Datasheet
2 V
USB
Connector
D -
D +
VBUS
Device Side
D- Out
D+ Out
CDP
Detect
Auto
Detect
2.7 V
TPS2543
<200W
Host Side
TPS2543
www.ti.com
SLVSBA6 –FEBRUARY 2012
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 500 mA/900 mA
per port. USB 2.0/3.0 communications is supported, and the host controller must be active to allow charging.
Charging Downstream Port (CDP)
A CDP is a USB port that follows USB BC1.2 and supplies a minimum of 1.5 A 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 two steps. During step one 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
an 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 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 read remains 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 0.3V and less than 0.8 V.
Dedicated Charging Port (DCP)
A DCP only provides power and does not provide data connection to an upstream port. A DCP is identified by
the electrical characteristics of its data lines. The TPS2543 emulates two common charging standards namely,
BC1.2 and Chinese Telecommunications Industry Standard YD/T 1591-2009, and one brand unique DCP
charging scheme which will be referred to as Divider scheme.
DCP BC 1.2 and YD/T 1591-2009
Both standards defines that the D+ and D- data lines should be shorted together with a maximum series
impedance of 200 Ω. This is shown in Figure 28.
Figure 28. DCP Supporting BC 1.2/YD/T 1591-2009
DCP Divider Charging Scheme
There are two Divider charging schemes supported by the device, Divider 1 and Divider 2 as shown in Figure 29
and Figure 30. In Divider 1 charging scheme the device applies 2.0V and 2.7V to D+ and D- data line
respectively. This is reversed in Divider 2 mode shown in Figure 30.
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