D-

D+

GND

5.0 V

2.7 V

2.0 V

D-

D+

GND

5.0 V

2.0 V

2.7 V

D-

D+

GND

200

Ÿ (max)

5.0 V

TPS2513

TPS2514

www.ti.com

SLVSBY8A – MAY 2013 – REVISED MAY 2013

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 8.

Figure 8. DCP Short Mode

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 9 and Figure 10. 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.

Figure 9. Divider 1 DCP

Figure 10. Divider 2 DCP

Applying 1.2 V to the D+ Line and 1.2 V to the D– Line

As shown in Figure 11, some tablet USB chargers require 1.2 V on the shorted data lines of the USB connector.

The maximum resistance between the D+ line and the D- line is 200

Ω.

Copyright © 2013, Texas Instruments Incorporated

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