UCS1003-3 datasheet(45/138 Pages) MICROCHIP

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DS20005346B-page 45

UCS1003-1/2/3

7.3

VBUS Discharge

The UCS1003-1/2/3 will discharge VBUS through an

internal 100

 resistor when at least one of the following

conditions occurs:

• The PWR_EN control is disabled (triggered on the

inactive edge of the PWR_EN control).

• A portable device Removal Detection event is flagged.

•The VS voltage drops below a specified threshold

(VS_UVLO) that causes the port power switch to be

disabled.

• When commanded into the Sleep power state via

the EM_EN, M1 and M2 controls.

• Before each charger emulation profile is applied.

• Upon recovery from the Error state.

• When commanded via the SMBus (for UCS1003-1

only, see Section 10.4 “Configuration Registers”)

in the Active state.

• Any time that the port power switch is activated

after the VBUS bypass switch has been on (i.e.,

whenever VBUS voltage transitions from being

driven from VDD to being driven from VS, such as

going from Detect to Active power state).

• Any time that the VBUS bypass switch is activated

after the port power switch has been on (i.e.,

going from Active to Detect power state).

When the VBUS discharge circuitry is activated, at the

end of the tDISCHARGE time, the UCS1003-1/2/3 will

confirm that VBUS was discharged. If the VBUS voltage

is not below the VTEST level, a discharge error will be

flagged (by setting the DISCH_ERR status bit in the

case of UCS1003-1) and the UCS1003-1/2/3 will enter

the Error state.

7.4

Battery Full (UCS1003-1 Only)

Delivery of bus current to a portable device can be

rationed by the UCS1003-1. When this functionality is

enabled, the host system must provide the UCS1003-1

with an accumulated charge maximum limit (in mAh).

The charge rationing functionality works only in the

Active power state. It continuously monitors the current

delivered, as well as the time elapsed since the mode

was activated (or since the data was updated). This

information is compiled to generate a charge rationing

number that is checked against the host limit.

Once the programmed current rationing limit has been

reached, the UCS1003-1 will take action as determined

by the RATION_BEH<1:0> bits, as described in

Table 7-2. Note that this does not cause the device to

enter the Error state.

Once the charge rationing circuitry has reached the

programmed threshold, the UCS1003-1 will maintain

the desired behavior until charge rationing is reset.

Once charge rationing has been reset or disabled, the

UCS1003-1 will recover, as shown in Table 7-3.

TABLE 7-2:

CHARGE RATIONING BEHAVIOR

RATION_BEH<1:0>

Behavior

Actions taken

Notes

Report

ALERT# pin asserted.

Report and

Disconnect

(default)

ALERT# pin asserted.

Charger emulation

profile removed.

Port power switch

disconnected.

The HSW will not be affected.

All bus monitoring is still active.

Changing the M1, M2, EM_EN, S0 and

PWR_EN controls will cause the device to

change power states as defined by the pin com-

binations; however, the port power switch will

remain off until the rationing circuitry is reset.

Furthermore, the bypass switch will not be

turned on if enabled via the S0 control.

Disconnect

and

Go to Sleep

Port power switch

disconnected.

Charger emulation

profile removed.

Device will enter the

Sleep state.

The HSW will be disabled.

All VBUS and VS monitoring will be stopped.

Changing the M1, M2, EM_EN, S0 and

PWR_EN controls will have no effect on the

power state until the rationing circuitry is reset.

Ignore

Take no further action.

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