Pericom Semiconductor Corporation

Lsi Logic Corporation

Other

Swift Microelectronics Corporation

Anthony Yap Wong

Daniel Wong

Trung T Nguyen

Charles Hsiao

David Kwong

Steven S Chan

Conrad J Dell'Oca

Kwong Shing Lin

Roger T Szeto

Robert M Walker, Iii

Brian Cheung

Alex C Hui

Michael B Cheng

Belle Wong

Anna Tam

Lee Yang

Eric Chan

A stable voltage that is independent of supply voltage is applied to a pair of current sources. A first current source generates a first current that passes through a first resistor, setting a compare-input voltage. A source-input voltage is applied to the first current source to vary the first current and the compare-input voltage. A second current source generates a stable current that passes through a second resistor, setting a reference voltage. The compare-input voltage and the reference voltage are applied to inputs of a comparator that generates an output voltage that indicates when the source-input voltage causes the compare-input voltage to rise past the reference voltage. The first and second currents track each other over temperature and process variations and are independent of supply voltage. A more accurate comparison of the source-input voltage is thus made.

Substrate-sensing voltage sensor for voltage comparator with voltage-to-current converters for both reference and input voltages

A stable voltage that is independent of supply voltage is applied to a pair of current sources. A first current source generates a first current that passes through a first resistor, setting a compare-in-put voltage. A source-input voltage is applied to the first current source to vary the first current and the compare-input voltage. A second current source generates a stable current that passes through a second resistor, setting a reference voltage. The compare-input voltage and the reference voltage are applied to inputs of a comparator that generates an output voltage that indicates when the source-input voltage causes the compare-input voltage to rise past the reference voltage. The first and second currents track each other over temperature and process variations and are independent of supply voltage. A more accurate comparison of the source-input voltage is thus made.

Accurate voltage comparator with voltage-to-current converters for both reference and input voltages

A voltage booster drives the gate of a bus-switch n-channel transistor to a theoretical maximum of triple the power-supply voltage Vcc. The gate node is first driven to Vcc. Then the back-side of a first capacitor is driven from ground to Vcc, coupling a first voltage boost to the gate node. After a Schmidt-trigger detects the back-side of the first capacitor near Vcc, the back-side of a second capacitor is driven from ground to Vcc. The front-side of the second capacitor is connected to the back-side of the first capacitor. A second voltage boost is coupled across the first and second capacitors to increase the voltage boost of the gate node to near triple Vcc rather than just double Vcc.

Voltage booster with increased voltage boost using two pumping capacitors

A fail-safe circuit for a differential receiver can tolerate noise. A latch is enabled when both differential inputs V&plus;, V&minus; rise above a reference voltage that is close to Vcc. The latch, once enabled, is set by an offset amplifier, signaling the fail-safe condition. The offset amplifier sets the latch when V&plus; is above or equal to V&minus;. The differential amplifier has a small offset voltage to allow the latch to remain set when V&plus; and V&minus; are equal in voltage. An output from a differential amplifier receiving V&plus; and V&minus; can be blocked by a gate when the fail-safe condition is latched. Pullup resistors pull V&plus;, V&minus; to Vcc when an open failure occurs. The latch remains set when common-mode noise occurs on V&plus;, V&minus;, preventing noise from prematurely disabling the fail-safe condition. Such noise coupled into a broken cable is usually common-mode.

Latched active fail-safe circuit for protecting a differential receiver

An active terminating circuit has buffers to produce wider voltage drives on clamping transistors. A transmission line drives coupling capacitors. One capacitor drives an upper node that drives the gate of an upper buffer transistor. The upper buffer transistor drives a p-gate node coupled to a gate of a p-channel clamping transistor. The other capacitor drives a lower node that drives the gate of a lower buffer transistor, which drives an n-gate node of an n-channel clamping transistor. The drains of the clamping transistors are connected to the transmission line. Resistors pull the lower node to the power-supply voltage and pull the upper node to ground when no transitions occur on the transmission line, achieving zero standby power. When a transition is detected, it is coupled through the capacitors and buffered to the p-gate and n-gate nodes. Limiting transistors limit upper and lower node swings.

