L9963E datasheet(37/184 Pages) STMICROELECTRONICS

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4.3.1

State transitions in case of failure detection

FAULT line is functional in the following states: Normal, Cyclic Wakeup, Silent Balancing and Sleep.

Table 33. FAULT line functionality and L9963E states

State

Functions available

State transition in case of failure

Normal

Fault self-detection and propagation. Heartbeat generation.

None

Cyclic Wakeup

Fault self-detection (during ON phase) and propagation (always)

Go to Normal

Silent Balancing Fault propagation

Go to Normal (in case of external failure)

Sleep

Fault propagation

Go to Normal (in case of external failure)

4.3.2

FAULT line configuration

In case a failure is detected, the FAULTL pin is driven to its active state, while if no failure occurs, the FAULTL pin

holds its inactive value. Pin states depend on FAULT line configuration (selectable via the HeartBeat_En bit) and

on L9963E state.

Table 34. FAULTH line configuration and FAULTL pin states

L9963E State

HeartBeat_En

FAULTL Inactive state

FAULTL Active state

Normal

Low

High

Programmable PWM

High

Sleep, Silent Balancing, Cyclic Wakeup

Low

High (once moved to Normal)

The FAULT line stays asserted and L9963E is kept in Normal unless communication timeout occurs. The MCU is

responsible for clearing any fault latch. Once all failures are cleared, the FAULTL pin returns to its inactive state.

When the heartbeat is activated, the PWM period THB_CYCLE can be programmed via the HeartBeatCycle

guarantee the integrity of the FAULT line. Moreover, each L9963E is capable of sensing its upper companion

activity by monitoring the heartbeat continuity.

In case the heartbeat is disabled, the MCU can still verify the continuity of the FAULT line by forcing the unit on

the top of the chain to raise its FAULTL pin. This can be done by setting FaultL_force = 1 via SPI.

Before moving L9963E moves to a low power state (Sleep, Cyclic Wakeup or Silent Balancing), MCU must

disable the heartbeat functionality by programming HeartBeat_En = 0. Such an operation must be performed at

least TFIL_H_LONG before sending the broadcast GO2SLP command, in order to avoid false fault detections

(refer to Figure 15 for an example).

4.3.3

Failure sources

There are two failure sources:

•

Internal: L9963E detects a failure (self-detection)

•

External: a failure incoming from an upper unit is being input to the FAULTH pin (propagation)

4.3.3.1

Internal failure detection

If L9963E self-detects a failure, it drives the FAULTL pin to its active state, regardless of any activity on the

FAULTH pin.

For further information about all the failures and the subsequent actions, refer to Section 4.11.28 Safety

mechanisms summary.

4.3.3.2

External failure detection

Failure detection from external sources is sensed on FAULTH pin only if FaultH_EN = ‘1’ and Farthest_Unit =

‘0’. The unit at the top of the stack does not receive any signal input to the FAULTH pin. Hence, external failure

detection must be disabled by setting FaultH_EN = ‘0’ and Farthest_Unit = 1 via SPI.

L9963E

FAULT line

DS13636 - Rev 12

page 37/184

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