UCS1002-2 datasheet(52/114 Pages) MICROCHIP

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Programmable USB Port Power Controller with Charger Emulation

Datasheet

Revision 1.4 (07-16-13)

SMSC UCS1002

DATASHEET

7.3.1.1

Dynamic Thermal Management

For the first stage (active in both current limiting modes), referred to as dynamic thermal management,

the UCS1002 automatically adjusts port power switch limits and modes to lower power dissipation

when the thermal regulation temperature value is approached, as described below.

If the internal temperature exceeds the TREG value, the port power switch is opened, the current limit

(ILIM) will be lowered by one step and a timer is started (tDC_TEMP). When this timer expires, the port

power switch is closed and the internal temperature will be checked again. If it remains above the TREG

threshold, the UCS1002 will repeat this cycle (open port power switch and reduce the ILIM setting by

one step) until ILIM reaches its minimum value.

APPLICATION NOTE: If the temperature exceeds the TREG threshold while operating in the DCE Cycle mode after

a charger emulation profile has been accepted, the profile will be removed. The UCS1002

will not restart the DCE Cycle until one of the control inputs changes states to restart

emulation.

APPLICATION NOTE: The UCS1002 will not actively discharge VBUS as a result of the temperature exceeding

TREG; however, any load current provided by a portable device or other load will cause

VBUS to be discharged when the port power switch is opened, possibly resulting in an

attached portable device resetting.

If the UCS1002 is operating using constant current limiting (variable slope) and the ILIM setting has

been reduced to its minimum set point and the temperature is still above TREG, the UCS1002 will

switch to operating using trip current limiting. This will be done by reducing the IBUS_R2MIN setting to

100 mA and restoring the ILIM setting to the value immediately below the programmed setting (e.g., if

the programmed ILIM is 1.8 A, the value will be set to 1.5 A). If the temperature continues to remain

above TREG, the UCS1002 will continue this cycle (open the port power switch and reduce the ILIM

setting by one step).

If the UCS1002 internal temperature drops below TREG - TREG_HYST, the UCS1002 will take action

based on the following:

1. If the current limit mode changed from CC mode to trip mode, then a timer is started. When this

timer expires, the UCS1002 will reset the port power switch operation to its original configuration

allowing it to operate using constant current limiting (variable slope).

2. If the current limit mode did not change from CC mode to trip mode, or was already operating in

trip mode, the UCS1002 will reset the port power switch operation to its original configuration.

If the UCS1002 is operating using trip current limiting and the ILIM setting has been reduced to its

minimum set point and the temperature is above TREG, the port power switch will be closed and the

current limit will be held at its minimum setting until the temperature drops below TREG - TREG_HYST.

7.3.1.2

Thermal Shutdown

The second stage thermal management consists of a hardware implemented thermal shutdown

corresponding to the maximum allowable internal die temperature (TTSD). If the internal temperature

exceeds this value, the port power switch will immediately be turned off until the temperature is below

TTSD - TTSD_HYST.

UCS1002-2 Datasheet(PDF) 52 Page - Microchip Technology

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