L9963E datasheet(65/184 Pages) STMICROELECTRONICS

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Each writing operation increments the NVM_CNTR counter by ‘1’. In case NVM_CNTR saturates to

NNVM_MAX_WRITE, writing operations are inhibited. User software shall inhibit any further Erase action in order

to avoid counter reset. Only reading operations are possible.

4.10.4

Electrical parameters

Table 52. NVM electrical parameters

Symbol

Parameter

Test conditions Min. Typ. Max.

Unit

NNVM_SIZE

NVM size allocated for external use

Design info

112

bit

TNVM_OP

Time interval required to perform each NVM operation. Tested by SCAN

NNVM_MAX_WRITE Maximum number of NVM writing operations allowed.

Design info

Write cycles

4.11

Safety and diagnostic features

L9963E provides an extended set of safety mechanisms to reach the required ASIL (Automotive Safety Integrity

Level) standard. Several diagnostics and integrity checks have been implemented. Faults can be notified

in a redundant way to the MCU: Global Status Word (GSW) allows failure notification over daisy chain

communication lines, while FAULT Line exploits a second independent pair. Every detected failure is available in

SPI registers.

4.11.1

Cell UV/OV diagnostic

It is possible to select the value for the Overvoltage threshold (VCELL_OV) as well as for the Undervoltage

threshold (VCELL_UV) of the cells.

It is also possible to specify an increment (VCELL_BAL_UV_ Δ) with respect to the undervoltage threshold VCELL_UV.

Such an increment will determine the position of the balance Undervoltage threshold (VBAL_UV_TH). Such a failure

can be masked through dedicated SPI bit. The actual balance undervoltage threshold will be placed according to

the following formula:

VBAL_UV_TH=VCELL_UV+ VCELL_BAL_UV

(7)

This diagnostic feature is completed by analyzing, inside the logic block, the digital information provided by the

Voltage measurement ADCs. Measurements will be performed just on enabled cells.

In case of cell UV/OV (VCELL_OV/UV):

•

Corresponding fault flag is set and latched into VCELL_OV / VCELL_UV register

•

Fault is propagated through the FAULT Line

•

Balance is stopped in case of UV event

–

A cell UV causes the balance activity to be stopped on the whole cell stack

–

A cell balance UV causes the balance activity to be stopped only on the affected cell

•

Conversion routine goes into Configuration Override

Balance UV (VBAL_UV_TH) fault can be masked via VCELLx_BAL_UV_MSK bit. When masking is activated:

•

Fault is not propagated through the FAULT Line

•

Conversion routine doesn’t go into Configuration Override

•

VCELLx_BAL_UV SPI flag is not set

4.11.2

Total battery VBAT diagnostic

The total stack voltage diagnostic is implemented through three different safety mechanisms:

•

Arithmetic sum of the digital information of cell ADC (within the Cell Conversion step of the Voltage

Conversion Routine): VBATT_SUM, stored in Vsum_batt(19:0). Such a value is then compared to the

digital thresholds VBAT_OV (SUM) or VBAT_UV (SUM) (programmable via the VBATT_SUM_OV_TH and

VBATT_SUM_UV_TH registers). This diagnostic is intended to catch stack undervoltage and overvoltage

events with a high precision.

L9963E

Safety and diagnostic features

DS13636 - Rev 12

page 65/184

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