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1/18/2017

2016-11-0004

PT0493-4

13

PI5USB2546

DCP-1.2V Charging Scheme

DCP-1.2V charging scheme is used by some handheld devices to enable fast charging at 2.0A. PI5USB2546 supports this

scheme in the DCP-Auto mode before the device enters BC1.2 shorted mode. To simulate this charging scheme D+/D- lines are

shorted and pulled-up to 1.2V for fixed duration then device moves to DCP shorted mode as defined in BC1.2 spec. This is

shown as Figure 3.

Figure 3, DCP-1.2V Charging Scheme

DCP Auto Mode

As mentioned above the PI5USB2546 integrates an auto-detect state machine that supports all the above DCP charging

schemes. It starts in Divider-1A scheme, however if a BC1.2 or YD/T 1591-2009 compliant device is attached, the

PI5USB2546 responds by discharging OUT, turning back on the power switch and operating in 1.2Vmode briefly and then

moving to BC1.2 DCP mode. It then stays in that mode until the device releases the data line, in which case it goes back to

Divider-1A scheme. When a Divider-1A compliant device is attached the PI5USB2546 will stay in Divider-1A state.

Also, the PI5USB2546 will automatically switch between the Divider-1A and Divider-2A schemes based on charging current

drawn by the connected device. Initially the device will set the data lines to Divider-1A scheme. If charging current of the

device >750mA is measured by the PI5USB2546, it switches to Divider-2A scheme and test to see if the peripheral device will

still charge at a high current. If it does then it stays in Divider-2A charging scheme otherwise it will revert to Divider-1A

scheme.

Figure 4, DCP_Auto 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

D-

D+

PI5USB2546

BC1.2 CDP

BC1.2 DCP

/DCP-1.2V

Divider-1A/

Divider-2A

To

USB

2.0

Host

Controlled by

CTL pins settings