MLX90804 Datasheet, PDF (2/12 Pages) List of Unclassifed Manufacturers – Speed regulator for universal motors

MLX90804
Speed regulator for universal motors
General Description
Speed Regulator
The speed is regulated by a PI regulator with
programmable parameters Kp and Ki.
Speed Measurement
The speed is measured either by a coil or by a hall
sensor with digital output. The type of sensor can be
defined by mask option. The sensor must be located
close to a cylindrical magnet. The number of pole
pairs can be programmed.
Speed Setting
The speed is selected by applying a voltage at pin
SET. The voltage at this pin is fed into an ADC
(referenced to VDD) and is converted to a 4 bit
value. This value is the address of a ROM table in
which the different speeds are programmed. This
means that 16 different speeds can be selected.
The relation between voltage at input SET and the
corresponding speed does not need to be linear. It
can be freely chosen.
Soft Start
A soft start procedure is activated at start up and is
implemented to guarantee a smooth startup of the
motor under all conditions. At very low speed the
speed can not yet be measured and therefore
several actions are taken so that the PI regulator can
smoothly take over once the speed has increased
sufficiently. The soft start function is configurable
with the option mask.
Just after applying power to the electronics there is a
delay time until the motor starts movement. The
maximum allowable delay time is 300 ms.
Speed Set Ramping
At any time when the speed setting is changed to a
new speed, the change is internally generated with a
ramp function to optimize the transient behavior of
the PI regulator. This ramp function is configurable
with the option mask.
Main Switch
It is possible to program one or more speed settings
with a zero speed. This will stop the motor. However
for security reasons it might be considered to
combine this setting with a switch to disconnect
motor and/or electronics from the mains.
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 320 ms, the motor speed is 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 than a
programmable value SLIMA for longer then 320ms,
the selected speed is permanently set to 0 rpm. This
state can only be left by disconnecting the power
from the electronics.
MLX90804 Speed regulator for universal motors
Page 2
Rev 1.0 30/Jun/00