AN2229

3 Proposed initialization sequences for L9903:

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3

Proposed initialization sequences for L9903:

Alternative 1:

Vs > 7V

EN = High

for >50

μs

PWM = Low

after 50

μs of EN

DIR = High

for >10

μs after min 50μs of EN

DIR = Low

for >10

μs after min 10μs DIR = High after min 50μs of EN

Alternative 2:

Vs > 7V

EN = High

after 50

μs of EN

PWM = Low

positive Edge after min 50

μs of EN

DIR = Low

for >10

μs after min 50μs of EN

DIR = High

for >10

μs after min 10μs DIR = Low after min 50μs of EN

Figure 4.

Two possible solutions. Important is that after enabling the L9903 both LS transistors willb be switched-on

(Sx forced o GND) for at least 10

realized by changing the DIR-input while PWM is low. The min 50

μs delay are needed for the internal

circuit to setup. A signal change within the 50

μs may not be detected.

VS

EN

VS should be >7V before EN=HI

>50us

PWM

DIR

Alternative 2:

neg. Pulse at DIR

with PWM=0

>10us

PWM

DIR

Alternative 1:

pos. Pulse at DIR

with PWM=0

>10us