Capacitively-coupled extended swing zero-DC-power active termination with CMOS overshoot/undershoot clamps

An active terminating circuit has n-channel and p-channel sensing transistors with gates connected to a transmission line. The sensing transistors drive a back node connected to a pair of capacitors. One capacitor drives a p-gate node coupled to a gate of a p-channel clamping transistor, while the other capacitor drives an n-gate node coupled to a gate of an n-channel clamping transistor. The drains of the clamping transistors are connected to the transmission line. Resistors pull the p-gate node to the power-supply voltage and pull the n-gate node to ground when no transitions occur on the transmission line to achieve zero standby power. When a transition is detected, it is inverted and coupled through the capacitors to the p-gate and n-gate nodes. The p-channel clamping transistor is turned on for rising transitions, while the n-channel clamping transistor is turned on for falling transitions. Limiting transistors limit gate-node swings.

Zero-DC-power active termination with CMOS overshoot and undershoot clamps

A fail-safe circuit for a differential receiver can tolerate high common-mode voltages. An output from a differential amplifier that receives a V&plus; and a V&minus; differential signal can be blocked by a NOR gate when the fail-safe condition is detected, such as when the V&plus;, V&minus; lines are open. Pullup resistors pull V&plus;, V&minus; to Vcc when an open failure occurs. A pair of comparators receive a reference voltage on the non-inverting input. Once comparator outputs a high when the V&plus; line is above the reference voltage, and the other comparator outputs a high when the V&minus; line is above the reference voltage. When both V&plus; and V&minus; are above the reference voltage, the NOR gate blocks the output from the differential amplifier, providing a fail-safe. Since the reference voltage is very close to Vcc, a high common-mode bias can exist on V&plus;, V&minus; without falsely activating the fail-safe circuit.

Active fail-safe detect circuit for differential receiver

A low-voltage differential signaling (LVDS) output buffer has an improved eye pattern. The LVDS buffer has two parallel stages. A primary stage generates enough current to generate a first voltage drop across a load resistor. At higher frequencies, parasitic capacitive coupling reduces this first voltage drop, closing the eye pattern. A boost stage generates an additional boost current through the load resistor, adding to the voltage drop and opening the eye pattern. The boost stage is coupled to the outputs by link transistors that are enabled by a pre-emphasis signal generated by resetable pulse generators. When outputs switch, the pre-emphasis signal pulses the link transistors on, adding the boost current. At high frequencies, the pulse generators are reset before the pre-emphasis signal ends. The boost current is continuously added at high frequencies, but at low frequencies the boost current only occurs during the pre-emphasis period after outputs switch.

Low-voltage differential-signalling output buffer with pre-emphasis

An amplifier designed from CMOS transistors provides a high current output, despite having a unity-gain configuration. A push-pull output stage drives the output using a p-channel pull-up transistor and an n-channel pull-down transistor. The pull-down transistor's gate is driven by an output from an inverting differential amplifier, that has one differential transistor gate driven by an input voltage and the other driven by the output voltage. A second differential amplifier is configured as a non-inverting differential amplifier, with one differential transistor gate driven by the input voltage and the other driven by the output voltage. The second differential amplifier drives an n-channel gate of an inverting stage, and the output of the inverting stage drives the p-channel pull-up transistor's gate. When the input voltage is above the output voltage, the inverting differential amplifier drives a lower voltage to the gate of the pull-down transistor, reducing sink current, while the inverting stage drives a lower voltage to the gate of the pull-up transistor, increasing source current. Both the pull-up and pull-down transistors work together to raise the output voltage.

Low-power CMOS voltage follower using dual differential amplifiers driving high-current constant-voltage push-pull output buffer

A gate-array cell uses smaller and larger transistors. Four larger transistors are provided: two n-channel and two p-channel. A small p-channel transistor is placed between the contact tabs of the polysilicon lines of the two larger p-channel transistors, and between the p-channel transistors and a N-well tap. A small n-channel transistor is similarly placed between the contact tabs of polysilicon lines of the two larger n-channel transistors, and between the n-channel transistors and a P-well tap. The cell is slightly expanded in height to accommodate the two smaller transistors. The smaller transistors enable a reduction in the number of transistors required for latches and flip-flops. The smaller transistors allow a feedback inverter to directly connect to an input, since the input can easily over-power the feedback current. This is not possible for standard gate array cells having only one transistor size. Transmission gates are eliminated when direct feedback is feasible. Thus, the smaller transistors enable a reduction in transistor count as well as being smaller in size. Clear and set are provided by larger pull-down or pull-up transistors rather than NAND gates, since the larger pull-down and pull-up transistors can easily over-power the feedback inverters.

