AMIS-30624_13 Datasheet, PDF (15/52 Pages) ON Semiconductor – I2C Micro-stepping Motor Driver

AMIS−30624, NCV70624
 Two DAC’s to set the correct current ratio through X
and Y.
Battery voltage monitoring is also performed by this
block, which provides the required information to the
control logic part. The same applies for detection and
reporting of an electrical problem that could occur on the
coils or the charge pump.
Control Logic (Position Controller and Main Control)
The control logic block stores the information provided by
the I²C interface (in a RAM or an OTP memory) and
digitally controls the positioning of the stepper motor in
terms of speed and acceleration, by feeding the right signals
to the motordriver state machine.
It will take into account the successive positioning
commands to properly initiate or stop the stepper motor in
order to reach the set point in a minimum time.
It also receives feedback from the motordriver part in
order to manage possible problems and decide on internal
actions and reporting to the I²C interface.
Motion Detection
Motion detection is based on the back−emf generated
internally in the running motor. When the motor is blocked,
e.g. when it hits the end position, the velocity, and as a result
also the generated back−emf, is disturbed. The
AMIS−30624/NCV70624 senses the back−emf, calculates
a moving average and compares the value with two
independent threshold levels. If the back−emf disturbance is
bigger than the set threshold, the running motor is stopped.
Miscellaneous
The AMIS−30624/NCV70624 also contains the
following:
 An internal oscillator, needed for the control logic
handler as well as the control logic and the PWM
control of the motordriver.
 An internal trimmed voltage source for precise
referencing.
 A protection block featuring a thermal shutdown and a
power−on−reset circuit.
 A 5 V regulator (from the battery supply) to supply the
internal logic circuitry.
FUNCTIONS DESCRIPTION
This chapter describes the following functional blocks in Position Controller
more detail:
 Position controller
 Main control and register, OTP memory + ROM
 Motordriver
The Motion detection and I²C controller are discussed in
separate chapters.
Positioning and Motion Control
A positioning command will produce a motion as
illustrated in Figure 7. A motion starts with an acceleration
phase from minimum velocity (Vmin) to maximum velocity
(Vmax) and ends with a symmetrical deceleration. This is
defined by the control logic according to the position
required by the application and the parameters programmed
by the application during the configuration phase. The
Ì Acceleration
range
ÌÌ _{Zero Speed}
Ì _{Hold Current}
ÌÌÌÌÌÌ _Pstart
Pmin
current in the coils is also programmable.
ÌÌ Velocity
Deceleration
range
ÌÌÌÌÌÌ _Vmax
Zero Speed
Hold Current
ÌÌÌÌ _Vmin
ÌÌÌÌÌÌÌÌ _P=0
Pstop
Position
Pmax
Figure 7. Positioning and Motion Control
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