Diodes PAM8003 - Manual (Page 8)

PAM8003
Document number: DSxxxxx Rev. 1 - 1
8 of 12
www.diodes.com
November 2012
© Diodes Incorporated
PAM8003
A Product Line of
Diodes Incorporated
Application Information
1. When the PAM8803 works with LC filters, it should be connected with the speaker before it’s powered on, otherwise it will damaged easily.
2. When the PAM8003 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 PAM8003 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 PAM8803 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.
Power Supply Decoupling
The PAM8003 is a high performance CMOS audio amplifier that requires adequate power supply decoupling to ensure the output THD and
PSRR as low as possible. Power supply decoupling affects low frequency response. Optimum decoupling is achieved by using two capacitors of
different types of noise on the power supply leads. For higher frequency transients, spikes, or digital hash on the line, a good low equivalent-
series-resisitance (ESR) ceramic capacitor, typically 1.0µF, works best, placing it as close as possible to the device V
DD
terminal. For filtering
lower-frequency noise signals, a large capacitor of 20µF (ceramic) or greater is recommended, placing it near the audio power amplifier.
Input Capacitor (C
I
)
Large input capacitors are both expensive and space hungry for portable designs. Clearly, a certain sized capacitor is needed to couple in low
frequencies without severe attenuation. But in many cases the speakers used in portable systems, whether internal or external, have little ability
to reproduce signals below 100Hz to 150Hz. Thus, using a large input capacitor may not increase actual system performance. In this case, input
capacitor (CI) and input resistance (RI) of the amplifier form a high-pass filter with the corner frequency determined by equation below.
In addition to system cost and size, click and pop perfor mance is affected by the size of the input the coupling capacitor, C
I
. A larger input
coupling capacitor requires more charge to reach its quiescent DC voltage (nominally ½ V
DD
). This charge comes from the internal circuit via the
feedback and is apt to create pops upon device enable. Thus, by minimizing the capacitor size based on necessary low frequency response,
turn-on pops can be minimized.
C R 2
1
f
I I
C 
