E-L8150 STMICROELECTRONICS [STMicroelectronics], E-L8150 Datasheet - Page 24

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

Precharge and hall effects filtering time description
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Precharge and hall effects filtering time description
Startup sequence with FS signal
●
Figure 14. Startup sequence forced by FS comparator, assuming the motor is not
When the signal coming from the FS comparator has a falling edge (corresponding to a Vsp
signal crossing the 1.23V threshold), the logic starts counting, to verify if the motor is
rotating or not. If the motor is stopped and no Hall effect commutation is detected, the
counter has reached its saturation time, given by the following equation:
N.B. TelMAX is equal to TMAX used in the previous sections of this document.
After this saturation time the logic has decided to do a precharge function, and for a period
of time given by the following equation all the output logic signals UL,VL,WL become high
while the signals UH, VH, WH are low.
When the precharge is over, the logic outputs start applying the right rectangular pattern to
accelerate the motor.
During this sequence the Hall filtering time is 400usec until the first rising edge on signal
HallU is detected. Then a filter given by the following equation is used:
T∆ZC is the elapsed time between two consecutive zero-crossing signals. By default a zero-
crossing signal is generated when a falling edge of the FS comparator is detected, and after
that a zero-crossing signal is generated when a rising edge on signal HallU is detected.
Let’s startup sequence forced by FS comparator, assuming the motor is not rotating:
FS
PRECHARGE
ZC
HALL BUS
FILTER TIME
PHASES
rotating
Tel
MAX
=
TelMax/6
T
(
7MHz
CHARGE
T
FILTER
)
–
1
≅
=
141.5msec
4096 T
=
PHASES EXCITED
MOTOR ACCELERATING
T∆zc
--------- - T∆
576
400 us
⋅
1
400 us
ck
⋅
≅
⇒
400µsec
ZC
400 us
Tel
-------------------- -
6
MAX
400 us
≅
24msec
400 us
U
T∆zc/576
Tel
L8150