UCS1002-2 datasheet(58/114 Pages) MICROCHIP

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Programmable USB Port Power Controller with Charger Emulation

Datasheet

Revision 1.4 (07-16-13)

SMSC UCS1002

DATASHEET

Chapter 8 Detect State

8.1

Device Attach / Removal Detection

The UCS1002 can detect the attachment and removal of a portable device on the USB port. Attach

and Removal Detection does not perform any charger emulation or qualification of the device. The

high-speed switch is “off” (by default) during the Detect power state.

8.2

VBUS Bypass Switch

The UCS1002 contains circuitry to provide VBUS current as shown inFigure 8.1In the Detect state,

VDD is the voltage source; in the Active state, VS is the voltage source. The bypass switch and the

port power switch are never both on at the same time.

While the VBUS bypass switch is active, the current available to a portable device will be limitedto

IBUS_BYP, and the Attach Detection feature is active.

8.3

Attach Detection

The Attach Detection feature is only active in the Detect power state. When active, this feature

constantly monitors the current load on the VBUS pin. If the current drawn by a portable device is

greater than IDET_QUAL for longer than tDET_QUAL, an Attach Detection event occurs. This will cause

the A_DET# pin to assert low and the ADET_PIN and ATT status bits to be set.

Until the port power switch is enabled, the current available to a portable device will be limited to that

used to detect device attachment (IDET_QUAL).Once an Attach Detection event occurs, the UCS1002

will wait for the PWR_EN control to be enabled (if not already). When PWR_EN is enabled and VS is

above the threshold, the UCS1002 will activate the USB port power switch and operate in the selected

Active mode (see Chapter 9, Active State).

8.4

Removal Detection

The Removal Detection feature will be active in the Active and Detect power states if S0 = 1. This

feature monitors the current load on the VBUS pin. If this load drops to less than IREM_QUAL_DET for

longer than tREM_QUAL, a Removal Detection event is flagged

When a Removal Detection event is flagged, the following will be done:

1. Disable the port power switch and the bypass switch.

Figure 8.1 Detect State VBUS Biasing

Port Power

Switch

VDD

VBUS

Bypass

Switch

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