Versatile gate-array cell with interstitial transistors for compact

A repeating cell structure in a semiconductor substrate for a BiCMOS logic gate array. The cell structure has three regions shaped as columns. The first columnar region is a P-well and has four vertically aligned active areas of N-type material formed within the columnar region. Each of the active areas has two gate electrodes to form two NMOS transistors. Similarly the second columnar region is a N-well and has four vertically aligned active areas of P-type material. Each such active region forms two PMOS transistors. The third column has two bipolar transistors, each with collector, base and emitter regions vertically aligned. The resulting BiCMOS logic array permits a flexible location of macrocells, which results in a compact implementation of the resulting integrated circuit.

BiCMOS compacted logic array

An n-channel bus switch has a transistor gate boosted above the power supply (Vcc) to increase current drive and reduce the channel resistance of the bus switch. No pulse generator is needed. The gate terminal is connected to a boosted node. When the bus switch is turned on, a pullup transistor drives the boosted node from ground to Vcc. The pulse generator is eliminated by using a Schmidt-trigger to sense the voltage of the boosted node. Once the Schmidt-trigger senses that the voltage of the boosted node is near Vcc, the pull-up is turned off. A delay line first drives the gate of the pullup transistor to a threshold below Vcc using an n-channel pullup, and then drives the gate to Vpp using a p-channel pullup. A delay line then drives the back-side of a capacitor from ground to Vcc. This voltage swing is coupled through the capacitor to the boosted node, driving the boosted node about 1.3 volts above Vcc. A small keeper transistor supplies a small current to the boosted node to counteract any leakage. Vpp current drain is reduced by using multiple stages to turn the pullup off.

Voltage booster with reduced Vpp current and self-timed control loop

A bus switch is constructed from an n-channel transistor. The gate terminal of the n-channel transistor is boosted above the power supply (Vcc) to increase current drive and reduce the channel resistance of the bus switch. The gate terminal is connected to a boosted node. When the bus switch is turned on, a pulse is generated to drive the boosted node from ground to Vcc. The boosted node is also an input of a delay line. After a delay through the delay line, the pulsed pull-up is turned off. Feeding the boosted node to the delay line allows the pulse to be self-timed. The delay line then drives the back-side of a capacitor from ground to Vcc. This voltage swing is coupled through the capacitor to the boosted node, driving the boosted node about 1.3 volts above Vcc. A small keeper transistor supplies a small current to the boosted node to counteract any leakage. This leaker transistor is connected to a charge pump, and the delay line that enables this keeper transistor is also connected to the charge pump. A precise sequence of events boosts the gate voltage of the bus switch above Vcc without drawing large currents from the charge pump.

Voltage booster with pulsed initial charging and delayed capacitive

A synchronizer that has reduced latency is used for synchronizing and conditioning a clock-enable signal to a free-running clock. Once the clock-enable signal is synchronized it is used to enable and disable gating of the free-running clock to a gated clock that suspends pulsing in response to the clock-enable signal. A first-stage flip-flop is `meta-stable hardened` to reduce the probability of it becoming meta-stable. Gating on the clock and the clear inputs reduces the chance that simultaneous inputs will violate the timing of the flip-flop and thus cause metastability. A clear pulse is generated to clear the flip-flop. The clear pulse skews the flip-flop to be more likely to become metastable for one edge of the asynchronous input than for the other edge. The settling time to the second stage flip-flop is then adjusted to account for this skew in metastability. Settling time in the second stage is increased for the edge that is more likely to become metastable. Clock-enable conditioning to prevent partial output pulses is merged with the synchronizing function to further reduce latency.

Meta-stable-resistant front-end to a synchronizer with asynchronous

An electronic system such as a Single-Chip-Module (SCM), a Multi-Chip-Module (MCM), or a Board-Level-Product (BLP) includes a plurality of units which are interconnected by a terminated transmission bus line. Each unit includes a CMOS circuit, a terminated bus line for signal transmission, and a driver/receiver circuit which is spaced from the CMOS circuit on a substrate. A guard ring is formed around at least a part of the CMOS circuit which faces the driver/receiver circuit. The driver/receiver circuit includes a driver for receiving an input logic signal from the CMOS circuit and inducing a corresponding signal onto the bus line, and a receiver for receiving an output signal from the bus line and providing a corresponding output logic signal to the CMOS circuit. The receiver includes a receiver transistor having a gate electrically connected to the bus line and producing a current in relation to the received signal, a comparator for comparing a voltage level of the received signal to a reference voltage level and for splitting the current into a first path having a current inversely proportional to the received signal and a second path having a current in proportion to the received signal, an output section for providing the CMOS logic signal at a first logic state when the current in the first path is greater than the current in the second path, and for providing the CMOS logic signal at a second logic state when the current in the first path is less than the current in the second path.

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Cupertino, CA, United States of America

Anthony Yap Wong