UCS2112 datasheet(30/64 Pages) MICROCHIP

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UCS2112

DS20005424B-page 30

 2015 Microchip Technology Inc.

7.3

Thermal Management and Voltage

Protection

7.3.1

THERMAL MANAGEMENT

The UCS2112 utilizes two-stage internal thermal man-

agement. The first stage is Dynamic Thermal Manage-

ment, and the second stage is Fixed Thermal

Shutdown.

7.3.1.1

Dynamic Thermal Management

For the first stage (active in both current-limiting

modes), referred to as Dynamic Thermal Manage-

ment, the UCS2112 automatically adjusts port power

switch limits and modes to lower power dissipation

when the thermal regulation temperature value is

approached, as described in the following paragraphs.

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 UCS2112 will repeat this cycle (open port power

switch and reduce the ILIM setting by one step) until

ILIM reaches its minimum value.

If the UCS2112 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 UCS2112 will switch to operat-

ing using trip current limiting. This will be done by

reducing the IBUS_R2MIN setting to 100 mA and restor-

ing the ILIM setting to the value immediately below the

programmed setting (e.g., if the programmed ILIM is

2.13A, the value will be set to 1.6A). If the temperature

continues to remain above TREG, the UCS2112 will

continue this cycle (open the port power switch and

reduce the ILIM setting by one step).

If the UCS2112 internal temperature drops below

TREG - TREG_HYST, the UCS2112 will take action

based on the following:

If the Current Limit mode changed from CC

mode to Trip mode, then a timer is started.

When this timer expires, the UCS2112 will reset

the port power switch operation to its original

configuration, allowing it to operate using Con-

stant Current Limiting (variable slope).

If the Current Limit mode did not change from CC

mode to Trip mode, or was already operating in

Trip mode, the UCS2112 will reset the port power

switch operation to its original configuration.

If the UCS2112 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 of thermal management consists of

a hardware implemented thermal shutdown corre-

sponding to the maximum allowable internal die tem-

perature (TTSD). If the internal temperature exceeds

this value, the port power switches (both ports) will

immediately be turned off until the temperature is

below TTSD -TTSD_HYST.

7.4

VBUS Discharge

The UCS2112 will discharge VBUS through an internal

100

 resistor when at least one of the following condi-

tions 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 if the Attach/Removal Detect feature is

enabled (by default it is disabled).

•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.

• Upon recovery from the Error state.

• When commanded via the SMBus in the Active

state.

• Any time the port power switch is activated after

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

ever VBUS voltage transitions from being driven

from VDD to being driven from VS, such as going

from Detect to Active power state) if the

Attach/Removal Detect feature is enabled (by

default it is disabled).

• Any time the VBUS bypass switch is activated after

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

from Active to Detect power state) if the

Attach/Removal Detect feature is enabled (by

default it is disabled).

When the VBUS discharge circuitry is activated at the

end of the tDISCHARGE time, the UCS2112 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(1/2) status bit)

and the UCS2112 will enter the Error state.

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