UCS2112 datasheet(25/64 Pages) MICROCHIP

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 2015 Microchip Technology Inc.

DS20005424B-page 25

UCS2112

6.0

DETECT STATE

6.1

Device Attach / Removal Detection

The UCS2112 can detect the attachment and removal

of a portable device on the VBUS1 or VBUS2 ports.

6.1.1

VBUS BYPASS SWITCH

The UCS2112 contains circuitry to provide VBUS cur-

rent as shown in Figure 6-1. In 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.

FIGURE 6-1:

Bypass Switch.

While the VBUS bypass switch is active, the current

available to a portable device will be limited to IBUS_BYP

and the Attach Detection feature will be active.

6.1.2

ATTACH DETECTION

The primary Attach Detection feature is only active in

the Detect power state. When active, this feature con-

stantly monitors the current load on the VBUS1 or VBUS2

pins. 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#

status bits to be set.

Until the port power switch is enabled, the current avail-

able to a portable device will be limited to that used to

detect device attachment (IDET_QUAL). Once an Attach

Detection event occurs, the UCS2112 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

UCS2112 will activate the VBUS port power switch and

operate in Active state.

6.1.3

REMOVAL DETECTION

The Removal Detection feature will be active in the

Active and Detect power states. This feature monitors

the current load on the VBUS1 and VBUS2 pins. 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 follow-

ing will be done:

Disable the port power switch and the bypass

switch.

Set the REM status register bit.

Enable an internal discharging device that will

discharge the VBUS line within tDISCHARGE.

Once the VBUS pin has been discharged, the

device will return to the Detect state regardless

of the PWR_EN control state.

Note:

By default, device attach / removal detec-

tion feature is disabled. It can be enabled

by clearing ATT_DISABLE bit 6 from

Port Power

Switch

VDD

VBUS

Bypass

Switch

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