LY8897_13 Datasheet, PDF (12/17 Pages) Lyontek Inc. – 2.7 Watt Audio Power Amplifier

®
Rev. 1.1
LY8897
2.7 Watt Audio Power Amplifier
Ci = 1 / ( 2πRifc)
Ci = 1 / ( 2π x20KΩ x20Hz)=0.1uF，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 / 10
Bypass Capacitor Value Selection
Besides minimizing the input capacitor size, careful consideration should be paid to value of Cbypass, the
capacitor connected to the BYPASS pin. Since Cbypass determines how fast the LY8897 settles to quiescent
operation, its value is critical when minimizing turn-on pops. The slower the LY8897’s outputs ramp to their
quiescent DC voltage (nominally 1/2 VDD), the smaller the turn-on pop. Choosing Cbypass value equal 1.0 to
10 uF along with a small value of Ci (in the range of 1 nF to 0.39 μF), produces a click-less and pop-less
shutdown function. As discussed above, choosing Ci no larger than necessary for the desired bandwith helps
minimize clicks and pops. 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 x 10
PARAMETER
Start-up time
from shutdown
Table 2. CBYPASS Reference Component Values
SYMBOL
TEST CONDITION
MIN. TYP.
VDD=5.0V,
Cbypass = 10μf
-
940
Ci=0.1uF,
Cbypass = 4.7μf
-
550
Ri=20KΩ,
Cbypass = 2.2μf
-
190
ZI
Av=10
Cbypass = 1.0μf
-
158
VDD=3.7V,
Cbypass = 10μf
-
780
Ci=0.1uF,
Cbypass = 4.7μf
-
480
Ri=20KΩ,
Cbypass = 2.2μf
-
180
Av=10
Cbypass = 1.0μf
-
126
MAX.
-
-
-
-
-
-
-
-
UNIT
ms
Power Supply Bypassing Capacitor
As with any amplifier, proper supply bypassing is critical for low noise performance and high power supply
rejection. The capacitor location on both the bypass and power supply pins should be as close to the device
as possible.
The LY8897 is a mono class AB 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 ceramic capacitor or electrolytic capacitors,
typically 10~220uF, placed as close as possible to the device VDD lead works best. Placing 0.1uF decoupling
capacitor close to the LY8897 is very important for the efficiency of the class AB amplifier, because any
resistance or inductance in the trace between the device and the capacitor can cause a loss in efficiency and
protect device damage. For filtering lower-frequency noise signals, a 10.0uF or greater capacitor placed near
the audio power amplifier would also help, but it is not required in most applications because of the high
PSRR of this device.
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: [phone]
FAX: [phone]
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