Trust Automation, Inc. TA333 High Power Linear Servo Amplifier
10-Apr-09 Page 7 of 38
1.0 Features and Setup
1.1 Introduction
The TA333 is a 4
th
generation Trust Automation Linear Drive featuring a true Class-AB linear amplifier
with pure analog throughput at virtually infinite resolution and is free from digital conversion losses. This
versatile linear drive is an excellent choice for a variety of different servo motors and applications that
require high resolution positioning and/or ultra low noise applications with sensitive measuring
equipment, (e.g., transducers, sensors).
The TA333 is a highly configurable device with four common configuration modes:
• Drive one brushless motor using external sinusoidal commutation.
• Use Hall Effect sensor feedback for smooth internally commutated trapezoidal operation.
• Supports one or two brush or voice coil type motors.
• Drive a two coil stepper motor under sinusoidal control.
The TA333 features digital on-the-fly gain control (Dynamic Transconductance or DTS). This allows an
application to modify the drive transconductance on-the-fly, permitting both high acceleration control
and high resolution control. Normally one of these parameters is sacrificed in favor of the other due to
DAC limitations at the driving motion controller.
Why use a Trust Automation linear amplifier?
The majority of motion control applications use PWM (Pulse Width Modulated) drives. PWM drives are
very efficient, but are electrically noisy as they operate by pulsing the motor at full supply voltage at
typical frequencies of 4 kHz to 30 kHz. This pulsing tends to saturate everything electrically in the
surroundings, often including the intended operation. A second side effect of using PWM drives shows
up in ultra-high precision systems requiring nanometer precision. Due to the pulsing nature of the PWM
drive, the motor will tend to dither causing position error that cannot be tuned out.
The TA333 features a true Class-AB linear power stage with a fast current feedback loop to put it in
torque mode. This means that the output is a pure current signal with virtually no distortion around zero,
eliminating all of the side effects of a PWM drive. Some Class-C linear designs, which have a dead
band at zero volts out, attempt to mask this with a fast current loop. This works for some applications,
but performance will suffer in ultra-high precision applications.
Two important considerations where linear servo amplifiers are utilized are cooling and power supply
selection. A linear servo amplifier acts similarly to a large electronic variable resistor. Any power supply
voltage not delivered to the load is dumped as heat into the heatsink. Power supply voltages should be
matched closely to the required load voltage with a small margin for overhead. Excessive supply
voltage will result in amplifier overheating. Cooling linear servo amplifiers is often overlooked or not well
understood. Many products are available with similar current output specifications, but require the user
to supply heatsinks or fans. The TA333 incorporates a large heatsink with integral cooling fans to
accommodate most demanding applications provided there is adequate air space around the chassis
and the ambient temperature does not exceed specification. The TA333 intelligently monitors
temperature and compensates its internal dissipation to protect the drive from damage due to high
temperatures. The TA333 has a serial diagnostics port to monitor application performance and power
levels to aid in assuring optimal performance and a long life.
All Trust Automation drive products are built for safety, installation ease and long life. The TA333 offers
a fully isolated user interface for safe operation in high voltage applications. In addition the TA333
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