BUS INTERFACES WITH UNPOWERED TERMINATION

摘要

A system including a device that is configured to communicate current sourcing capabilities to an external power source over a wired connection containing a plurality of wires. The device includes a power supply circuit configured to provide operating power for the device. A first pull-down circuit is configured to provide a pull-down for a particular wire of the wired connection using a first resistive element that is actively trimmed using the operating power. A second pull-down circuit includes at least one transistor that, in the absence of the operating power, is configured to enable a current path, in response to a gate voltage generated from a voltage on the particular wire, between the particular wire and a second resistive element.

主权项

1. A system comprising:
a device configured to communicate current sourcing capabilities to an external power source over a wired connection containing a plurality of wires, the device including:
a power supply circuit configured to provide operating power for the device;a first pull-down circuit configured to provide a pull-down for a particular wire of the wired connection using a first resistive element that is actively trimmed using the operating power; anda second pull-down circuit including at least one transistor that, in the absence of the operating power, is configured to enable a current path, in response to a gate voltage generated from a voltage on the particular wire, between the particular wire and a second resistive element.