L9026 datasheet(17/60 Pages) STMICROELECTRONICS

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6.10

Limp Home mode

Device enters Limp Home mode when IDLE pin is “low” and one of the input pins is set to “high”, switching ON

the channel connected to it. SPI communication is possible but in read-only mode (SPI registers can be read but

cannot be written).

More in detail, Limp Home mode has the following effects:

•

IN0 is mapped as channel 2 input command, IN1is mapped as channel 3 input command

•

MODE bits are set to “01B” (Limp Home mode)

•

Overload and Over temperature diagnostics on channel 2 and 3 are available and the related

DIAG_OVC_OVT bits can be read.

Entering Limp Home mode from sleep means that all other registers are set to their default value and cannot be

programmed as long as the device is in Limp Home mode (SPI in in read only mode) so far a special feature

for Channel 2 and 3 is implemented and channels are able of auto-configuring as LS or HS depending on the

configuration of the external load.

Open in ON diagnosis is not performed in Limp Home mode. This is true also if Limp Home mode has been

entered from Active mode and DIAG_OPL_ON_EN.OUTn bits are set to '1'. In this case, the diagnostic cycles will

be performed only when back in ACTIVE mode.

See Table 9 for a detailed overview of supply voltage conditions required to switch ON channels 2 and 3 during

Limp Home. All other channels are kept OFF.

6.11

Power supply transition

The channel turn-ON time is defined by parameter tON when device is in Active mode or in Limp Home mode. In

all other cases, it is necessary to add the transition time required to reach one of the two above mentioned Power

Supply modes, as reported in Figure 7.

Figure 7. Transition times block diagram

L9026

Limp Home mode

DS13397 - Rev 5

page 17/60

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