Description

This reference design includes a power management circuit  capable of controlling a remote USB charging port in an automotive application environment. The circuit can be supplied directly from the car battery rail. It uses a small and highly efficient step-down converter: the TPS62130A-Q1: to regulate the required USB bus voltage for charging with charge currents up to 2.5A.The USB charging port is controlled and protected by using a USB charging controller: the TPS2549-Q1: which is also used to monitor the charge current for adjusting the output voltage of the TPS62130A-Q1. This enables the voltage drop across the cable connection to the USB port to be compensated. In addition: the TPS2549-Q1 generates all required signals to indicate a USB charging port to the equipment connected to the port.The required compensation for  the voltage drop across the cable connection to USB varies with the cable length.  This reference design presets the cable compensation for different cable lengths. It uses a rail-to-rail operational amplifier: OPA348:  to adjust the current sinked  from the TPS2549-Q1 into the TPS62130-Q1 and set the output voltage of the TPS62130A-Q1 accordingly.