User`s guide

Test Results

B.2 DYNAMIC LOAD RESPONSE

Dynamic load response is measuring the under/overshoot voltage and settling time of

the output voltage when performing a load step. The SMPS AC/DC Reference Design

has the following load step parameters when the outputs are loaded individually:

• 12V full load step of 30A

• 5V full load step of 23A

• 3.3V full load step of 69A

When the Single-Phase and Multi-Phase converters are loaded simultaneously, the

following are the max load steps:

• 5V full load step of 23A

• 3.3V full load step of 56A

The load response of each unit is tested with the following load steps with a maximum

slew rate of 1A/us:

• 0-15A and 15-0A (for the 12V output)

• 0-35A and 35-0A (for the 3.3V output)

• 0-12A and 12-0A (for the 5V output)

B.2.1 Test Procedure

1. Ensure that the system is off and that all probes are disconnected.

2. Connect a programmable DC load to any one of the three outputs.

3. Connect the oscilloscope probe across the output terminals with the DC load.

4. Connect the current probe to one of the load cables making sure of the direction

of current flow.

5. Set up the oscilloscope for a single capture and trigger on the current probe on

either edge and set the oscilloscope channel for AC coupling.

6. Perform the load steps and measure the settling time and under/overshoot

voltage.

7. Turn off the system and disconnect all probes.

Figure B-3 through Figure B-8 show the dynamic load response and settling time with

50% load steps.