Charging a provider/consumer with a dead battery via USB power delivery
A method and apparatus are provided. The VBUS conductor is checked to determine whether the voltage on the VBUS conductor is greater than a vSafe0V voltage within a dead battery detect time interval, and the device policy manager is instructed to apply a vSafeDB voltage to the VBUS conductor if the voltage on the VBUS conductor is greater than the vSafe0V voltage. The policy engine waits for a bit stream to be detected within a bit stream detect timer interval. If the bit stream is not detected within the bit stream detect timer interval, then the device policy manager is instructed to apply the vSafe0V voltage to the VBUS conductor. The device policy manager is instructed to apply a vSafe5V voltage to the VBUS conductor if the bit stream is detected, and the policy engine waits for the bit stream to stop within a device ready timer interval. If the bit stream has stopped within the device ready timer interval, then the policy engine sends capabilities as a source port.
1. An apparatus that is configured to operate as a consumer/provider, the apparatus comprising:
an interface having a power bus and a data bus, wherein the interface is configured to be coupled to a cable, and wherein the power bus includes a VBUS conductor and a ground conductor;
an isolation circuit that is coupled to the VBUS conductor;
a power system that is configured to be coupled to a power source and that is coupled to an inductor;
a power transceiver that is coupled to the power system and the VBUS conductor, wherein the power transceiver has a device policy manager and a policy engine, wherein the policy engine is configured to interact with the device policy manager, wherein the power transceiver is configured to:
check the VBUS conductor to determine whether the voltage on the VBUS conductor is greater than a vSafeOV voltage within a dead battery detect time interval;
instruct the device policy manager to apply a vSafeDB voltage to the VBUS conductor if the voltage on the VBUS conductor is not greater than the vSafe 0 V voltage;
wait for a bit stream to be detected within a bit stream detect time interval;
instruct the device policy manager to apply the vSafeOV voltage to the VBUS conductor if the bit stream is not detected within the bit stream detect timer interval; and
instruct the device policy manager to apply a vSafe 5 V voltage to the VBUS conductor if the bit stream is detected; and
send capabilities as a source port after the bit stream has stopped; and
a capacitor that is coupled between the power transceiver and the VBUS conductor;
wherein the power transceiver is configured to wait for source port capabilities if the voltage on the VBUS conductor is greater than the vSafe 0 V voltage;
wherein the power transceiver is configured to instruct the device policy manager to apply the vSafe 0 V voltage to the VBUS conductor if the device ready timer interval lapses;
wherein the power transceiver further comprises a controller that is coupled to the VBUS conductor;
wherein the controller further comprises:
the device policy manager;
the policy engine that is configured to communicate with the device policy manager;
a transmitter that is configured to communicate with the policy engine;
a receiver that is configured to communicate with the policy engine;
an interface that is configured to communicate with the transmitter and the receiver and that is coupled to the VBUS conductor;
wherein the power system further comprises a switching circuit that is coupled between the power converter and the inductor;
wherein the power transceiver further comprises a state machine that is coupled to the controller;
wherein the bit stream is detected after a plurality of consecutive bits match an alternating 0 and 1 pattern;
wherein the power transceiver is configured to:
wait for the bit stream to stop within a device ready timer interval; and
send capabilities as the source port if the bit stream has stopped within the device ready timer interval.
2. The apparatus of claim 1 , wherein the plurality of consecutive bit matches is 150 or 128.
3. The apparatus of claim 2 , wherein the power transceiver further comprises a processing circuit that is configured to communicate with the device policy manager.