®
LY8321
Rev. 1.0
30Wx2 Stereo Class D Audio Power Amplifier
For example
Ci is 0.1 μF, so one would likely choose a value in the range of 0.1 μF to 1.0 μF. Ri is 50 kΩ and the
specification calls for a flat bass response down to 30 Hz.
Ci = 1 / ( 2πRi fc)
Ci = 1 / ( 2π x 50KΩ x 30Hz)=0.106uF，One would likely choose a value of 0.1uF as this value is
commonly used.
Note that it is important to Ci must be 10 times smaller than the bypass capacitor to reduce clicking and
popping noise from power on/off and entering and leaving shutdown. After sizing Ci for a given cutoff
frequency, size the bypass capacitor to 10 times that of the input capacitor.
Ci ≦ Cbypass
Bypass Capacitor (Cbypass)
The Bypass Capacitor (C3 ) is the most critical capacitor and serves important functions.
During start-up or recovery from shutdown mode, Cbypass determines the rate at which the amplifier starts up.
The Cbypass will to reduce noise caused by the power supply coupling into the output drive signal. This noise
is from the internal analog reference to the amplifier, which appears as degraded the PSRR and THD+N
values.
The bypass capacitor (C3 ) with values of 1.0μF to 10.0μF is recommended for the best THD and noise
performance. Therefore, increasing the bypass capacitor reduces clicking and popping noise from power
on/off and entering and leaving shutdown. To have minimal pop, Cbypass should be 10 times larger than Ci.
Cbypass ≧ Ci
Power Supply Decoupling Capacitor (CS)
The LY8321 is a high-performance class-D audio amplifier that requires adequate power supply decoupling to
ensure the efficiency is high and total harmonic distortion (THD) is low. For higher frequency transients,
spikes, or digital hash on the line, a good low equivalent-series-resistance (ESR) ceramic capacitor, typically
0.1uF~1.0uF, placed as close as possible to the device PVCC lead works best. Placing this decoupling
capacitor close to the LY8321 is very important for the efficiency of the class-D amplifier, because any
resistance or inductance in the trace between the device and the capacitor can cause a loss in efficiency. For
filtering lower-frequency noise signals, a 470uF or greater capacitor placed near the audio power amplifier
would also help, so 470uF or larger capacitor should be placed on each PVCC terminal.
Single-Ended Output Capacitor, (CO)
In single-ended (SE) applications, the dc blocking capacitor forms a high-pass filter with the speaker
impedance. The frequency response rolls off with decreasing frequency at a rate of 20 dB/decade. The cutoff
frequency is determined by
fc = 1 / (2πRLCo)
Table 3. Filter Responses Reference Values
SE mode - Co Capacitor select(uF)
Speaker Load (Ω)
fc = 60 Hz
680
fc = 40 Hz
1000
fc = 20 Hz
2200
4
6
8
470
680
1500
330
470
1000
Lyontek Inc. reserves the rights to change the specifications and products without notice.
5F, No. 2, lndustry E . Rd. IX, Science-Based Industrial Park, Hsinchu 300, Taiwan
TEL: 886-3-6668838
FAX: 886-3-6668836
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