L9026 datasheet(35/60 Pages) STMICROELECTRONICS

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Limp Home mode

The Limp is intended to handle limited functionality of the device in critical faulty situations.

A typical application scenario is reported in Figure 17, with a system which is reconfigured during Limp Home as

shown in Figure 18.

Shall the micro that controls the device fail, an external safety micro takes over controlling parallel inputs IN0 and

IN1. The SBC will force the IDLE signal low which brings the device in Limp Home. Once the switching activity on

IN0, IN1 is over, being the IDLE pin still de-asserted, the device will reach Sleep mode.

During this mode active, L9026 is only capable of driving two outputs i.e. OUT2 through IN0 and OUT3 through

IN1; such a mapping is fixed and overcomes an eventual different mapping programmed via SPI once the Limp

Home is reached.

Figure 17. Possible system configuration during normal operating conditions

In Figure 17 the dotted green lines mark the signals path when the device is operating in normal node, IDLE, IN0,

IN1 are provided by the main MCU. Figure 18 shows a possible Limp Home configuration where the dotted blue

lines mark the signals path.

L9026

Limp Home mode

DS13397 - Rev 5

page 35/60

L9026 Arkusz danych(PDF) 35 Page - STMicroelectronics