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SLGC55544C 데이터시트(PDF) 11 Page - Dialog Semiconductor |
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11 / 20 page 000-000C55544C-105 Page 11 of 20 SLGC55544C 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-pow- ered 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 has become insufficient for many handset and personal media players which need a higher charging rate. On the other hand, wall adapters can provide much more current than 500 mA. Several new standards have been introduced defining protocol handshaking methods that allow host and client devices to acknowledge and draw additional current beyond the 500 mA minimum defined by USB 2.0 while still using a single micro-USB input connector. The SLGC55544C supports three of the most common protocols: • USB 2.0 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. The table below shows the differences between these ports according to BC1.2 (draft). BC1.2 (draft) 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. Operating Modes Port Type Supports USB 2.0 Communication Maximum Allowable Current Draw By Portable Equipment (A) SDP (USB 2.0) Yes 0.5 SDP (USB 3.0) Yes 0.9 CDP Yes 1.5 DCP No 1.5 |
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