E-L8150 STMICROELECTRONICS [STMicroelectronics], E-L8150 Datasheet - Page 22

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

Operating description
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Figure 12. Filter Block Diagram
The filter working principle is explained in the previous diagram
component of the filter circuit is a 12-bit counter that is reset (to the value 0) whenever the
PosFil signal is equal to the Pos one. When the two signals are different (meaning that a
transition is happening), the counter will start counting as long as one of the following
conditions will occur:
●
●
At the same time (at the end of the filtering time), a flip-flop detecting the direction is
updated with the right direction information according to the former Hall decoding PosFil and
the new one Pos, immediately before latching it into the register.
12-bit Filter Length is set to two values according to different possibilities:
●
●
A ZC signal is produced every time one of these situations happens:
●
●
●
Pos signal is again equal to former PosFil: in this case a noise is generating some Hall
comparator commutation,
the counter has reached or overcome the value set by Filter Length signal: in this case
the internal Hall signals will be latched into the PosFil register; immediately after this
event, PosFil will become equal to Pos and the counter will be reset.
maximum filtering time, corresponding to 4096 clock periods (≈420us in the typical
case, same used for pre-charge function) when an hall effect commutation is detected
just after a startup signal edge (SD or FS) and before TMAX/6 is elapsed. This filtering
time is also used when the motor accelerate starting from a stopped condition (no hall
effect commutation is detected from FS or SD edge to TMAX/6)
the filter length is a fraction of the elapsed time between two Zero Crossing signal (ZC).
During normal working (in case motor period is shorter than TMAX) it is equivalent to
0.625 electrical degrees.
a falling edge of the FS signal is detected
a rising edge of the HallU signal is detected
any hall effect commutations when the high impedance condition is forced by the IC
and the motor is in free-run condition
PosFil
PosFil
Pos
Pos
DELAY
DELAY
1 Tclk
1 Tclk
¹
¹
=
=
ck
ck
Reset
Reset
COUNTER
COUNTER
12 BIT
12 BIT
(Figure
Enable
Enable
Latch
Latch
REGISTER
REGISTER
12
12
12
12
POS FIL
POS FIL
12): the main
Length
Length
Filter
Filter
>=
>=
PosFil
PosFil
3
3
L8150