Trust Automation, Inc. TA333 High Power Linear Servo Amplifier
10-Apr-09
Page 10 of 38
g
m
= current gain (Transconductance)
I
o
= output current
V
c
= command voltage
Example:
If:
I
o
desired = 15A and V
c
(max) = 10V
Then:
g
m
= 15 / 10 or 1.5A/V
For every 1 volt of command 1.5A of current will be driven.
Note: Current output is limited by Ohm’s Law (I = V
supply
/ R
motor
)
TA333 is factory configured for 10A, 15A, 20A and 25A for a commanded input voltage of ±10V, set at
SW1, positions 3 and 4.
(See table 4.9)
Note: 25A output duration is limited by the SOA graph and temperature.
(See SOA section 2.4)
Custom Transconductance ratios can be preset by the factory. Please contact
to discuss your requirements.
1.7 Thermal Limits
The TA333 is internally thermally protected with integral variable speed cooling fans. The heatsink
temperature is monitored and the fan speed is automatically adjusted to maintain a safe operating
temperature. If the heatsink temperature rises to 70°C, a FAULT output is generated but the drive will
continue to operate. If FAULT is ignored and the heatsink temperature rises to 90°C, the drive will
shutdown. When the heatsink temperature drops below 40°C, the drive can be re-enabled by toggling
the enable line.
1.8 Dynamic Transconductance Selection
A feature pioneered by Trust Automation, Dynamic Transconductance, or DTS, enables on-the-fly
changes to the transconductance settings. This feature is advantageous in frictionless systems (i.e., air
bearing systems) where start, stop and turn around currents are high, but moving currents are very low.
Due to the digital nature of most motion controllers there is limited DAC resolution to cover both the
high and low currents with sufficient resolution. By switching the transconductance on the fly, the
motion controller’s DAC can be utilized at its full resolution for both high current moves and precision
motion.
The DTS inputs are logically “OR”ed with the DTS switch inputs. In this way a highest current setting
can be chosen by the switches and logic can “OR” with this data to set a lower setting.
The TA333 accomplishes this by allowing the motion controller to logically control the DTS bits D0 and
D1 through pins 5 and 6 of J3 (5V TTL).
(See application example 5.4)
