UCHQ613

Preliminary

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

7 of 9

www.unisonic.com.tw

QW-R121-030.a



FUNCTIONAL DESCRIPTION (Cont.)

The BC1.2 Specification defines the protocol necessary to allow portable equipment to determine what type of port

it is connected to so that it can allot its maximum allowable current drawn. The hand-shaking process is two steps.

During step one, the primary detection, the portable equipment outputs a nominal 0.6 V output on its D+ line and

reads the voltage input on its D– line. The portable device concludes it is connected to a SDP if the voltage is less

than the nominal data detect voltage of 0.3 V. The portable device concludes that it is connected to a Charging Port

if the D– voltage is greater than the nominal data detect voltage of 0.3V and less than 0.8 V. The second step, the

secondary detection, is necessary for portable equipment to determine between a CDP and a DCP. The portable

device outputs a nominal 0.6 V output on its D– line and reads the voltage input on its D+ line. The portable device

concludes it is connected to a CDP if the data line being remains is less than the nominal data detect voltage of 0.3

V. The portable device concludes it is connected to a DCP if the data line being read is greater than the nominal data

detect voltage of 0.3 V and less than 0.8 V.

Dedicated Charging Port (DCP)

A dedicated charging port (DCP) is a downstream port on a device that outputs power through a USB

connector,but is not capable of enumerating a downstream device, which generally allows portable devices to fast

charge at their maximum rated current. A USB charger is a device with a DCP, such as a wall adapter or car power

adapter. A DCP is identified by the electrical characteristics of its data lines. The following DCP identification circuits

are usually used to meet the handshaking detections of different portable devices.

Short the D+ Line to the D– Line

The USB BC1.2 Specification and the Chinese Telecommunications Industry Standard YD/T 1591-2009 define

that the D+ and D– data lines should be shorted together with a maximum series impedance of 200 Ω. This is shown

in Figure 1.

Divider 1 (DCP Applying 2 V on D+ Line and 2.7 V on D– Line) or Divider 2 (DCP Applying 2.7 V on D+ Line

and 2 V on D– Line)

There are two charging schemes for divider DCP. They are named after Divider 1 and Divider 2 DCPs that are

shown in Figure 2 and Figure 3. The Divider 1 charging scheme is used for 5-W adapters, and applies 2 V to the D+

line and 2.7 V to the D– data line. The Divider 2 charging scheme is used for 10-W adapters, and applies 2.7 V on

the D+ line and 2 V is applied on the D– line.