PAM8202 datasheet(7/8 Pages) ETC1

7 / 8 page

FCL = 1/ [2

X Cin X (Rin + 10k)]

FCL is the lower corner on frequency response curve.

Cin is very important consider to the lower frequency performance. The Cin should not be too large with small

speakers as the load, because such small speakers usually can not response with lower frequency, delivering too

much low frequency energy into a small speaker which usually got resonant frequency (Fs) around 150Hz is

meaningless and dangerous. This will easily over drive the small speakers. The movement of speaker cone will be

too much under such condition and this also creates unnecessary distortion on mid-to high frequency range

because the speaker is now operating in non-linear area. Speakers can only generate heat but not low frequency

sound when it is over driven, the will cause speaker or amplifier failure in some cases.

Cin should have 10% tolerance or less because the tolerance can cause the input impedance mismatch at FCL

and below.

Output filter

The L and C on each output node of PAM8202 form the low-pass-filter (LPF), the higher corner frequency (FCH) is

determine by equation below.

FCH = 1/ [2

X sqr (L X C)]

FCH is the higher corner on frequency response curve.

Important Notice

The L-C filters (-12dB/Oct) gives twice much attenuation and lower impedance (means lower insertion loss)

compare to those R-C filters

(-6dB), but remember, the FCH above is also the resonant frequency of this LC

network. The quality factor (Q) of this resonant network can be very high, depended on the Q of L and C. The high

resonant Q which is usually caused by open-load can generate a very high voltage on speaker terminal, and the

impedance of the L-C network can be very low, thus induces large amount of current flows from output stage of

PAM8202. This always causes part failure. So Do Not test open-load on any class D amplifier with output filters.

LC filter calculator with output load impedance and cut-off frequency

f =

, X = 2 fL , X =

2 fC

Power Analog Microelectronics, Inc.

CONFIDENTIAL. DO NOT DISTRIBUTE OR REPRODUCE WITHOUT PERMISSION FROM P.A.M.

PAM8202 Rev. 1.1

PRELIMIARY DATASHEET

PAM8202

Tiny Package 2 Watt Class-D Stereo Audio Amplifier

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