UCS81003 datasheet(29/108 Pages) MICROCHIP

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 2014 Microchip Technology Inc.

DS20005334A-page 29

UCS81003

5.1.3

DETECT STATE OPERATION

When the UCS81003 is in the Detect state, the port

power switch will be disabled. The high-speed switch is

also disabled by default. The VBUS output will be

connected to the VDD voltage by a secondary bypass

switch (see Section 8.0 “Detect State”).

There is one non-recommended configuration which

places the UCS81003 in the Detect state, but VBUS will

not be discharged and a portable device attachment

will

not

detected.

For

the

recommended

configurations, see Table 5-2.

There are two methods for transitioning from the Detect

state to the Active state: automatic and host-controlled.

5.1.3.1

Automatic Transition

from Detect to Active

For the Detect state, set S0 to ‘1’, enable PWR_EN, set

the EM_EN, M1 and M2 controls to the desired Active

mode (Table 9-1), and supply VS >VS_UVLO. When a

portable device is attached and an Attach Detection

event

occurs,

the

UCS81003

will

automatically

transition to the Active state and operate according to

the selected Active mode.

5.1.3.2

Host-Controlled Transition from

Detect to Active

For the Detect state, set S0 to ‘1’, set the EM_EN, M1

and M2 controls to the desired Active mode (Table 9-1),

and configure one of the following:

• disable PWR_EN and supply VS,

• enable PWR_EN and don’t supply VS. When a

portable device is attached and an Attach

Detection event occurs, the host must respond to

transition to the Active state.

Depending on the control settings in the Detect state,

this could entail:

• enabling PWR_EN

• supplying VS above the threshold.

5.1.3.3

State Change from Detect to Active

When conditions cause the UCS81003 to transition from

the Detect state to the Active state, the following occurs:

The Attach Detection feature will be disabled;

the

Removal

Detection

feature

remains

enabled, unless S0 is changed to ‘0’.

The bypass switch will be turned off.

The discharge switch will be turned on briefly

for tDISCHARGE.

The port power switch will be turned on.

5.1.4

ACTIVE STATE OPERATION

Every time that the UCS81003 enters the Active state

and the port power switch is closed, it will enter the

mode as instructed by the host controller (see

Section 9.0 “Active State”). The UCS81003 cannot

be in the Active state (and therefore, the port power

switch cannot be turned on) if any of the following

conditions exist:

•VS <VS_UVLO

• PWR_EN is disabled

• M1, M2 and EM_EN are all set to '0'

• S0 is set to ‘1’ and an Attach Detection event has

not occurred

5.1.5

ERROR STATE OPERATION

The UCS81003 will enter the Error state from the

Active state when any of the following events are

detected:

• The maximum allowable internal die temperature

(TTSD) has been exceeded (see Section 7.2.1.2

“Thermal Shutdown”).

• An overcurrent condition has been detected (see

Section 7.1.1 “Current Limit Setting”).

• An undervoltage condition on VBUS has been

detected (see Section 5.2.5 “Undervoltage

Lockout on VS”).

• A back-drive condition has been detected (see

Section 5.2.3 “Back-voltage Detection”).

• A discharge error has been detected (see

Section 7.3 “VBUS Discharge”).

• An overvoltage condition on the VS pins.

The UCS81003 will enter the Error state from the

Detect state when a back-drive condition has been

detected or when the maximum allowable internal die

temperature has been exceeded.

The UCS81003 will enter the Error state from the Sleep

state when a back-drive condition has been detected.

When the UCS81003 enters the Error state, the port

power switch, VBUS bypass switch and the high-speed

switch are turned off, and the ALERT# pin is asserted

(by default). They will remain off while in this power

state. The UCS81003 will leave this

state as

determined by the fault handling selection (see

Section 7.5 “Fault Handling Mechanism”).

Note:

If S0 is '1', PWR_EN is enabled and VS is

not present, the A_DET# pin will cycle if

the current draw exceeds the current

capacity of the bypass switch.

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