L9026 datasheet(23/60 Pages) STMICROELECTRONICS

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7.2

Inverse current behavior

Inverse current (VOUTn_S > VOUTn_D) in high-side configuration may occur with channels in ON or in OFF state. A

reverse current applied to a specific channel has no impact on the general functionality (switch ON and OFF,

protection, diagnostic) of unaffected channels.

The channels affected by the current inversion can show driving capability degradation besides off diagnosis and

overcurrent protection unavailability. The reliability in Limp Home condition for the unaffected channels remains

unchanged.

7.3

Bulb inrush mode

The device is made especially for drives relays and LED but could happen that one or more output can be used

as high-side switches to drive small lamps or electronic loads with a big capacitor. In such a case the inrush

current at startup may trigger the overload diagnostic, switching the channel OFF.

In normal operation in order to re-engage the channels from an overload condition, an SPI command to clear the

latches (register DIAG_OVC_OVT) is needed, to allow the channel turning ON again; for some applications this

re-engagement procedure takes too long to transfer enough energy to activate the load.

The IC provides the means to overcome this issue by setting BIM.OUTn bit to “1”.

Once this feature is enabled, in case the channel reaches the overload current threshold and latches OFF, it

restarts automatically after a time tINRUSH, allowing the load to go out of the inrush phase. The automatic re-

engagement of the faulty channels lasts for a BIM time (tBIM). Once the tBIM counter is started, it is reset only

once the tBIM is expired, unless a reset condition occurs (VDDIO_uv, hardware or software reset).

A time diagram is shown in Figure 11. The channel configured with BIM option can be either driven by an SPI

command, PWM command (internal generator) or INn parallel input. Once programmed to “1” via SPI, the

BIM.OUTn bit is set back to “0” at the end of BIM time (tBIM), unless a reset condition occurs (VDDIO_uv,

hardware or software reset): an eventual switch off of the channel commanded by the user has no impact on

BIM.OUTn configuration.

Figure 11. Bulb inrush mode

When BIM.OUTn are set to “1”, eventual overcurrent/overtemperature conditions will flag DIAG_OVC_OVT.OUTn

bit, but the affected channels will not be permanently switched OFF. Once asserted, eventual SPI attempt to clear

DIAG_OVC_OVT.OUTn will be ignored, until the BIM counter is expired. In order to resume the normal behavior

when the BIM counter is expired, the DIAG_OVC_OVT.OUTn shall be cleared in order to allow IC to perform open

load ON diagnosis.

The bit BIM.OUTn is set to “0” by an internal timer sets after 40 ms (refer to parameter tBIM) starting from the first

overcurrent event latched to avoid the thermal stress of the channel in case of short circuit at the output.

L9026

Power stages

DS13397 - Rev 9

page 23/60

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