VBUS power switch

摘要

This document discusses, among other things, an electronic circuit and method for defaulting to a valid battery supply to power an electronic device. In an example, an electronic circuit can be configured to receive information about the battery supply (e.g., an internal battery), such as the battery supply voltage (VBAT), and to determine if the battery supply is valid or invalid using the received information (e.g., comparing the VBAT to a threshold). If VBAT is valid, the electronic device can default to receiving power from the battery supply. If VBAT is invalid, the electronic device can receive power from another power supply, such as an external supply.

主权项

1. A system, comprising:
a USB switch circuit configured to receive a battery supply voltage, to receive a USB bus voltage, and to provide an internal device voltage for the USB switch circuit, the USB switch circuit including: a comparator configured to determine if the battery supply voltage is valid; and a power supply override circuit configured to receive an override selection; and wherein, in normal operation, when the power supply override circuit does not receive the override selection, the USB switch circuit is configured to provide the internal device voltage using only the battery supply voltage if the battery supply voltage is valid and the USB bus voltage is valid, and using only the USB bus voltage if the battery supply voltage is invalid; and wherein, in override operation, when the power supply override circuit receives the override selection, the USB switch circuit is configured to provide the internal device voltage using only the USB bus voltage if the USB bus voltage is valid.