Abstract: A BICMOS memory performs address transition detection on each address signal. A first ECL difference amplifier detects a low-to-high transition with a first input being the address signal, and a second input being the address signal delayed and level-shifted. A second ECL difference amplifier uses a complement of the first and second inputs to detect a high-to-low transition. The outputs of two corresponding ECL difference amplifiers for each address signal are wire-ORed together to form the address transition detection signal, which is delayed for first, second, and third predetermined times to sequentially perform row predecoding, row decoding, and block decoding, respectively. The decoding is performed by logic circuits using modified Widlar current sources, which decrease the current required except during decoding, as indicated by a corresponding address transition detection signal. The saving in current allows faster ECL circuits to be used and decreases peak current on internal power supply lines.

Abstract: A sigma-delta digital-to-analog converter (20) reduces even order distortion, such as a DC offset, in an output signal by chopping the output signal alternately with set and reset pulses. The sigma-delta digital-to-analog converter (20) includes a sigma-delta modulator (25), a chop circuit (261) associated with a corresponding bit of the sigma-delta modulator (25), and an output buffer (264) for providing the output signal. The chop circuit (261) alternately inserts first and second logic levels into an output data stream of the sigma-delta modulator (25) before providing it to the output buffer (264). Even-order distortion is eliminated with only a tolerable attenuation of the output signal.

Abstract: A bipolar complementary metal oxide semiconductor (BICMOS) sense circuit for sensing data on read data lines during a read cycle of a memory comprises a load portion and a sense amplifier portion. In one form, the load portion couples true and complement read data lines to a first voltage in response to a start of a read cycle. When the true and complement read data lines exceed a predetermined voltage, the sense amplifier is enabled. The load portion becomes inactive when the voltage on the read data lines reaches approximately the first voltage. Then a selected memory cell provides a differential voltage on a bit line pair, which is coupled to the read data lines, indicating the contents of the selected memory cell. The sense amplifier provides a differential current onto a corresponding read global data line pair in response to the differential voltage.

Abstract: A continuous-time differential amplifier (52, 100) preserves fast settling time while reducing a relatively-high offset voltage-normally associated with a continuous-time differential amplifier using MOS load transistors. The differential amplifier (52, 100) includes a first transistor (81) biased as a current source to provide current into emitters of second (82) and third (83) emitter-coupled input transistors. Fourth (84) and fifth (85) load transistors are respectively coupled between collectors of the second (82) and third (83) input transistors and a power supply voltage terminal. An amplifier (70) having a positive input terminal coupled to the collector of the second input transistor (82) and a negative input terminal receiving a bias voltage biases the control electrodes of the load transistors (84, 85). The amplifier (70) increases the effective transconductance of the load transistors (84, 85) to allow larger control electrode areas, which reduces the effect of transistor mismatch.

Abstract: A digital-to-analog converter (20) with improved performance includes an offset/scaler (23), a sigma-delta modulator (25), and an analog summing network (26). In one embodiment, the offset/scaler (23) scales an input signal by a predetermined amount, such as three-quarters, to compensate for nonlinearities in a transfer characteristic of the sigma-delta modulator (25). In another embodiment, the sigma-delta modulator (25) is a sufficiently-resolved sigma-delta modulator. The offset/scaler (23) provides an offset to the sufficiently-resolved sigma-delta modulator (25) sufficient to force a coarse bit thereof into an idle pattern.

Abstract: An in-phase signal is sampled at an input of a first analog-to-digital converter (41), and a quadrature signal is sampled at an input of a second analog-to-digital converter (42). The output of the first analog-to-digital converter (41) is delayed by an amount equal to one, plus an integer number times four, sample periods to provide a delayed in-pahse signal. Then the delayed in-phase signal is added to the quadrature signal to provide a sum signal. Then a tone is detected in the sum signal. In one embodiment, a data processor (32) stores the output of the analog-to-digital converters (41, 42) in memory (34) and processes the data as programmed by microcode (33).

Abstract: A BICMOS bit line load for a memory includes first and second bipolar transistors having emitters respectively coupled to first and second bit lines of a differential bit line pair. Collectors of the first and second bipolar transistors receive a reference voltage. An equalization signal is applied to bases of the first and second bipolar transistors. The equalization signal is at a logic low voltage during a write cycle, and at a logic high voltage otherwise. In order to decrease the worst-case reverse bias, which causes bipolar transistors to degrade over time, a difference between the logic high voltage and the logic low voltage of the equalization signal is limited to a predetermined voltage.

