E-L8150 STMICROELECTRONICS [STMicroelectronics], E-L8150 Datasheet - Page 26

• Manufacturer Part Number: E-L8150
• Description: Brushless motor predriver
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Precharge and hall effects filtering time description
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Figure 16. Startup sequence forced by FS comparator, supposing the motor rotating
This situation is similar to the one described before, except DM behaviour. Let's suppose the
FS signal high, which means all phases in high impedance state. Even if the signal FS is
high, the logic is able to detect if the motor is rotating in the desired direction or not. So
when the signal coming from the FS comparator has a falling edge, by default a zero-
crossing signal is generated and the DM signal is already low, indicating that the detected
direction is not equal to desired direction.
From now on the logic waits for a Hall effect commutation and applies to it a filtering time of
T
Also the second Hall effect commutation is filtered using T
crossing signal is generated.
Starting form the second Hall effect commutation, after the acquisition of the filtered Hall
commutation, the logic outputs start applying the rectangular pattern, and the motor is able
to decelerate until the rotation direction changes becoming equal to the desired one.
After the first two Hall commutations, the filtering time used is a fraction of the elapsed time
between the first two Hall effect commutations, according to the previous T
This filtering time is used until the first rising edge on signal HallU is detected and a zero-
crossing signal is generated. After that the filtering time used is a fraction of the elapsed
time between the last two detected zero-crossing signals, in other words between the
second Hall effect commutation and the rising edge on signal HallU. Finally, when the
second rising edge on signal HallU is detected, the filtering time used is a fraction of the
electrical period, as described in previous T
Only when a Hall effect commutation consistent with the desired direction is detected the
DM signal becomes high, indicating the right direction detection.
●
PRECHARGE
Let's consider a startup sequence forced by FS comparator, supposing the motor
rotating too quickly:
FS
DM
ZC
HALL BUS
FILTER TIME
PHASES
quickly in the direction opposite to that imposed by the FR signal
=400µsec. The first significant zero-crossing signal is generated.
400 us
400 us
T∆zc’
MOTOR DECELERATING
PHASES EXCITED
T∆zc’/576
FILTER-ROTATING
MOTOR ACCELERATING
PRECHARGE
T∆zc’/576
equation.
T∆zc’/576
, and the second zero-
FILTER
T∆zc’/576
equation.
L8150