MAXREFDES1283

説明

Many applications today use a 24V power source whenever size, portability of the equipment and low heat are required in audio, lighting, and sensors applications. This typically involves a heavy 24V AC/DC adapter to plug into the mains. This reference design shows how to achieve the same power supply from a USB C-Type power delivery (PD) source with a small highly efficient DC-DC switching converter. USB-C PD allows communication between compatible devices to negotiate a power contract to determine at what voltage and how much power can be pulled. It can deliver 3A with the supporting voltages between 5V and 20V using a standard USB-C cable, and it is possible to deliver 5A at 20V using a designated Electronically Marked Cable Assembly (EMCA) cable to achieve a maximum power contract of 100W.

This reference design facilitates the PD contract and outputs 24V DC up to 1A to enable applications and products that need a 24V power source to connect to a USB-C PD socket. It utilizes the MAX77958 USB-C PD controller to request 15V from a capable USB-C source, and the MAX668 boost converter to output 24V with an output power capability of up to 30W.

This reference design also includes the MAX17613A circuit protection integrated circuit (IC) that is configured to assert a undervoltage lockout (UVLO) if the input voltage is less than 14V, an overvoltage lockout (OVLO) if the input voltage is greater than 22V and a 2.2A current limiter. The purpose is to make sure that the connected USB source can deliver the required voltage level, to protect the DC-DC converter from sourcing more current than it is designed to handle, and to act as a switch between the USB voltage and the MAX668 so that the MAX668 only turns on once the input voltage has been correctly set.

機能と利点

USB-C PD controller

Under-voltage and over-voltage lockout

Over-current limit protection