AMIS-30622 Datasheet, PDF (14/42 Pages) AMI SEMICONDUCTOR – I2C Microstepping Motordriver

AMIS-30622
9. 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.
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 term 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.
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