DocID025336 Rev 1

7/23

AN4370

BEMF Zero crossing detection internal peripheral

22

Figure 3. Ringing noise

The BEMFCNT can be updated via SPI by writing its new value on it, or through a positive

pulse (the width of the pulse must be greater than 200ns) at the BC input pin. The update

mode, set by the BEMFCM bit is exclusive, this means that in SPI mode, a pulse over the

0

1 (PWM on

LS)

0

LS turn-on

To be used for passive

freewheeling. We recommend

output for low PWM duty cycles.

0

1 (PWM on

LS)

1

HS turn-off

To be used for active

freewheeling. We recommend

output for low PWM duty cycles.

1

0 (PWM on

HS)

X

HS turn-off

We recommend selecting the

high PWM duty cycles.

1

1 (PWM on

LS)

X

LS turn-off

We recommend selecting the

high PWM duty cycles.

Table 1. PWM edge used for filtering the selected BEMF Z crossing comparator output

BEMFMOD

BEMFSW

BEMF comparator

selected

BEMFPOL

BEMF

sampling

Comment