USB Type-C PD Technology: From Connection to 100W Negotiation

Introduction

The USB Type-C connector is known for its reversible plug, but it also carries a smart communication protocol-USB Power Delivery (PD). With PD, devices can negotiate up to 100W of charging power. Using the ET7303/ET7304 controllers from ETEK as an example, this article explains how Type-C detects connection, identifies current capability, and adjusts voltage through the PD protocol.

PD Controller Application Circuit

A typical application circuit of the ET7303/ET7304 is built around the Type-C receptacle. The CC1/CC2 pins of the controller connect directly to the CC lines of the receptacle, utilizing the integrated Rp pull-up current source and Rd pull-down resistor for connection detection, orientation identification, and PD protocol communication. The chip interfaces with the system host (AP) via an I²C bus. Figure 1 shows the example connection diagrams for the typical application circuit.

Figure 1

Source-to-Sink Connection

Figure 2

The Sink pull-down resistor Rd is defined to be 5.1kΩ. The CC line voltage is now defined by the Source pull-up resistor Rp values (or current source values). These are defined for 3 different Bus current capabilities :

The lowest voltage on the CC line (around 0.41V) means default USB power (current = 500mA for USB2.0 or 900mA in USB3.0).

A higher CC line voltage (around 0.92V) defines a current capability of 1.5A.

When the CC line voltage is around 1.68V, the maximum current capability is defined at 3A.

Bi-phase Mark Code (BMC)

USB PD communication makes use of the Bi-phase Mark Code (BMC). This code is a single wire communication, where a logic 1 is transmitted by a hi-low change and a logic zero is transmitted as either a fixed high level or a fixed low level. Each data packet consists of a low-high-low sequence preamble, SOP (Start Of Packet), Header, message data bytes, CRC error checking and EOP (End Of Packet).

Figure 3

PD power negotiation

This is an example of a PD request where the Sink requests a higher bus voltage. The VBUS is stepped up from 5V to 9V.

Figure 4

The CC line communication between Sink and Source will look like below:

1. Type-C plug in and establish connection.

2. The Source will send its Source capabilities message.for example, 5V,9V,12V,20V;

3. The Sink will then request a suitable power profile from the Source capability list.

4. The Source will accept the request and start to make changes to the VBUS voltage.

5. After the VBUS voltage has reached its final value, the source will wait until the VBUS has stabilized and then will send a Power Supply Ready signal. the Sink will now increase the VBUS loading.

Description of ET7303/ET7304 PD Controller

ET7303/ET7304 are USB Type-C controllers that comply with the latest USB Type-C and PD standards. ET7303/ET7304 integrates a complete Typec BMC transceiver, including a pull-up current source Ip and Rd resistor.It is used for USB Type-C detection, including connection and orientation detection.ET7303/ET7304 integrates the physical layer of the USB BMC power transmission protocol, allowing power charging up to 100W.

Main characteristics and Application scenarios of ET7303/ET7304

• Compatible with PD dual roles

• Disconnection detection when acting as a host, device, or DRP

• Definition and detection of current capability

• Dead battery support

• Connection detection in low-power mode

• Simple I²C AP or EC interface

PD Controller Product Application

• Mobile

• Pad

• NB

• Charging adapter

• Power bank

• Portable charging device

More choices of ETEK’s PD Controller

Contact ETEK today to request samples or technical datasheets.

Email: marketing@etekmicro.com

Request samples: https://www.etekmicro.com/sample/