UCS81003 datasheet(38/108 Pages) MICROCHIP

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UCS81003

DS20005334A-page 38

 2014 Microchip Technology Inc.

7.5

Fault Handling Mechanism

The UCS81003 has two modes for handling faults:

• Latch (latch-upon-fault)

• Auto-Recovery (automatically attempt to restore

the Active power state after a fault occurs).

If the SMBus is actively utilized, Auto-Recovery Fault

Handling is the default error handler as determined by

the

LATCHS

bit

(see

Section 10.4.3

“Switch

Configuration

Otherwise,

the

fault

handling mechanism used depends on the state of the

LATCH pin. Faults include overcurrent, overvoltage (on

VS), undervoltage (on VBUS), back-voltage (VBUS to VS,

or VBUS to VDD), discharge error and maximum

allowable internal die temperature (TTSD) exceeded

(see Section 5.1.5 “Error State Operation”).

7.5.1

AUTO-RECOVERY FAULT

HANDLING

When the LATCH control is low, Auto-Recovery Fault

Handling is used. When an error condition is detected,

the UCS81003 will immediately enter the Error state

and assert the ALERT# pin (see Section 5.1.5 “Error

State Operation”). Independently from the host

controller, the UCS81003 will wait a preset time

(tCYCLE), check error conditions (tTST) and restore

Active operation if the error condition(s) no longer

exist. If all other conditions that may cause the

ALERT# pin to be asserted have been removed, the

ALERT# pin will be released.

FIGURE 7-1:

Error Recovery Timing (Short Circuit Example).

7.5.2

LATCHED FAULT HANDLING

When the LATCH control is high, Latch Fault Handling

is used. When an error condition is detected, the

UCS81003 will enter the Error power state and assert

the ALERT# pin. Upon command from the host

controller (by toggling the PWR_EN control from

enabled to disabled or by clearing the ERR bit via

SMBus), the UCS81003 will check error conditions

once and restore Active operation if error conditions no

longer exist. If an error condition still exists, the host

controller is required to issue the command again to

check error conditions.

tRST

VBUS

IBUS

SHORT

applied.

ITST

tDISCHARGE

ITST

VTEST

Short Detected.

VBUS discharged.

Enter Error state.

Check short

condition.

Short still

present.

Return to

Error State.

Wait tCYCLE.

Check short

condition.

Short

removed.

Return to

normal

operation.

tCYCLE

tRST

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