Abstract: A fully-differential relaxation-type voltage controlled oscillator (VCO) (30) includes an operational transconductance amplifier (OTA) (31) for receiving a differential input voltage. The OTA (31) provides a charging current to a capacitor (33) proportional to the differential input voltage during a first phase of an output signal, and provides a discharging current to the capacitor (33) proportional to the differential input voltage during a secon d phase of the output signal. A comparator having hysteresis (34) detects the charge on the capacitor. A latching portion (35) latches the output of the comparator (34) to provide non-overlapping clock signals.

Abstract: A method for ensuring CRC error generation by a data communication station after a transmitter exception such as an underrun whereby a parity bit is preset to a binary one, and toggled in response to successive binary ones of a serial bit stream. Each byte of the serial bit stream is transmitted sequentially. If a transmitter exception occurs, the byte before the exception is transmitted normally. However, only the first seven bits of the last byte are transmitted. The parity bit is sent as an eighth bit of the last byte, ensuring odd parity for the previous bit stream. Thereafter, a byte even parity is sent to assure that the overall message has odd parity. A receiving station interprets two consecutive bytes having the predetermined data pattern as the CRC, thus ensuring that the receiving station will reject the frame.

Abstract: A differential amplifier (60,60') enhances common-mode stability by making two nodes (86,87) of a first stage low common-mode impedance nodes and thus shifting a common-mode dominant pole from the two nodes (86,87). The first stage includes an input portion (80,80') and a differential load (110,110'). The input portion (80,80') provides first and second currents respectively to the differential load (110,110') in response to a differential input voltage. The first and second currents have a differential component and a common-mode component. The differential load (110,110') converts the differential and common-mode components of the first and second currents into differential and common-mode voltages, respectively, and provides a high impedance to the differential component and a low impedance to the common-mode component.

Abstract: A tuning circuit (30) provides selection signals to a passive component array (80) in a continuous-time filter (70) to compensate for wide variations in values which are encountered in integrated circuit processing. The tuning circuit (30) includes at least one capacitor (46) and at least one resistor (31), and a plurality of either capacitors or resistors. A largest component is enabled and an integration of a reference current during a predetermined period is performed. If the integration provides a voltage greater than a reference voltage, then a corresponding selection signal is set and the component is selected. Successive integrations are performed to determine which components are enabled by corresponding selection signals in order to enable a combination of components which most closely integrates the reference current to the reference voltage. When selection signals corresponding to all components have been determined, the selection signals are applied to corresponding components in the filter (70).

Abstract: A regulated BiCMOS output buffer (34) regulates a logic high voltage of an output signal to improve interfacing to loads such as 3.3 volt integrated circuits. The output buffer (34) provides a first voltage to a base of a pullup transistor (116) in response to a difference between an input voltage and a reference voltage. An emitter of the pullup transistor (116) provides an output signal. A second transistor (102) having characteristics matching those of the pullup transistor (116) receives the first voltage at its base, and provides the input voltage at its emitter. The output buffer (34) changes the first voltage until the voltage at the base of the second transistor (102) equals the reference voltage. Thus, signal reflections on the output signal do not affect the performance of the output buffer. Clamps (99, 120) coupled to the base and emitter of the pullup transistor (116) provide soft clamping according to a square law.

Abstract: A BiCMOS (Bipolar Complementary Metal Oxide Semiconductor) bit line load for a memory with improved speed write recovery and improved reliability. Comprises a first bipolar transistor, a resistor, and a second and third bipolar transistors respectively coupled to first and second bit lines of a differential bit line pair. The improvement in speed is accomplished through the use of the bipolar transistors which generally switch faster than corresponding MOS transistors. The first bipolar transistor has a collector coupled to a power supply voltage terminal, a base for receiving a bias signal, and an emitter coupled to the collectors of the second and third bipolar transistors. The resistor is coupled between the collector and emitter of the first bipolar transistor. The bit line load has improved reliability by preventing self-boosting at the bases of the second and third bipolar transistors by decreasing their collector voltages enough during switching to bias them into saturation.

