L9305 datasheet(40/107 Pages) STMICROELECTRONICS

40 / 107 page

8.1.4

Bandgap regulators, internal analog and digital supply monitoring

There are two internal bandgap regulators, main and auxiliary and two internal low voltage regulators, V3VA and

V3VD. These regulators are monitored for over and under voltage conditions and a fault on any regulator

regardless of the type of the result in a Power On Reset (POR). There are no flags dedicated to these fault

conditions other than the POR flag. A POR event resets all registers and disables all solenoids and fail safe. The

POR flag is available as shown below.

Table 26. POR fault summary

Location

Bit Name

SERVFLT1

POR Flag

In addition to the static voltage monitoring function, the L9305 includes a self-test to verify the proper operation of

all comparators and fault logic thus preventing latent faults from influencing the device operation. The self-test

function verifies the voltage comparison and logic to ensure the entire path is verified. The self-test is run on

demand by setting the ODTEST [D0]. The sequence for initiating the self-test and reading the response is shown

below:

•

In ODTEST register set bit D[0] = 1

•

Monitor ODTEST register bit D[0] for test status, 1 = test in process, 0 = test complete.

•

If ODTEST register bit D[0] = 1 the test has succeeded; if the test fails device executes a POR and the

related bit will be set on SPI register.

8.1.5

GND loss detection

GNDA and GNDD are continuously monitored for loss of ground connection. Ground loss comparators and fault

logic are monitored for latent faults using a self-test function. The self-test is automatically performed upon a POR

event. Should a ground loss or self-test fault be detected, the corresponding fault bits are set and are summarized

below.

Table 27. GNDA and GNDD fault summary

Location

Bit Name

SERVFLT1

D15

GNDD Loss

SERVFLT1

D14

GNDA Loss

SERVFLT2

GNDA Loss Self Test

SERVFLT2

GNDD Loss Self Test

A GNDA or GNDD Loss fault will disable all solenoid drivers and the fail-safe pre-driver. The fault is cleared on

SPI read but solenoid and fail-safe operation must be re-enabled through the SPI.

Each solenoid driver channel has a dedicated ground connection, GND_SOL0, GND_SOL1, GND_SOL2 and

GND_SOL3. Should a fault be detected, the faulted channel will be disabled and fault flag set as shown below:

Table 28. Solenoid GND fault summary

Location

Bit Name

EXCEPTIONS2

Ground Loss

Each solenoid ground connection is continuously monitored for loss of connection. Each loss of ground

monitoring circuit also contains a self-test function that must be requested by the user. The sequence for initiating

the self-test and reading the response is shown below:

•

For the desired channel, in CONFIGURATION2 register set bit D[0] = 1

•

Monitor EXCEPTIONS2 register, bit D[5] for test status, 1 = test in process, 0 = test complete.

•

Read EXCEPTIONS2 register, bit D[3]; 0 = no fault; 1 = fault

L9305

Safety features

DS12774 - Rev 10

page 40/107

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