Datasheet

TPS2543
SLVSBA6 FEBRUARY 2012
www.ti.com
DETAILED DESCRIPTION
Overview
The following overview references various industry standards. It is always recommended to consult the most up-
to-date standard to ensure the most recent and accurate information. Rechargeable portable equipment requires
an external power source to charge its batteries. USB ports are a convenient location for charging because of an
available 5 V power source. Universally accepted standards are required to make sure host and client-side
devices operate together in a system to ensure power management requirements are met. Traditionally, USB
host ports following the USB 2.0 specification must provide at least 500 mA to downstream client-side devices.
Because multiple USB devices can be attached to a single USB port through a bus-powered hub, it is the
responsibility of the client-side device to negotiate its power allotment from the host to ensure the total current
draw does not exceed 500 mA. In general, each USB device is granted 100 mA and may request more current in
100 mA unit steps up to 500 mA. The host may grant or deny based on the available current.
Additionally, the success of USB has made the mini-USB connector a popular choice for wall adapter cables.
This allows a portable device to charge from both a wall adapter and USB port with only one connector. One
common difficulty has resulted from this. As USB charging has gained popularity, the 500 mA minimum defined
by USB 2.0 or 900 mA for USB 3.0 has become insufficient for many handset and personal media players which
need a higher charging rate. Wall adapters can provide much more current than 500mA/900mA. Several new
standards have been introduced defining protocol handshaking methods that allow host and client devices to
acknowledge and draw additional current beyond the 500mA/900mA minimum defined by USB 2.0/3.0 while still
using a single micro-USB input connector.
The TPS2543 supports three of the most common protocols:
USB Battery Charging Specification BC1.2
Chinese Telecommunications Industry Standard YD/T 1591-2009
Divider Mode
All three methods have similarities and differences, but the biggest commonality is that all three define three
types of charging ports that provide charging current to client-side devices. These charging ports are defined as:
Standard Downstream Port (SDP)
Charging Downstream Port (CDP)
Dedicated Charging Port (DCP)
BC1.2 defines a Charging Port as a downstream facing USB port that provides power for charging portable
equipment.
Table 1 shows the differences between these ports according to BC1.2 .
Table 1. Operating Modes
SUPPORT USB MAX. ALLOWABLE CURRENT
PORT TYPE
2.0 COMMUNICATION DRAW BY PORTABLE DEVICE (A)
SDP (USB 2.0) Yes 0.5
SDP (USB 3.0) Yes 0.9
CDP Yes 1.5
DCP No 1.5
BC1.2 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 draw. The hand-shaking process has 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 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 0.3 V 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 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.
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