Abstract: A voltage control mode buck converter circuit includes a feedback amplifier providing a comparison signal and a storage circuit in communication with the comparison signal to store a storage comparison signal value. The storage circuit stores the operating conditions for the circuit during normal continuous conduction mode operation in response to sensing a load drop for the circuit. A switching circuit locks the feedback amplifier into the stored operating parameters while the converter circuit operates in non-continuous conduction mode. When the circuit transitions back into the continuous conduction operation mode, the feedback amplifier is already operating at conditions that are compatible with a continuous conduction operation mode.

Abstract: An over-current condition is detected in a synchronous DC-DC converter by sampling and holding a measured load current value. The load current is sampled while a low-side transistor is ON and then held when the low-side transistor is OFF. The held value is compared to a threshold value while the low-side transistor is OFF. The comparison occurs during the portion of the cycle when the low-side transistor is OFF so that a comparator has sufficient time in which to detect the over-current condition, even in high duty cycle applications.

Abstract: A synchronous buck converter operates in a PWM mode of operation and switches to light-load mode of operation under a light-load condition. When operating in the light-load mode, the synchronous buck converter transitions between a burst mode and an idle mode of operation. In the burst mode of operation, the converter operates with a fixed but increased duty ratio, with respect to the PWM mode of operation, that installs additional energy in an output capacitor. In the idle mode of operation, the high-side and low-side transistors are each turned off. To maximize energy savings and to quickly transition back to the PWM mode of operation if the load increases, a limit as to the number of allowed switching cycles when bursting is imposed and a minimum ratio of the number of clock cycles when idling to the number of switching cycles when bursting is set. Additionally, a comparator is provided to detect a sudden step-increase in the load to quickly switch the converter back to the PWM mode of operation.

Abstract: An over-current condition is detected in a synchronous DC-DC converter by sampling and holding a measured load current value. The load current is sampled while a low-side transistor is ON and then held when the low-side transistor is OFF. The held value is compared to a threshold value while the low-side transistor is OFF. The comparison occurs during the portion of the cycle when the low-side transistor is OFF so that a comparator has sufficient time in which to detect the over-current condition, even in high duty cycle applications.

Abstract: A synchronous buck converter operates in a PWM mode of operation and switches to light-load mode of operation under a light-load condition. When operating in the light-load mode, the synchronous buck converter transitions between a burst mode and an idle mode of operation. In the burst mode of operation, the converter operates with a fixed but increased duty ratio, with respect to the PWM mode of operation, that installs additional energy in an output capacitor. In the idle mode of operation, the high-side and low-side transistors are each turned off. To maximize energy savings and to quickly transition back to the PWM mode of operation if the load increases, a limit as to the number of allowed switching cycles when bursting is imposed and a minimum ratio of the number of clock cycles when idling to the number of switching cycles when bursting is set. Additionally, a comparator is provided to detect a sudden step-increase in the load to quickly switch the converter back to the PWM mode of operation.

Abstract: A voltage control mode buck converter circuit includes a feedback amplifier providing a comparison signal and a storage circuit in communication with the comparison signal to store a storage comparison signal value. The storage circuit stores the operating conditions for the circuit during normal continuous conduction mode operation in response to sensing a load drop for the circuit. A switching circuit locks the feedback amplifier into the stored operating parameters while the converter circuit operates in non-continuous conduction mode. When the circuit transitions back into the continuous conduction operation mode, the feedback amplifier is already operating at conditions that are compatible with a continuous conduction operation mode.

Abstract: Power selection circuitry that may be employed in redundant power supplies. The power selection circuitry includes a comparator, a symmetric resistor array coupled between the comparator inputs and multiple input voltage sources, a plurality of first switching elements, and control logic/drive circuitry coupled between the comparator output and the first switching elements. The first switching elements connect a selected input voltage source to a load. The comparator compares the voltage levels of the respective voltage sources, and provides a voltage indicating which one of the voltage sources is operational to the control logic/drive circuitry, which applies control signals to the first switching elements to connect the operational voltage source to the load. The symmetric resistor array and a plurality of second switching elements assure that symmetric trip voltages with hysteresis are provided to the comparator.

Abstract: Power selection circuitry that may be employed in redundant power supplies. The power selection circuitry includes a comparator, a symmetric resistor array coupled between the comparator inputs and multiple input voltage sources, a plurality of first switching elements, and control logic/drive circuitry coupled between the comparator output and the first switching elements. The first switching elements connect a selected input voltage source to a load. The comparator compares the voltage levels of the respective voltage sources, and provides a voltage indicating which one of the voltage sources is operational to the control logic/drive circuitry, which applies control signals to the first switching elements to connect the operational voltage source to the load. The symmetric resistor array and a plurality of second switching elements assure that symmetric trip voltages with hysteresis are provided to the comparator.

Abstract: A micromachined hot-wire anemometer having fast response times and higher sensitivities than conventional hot-wire anemometers is provided by micromachining doped polysilicon wires carried on silicon supports cantilevered from a substrate including one or more insulating layers disposed between said substrate and supports. The micromachined polysilicon hot-wire anemometer is fabricated using surface micromachining techniques.A shear stress sensor is micromachined to define a thin diaphragm over a cavity defined in a substrate underlying the diaphragm. The cavity is evacuated, sealed, and a thermistor disposed over the diaphragm. The thermistor is thus thermally insulated from the substrate and provides a low profile shear stress sensor for measuring flow rates in boundary layers above a flow surface.