APS 42L Series, Operation Manual

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SECTION 3: PRODUCT OVERVIEW
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2014 by Adaptive Power Systems, Inc. (APS) • All Rights Reserved • No reproduction without written authorization from APS.
42L Series Modular DC Load Operation Manual Page 16 of 88
3.3.1 Programmable Parameters
There are six programmable parameters to generate dynamic wave form or pulse wave
form, the 42L Series loads will sink current from power source proportional to the dynamic
wave form, the dynamic wave form definition is shown in Figure 3-1. Available settings are:
Parameter Description Type
Current High Highest programmed load current Current Setting
Current Low
Lowest programmed load current Current Setting
T-High Duration at High current setting Time (secs)
T-Low Duration at Low current setting Time (secs)
Rising Slew Rate Current Slew Rate from Low to High Current A/sec
Falling Slew Rate Current Slew Rate from High to Low Current A/sec
Table 3-1: Dynamic Current Mode Parameters
The resulting current waveform has the following characteristics:
Period = T-High + T-Low
Frequency = 1 / ( T-High + T-Low )
Duty Cycle = T-High / ( T-High + T-Low )
3.3.2 Slew Rates
Slew rate is defined as the change in current or voltage over time. A programmable slew
rate allows a controlled transition from one load setting to another to minimize induced
voltage drops on inductive power wiring, or to control induced transients on a test device
(such as would occur during power supply transient response testing).
In cases where the transition from one setting to another is large, the actual transition time
can be calculated by dividing the voltage or current transition by the slew rate. The actual
transition time is defined as the time required for the input to change from 10% to 90% or
from 90% to 10% of the programmed current excursion. In cases where the transition from
one setting to another is small, the small signal bandwidth of the load limits the minimum
transition time for all programmable slew rates. Because of this limitation, the actual
transition time is typically longer than the expected time based on the slew rate setting, as
shown in Figure 3-2.
Therefore, both minimum transition time and slew rate must be considered when
determining the actual transition time. See also section 5.13 “ Load Current Slew Rate ” on
page 34.