L9300 datasheet(152/178 Pages) STMICROELECTRONICS

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Functional safety

17.1

Power supply

17.1.1

VDD3(4) Regulator

Under Voltage Comparator

Voltage monitor compares regulator feedback value with a reference threshold, independent from the regulator

one, to understand if a fault condition is present on regulator output. To prevent latent fault, an analog self-test is

implemented in the monitor circuitry: comparator inputs are choppered by a diagnostic clock and the output of the

comparator is XORed with diagnostic clock itself (see next figure); in case comparator is not able to toggle its

output will start toggling the following diagnostic clock and setting the fault. Self-test is enabled by SPI bit and is

kept running until the enable bit is cleared; in case of fault same actions as under voltage fault are taken leading

to ASIC reset, setting uv fault bit plus a self test fault bit to let the user know, after recovering from RES condition,

that the fault has been generated during self test procedure.

Over Voltage Comparator

Voltage monitor compares regulator feedback value with a reference threshold, independent from the regulator

one, to understand if a fault condition is present on regulator output. To prevent latent fault an analog self-test is

implemented in the monitor circuitry: comparator inputs are choppered by a diagnostic clock and the output of the

comparator is XORed with diagnostic clock itself (see next figure); in case comparator is not able to toggle its

output, it will start toggling the following diagnostic clock and setting the fault. Self-test is enabled by SPI bit and is

kept running until the enable bit is cleared; in case of fault, the same actions as overvoltage fault (setting OV fault

bit and a Selftest fault bit) are taken leading to device reset, and warn, after recovering from RES condition, that

the fault has been generated during self-test procedure.

Figure 64. voltage monitor self test basic implementation

No fault

Fault condition

GADG2407171510PS

L9300

Functional safety

DS12258 - Rev 5

page 152/178

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