®
LY8602
Dual 2.0W/CH Stereo Audio Amplifier
Rev. 1.3
APPLICATION INFORMATION
POWER SUPPLY BYPASSING
As with any power amplifier, proper supply bypassing is critical for low noise performance and high power
supply rejection. Applications that employ a 5V regulator typically use a 10 μF in parallel with a 0.1 μF filter
capacitor to stabilize the regulator’s output, reduce noise on the supply line, and improve the supply’s
transient response. However, their presence does not eliminate the need for a local 1.0 μF tantalum bypass
capacitance connected between the LY8602’s supply pins and ground. Do not substitute a ceramic capacitor
for the tantalum. Doing so may cause oscillation. Keep the length of leads and traces that connect capacitors
between the LY8602’s power supply pin and ground as short as possible.
MICRO-POWER SHUTDOWN
The voltage applied to the SHUTDOWN pin controls the LY8602’s shutdown function. Activate micro-power
shutdown by applying GND to the SHUTDOWN pin. When active, the LY8602’s micro-power shutdown
feature turns off the amplifier’s bias circuitry, reducing the supply current. The low 0.1 μA typical shutdown
current is achieved by applying a voltage that is as near as GND as possible to the SHUTDOWN pin.
Bypass Capacitor Value Selection
Besides minimizing the input capacitor size, careful consideration should be paid to value of C3, the capacitor
connected to the BYPASS pin. Since C3 determines how fast the LY8602 settles to quiescent operation, its
value is critical when minimizing turn-on pops. The slower the LY8602’s outputs ramp to their quiescent DC
voltage (nominally 1/2 VDD), the smaller the turn-on pop. Choosing C6 equal to 1.0 μF along with a small
value of C1,C2 (in the range of 0.1 μF to 0.39 μF), produces a click-less and pop-less shutdown function. As
discussed above, choosing C1,C2 no larger than necessary for the desired bandwith helps minimize clicks
and pops.
OPTIMIZING CLICK AND POP REDUCTION PERFORMANCE
The LY8602 contains circuitry that minimizes turn-on and shutdown transients or “clicks and pop”. For this
discussion, turn-on refers to either applying the power supply voltage or when the shutdown mode is
deactivated. When the part is turned on, an internal current source changes the voltage of the BYPASS pin in
a controlled, linear manner. Ideally, the input and outputs track the voltage applied to the BYPASS pin. The
gain of the internal amplifiers remains unity until the voltage on the bypass pin reaches 1/2 VDD. As soon as
the voltage on the bypass pin is stable, the device becomes fully operational. Although the BYPASS pin
current cannot be modified, changing the size of C3 alters the device’s turn-on time and the magnitude of
“clicks and pops”. Increasing the value of C3 reduces the magnitude of turn-on pops. However, this presents
a tradeoff: as the size of C3 increases, the turn-on time increases. There is a linear relationship between the
size of C3 and the turn-on time. Here are some typical turn-on times for various values of C3:
In order eliminate “clicks and pops”, all capacitors must be discharged before turn-on. Rapidly switching VDD
on and off may not allow the capacitors to fully discharge, which may cause “clicks and pops”. In a single
-ended configuration, the output is coupled to the load by C1,C2. This capacitor usually has a high value.
C1,C2 discharges through internal 20kꢀ resistors. Depending on the size of C1,C2, the discharge time
constant can be relatively large. To reduce transients in single-ended mode, an external 1kꢀ - 5kꢀ resistor
can be placed in parallel with the internal 20kꢀ resistor. The tradeoff for using this resistor is increased
quiescent current.
TABLE 2. C3 and TON Truth Table
C3
1.0uF
0.47uF
0.33uF
0.22uF
0.1uF
TON (Typ.) at 5.0V
172 ms
76 ms
60 ms
50 ms
36 ms
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
6
FAX: 886-3-6668836
