L9396 datasheet(87/109 Pages) STMICROELECTRONICS

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DS12539 Rev 10

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L9396

System functional safety implementations

109

7.6

Temperature sensor

The device provides an internal analog temperature sensor. The sensor is aimed at having a

reference for the average junction temperature on silicon surface. The sensor is placed far

away from power dissipating stages and drivers. The output of the temperature sensor is

available via SPI through ADC conversion. The formula to calculate temperature from ADC

reading is the following one:

T(°C) = (0.154 - 2.5 * ADCdec / (2^10*4.5)) * 220 / 0.369 + 180

where ADCdec is ADC reading in decimal.

7.7

Over temperature protection

Device is equipped with 9 independent thermal protection circuits placed close to circuits

that can experience over temperature in fault condition.

These circuits are: 4 remote sensor interfaces (WSS), GPO driver, one shared between

VCC and VCC5, VPREREG, Charge Pump, Boost.

The effect of thermal protections and how to manage this kind of fault is described in the

paragraphs related to those blocks.

7.8

Bist

7.8.1

Logic Bist

In order to test the correct operation of the main safety relevant digital blocks, a logic bist is

implemented.

The logic bist check can be controlled via SPI using the register BIST_CTRL.

The digital blocks checked are:

Wheel Speed Sensor Logic

Driver Controllers Logic

BATTERY SWITCH

PUMP MOTOR PRE DRIVER

GPO

FAIL SAFE PRE DRIVER

ADC Controller Logic

If Logic BIST runs the logic under test and the SPI registers related to these digital blocks

are not available and reset to its default values at Logic Bist Exit.

Microcontroller can activate Logic bist setting the bit LOGIC BIST RUN = 1 in the register

BIST_CTRL. After that, the Logic Under Test is in BIST mode: the sequential cells are

Table 58. Temperature sensor

Symbol

Parameter

Conditions/Comments

Min.

Typ.

Max.

Unit

TMON

Monitoring temperature range

-40

175

°C

TACC

Temperature accuracy

-15

°C

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