L9952GXP datasheet(27/68 Pages) STMICROELECTRONICS

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L9952GXP

Protection and diagnosis

Doc ID 13518 Rev 5

27/68

3.4

High side driver outputs

The component provides a total of 4 high side outputs Out1...4, (7

Ω typ. @ 25C) to drive

e.g. LED' s or hall sensors and 1 high side output OUT_HS with 1

Ω typ. @ 25 C).

The high side outputs are protected against

●

Over- and under voltage

●

Overload (short circuit)

●

Over temperature with pre warning

If the output current exceeds the current shutdown threshold the output transistor is turned

off and the corresponding diagnosis bit of the output is set.

The switches are automatically disabled in case of reset condition, Vs-under, Vs-over

voltage or thermal shutdown (TSD1&2).

For OUT_HS an auto recovery feature is available in active mode.

If the OUT_HS output current exceeds the current shutdown threshold, the output transistor

is turned off and the corresponding diagnosis bit of the output is set.

Via SPI command the auto recovery feature can be enabled in order to restart the driver in

case of over current shutdown. This over current recovery feature is intended for loads

which have an initial current higher than the over current limit of the output (e.g. Inrush

current of cold light bulbs).

The device itself can not distinguish between a real overload and a non linear load like a

light bulb. A real overload condition can only be qualified by time. As an example, the micro

controller can switch on light bulbs by setting the over current recovery bit for the first 50ms.

After clearing the recovery bit, the output will be automatically disabled if the overload

condition still exists.

The status of all high side outputs (over-current, open load) can be monitored by SPI

interface.

In case of a watchdog failure, the high side drivers are switched off. The control bits are not

cleared, i.e. the drivers will go to the previous state once the watchdog failure condition

disappears.

ESD structures are configured for nominal currents only. If external loads are connected to

different grounds, the current load must be limited to this nominal current.

Note:

Loss of ground or ground shift with externally grounded loads.

3.5

Low side driver outputs Rel1, Rel2

The outputs provide an active output zener clamping feature for the demagnetisation of the

relay coil, even though a load dump condition exists. For safety reasons the relay drivers

are linked with the Watchdog: in case of failure, or missing trigger signal the relay drivers will

switch off.

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