E-L8150 STMICROELECTRONICS [STMicroelectronics], E-L8150 Datasheet - Page 30

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

Precharge and hall effects filtering time description
30/37
Only when an Hall effect commutation consistent with the desired direction is detected, the
DM signal becomes high, indicating the right direction detection.
●
Figure 21. Startup sequence forced by SD signal, supposing the motor rotating too
When the SD signal has a falling edge the logic waits for an Hall effect commutation. If the
motor is rotating too quickly the next Hall effect commutation occurs before the filtering time
has elapsed.
This means that a new Hall filter count is performed and no Hall effect codification is
acquired until T
Until the motor rotates too quickly no Hall effect commutation is acquired by the logic, thus
the logic outputs force high impedance condition.
Only when the motor speed becomes lower than the speed necessary to obtain a
Tel/6>400µsec the Hall effect commutation are filtered and acquired.
After the first two or three filtered Hall effect commutations (because they have to be
consecutive), the logic outputs start applying the right pattern to the motor windings.
The motor rotation direction is not important, in fact this can influence only the kind of
pattern applied after the two or three filtered Hall effect commutation. In the picture is
reported the less likely situation.
●
When the signal coming from the SD-Comparator has a falling edge, the logic waits for an
Hall effect commutation for a period of time equal to TelMAX/6. If no Hall effect commutation
occurs during this time, the behaviour is that described in the previous section, when a
startup sequence with motor stopped is described.
Let's suppose that during the counting period of TelMAX/6 an Hall effect commutation is
detected. This commutation is filtered using 400µsec. Considering the hypothesis done,
starting from the Hall effect commutation detection, no more commutation will be detected
for the following TelMAX/6 and the behaviour is the one described in the startup sequence
with motor stopped.
Let's consider a startup sequence forced by SD signal, supposing the motor rotating
too quickly:
Let's consider a startup sequence forced by SD, supposing the motor rotating slowly.
SD
ZC
HALL BUS
FILTER TIME
PHASES
quickly
PRECHARGE
MOTOR ROTATING TOO FAST
has elapsed while the Hall bus is not changed.
400 us
T∆zc’
400 us
T∆zc’’
T∆zc’/576
PHASES EXCITED
U
Tel
T∆zc’’/576
L8150