Fast Turn-On Power Switch

A method of controlling a power switch at an interface of an electronic device, the method comprising:

• in response to a voltage at an external power terminal falling below a safe limit:
• operating a charge pump at a first frequency to produce a voltage at a charge pump node;
• and coupling a first controlled current from the charge pump node to a control terminal of a power switch transistor having a conduction path coupled between the external power terminal and an internal power terminal at which an internal power source is connected;
• and
• in response to the voltage at the external power terminal reaching a selected level:
• operating the charge pump at a second frequency, lower than the first frequency;
• and coupling a second controlled current, lower than the first controlled current, from the charge pump node to the control terminal of the power switch transistor.

An electronic system, comprising:

• a hub device including:
• logic coupled to generate a role swap signal responsive to a disconnection of the hub device from an external power source;
• and interfaces that include terminals, wherein the terminals include a power bus terminal connected in common among the interfaces, and wherein the external power source is removably coupled to the power bus terminal;
• and
• a host device including:
• a processor;
• an internal power source;
• and a power switch circuit;
• wherein the power bus terminal at one of the interfaces is coupled to a power bus terminal of the power switch circuit;
• wherein the power switch circuit includes:
• a power switch transistor having:
• a conduction path coupled between the power bus terminal of the power switch circuit and an internal power bus coupled to the internal power source of the host device;
• and a control terminal;
• a charge pump coupled to generate a voltage at a charge pump node responsive to a clock signal at a first frequency;
• a first current source coupled to apply a first current from the charge pump node to the control terminal of the power switch transistor;
• a boost current source coupled, in parallel with the first current source, to apply a boost current from the charge pump node;
• and
• control logic coupled to control the charge pump to generate a voltage responsive to a clock signal at a second frequency higher than the first frequency and to couple the boost current source to the control terminal of the power switch transistor, both responsive to receiving the role swap signal from the hub device.