UCS1003-2 datasheet(44/138 Pages) MICROCHIP

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UCS1003-1/2/3

DS20005346B-page 44

 2014-2015 Microchip Technology Inc.

Trip Current-Limiting mode is used by default when the

UCS1003-1/2/3 family is in Data Pass-Through and

Dedicated Charger Emulation Cycle mode (except

when the BC1.2 DCP charger emulation profile is

accepted), and when there’s no handshake. This

method is also used when charger emulation is active.

7.1.4.2

Constant-Current Limiting

(Variable Slope)

Constant-Current Limiting is used when a portable

device handshakes using the BC1.2 DCP charger

emulation profile and the current drawn is greater than

ILIM (and ILIM < 1.68A). It is also used in BC1.2 CDP

mode and during the DCE Cycle when a charger

emulation profile is being applied, and the emulation

time-out is active.

In CC mode, the port power switch allows the attached

portable device to reduce VBUS output voltage to less

than the input VS voltage, while maintaining current

delivery. The V/I slope depends on the user set ILIM

value. This slope is held constant for a given ILIM value.

7.2

Thermal Management and

Voltage Protection

7.2.1

THERMAL MANAGEMENT

The UCS1003-1/2/3 family utilizes two-stage internal

thermal management. The first is named Dynamic

Thermal Management and the second is a Fixed

Thermal Shutdown.

7.2.1.1

Dynamic Thermal Management

For the first stage (active in both Current-Limiting

modes), referred to as Dynamic Thermal Management,

the UCS1003-1/2/3 devices automatically adjust port

power switch limits and modes to lower power dissipa-

tion 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) is low-

ered by one step and a timer is started (tDC_TEMP). When

this timer expires, the port power switch is closed and the

internal temperature is checked again. If it remains above

the TREG threshold, the UCS1003-1/2/3 devices repeat

this cycle (open port power switch and reduce the ILIM

setting by one step) until ILIM reaches its minimum value.

If the UCS1003-1/2/3 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 UCS1003-1/2/3 will

switch to operating using Trip Current-Limiting mode.

This will be done by reducing the IBUS_R2MIN setting to

120 mA and restoring the ILIM setting to the value

immediately below the programmed setting (e.g., if the

programmed ILIM is 2.05A, the value will be set to

1.68A). If the temperature continues to remain above

TREG, the UCS1003-1/2/3 will continue this cycle (open

the port power switch and reduce the ILIM setting by

one step).

If the UCS1003-1/2/3 internal temperature drops below

TREG –TREG_HYST, the UCS1003-1/2/3 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 UCS1003-1/2/3 will reset

the port power switch operation to its original

configuration, allowing it to operate using

Constant-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 UCS1003-1/2/3 will reset the port

power switch operation to its original configuration.

If the UCS1003-1/2/3 family is operating using Trip

Current-Limiting mode 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.

7.2.1.2

Thermal Shutdown

The second stage 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.

Note:

To avoid cycling in Trip mode, set ILIM

higher than the highest expected portable

device current draw.

Note 1:

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 UCS1003-1/2/3 will not restart the

DCE Cycle mode until one of the control

inputs changes states to restart emulation.

The UCS1003-1/2/3 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.

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