UCS1001 datasheet(37/59 Pages) MICROCHIP

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USB Port Power Controller with Charger Emulation

Datasheet

SMSC UCS1001

Revision 1.2 (05-21-12)

DATASHEET

6.2.4.2

Constant Current Limiting (Variable Slope)

Constant current limiting is used when a portable device handshakes using the BC1.2 DCP or Legacy

2 charger emulation profiles and the current drawn is greater than ILIM (and ILIM < 1.5 A). It’s also

used in BC1.2 CDP mode and during the DCE Cycle when a charger emulation profile is being applied

and the timeout is active.

In CC mode, the port power switch allows the attached portable device to reduce VBUS output voltage

to less than the input VS voltage while maintaining current delivery. The V/I slope depends on the user

set ILIM value. This slope is held constant for a given ILIM value.

Figure 6.1 Trip Current Limiting Operation

0.5

1.0

1.5

2.0

2.5

5.25

4.75

IBUS (Amps)

Operating

Current

0.9

1.2

1.0

0.9

0.5

1.5

2.5

1.8

2.0

= ILIM’s

1.8

Power Switch Voltage and Current Output

go to Zero when ILIM is Exceeded

Trip action

(ILIM = 0.5 A)

Trip action

(ILIM = 2.5 A)

ILIM (Amps)

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