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All trademarks are property of their respective owners 2014-08-0001

www.pericom.com

PT0516

8/27/14

11

PI5USB2549

USB Charging Port Controller and Load Detection Power Switch

DCP-1.2V Charging Scheme

DCP-1.2V charging scheme is used by some handheld devices to enable fast charging at 2.0A. PI5USB2549 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 4, DCP-1.2V Charging Scheme

Output Discharge

To allow a charging port to renegotiate current with a portable device, PI5USB2549 uses the OUT discharge function. It

proceeds by turning off the power switch while discharging OUT, then turning back on the power switch to reassert the OUT

voltage.

Over-Current Protection

When an over-current condition is detected, the device maintains a constant output current and reduces the output voltage

accordingly. Two possible overload conditions can occur. In the first condition, the output has been shorted before the device is

enabled or before VIN has been applied. The PI5USB2549 senses the short and immediately switches into a constant-current

output. In the second condition, a short or an overload occurs while the device is enabled. At the instant the overload occurs,

high currents may flow for nominally one to two microseconds before the current-limit circuit can react. The device operates in

constant-current mode after the current-limit circuit has responded. Complete shutdown occurs only if the fault is presented

long enough to activate thermal limiting. The device will remain off until the junction temperature cools approximately 20°C

and will then re-start. The device will continue to cycle on/off until the over-current condition is removed.

GND

USB

Connector

2.0V

1.2V

2.7V

Auto

Detect

D-

D+

PI5USB2549

VBUS