AMIS-30622 Datasheet, PDF (10/35 Pages) AMI SEMICONDUCTOR – I2C Microstepping Motordriver

AMIS-30622 I²C Microstepping Motordriver
Data Sheet
8.5.2 Secure Position
A secure position can be programmed. It is coded on 11-bit,
thus having a lower resolution than normal positions, as
Stepping Mode
Half-stepping
1/4^th micro-stepping
1/8^th micro-stepping
1/16^th micro-stepping
Secure Position Resoultion
4 half-steps
8 micro-steps (1/4^th)
16 micro-steps (1/8^th)
32 micro-steps (1/16^th)
Important note
The secure position is disabled in case the programmed value
is the reserved code “10000000000”
(most negative position).
8.5.3 Shaft
A shaft bit can be programmed to define whether a positive
motion is an outer or an inner motion:
• Shaft = 0 ➞ MOTXP is used as positive pin of the X coil,
while MOTXN is the negative one.
• Shaft = 1 ➞ opposite situation.
9.0 Functional Description
9.1 Structure Description
9.1.1 Stepper Motordriver
The motordriver receives the control signals from the
control logic. It mainly features:
• Two H-bridges designed to drive a two separated coils
stepper motor. Each coil (X and Y) is driven by one H-
bridge, and the driver controls the currents flowing
through the coils.
• The rotational position of the rotor, in unloaded
condition, is defined by the ratio of current flowing in X
and Y. The torque of the stepper motor when unloaded is
controlled by the magnitude of the currents in X and Y.
• The control block for the H-bridges including the PWM
control, the synchronous rectification and the internal
current sensing circuitry.
• The charge pump to allow driving of the H-bridges’ high
side transistors.
• Two pre-scale 4-bit DACs to set the maximum magnitude
of the current through X and Y.
• Two DACs to set the correct current ratio through X
and Y.
Battery voltage monitoring is also performed by this block,
which provides needed 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.
shown in the table below. See command
GotoSecurePosition.
9.1.2 Control Logic (Position Controller and Main Control)
The control logic block stores the information provided by
the I²C interface (in the RAM or 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 initiate or stop properly 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 about internal
actions and reporting to the I²C interface.
9.1.3 Miscellaneous
The AMIS-30622 also implements the followings:
• An internal oscillator, needed for the Control logic and for
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 5V regulator (from the battery supply) to supply the
internal logic circuitry.
AMI Semiconductor - Rev. 2.3
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