Chapter 4: servo control operation, Current command input, Chapter 4 – ElmoMC SimplIQ Analog Servo Amplifiers-Piccolo Installation User Manual

Page 23: Servo control operation, Current command input 4.2. cfm

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Piccolo Installation Guide

Servo Control Operation

MAN-PICIG (Ver. 2.301)

www.elmomc.com

23

Chapter 4:

Servo Control Operation

4.1. Current Command Input

The Piccolo has 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:

R

in (KΩ)

= (5.33 * V

in

) - 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. CFM

The amplifier is equipped with a current feedback multiplier (CFM). Connecting pin J1/10 to
J1/8 multiplies the signal of the current feedback by 2 and consequently causes the following
changes to occur:

Current gains are divided by 2.

Current monitor is multiplied by 2.

Current limits are divided by 2.

This function should be activated whenever the rated current and the peak current of the
motor are less than 50% of the amplifier rated continuous and peak limits, respectively.

Continuous
Current
Limit

Peak Current
Limit

Current
Gain(A/V)

Current
Monitor
(V/A)

Differential
Input
Impedance

Without CFM Ic

Ip

Ip/3.75

3.9/Ip

40 kΩ

With CFM

Ic/2

Ip/2

Ip/7.5

7.8/Ip

40 kΩ

Table 7: CFM Effects

The default (pin J1/10 left open) is the low current feedback.

For permanent selection, a simple short is recommended.

For remote selection, the scheme in Figure 5 should be used.

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