UCS81003 datasheet(35/108 Pages) MICROCHIP

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 2014 Microchip Technology Inc.

DS20005334A-page 35

UCS81003

When the VBUS discharge circuitry is activated, at the

end of the tDISCHARGE time, the UCS81003 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) and the

UCS81003 will enter the Error state.

7.4

Battery Full

Delivery of bus current to a portable device can be

rationed by the UCS81003. When this functionality is

enabled, the host system must provide the UCS81003

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 UCS81003 will take action as determined by

the RATION_BEH bits, as described in Table 7-1. Note

that this does not cause the device to enter the Error state.

Once the charge rationing circuitry has reached the

programmed threshold, the UCS81003 will maintain

the desired behavior until charge rationing is reset.

Once charge rationing has been reset or disabled, the

UCS81003 will recover as shown in Table 7-2.

TABLE 7-1:

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

combinations; 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.

TABLE 7-2:

CHARGE RATIONING RESET BEHAVIOR

Behavior

Reset Actions

Report

Reset the Total Accumulated Charge registers.

Clear the RATION status bit.

Release the ALERT# pin.

Report

and Disconnect

Reset the Total Accumulated Charge registers.

Clear the RATION status bit.

Release the ALERT# pin.

Check the M1, M2, EM_EN, S0 and PWR_EN controls and enter the indicated power state

if the controls changed (Note 1).

Note 1:

Any time the charge rationing circuitry checks the pin conditions when changing rationing behavior or

resetting charge rationing, if the external pin conditions have changed, then charger emulation will be

restarted (provided emulation is enabled via the pin states). If the pin conditions have not changed, the

UCS81003 returns to the previous power state as if the rationing threshold had not been reached (e.g., it

will not discharge VBUS or restart emulation).

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