Abstract: A low di/dt BiCMOS output buffer with improved speed for a device such as a memory includes an input portion, a level shifter, first and second logic portions, and an output stage. The input portion provides first and second signals respectively in response to positive and negative differences between true and complementary input signals. The level shifter decreases the first and second signals by a predetermined amount to provide third and fourth signals. When selected, the first and second logic portions provide a pullup signal and a pulldown signal respectively in response to the third and fourth signals to the output stage. The output stage provdes a data output signal at a logic high voltage in response to the pullup signal and at a logic low voltage in response to the pulldown signal.

Abstract: A CMOS bus driver circuit with improved speed attributable to reduced capacitive loading on a control signal line and reduced capacitance added to the capacitance of a bus line. In one form, the bus driver circuit comprises a P-channel transistor and two N-channel transistors. The P-channel transistor has its current conducting path connected between a data line signal and a control electrode of the first N-channel transistor, and receives a control signal on its control electrode. A first N-channel transistor has its current conducting path connected between the bus line and a power supply voltage terminal. A second N-channel transistor has its current path connected between the gate of the first N-channel transistor and the power supply voltage terminal, and receives the control signal on its control electrode.

Abstract: An output buffer for a device such as a memory comprises a voltage regulator, a current source portion, a switching portion, and an output portion. The voltage regulator provides a constant voltage independent of fluctuations between first and second power supply voltages. The current source portion provides first and second currents to first and second nodes to limit the rate at which transistors in the output portion become conductive. The switching portion provides voltage signals on the first and second nodes respectively in response to positive and negative voltage differences between first and second input voltages. The output portion provides an output signal at either a logic high or a logic low voltage respectively in resonse to the voltage signals at the first and second nodes. The current source portion allows the use of faster bipolar transistors to improve the speed of the output buffer while maintaining accepable di/dt.

Abstract: A BiCMOS logic circuit with self-boosting immunity comprises a resistor, first and second transistors, a switching portion, and a discharge portion. The resistor and first transistor bias the switching portion to first and second reference voltages, which may be equal. The second transistor is a bipolar transistor providing an output signal to a load. The switching portion couples the bias voltage provided by the resistor and the first transistor to the base of the second transistor in response to a true result of a logic operation on at least one input signal and couples the base of the second transistor to a second power supply voltage terminal in response to a false result of the logic operation. The discharge portion couples the output signal to a logic low or pulldown voltage in response to a false result of the logic operation. In one form, the logic operation is a logical inversion of an input signal.

Abstract: A method of detecting a wideband tone, having a nominal frequency but occurring anywhere within a wide range of frequencies, includes a step of bandpass filtering input data. The bandpass-filtered data is used to predict a value of the input data using an algorithm such as least-mean-squares (LMS) adaptive linear prediction. An error signal is provided as a difference between the actual and predicted values of the input data. By computing the power in the error signal, the presence or absence of a tone can be detected, because a tone causes a smaller prediction error and power than other, non-tone processes such as white noise. A high-to-low transition in power represents a start of a tone, whereas a low-to-high transition in power represents an end of a tone. A tone flag signal is provided in response to a predetermined relationship between two power computations, such as a low-to-high transition.

Abstract: An apparatus for performing multiplications with reduced power includes an arithmetic logic unit and a decode block for performing an equivalent of a multiply instruction. A frequently-encountered multiply instruction occurs between a variable and a known constant. If the known constant is positive or negative one, the decode block enables the arithmetic logic unit to either add the variable to zero, or subtract the variable from zero, in response to the sign bit of the known constant. In response to a mulitply and accumulate instruction between a variable and a known constant of positive or negative one, the decode block enables the arithmetic logic unit to either add the variable to the prior accumulated result or to subtract it therefrom, in response to the sign bit of the known constant. In either case, a high-speed multiplier is disabled and its power saved.

Abstract: A low voltage precision current generator includes an amplifier, a first transistor, a current portion, and an output portion. The amplifier has first and second input terminals and changes an output voltage until voltages at the first and second input terminals are equal. An input voltage which may be a stable reference voltage or a variable voltage is received at the first input terminal. The second input terminal is connected to the current portion in order to provide a reference current proportional to a voltage difference between the voltage at the second input terminal and a power supply voltage. The amplifier controls the conductivity of the first transistor in order to regulate the voltage at its second input terminal. A precision current precision current proportional to the reference current is then provided.