Repeat steps iii-vi Attach a resistive load to equivalent to 1.25 amps on the output of the 5V converter Repeat steps iii through vi Reduce the load resistor to .5 amps and add the test power MOSFET circuit as specified in . Figure 71 DC/DC Test Configuration – Attach a function generator from gate to source Set the function generator to square wave at TTL output at 100Hz. Apply 12VDC to the input of the converter. Verify that the output voltage is 5VDC +/- 5% with multi-meter. Attach the oscilloscope to the output of the convertor and verify that the voltage transients are less than 10%. See below. There are variations in the DC component of the voltages when the load is switched from 50% duty cycle to near 100% duty cycle. This is expected. This is a test of the dynamic loop response of the output voltage regulation. The loop bandwidth should be at least greater than 1 kHz to guarantee that fast transient loads will not cause major fluctuations in the output voltage regulation. The use of large bypass capacitors at the microcircuit power supply pins will provide both the power source and power sink for these fast transients power fluctuation created by the microcircuits. This will help alleviate the demand on the voltage regulator output control loop. Figure 72 - Output Waveform for DC/DC Testing Turn off the power supply and the function generator To test the 3.3V DC to DC Power Conversion Modify the LM2596 circuit from the previous test into the 3.3VDC configuration from the design section. This procedure will ensure the proper operation of the 3.3VDC converter and that it has sufficient design margin. The voltage is varied to test for output voltage regulation. Attach a resistive load equivalent to .5amps on the output of the 3.3V converter. Verify that none of the components have a temperature rise greater than 30 degrees during any of the testing
Repeat steps iii-vi Attach a resistive load to equivalent to 1.25 amps on the output of the 5V converter Repeat steps iii through vi Reduce the load resistor to .5 amps and add the test power MOSFET circuit as specified in . Figure 71 – DC/DC Test Configuration Attach a function generator from gate to source Set the function generator to square wave at TTL output at 100Hz. Apply 12VDC to the input of the converter. Verify that the output voltage is 5VDC +/- 5% with multi-meter. Attach the oscilloscope to the output of the convertor and verify that the voltage transients are less than 10%. See below. There are variations in the DC component of the voltages when the load is switched from 50% duty cycle to near 100% duty cycle. This is expected. This is a test of the dynamic loop response of the output voltage regulation. The loop bandwidth should be at least greater than 1 kHz to guarantee that fast transient loads will not cause major fluctuations in the output voltage regulation. The use of large bypass capacitors at the microcircuit power supply pins will provide both the power source and power sink for these fast transients power fluctuation created by the microcircuits. This will help alleviate the demand on the voltage regulator output control loop. Figure 72 - Output Waveform for DC/DC Testing Turn off the power supply and the function generator To test the 3.3V DC to DC Power Conversion Modify the LM2596 circuit from the previous test into the 3.3VDC configuration from the design section. This procedure will ensure the proper operation of the 3.3VDC converter and that it has sufficient design margin. The voltage is varied to test for output voltage regulation. Attach a resistive load equivalent to .5amps on the output of the 3.3V converter. Verify that none of the components have a temperature rise greater than 30 degrees during any of the testing