Small electromechanical drives include solenoid drives, single direction DC, bi-directional DC, or brushless DC systems and are typically sized according to their frame size and power in watts. Digital controllers, software, and complimentary analog and digital solutions from TI can help solve most drive requirements.
The Core Subsystems Include :
Controllers :
TI offers a range of solutions for the control processor; from the ultra-low power MSP430 microcontroller to the ARM® Cortex™-R4F-based Hercules™ Safety MCUs and C2000 Digital Signal Controllers (DSC). The right controller can optimize motor drive efficiency, improve reliability and lower overall system costs. The 32-bit DSP-class performance and motor-control optimized on-chip peripherals of the C2000 controllers enable users to easily implement advanced algorithms such as sensor-less vector control of three-phase motors. The C2000 family offers software-compatible controllers ranging from the low-cost F28016 to the industry’s first floating-point DSC, the TMS320F28335.
Motor/Solenoid Drive Circuit :
PWM drivers like the 1.2A DRV104 are compatible with resistive or inductive loads for driving solenoids or valves from a single +8V to +32V supply. Small voltage DC motor designers may opt for the TPIC2101 Pre-FET driver with 0V to 16V, 50mA PWM gate drive output. TPIC2101 drives the gate of an external, low side NMOS power transistor to provide PWM controlled power to a motor or other load. Included is soft start, over/under voltage protection, and 100% duty cycle capability. Use TPIC2101 to control the rotor speed of a permanent magnet DC motor or to control power to solenoids, heaters, or incandescent bulbs. For higher drive currents, a high-voltage high-current op-amp with a current limit between 0 and 5A (OPA548) externally controlled via a resistor/potentiometer or current-out DAC like DAC7811 or DAC8811, may be necessary. Alternatively, MOSFET drivers such as UCC37321 or UCC37323 can be considered to drive small motors directly or drive power devices such as MOSFETs or IGBTs.
Isolation :
TI Digital isolators have logic input and output buffers separated by TI’s silicon dioxide (SiO2) isolation barrier, providing 4kV of isolation. Used in conjunction with isolated power supplies, these devices block high voltage, isolate grounds, and prevent noise currents from entering the local ground and interfering with or damaging sensitive circuitry.
Controller Interface :
RS-232 or RS-422 are adequate for many systems. RS-485 signaling may be bundled with protocols such as Profibus, Interbus, Modbus or BACnet, each tailored for the specific requirements of the end user.
Sometimes controller area network (CAN) or EtherNet/IP (Industrial Protocol) are preferred do to network requirements. M-LVDS can provide lower power dissipation alternative. See app note http://focus.ti.com/lit/an/slla067a/slla067a.pdf for additional information on interface selection.
Motion Feedback using external circuits :
Isolated delta-sigma modulators (AMC1203/AMC1210) are ideal for shunt measurements to flatten glitches and increase current feedback resolution. These modulators are easy to use and provide oversampling and filtering for an encoder. For measuring controller inputs and system feedback, the INA159 difference amplifier provides ±10V (20Vpp) signals for an analog-to-digital converter (ADC) using 5V or 3.3V supplies. ADCs like ADS7861/ADS7864 or ADS8361/ADS8364 provide 4-channel or 6-channel simultaneous current sampling. The INA19x (x=3 to 8) and INA20x (x=1 to 9) provide wide common-mode voltages and are capable of both low-side and high-side current shunt monitoring.
Recommended Resources
C2000 Tools and Software
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