Diodes PAM8004 - Manual (Page 8)

PAM8004
Document number: DSxxxxx Rev. 1 - 0
8 of 11
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November 2012
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PAM8004
A Product Line of
Diodes Incorporated
Application Information (cont.)
How to Reduce EMI (Electro Magnetic Interference)
A simple solution is to put an additional capacitor 1000μF at power supply terminal for power line coupling if the traces from amplifier to speakers
are short (< 20cm).
Most applications require a ferrite bead filter as shown in Figure 2. The ferrite filter reduces EMI of around 1 MHz and higher. When selecting a
ferrite bead, choose one with high impedance at high frequencies, and low impedance at low frequencies.
Figure 2. Ferrite Bead Filter to Reduce EMI
Application Notes
1. When the PAM8804 works with LC filters, it should be connected with the speaker before it’s powered on, otherwise it will damaged easily.
2. When the PAM8004 works without LC filters, it’s better to add a ferrite chip bead at the outgoing line of speaker for suppressing the possible
electromagnetic interference.
3. The recommended operating voltage is 5.5V. When the PAM8004 is powered with four battery cells, it should be noted that the voltage of four
new dry or alkaline batteries is over 6.0V, higher that its operation voltage, which will probably damage the device. Therefore, its
recommended to use either four Ni-MH (Nickel Metal Hydride) rechargeable batteries or three dry or alkaline batteries.
4. One should not make the input signal too large. Large signal can cause the clipping of output signal when increasing the volume. This will
damage the device because of big gain of the PAM8004.
5. When testing the PAM8804 without LC filters by using resistor instead of speakers as the output load, the test results, e.g. THD or efficiency,
will be worse than those of using speaker as load.
Test Setup for Performance Testing
Notes:
1. The AP AUX-0025 low pass filter is necessary for class-D amplifier measurement with AP analyzer.
2. Two 22μH inductors are used in series with load resistor to emulate the small speaker for efficiency measurement.