UCS1003-3 datasheet(51/138 Pages) MICROCHIP

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DS20005346B-page 51

UCS1003-1/2/3

8.0

DETECT STATE

8.1

Device Attach/Removal Detection

The UCS1003-1/2/3 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 UCS1003-1/2/3 family contains circuitry to provide

VBUS current, as shown in Figure 8-1. 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.

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 is active.

FIGURE 8-1:

Detect State VBUS Biasing.

8.3

Attach Detection

The primary 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 UCS1003-1

or UCS1003-3 to assert the A_DET# pin low and the

ADET_PIN and ATT status bits to be set in the

UCS1003-1 registers. The UCS1003-2 internally flags

the event.

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 UCS1003-1/2/3 will wait for

the PWR_EN control to be enabled (if not already).

When PWR_EN is enabled and VS is above the thresh-

old, the UCS1003-1/2/3 will activate the USB port

power switch and operate in the selected Active mode

(see Section 9.0 “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 this event occurs, the following will be

performed:

Disable the port power switch and the bypass

switch.

Deassert the A_DET# pin (UCS1003-1 and

UCS1003-3 only) and set the REM status

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.

Port Power

Switch

VDD

VBUS

Bypass

Switch

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