UCS1002-2 datasheet(53/114 Pages) MICROCHIP

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Programmable USB Port Power Controller with Charger Emulation

Datasheet

SMSC UCS1002

Revision 1.4 (07-16-13)

DATASHEET

7.4

VBUS Discharge

The UCS1002 will discharge VBUS through an internal 100 Ω 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 (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 UCS1002 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 DISCHARGE_ERR status bit) and the UCS1002 will enter the Error

state.

7.5

Battery Full

Delivery of bus current to a portable device can be rationed by the UCS1002. When this functionality

is enabled, the host system must provide the UCS1002 with an accumulated charge maximum limit

(in milliampere-hours). 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 UCS1002 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 UCS1002 will maintain

the desired behavior until charge rationing is reset. Once charge rationing has been reset or disabled,

the UCS1002 will recover as shown in Table 7.2.

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