L9918 datasheet(29/109 Pages) STMICROELECTRONICS

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Figure 13. Pre-excitation specific mode: example 2

4.2.4

Excitation OFF command

Behaviour of EXC signal in case of VBSPLINRG = 10.6 depends on REG_AUS NVM bits programming into NVM.

Here below a short description of the device behavior for all the possible REG_AUS selection:

•

REG_AUS = 0x00: EXC DC is set to 0 % in case N < Nstart and VBSPLINRG = 10.6. In case N > Nstart

(regulation state) the regulator uses 10.6 as a valid set point and it try to regulate B+ to that target.Once the

EXC OFF command is receipt, EXC power stage is kept in OFF until a different VBSPLINRG is received,

independently of the PH signal.

•

REG_AUS = 0x01: When VBLINSPRG = 10.6, EXC power stage is switched OFF. EXC signal DC remains

to 0 % until the OFF command is removed (VBSPLINRG ≠ 10.6).

•

REG_AUS = 0x02:EXC DC is set to 0 % in case N < Nstart and VBSPLINRG = 10.6. In case N > Nstart

(regulation state) the regulator uses 10.6 as a valid set point and it try to regulate B+ to that target. Once

the EXC OFF command is receipt, EXC power stage is kept in OFF state independently of the PH signal.

After 2.5 minutes L9918 restart the regulation if a valid phase signal (N > Nstart) is detected on PH pin.In any

moment the EXC OFF condition can be removed by sending VBSPLINRG ≠ 10.6.

•

REG_AUS = 0x03:Same as for REG_AUS = 0x02, the only difference is that the OFF state is 5 minutes long

instead of 2.5.

4.2.5

Excitation behavior during phase regulation

The phase regulation function starts if the phase signal has low voltage amplitude. Please refer to

Section 3.2.2 Phase regulation for detailed behaviour description.

4.2.6

Excitation current measurement

The excitation current measure is performed sensing the current flowing in the HS power that drives the EXC pin.

The working principle is showed in Figure 14.

L9918

EXC characteristics

DS13000 - Rev 2

page 29/109

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