MLX90804SA-X ETC, MLX90804SA-X Datasheet - Page 8

• Manufacturer Part Number: MLX90804SA-X
• Description: Speed regulator for universal motors
• Manufacturer: ETC

Speed Set Ramping
The SETP integrator is built around a 8 bit counter
and guarantees a smooth transition when changing
the speed setting. There is a comparator between
SETP and IP. If SETP changes then the comparator
enables the IP-counter until IP gets equal to SETP.
The clock, which defines the rate of change, can be
defined for up and down counting independently, and
equals Fclkip= 102.3KHz/(128*(UPR[4:0]+1)) in case
of counting up.
Since the value for the desired speed is 10 bit wide,
and the counter only 8, the setpoint ramp speed from
the table is effectively multiplied by 4.
FLL
A frequency locked loop circuit is implemented to
obtain a master frequency (approximately 100KHz )
from a free running on-chip oscillator. Both FLL and
frequency multiplier have the same functional blocks,
MLX90804 Speed regulator for universal motors
SSE1
0
0
1
1
S T A R T
V Z C
S E T P
P r e l o a d C o u n t e r
A
D
U / D
R e s e t
REAL
SSE2
0
1
0
1
E N B
Carry out
L o a d
IP
Q
Q
1
4
x
x
1
n
S U B
Ki
1/ 8
1/ 16
1/ 32
1/ 64
P
Q
C O M P
u
1
MIN_ANGLE
P>Q
P=Q
E R R
E Q U
Speed regulator for universal motors
Page 8
D E L A Y
K p
K i
but the FLL uses the AC line frequency as his
reference.
Overload shutoff feature
625 ms after starting the motor (i.e. selecting a
speed setting different from 0 rpm) the following
function will be enabled: if the speed of the motor
gets lower then a programmable value SLIM for
longer then
permanently set to 0 rpm. As a consequence the
first possible timeout to recognize a blocked motor
after start will be approximately 1 sec.
This state can only be left by disconnecting the
power from the electronic circuit.
Overspeed shutoff feature
If the speed of the motor gets higher then a
programmable value SLIMA for longer than 320ms,
the selected speed is permanently set to 0 rpm.
This state can only be left by disconnecting the
power from the electronics.
Firing
The PI regulator gives an ignition angle IGN. The
resolution is 10 us. The firing circuit compares the
ignition point with a maximum and minimum
allowed angle MIN and MAX. MAX corresponds to
E R R P
ERRI
x
x
x
x
1
n
1
n
S U M
S U M
320 ms, the motor
u
1
u
1
ERRPI
x
x
1
n
S U B
MLX90804
u
1
Rev 1.0
IGN
speed
30/Jun/00
is