L9026 datasheet(33/60 Pages) STMICROELECTRONICS

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Diagnosis

The diagnosis information about the load status and the device is provided by the SPI, this information related to

each channel is independent, a fault condition detected on one channel, has no effect on the other.

9.1

Overload and overtemperature

The diagnosis bit DIAG_OVC_OVT is set when both overload and overtemperature happens. In order to

reactivate the channels DIAG_OVC_OVT_RLW bit must be set to "1." The writing operation is necessary to

remove the fault as a consequence of the fact that DIAG_OVC_OVT register is clear on write.

9.2

OFF diagnosis

This diagnosis is available only in Active mode.

The device is able to detect two kind of faults in OFF, open load and short (to battery in HS configuration or to

ground in LS configuration).

This diagnosis is available upon SPI request; Once the diagnosis has been started on one or more channels, a

new eventual diagnosis request is ignored until the ongoing cycle is finished.

The diagnosis strategy is implemented over two different phases:

•

First the IC distinguishes between faulty and no faulty condition.

•

In case of trouble found in the previous step, a specific procedure is put in place to detect the nature of the

fault.

The diagnosis is slightly different depending on a LS or HS configured output.

The strategy in LS configuration is reported below and referred to Figure 15; the HS case is quite similar, except

for the order in which pull-up and pull-down current generators are activated and for the pin involved (SOURCEn

for a HS configured channel, DRAINn for a LS).

•

This first phase lasts for tOFF1LS.

The current generator marked with ‘pldw’ (driven by dw_on) is active while the current generator marked as

‘plup’ is off..

In this condition, if the drain voltage remains above the threshold VDS(OL), the comparator output is low

which means that a load is present.

If the drain voltage decreases below the threshold, instead, the comparator flags the presence of a fault.

•

This second phase lasts for tOFF2LS.

After the first diagnosis step the output of the comparator is set to ‘1’ if a faulty condition has been found.

The current generator marked with ‘plup’ (driven by the signal up_on) is activated while ‘pldw’ is off.

In case, after the pull-up activation, the drain voltage rises and overcomes the comparator threshold again,

an Open Load fault is reported.

If the voltage remains constant and equal to zero for the whole diagnosis time, instead, a Short to ground

fault is recognized.

L9026

Diagnosis

DS13397 - Rev 9

page 33/60

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