LP3952 Datasheet, PDF (29/44 Pages) National Semiconductor (TI) – 6-Channel Color LED Driver with Audio Synchronization

Application Examples
EXAMPLE 1
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There may be cases where the audio input signal going into the LP3952 is too weak for audio synchronization. This figure presents a single-supply inverting
amplifier connected to the ASE input for audio signal amplification. The amplification is +20 dB, which is well enough for 20 mVp-p audio signal. Because the
amplifier (LMV321) is operating in single supply voltage, a voltage divider using R3 and R4 is implemented to bias the amplifier so the input signal is within the
input common-mode voltage range of the amplifier. The capacitor C1 is placed between the inverting input and resistor R1 to block the DC signal going into the
audio signal source. The values of R1 and C1 affect the cutoff frequency, fc = 1/(2π*R1*C1), in this case it is around 160 Hz. As a result, the LMV321 output
signal is centered around mid-supply, that is V_DDA/2. The output can swing to both rails, maximizing the signal-to-noise ratio in a low voltage system
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