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Chapter 4: Servo Control Operation
4.1 Current Command Input
The Dragonfly and Butterfly have a single differential input. The input operating voltage
range is ± 3.75 V, meaning that a 3.75 V signal will result in a fully rated peak current. The
current limit circuits will override this signal if the peak duration exceeds 2.7 seconds and/or
the required current exceeds the values set by the ECLC and ECLP signals. If the input
command voltage exceeds 3.75 V, input scaling must be implemented by adding a pair of
external resistors, according to the following formula:
Rin (kΩ) = (5.33 * Vin) - 20
Be careful not to apply input voltage above the maximum allowed input voltage as this will
cause the input operational amplifier to operate beyond its limits (±20 V) and in extreme
cases, may even damage it.
4.2 External Current Limit - Continuous (ECLC)
The continuous current limit of the Dragonfly and Butterfly amplifiers can be scaled down by
an external voltage or by an external resistor connected from pin J1/9 (ECLC) to pin J1/8
(ECLRET).
4.2.1 External Voltage
An external positive voltage (0 to 3.75 V) to terminal J1/9 (ECLC) in reference to terminal J1/8
(ECLRET) will control the continuous current limit from zero to Ic (nom).
The voltage is internally clamped to 3.75 V whenever the external VECLC is greater than
3.75V.
The external voltage source must be able to source/ sink at least ± 0.2 mA.
The maximum absolute VECLC allowed to be connected is 5 V.
V
ECLC
IC(new) =
3.75V
* Ic(nom)
V
ECLC
IC(new) =
3.75V
* Ic(nom)
Dragonfly/Butterfly Installation Guide
MAN-DRBUIG (Ver. 1.1)
4-1