UCS1002-2 datasheet(49/114 Pages) MICROCHIP

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Programmable USB Port Power Controller with Charger Emulation

Datasheet

SMSC UCS1002

Revision 1.4 (07-16-13)

DATASHEET

7.2.4.1

Trip Mode

When using trip current limiting, the UCS1002 USB port power switch functions as a low resistance

switch and rapidly turns off if the current limit is exceeded. While operating using trip current limiting,

the VBUS output voltage will be held relatively constant (equal to the VS voltage minus the RON * IBUS

current) for all current values up to the ILIM.

If the current drawn by a portable device exceeds ILIM, the following occurs:

1. The port power switch will be turned off (trip action).

2. The UCS1002 will enter the Error state and assert the ALERT# pin.

3. The fault handling circuitry will then determine subsequent actions.

Trip current limiting is used by default when the UCS1002 is in Data Pass-through and Dedicated

Charger Emulation Cycle (except when the BC1.2 DCP charger emulation profile is accepted), and

when there’s no handshake.

APPLICATION NOTE: To avoid cycling in trip mode, set ILIM higher than the highest expected portable device

current draw.

Figure 7.1 shows operation of current limits in trip mode with the shaded area representing the USB

2.0 specified VBUS range. Dashed lines indicate the port power switch output will go to zero (e.g., trip)

when ILIM is exceeded. Note that operation at all possible values of ILIM are shown in Figure 7.1 for

illustrative purposes only; in actual operation only one ILIM can be active at any time.

UCS1002-2 数据表(PDF) 49 Page - Microchip Technology