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1/18/2017

2016-11-0004

PT0493-4

11

PI5USB2546

Standard Downstream Port (SDP) USB 2.0/USB 3.0

An SDP is a traditional USB port that follows USB 2.0/3.0 protocol and supplies a minimum of 500mA/900mA per port. USB

2.0/3.0 communications is supported, and the host controller must be active to allow charging. PI5USB2546 supports SDP

mode in system power state S0 when system is completely powered ON and fully operational. For more details on control pin

(CTL1, CTL2, CTL3 and ILIM_SEL) settings to program this state please refer to device truth table.

Charging Downstream Port (CDP)

A CDP is a USB port that follows USB BC1.2 and supplies a minimum of 1.5A per port. It provides power and meets USB 2.0

requirements for device enumeration. USB 2.0 communications is supported and the host controller must be active to allow

charging. What separates a CDP from an SDP is the host-charge handshaking logic that identifies this port as a CDP. A CDP is

identifiable by a compliant BC1.2 client device and allows for additional current draw by the client device.

The CDP hand-shaking process is done in two steps. During step one the portable equipment outputs a nominal 0.6V output on

its D+ line and reads the voltage input on its D- line. The portable device concludes it is connected to an SDP if the voltage is

less than the nominal data detect voltage of 0.3V. 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 optionally less than 0.8V.

The second step is necessary for portable equipment to determine if it is connected to CDP or DCP. The portable device outputs

a nominal 0.6V 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 read remains less than the nominal data detect voltage of 0.3V. 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 0.3V.

PI5USB2546 supports CDP mode in system power state S0 when system is completely powered ON and fully operational. For

more details on control pin (CTL1, CTL2, CTL3 and ILIM_SEL) settings to program this state please refer to device truth table.

Dedicated Charging Port (DCP)

A DCP only provides power but does not support data connection to an upstream port. As shown in following sections, a DCP

is identified by the electrical characteristics of its data lines. The PI5USB2546 emulates DCP in two charging states, namely

DCP Forced and DCP Auto as shown in Figure 4. In DCP Forced state the device will support one of the two DCP charging

schemes, namely Divider-1A or DCP_Shorted. In the DCP Auto state, the device charge detection state machine is activated to

selectively implement charging schemes involved with the Shorted DCP mode, Divider-1A, Divider-2A and DCP-1.2V modes.

Shorted DCP mode complies with BC1.2 and Chinese Telecommunications Industry Standard YD/T 1591-2009, while the

Divider-1A, Divider-2A and DCP-1.2V modes are employed to charge devices that do not comply with BC1.2 DCP standard.

DCP BC1.2 and YD/T 1591-2009

Both standards define that the D+ and D- data lines should be shorted together with a maximum series impedance of 200 Ω.

This is shown as Figure 1.

Figure 1, DCP mode

GND

USB

Connector

2.0V

1.2V

2.7V

CDP

Detect

Auto

Detect

D-

D+

D- OUT

D+OUT

PI5USB2546

VBUS

USB

Host/Hub