33480 datasheet(20/39 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33480

FUNCTIONAL DEVICE OPERATION

OPERATIONAL MODES

AUTORESTART STRATEGY

The autorestart circuitry is used to supervise the outputs

and reactivate high-side switches in case of overload or

undervoltage failure conditions to provide a high availability

of the outputs.

Autorestart feature is available in Fail mode when no

supervising intelligence of the microcontroller is available.

Autorestart is activated in case of overload condition (OCHI2

or OCLO) or undervoltage condition on VBat (see Fig10).

The autorestart switches ON the outputs. During ON state

of the switch OCHI1 window is enable for tochi_Auto then

after the output is protected by OCLO.

Figure 7. Overcurrent window in case of Autorestart

In case of OCHI1 or OT, the switch is latched OFF until

wake up (wake=0 then1).

In case of OCLO or undervoltage, the output switch OFF

and after autorestart period (150ms for 10mohm or 75ms for

35mhom) turn ON again.

In case of under voltage occurred in fail mode, it will be

latched twice: one latch for outputs 1 and 5 and the second

latch for output 2. That means the corresponding output is

switched on only after its autorestart period (tAUTORST-T1 or

tAUTORST-T2).

The Autorestart is not limited in time.

TRANSITION FAIL TO NORMAL MODE

To leave the fail mode, the fail condition must be removed

(fail=0). The microcontroller has to send a SPI command with

D10 must be to logic [1] to reset the watchdog bit ; the other

bits are not considered. The previous latched faults are reset

by the transition into Normal mode.

TRANSITION NORMAL TO FAIL MODE

To leave the Normal Mode, a fail condition must occur

(fail=1). The previous latched faults are reset by the transition

into Fail mode.

Output current

OCHI1

OCLO

time

tochi_auto

Auto period

OCLO or UV fault

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