Using LT8697 to Power USB VBUS in Cars

As the use of portable devices continues to rise, more and more car models are beginning to be equipped with USB sockets. The USB interface delivers power to portable devices through the 5V VBUS and ground wires. Depending on the USB version and the portable device, VBUS can provide up to 2.1A. In automobiles, this high VBUS current creates a problem. Typically, car electronics (including VBUS regulators) are placed in a box within the dashboard, while some USB sockets may be placed in the back seat of the car. The wiring length between the VBUS regulator and the socket can be several meters, and this length is doubled when including return wires. Long cables mean high resistance, so the 5V VBUS supply voltage will drop significantly under high USB device current conditions. LT®8697 solves this problem. It is a compact, high-efficiency, high-speed, synchronous, monolithic, step-down switching regulator designed to power 5V USB applications. A precise (<1% initial tolerance) output voltage and programmable cable drop compensation maintain accurate 5V regulation at the USB socket at the end of a long cable. Accurate and programmable output current limit, a power good indicator pin and an output current monitor pin improve system reliability and safety and eliminate the need for a USB switch IC. These features allow users to implement lockout or automatic retry functionality. Despite cable drop compensation, dual input feedback limits the output voltage to 5.85V, protecting the USB device and allowing 5V regulation on the output of a USB switch.

• Chapter 1：Using LT8697 to Power USB VBUS in Cars (7 minutes and 57 seconds)