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Application Notes
174
Atlas® Digital Amplifier Complete Technical Reference
B
B.4
DC Brush Atlas with PIC
Microcontroller
The following schematic shows a DC Brush Atlas amplifier connected to a Microchip Technologies' PIC
microcontroller. Atlas receives torque commands through the PIC's SPI interface.
A wide variety of microcontrollers, DSP-type devices, or FPGAs supporting SPI interfaces can control Atlas directly.
Microchip’s dsPIC33FJ64GS606 is used in this example. It supports encoder inputs and other feedback inputs. Users
design their own motion control algorithms on the microcontroller, which in turn commands Atlas to drive the motor.
B.4.1
Atlas Power Input and Motor Output
Atlas is powered through pin pairs HV and Pwr_Gnd, and the power source is a transformer-isolated DC power
supply.
For DC Brush motors pins MotorA and MotorB are wired to motor windings Motor+ and Motor-, respectively. Pins
MotorC and MotorD are left un-connected.
Please refer to B.1 for layout and wiring recommendation on power input and motor outputs.
B.4.2
Atlas SPI Interface
Atlas functions as an SPI slave, receiving control commands from the PIC through its SPI interface. Atlas SPI
communication is enabled when ~SPICS is pulled down.
Please refer to B.1 for layout recommendation on SPI interface.
B.4.3
Atlas ~Enable and FaultOut Signals
Atlas has one dedicated input signal, ~Enable, which must be pulled low for the Atlas output stage to be active.
FaultOut is a dedicated output. During normal operation it outputs low. When a fault occurs it will go into a high
impedance state. In this example, FaultOut is pulled up by Vpullup through resistor R1. Vpullup can be up to 24V to
meet the system requirement. For example, if the fault signal is wired to a 5V TTL input, Vpullup can be 5V.
B.4.4
Microcontroller Configuration
In this schematic, the host controller is Microchip’s dsPIC33FJ64GS606. The microcontroller’s SPI port (SDI1/
SDO1/SCK1) is used for SPI communication.
In this example output pin #12 of U1 (PIC processor) is used to control Atlas' ~SPICS input. ~SPICS has an internal
pull-up, therefore, during power up and after reset, the control pin should be in high-impedance or output high state
to disable the SPI. Resistor R2 is optional.