operable to receive a first logic signal and a second logic signal. The first translating circuit has a first signal path coupled between the first and second nodes, is operable to sense a transition of the first logic signal on the first node, and, in response to the transition, is operable to couple the first logic signal to the second node via the first signal path. The second translating circuit has a second signal path that is coupled between the first and second nodes and that is parallel to the first signal path, is operable to sense a transition of the second logic signal on the second node, and is, in response to the transition of the second logic signal, operable to couple the second logic signal to the first node via the second signal path.

Bidirectional signal interface and related system and method

An FET switch comprising a single or parallel opposite polarity FETS is illustrated with wells that are driven from internal power rails. The internal power rails are logically coupled by other driving FET switches to, in one case, the higher of a positive power supply or signal level wherein the well of the PMOS FET switch will not allow the drain/source to well diode to be forward biased. In a second case, a second power rail is logically coupled to the lower of either and input signal or ground, wherein the well of the NMOS FET will not allow the drain/source to well diode to be forward biased.

Method for reducing insertion loss and providing power down protection for MOSFET switches

A pass-gate having a single or parallel opposite polarity FETs is disclosed. The wells of the primary transistor switches are driven from circuitry that reduces over-voltage leakage and other malfunctions. A circuit that drives the wells is also used to power enable circuits that drive the gates of the pass transistors. The use of separate circuits to the gate and the wells further reduces leakage. In the condition of power supply voltage and signal levels that are near the thresholds of the FETs involved, one or more Schottky diodes may be used across pn junctions in the FETs that will prevent turning on the pn junctions.

Over-voltage tolerant pass-gate

An ESD protection circuit for an input/output pad of an IC is disclosed with discharge paths to both a power rail and ground. The ESD circuit is arranged with NMOS and PMOS transistors arranged with their drains connected to the pad. However, the drain capacitances have voltage sensitivities that compensate or cancel each other, and with proper sizing the capacitance load on the pad can be made substantially constant over a given voltage range. By providing a discharge path to a power rail, the ESD circuit may be designed to be more tolerant of overvoltages on the power rail.

Method of linearizing ESD capacitance

A DC symmetrical FET switch includes second and third switches connecting the well of the symmetrical FET switch to the drains and the source when the symmetrical FET switch is on. When the three FET's are on, the well, source and drain of the symmetric FET switch all exhibit the same input signal, wherein the drains and source to well capacitances are substantially prevented from draining off any of the input signal, thereby increasing the bandwidth and decreasing the insertion loss of the switch. The second and third switches are also FET switches. An enable signal is connected to the gates of all three FET's turning them on and off together. When the enable is false the FET switches are turned off and their wells are driven to a potential a proper potential. When the FET's are n-type the potential is low and when the FET's are p-types the potential is high. A resistor is provided in the gate drive of the first FET switch that further increases bandwidth and decreases insertion loss of the switch by moving the break frequency of the drain and source to gate capacitances.

Circuit and method for lowering insertion loss and increasing bandwidth in MOSFET switches

A bus hold circuit of CMOS components that draws no DC current and is over voltage tolerant is described. No leakage current is drawn from the input when the input voltage is greater than the bus hold circuit supply voltage. A feedback inverter is used to s latch the Vin logic in the bus hold circuit. When Vin is low, it turns on a first switch that drives the gate of a PMOS switch low turning it on. The PMOS switch connects the power connection of the feedback inverter to Vcc. The gate remains low, keeping the PMOS switch turned on as Vin increases. The first switch is turned off, but the gate of the PMOS switch remains low, until Vin exceeds Vcc. At that point, a comparator drives the gate of the PMOS to Vin shutting the PMOS switch off. An arbiter circuit selects the higher of Vcc and Vin to bias the N-well of the PMOS switch and other PMOS components in the comparator and arbiter circuit. This biasing ensures that the N-wells are never forward biased, thereby preventing leakage from the Vin.

Bus hold circuit with power-down and over-voltage tolerance

A bus switch for transferring logic signals between nodes without the problems associated with undershoot conduction. The bus switch is an FET switch including a single primary transfer transistor. The bulk of the transfer transistor is coupled to a differential logic sense circuit that is designed to establish a pseudo low-potential power rail. The logic sense circuit is coupled to the two transfer nodes and a standard low-potential power rail. It compares the potentials associated with the transfer node signals and the low-potential rail and selects the one with the lowest potential to establish the potential of the pseudo low-potential rail. The logic sense circuit provides for active selection of the lowest potential element, including under very small undershoot conditions. The logic sense circuit may be established in a variety of ways, preferably by including a differential comparator pair, one of associated with one of the two transfer nodes and the other differential comparator associated with the other transfer node. Outputs of the differential pair control logic drivers that in turn regulate the transfer node, or standard low-potential rail to be coupled to the pseudo low-potential power rail. This arrangement ensures that there will be no parasitic conduction of the transfer transistor during undershoot conditions.

Active undershoot hardened fet switch

A transfer gate or pass gate circuit for transferring logic signals between nodes for a range of available high-potential supply levels. The primary transfer gate is designed to protect against potentials that either exceed either a high-potential or a low-potential level or that undershoot such potential levels. For overshoot (overvoltage) tolerance, this is achieved by coupling a NMOS transistor in parallel with a pair of PMOS transistors that are coupled in series. All three transistors are located between two nodes, either of which can be the input or the output of the transfer gate. The NMOS transistor is designed to be larger than the PMOS transistors and carries most of the transfer capability. The smaller PMOS transistors are designed to eliminate potential drops that would otherwise occur with a single NMOS transistor or with a complementary pair of transistors. For undershoot (undervoltage) tolerance, a PMOS transistor is coupled in parallel with a pair of NMOS transistors that are coupled in series.

Overvoltage/undervoltage tolerant transfer gate

A bus switch for transferring logic signals between nodes without the problems associated with undershoot conduction. The bus switch is an FET switch including a single primary transfer transistor. The bulk of the transfer transistor is coupled to a bulk regulating circuit including a pseudo low-potential power rail. The pseudo low-potential rail is coupled to one arbiter circuit associated with one of the two circuit transfer nodes and a second arbiter circuit associated with the other of the two transfer nodes. The arbiter circuits are coupled to their respective nodes or pads and to a common low-potential supply rail. The arbiter selects for coupling to the pseudo low-potential rail the signal of the lower potential between that at the pad and that of the low-potential rail. This arrangement ensures that there will be no parasitic conduction of the transfer transistor during undershoot conditions. In an alternative embodiment that may be used to minimize the vagaries associated with process variations, the transfer transistor's gate may be independently coupled to a second pseudo low-potential power rail.

Growing community of inventors

Newfields, NH, United States of America

Myron J Miske