E-12 Applications Model 6220/6221 Reference Manual
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Effect of compliance setpoint on settling times
If the compliance voltage is set to close to the expected load voltage (load current
times load resistance), then the settling time of the step response will increase
from the specified level. In order to reduce this side effect, the compliance voltage
needs to be set >2V higher than the expected load voltage.
For example, if a zero to 20mA step is sourced into a 100W load, the resulting
voltage would be a 0 to 2V step that would settle within 2µs, assuming the compli-
ance setpoint is >4V. However, if the compliance setpoint is set to 2.5V, the set-
tling time could be expected to increase by several microseconds.
Preventing compliance overshoot
There are three options that can be considered to prevent or minimize compliance
overshoot:
• Set compliance 2V above the operating voltage.
• Use small current step changes.
• Shunt the output with a capacitor.
Set compliance 2V above operating voltage
One way to avoid compliance overshoot is to set a compliance that is at least 2V
above the expected static output voltage. For example, if the normal operating
voltage across the load is 10V, set the compliance to at least 12V.
Use small current step changes
As explained in “Calculating overshoot”, a small current step change in relation to
the selected source range results in smaller overshoot. If you limit the step size to
1% of the current range, the maximum overshoot will typically only be 20mV.
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