AN4324 datasheet(22/31 Pages) STMICROELECTRONICS

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Software

AN4324

22/31

DocID024963 Rev 2.0

6.2

Chip initialization

The STC3115 has to be initialized from a specific value. The initialization process is

different depending on the history of the application before startup. We can identify two

main situations:

New battery plug-in. Full battery initialization has to be performed starting from the

default software point and using the initial battery model. The initial open circuit

voltage (OCV) measurement and state of charge (SOC) have to be used as the initial

battery state. This information can be retrieved from the STC3115 registers.

The battery has not been removed. When the battery has not been removed since the

last application switch off, the last recorded data can be recovered and stored in the

STC3115 using the data saved in the RAM memory.

At every application startup, the following steps are recommended to correctly configure

the STC3115 registers:

Read the chip ID in the REG_ID at address 0x18

Check the RAM memory status (test and CRC words)

If the RAM content is incorrect, initialize the RAM and the chip with default parameters

If the RAM content is correct, check the PORDET and BATFAIL bits

If BATFAIL = 1, the battery voltage was previously decreased below 2.6 V (UVLO

threshold), the Batd pin detected a battery removal/switch event, and the chip has to

be fully initialized. If PORDET = 1, the battery voltage was previously decreased

below 2 V (POR threshold), the battery was removed/switched, and the chip has to be

fully initialized. The STC3115 cannot be restored and full STC3115 initialization is

required (i.e. STC3115 initialization steps).

If the BATFAIL/PORDET = 0, the battery has not been removed and chipset

configuration can be recovered from the RAM data information (e.g. from the RAM

memory content description). STC3115 restoration is possible; the saved RAM data

can be used to restart the STC3115 from a previous application status (i.e. STC3115

restoration steps).

Once the validity of the STC3115 RAM memory and the status of the REG_CTRL register

has been checked, the STC3115 can then be initialized with default parameters or with

restored parameters (see Section 6.1 for RAM content clarification).

STC3115 initialization steps

This is the standard STC3115 initialization flow: all registers have to be initialized using

default values and the first open circuit voltage (OCV) measurement. Carry out the

following three steps when no data can be retreived from the last STC3115 running mode.

Read the OCV register. The first OCV measurement reflects the initial battery state of

charge (SOC). Read it and save it into a temporary variable.

Set the STC3115 parameters (ensuring first that the GG_RUN bit is set to 0). The

REG_OCVTAB registers have to be filled with their previously calculated values as

well as the values of the REG_CC_CNF and REG_VM_CNF registers. Then configure

the

application

parameters

setting

the

REG_ALARM_SOC,

REG_ALARM_VOLTAGE,

REG_CURRENT_THRES,

REG_RELAX_MAX,

REG_ALARM_SOC, and REG_ALARM_VOLTAGE registers as required by the

application to provide an HW interruption signal on the ALM pin when one of the

measurements

detected

being

below

the

defined

threshold.

The

REG_CURRENT_THRES and REG_RELAX_MAX registers are used to configure the

internal behavior of the STC3115. Default values are enough to provide good

accuracy.

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