DER-34

13W Integrated Digital TV PSU

April 1, 2004

Page 14 of 19

Power Integrations

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9

Operating Waveforms

9.1

Output Ripple

For DC output ripple measurements, a modified oscilloscope test probe must be utilized

in order to reduce spurious signals due to pickup. Details of the probe modification are

provided in Figure 7 and Figure 8.

The 5125BA probe adapter is affixed with two capacitors tied in parallel across the probe

tip. The capacitors include one (1) 0.1

µF/50 V ceramic type and one (1) 1.0 µF/50 V

aluminum electrolytic.

The aluminum electrolytic type capacitor is polarized, so

proper polarity across DC outputs must be maintained (see below).

Figure 7 - Oscilloscope Probe Prepared for Ripple Measurement. (End Cap and Ground Lead Removed)

Figure 8 - Oscilloscope Probe with Probe Master 5125BA BNC Adapter. (Modified with wires for probe

ground for ripple measurement, and two parallel decoupling capacitors added)

Probe Ground

Probe Tip