L9779WD datasheet(77/170 Pages) STMICROELECTRONICS

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L9779WD

Functional description

169

Note:

The bit OUT21,25_EN_LB has priority over CPS_CONFx bit, this means that if one of

OUT21,25_EN_LB is set to 1 the OUT21…28 become independent power stages.



Two H-Bridge for stepper motor driving (no half-bridge arrangement is possible).

The over current threshold is the same as the single power stages.

When configured for stepper motor driving the motor movement is controlled through bit EN,

DIR and PWM (see Table 31).

In stepper motor configuration HS and LS power stages (OUT21...OUT28) can be used as

single power stages, and any of them can be connected in parallel to each other (same

type).

If the bit EN=1, the writing of bit PWM from 0 to 1 lead to the next step of the turn on

sequence. The writing of bit PWM to 0 left unchanged the MOS of the bridge that is ON. The

step is done only if the PWM bit goes from 0 to 1.

The order of the turn-on sequence is defined by the bit DIR.

The initial stepper position, after power-on, is the one with OUT21 and OUT24 ON in

Hbridge1 and with OUT26 and OUT27 ON in Hbridge2.

If configured as H-bridges the internal logic prohibits that the low-side and the high-side

switch of the same half-bridge will be switched on simultaneously.

In the below diagram the stepper motor operation is available.

Table 31. Configuration of the stepper motor

PWM

DIR

H-bridge 1 Power on

H-bridge 2 Power on

None

OUT21, OUT24

OUT26, OUT27

OUT21, OUT24

OUT25, OUT28

OUT23, OUT22

OUT25, OUT28

OUT23, OUT22

OUT26, OUT27

OUT21, OUT24

OUT26, OUT27

OUT23, OUT22

OUT26, OUT27

OUT23, OUT22

OUT25,OUT28

OUT21, OUT24

OUT25,OUT28

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