L9963E datasheet(71/184 Pages) STMICROELECTRONICS

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4.11.11

Oscillator main clock monitoring

The oscillator used for the main logic functionalities and digital timings is monitored with a redundant oscillator

that is electrically independent from the main one. Redundant oscillator is used just for safety purpose, in order

to check a possible stuck condition. It can be activated by setting clk_mon_en = 1, and the confirmation of its

activation can be read back via the clk_mon_init_done bit.

If a frequency difference greater than Freq_diff occurs between the two redundant clocks, the OSCFail flag is

set.

4.11.11.1

Electrical parameters

All parameters are tested and guaranteed in the following conditions, unless otherwise noted:

9.6 V < VBAT < 64 V; -40 °C < Tambient < 105 °C

Main Oscillator Electrical parameters

Table 53. Main oscillator electrical parameters

Symbol

Parameter

Test conditions

Min.

Typ.

Max.

Unit.

FMAIN_OSC

Internal MAIN Oscillator frequency

MHz

FAUX_OSC

Internal redundant Oscillator frequency

MHz

Freq_diff

Delta oscillator check

4.11.12

Stand-by oscillator main clock monitoring

The Stand-by oscillator is used in both Normal operation and low power modes. It keeps alive all the standby

functionalities, including wakeup circuitries, during Sleep, Silent Balancing and Cyclic Wakeup. It is also

responsible for clocking the balancing activity during Normal, Cyclic Wakeup and Silent Balancing operation.

Thanks to this oscillator, balancing drivers can be continuously protected against a sudden short event, even

in low power modes. In order to guarantee a maximum coverage against latent failures that could prevent from

balancing short detection, such oscillator is monitored with a redundant oscillator that is electrically independent

from the main one. Redundant oscillator is always available and is used just for safety purposes, in order to

check a possible stuck condition of the main one. In case the main oscillator gets stuck, the Balancing Drivers are

automatically switched off. This guarantees a fail safe operation, preventing infinite balancing duration.

If the failure happens while the device is in Normal mode, the communication with L9963E will still be functional.

If the failure occurs while the device is in a Low Power mode, L9963E will fail safely, but it will be impossible to

wake up.

4.11.13

Regulator UV/OV diagnostic

VTREF, VCOM, VREG regulators have dedicated UV/OV diagnostic implementation. If one of these regulated

voltages goes lower than the corresponding UV threshold or higher than the corresponding OV threshold for a

time longer than the corresponding digital filter, the related fault flag is latched. Failure is then propagated through

the FAULT Line.

In case of UV/OV detection:

•

Corresponding fault flag is set and latched into Faults1 register

•

Fault is propagated through the FAULT Line

•

In the specific case of VREG OV, Bootstrap and Balance functions are disabled

•

In the specific case of VREG UV, Balance is disabled

4.11.14

Regulator self test

All power supplies are provided with a dedicate undervoltage or overvoltage test.

An analog self test on UV/OV comparators is implemented in order to guarantee high robustness safety

requirements. Such a BIST can be requested via Voltage Conversion Routine:

•

VTREF

•

VCOM

•

VREG

L9963E

Safety and diagnostic features

DS13636 - Rev 12

page 71/184

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