L9918 datasheet(9/109 Pages) STMICROELECTRONICS

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Device remains in wake up state as long as at least one of the listed wake up source is present. If wake up

sources are no longer detected, the device goes back in stand-by with a proper time-out.

Every time the device enters the wake up state from standby state, an initialization procedure consisting in an

NVM download procedure is triggered. Every volatile data so far acquired (i.e. setup commanded through LIN Rx

frames) are lost.

In wake up state:

•

All the blocks are ON, the current consumption is higher than standby current consumption.

•

The duty cycle on EXC pin is equal to zero.

•

The phase sensitivity is VPStartTh (peak to peak).

In case of cranking event, due to low battery voltage value, LIN protocol could not be working. LIN timeout can

occur and the parameters sent by LIN protocol will be lost.

One particular behavior related to Wake Up state is the behavior occurring when device detects activity (i.e.

TX frames or RX frames with unrecognized ID or checksum) on LIN bus. Once this activity is detected, device

doesn’t move toward regulation state even if valid PH is present. It keep EXC OFF, waiting for a valid set point

command.

Phase regulation is active into Wake-up state. It is performed just in case phase rotation greater than Nstart.

1.5.3

Pre-excitation

The pre-excitation state is reached as soon as VBSPLINRG differs from 10.6 V and the engine rotation is lower

than Nstart.

The purpose of pre-excitation is to increase the alternator magnetization in order to guarantee proper conditions

for PH signal measurement in case the engine start to rotate. The pre-excitation is done driving the alternator

rotor with a PWM signal that has fixed frequency (fFSWpreexc) and fixed duty cycle (25 %).

If the battery voltage is higher than the maximum set-point value selectable by LIN protocol (VB+_LIM) the duty

cycle is reduced to 8 % or to 0 %, depending on NVM bit SST_ULIM_TV0_EN.

In pre-excitation state:

•

LRC function is disabled.

•

Phase regulation is disabled.

•

Current limitation control by LIN disabled except for specific pre-excitation mode (described below).

•

Default EXC current limitation is activated by dedicated NVM bits (IMAX_VE and IMAX_VE_VAL).

•

Safety functions are enabled.

Device is even featured with a specific pre-excitation mode, selectable by SV_FORD_EN NVM bit. When this is

enabled, EXC signal behavior depends on B+ value respect to the set point (VBSPLINRG) and on LIN frame data

carried by the LIN RX frame.

More detailed explanations and examples on special mode can be found in Section 4.2.3 Pre-excitation specific

mode selection.

1.5.4

Regulation mode

1.5.4.1

LIN regulation mode

This state can be reached: from pre-excitation state when alternator rotation is higher than Nstart; from

Regulation default state when valid set-point (VBSPLINRG > 10.6 V) is provided.

In particular, more detailed explanations must be dedicated to the last of these cases (LIN Regulation entered

from Regulation Default). If the Regulation Default state persists for more than LIN TO, two frames are needed

to enter the LIN Regulation mode: the first one to wake up the LIN block, the second one to communicate LIN

regulation data. On the other hand, if Default Regulation persist for less than LIN TO, the device is ready to

receipt LIN regulation information by a single LIN RX frame. In such case LIN Regulation mode can be entered

sending just one RX frame.

In this state the device modulates the EXC output current in order to set the battery line voltage to the LIN set

point (VBSPLINRG).

In LIN regulation mode state:

•

LRC function enabled accordingly to LIN communication.

•

Phase regulation enabled.

L9918

State diagram

DS13000 - Rev 2

page 9/109

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