L9374TRLF datasheet(35/80 Pages) STMICROELECTRONICS

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L9374LF

Circuit description

RL_real

 RL_SPI · (1 + ISAT)

ISAT is the relative error of the SPI-Value RL_SPI to the real load RL_real (within an ideal

system).

ISAT is a twos complement. The range value is {-1 … +(1-LSB)} and

With this algorithm a fast controller dynamic can be achieved. Figure 21 shows the load

current response for different target currents. The ISAT_Qx value integration is disabled for

commanded target current values less than 29(DEC). This corresponds to a target current of:

Figure 21. Load current response for different target currents diagram

Starting at time zero a load error is corrected by modifying the programmed load resistor

value with an integral correction factor ISAT. This integration function is valid for target

currents higher than 110mA. If the ISAT value is once corrected in the system the load

model will respect the required precision immediately if the target current is reached in the

load. To avoid a long error integration phase during actuation of the ABS system it is

recommended that the current controlled outputs (Q3 & Q4) be activated periodically. This

will allow the L9374LF to adjust the ISAT parameter for any possible load resistance changes

due to temperature.

The integral correction factor (ISAT) is remembered and potentially modified at every load

actuation. It can be reset by changing RL or resetting the Current controller (see

Section 5.1.9). If reset, the load resistance error correction will be recalculated upon the

next output actuation.

LSB ISAT



512

----------

1.8A

512

----------



102mA

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