STE12PS datasheet(12/44 Pages) STMICROELECTRONICS

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Functional description

STE12PS

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3.2.3

Detection and classification FSM

This FSM manages all operations related to the detection and classification procedures.

For these two procedures, the following assumptions are made:

A channel is detected ONLY if:

the channel has not yet been detected,

and Channel Detection has been enabled,

and

the Backoff Detection timer

and Subsequent Attempt timer are NOT running (after

a corresponding fault detection or failed signature).

A channel is classified ONLY if:

Channel Classification is enabled,

and

the previous related detection procedure has reported an Rgood/Ggood value

(Auto and SemiAuto modes).

Three general macro operations can be performed:

●

STARTUP: the following operations are related to the startup procedure:

–

RESET: reset and initialize all digital aspects of the STE12PS,

–

WAIT_POWER_UP: wait 100ms for completion of the power-up procedure. During

this period, the I2C bus is active - allowing the host to initialize registers while the

detection procedure is waiting to start.

–

DETECTION START: all setting-up needed to start operations is performed in this

state. The first battery voltage sample is latched in a dedicated register.

●

DETECTION: the following operations are related to the detection procedure for the

channel selected:

–

Low voltage detection command (4V) is issued via registers; detection timer is

started to execute the command for a duration of ½Tdet ms.

–

Wait for 5ms to acquire a stable measurement.

–

Sampled sensing current values are acquired via A/D converter.

–

The samples previously acquired are averaged and the resulting value, reported

into the Channels Monitor register, is compared against programmed min/max

values. If the sensing current is higher than maximum allowed value, the detection

procedure is considered as having FAILED: backoff timer is started (Alternative B)

and an alarm flag raised according to the Channel Status registers.

–

If the sensing current results lower than the minimum allowed value the detection

procedure is continued: the alarm flag is raised in the Channel Status registers.

–

The described operations are repeated for the High-Voltage detection command

(8 V).

–

Signature Resistance is calculated:

–

If 2µsec < Gmeas < Glow

or Ghigh < Gmeas, then backoff timer is started

(Alternative B) and detection result failure is reported in the Channel Status

registers.

–

Else, Glow < Gmeas < Ghigh and the result of a successful detection is reported

in the Channel Status registers.

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