Hewlett-packard Development Company, L.P.

Wayne Tangen

Robert G Mejia

Fernando Bolanos

Jim Jensen

A device includes a current sensor, a first current monitor, and a second current monitor. The current sensor is to sense a current between an input node and an output node. The first current monitor is to disconnect the input node from the output node in response to the sensed current exceeding a first threshold current for a period exceeding a threshold period. The second current monitor is to disconnect the input node from the output node in response to the sensed current exceeding a second threshold current greater than the first threshold current.

Devices including two current monitors

A two-wire serial (TWS) bus allows bus mastering by any device on the bus utilizing pull-ups. The bus is actively driven low, but typically pulled high by pull-up resistors for each device on the bus. When some of the devices on such a bus have backup power, draining of backup power whenever primary power is lost is avoided by isolating the devices with backup power from the devices without backup power on the TWS bus.

Method and apparatus for connecting devices to a bus

A serial bus expansion circuit, system, and method are provided. In one embodiment, the serial bus expansion circuit comprises a bus distribution circuit selectively coupling a serial bus to one of a number of serial bus outputs. The serial bus expansion circuit also includes a distribution controller having a control output coupled to a control input of the bus distribution circuit, and, a number of power-up pull resistors coupling each of the serial bus outputs to a power-up pull source.

Circuit and method for expanding a serial bus

A two-wire serial bus allows bus mastering by any device on the bus utilizing bus pull-ups. In systems with long bus lengths or large numbers of devices, rise times suffer unless accelerated. An operational amplifier (Op Amp) controlled current source is utilized to provide pull-up current for bus lines. The Op Amp provides precise control of the current value and the slew rate required to meet stringent demands of the two-wire serial bus. A voltage divider sets the input voltage to the Op Amp, and a transistor gates the Op Amp current to the bus until it saturates.

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Meridian, ID, United States of America

Wayne Tangen