AMIS-30621 LIN Micro-stepping Motor Driver
Data Sheet
13.0 Structural Description
See
Figure 1.
13.1 Stepper Motor Driver
The motor driver receives the control signals from the control logic. The main features are:
• Two H-bridges designed to drive a stepper motor with separated coils. 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 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.
13.2 Control Logic (Position Controller and Main control)
The control logic block stores the information provided by the LIN 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 motor driver 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 motor driver part in order to manage possible problems and decide on internal actions and reporting
to the LIN interface.
13.3 LIN Interface
The LIN interface implements the physical layer and the MAC and LLC layers according to the OSI reference model. It provides and
gets information to and from the control logic block, in order to drive the stepper motor, to configure the way this motor must be driven,
or to get information such as actual position or diagnosis (temperature, battery voltage, electrical status, etc.) and pass it to the LIN
master node.
13.4 Miscellaneous
The AMIS-30621 also contains the following:
• An internal oscillator needed for the LIN protocol handler as well as the control logic and the PWM control of the motor driver.
• An internal trimmed voltage source for precise referencing.
• A protection block featuring a thermal shutdown and a power-on-reset (POR) circuit.
• A 5V regulator (from the battery supply) to supply the internal logic circuitry.
AMI Semiconductor – Sept. 2007, Rev 1.5
14
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