apa0712 Anpec Electronics Corporation, apa0712 Datasheet - Page 14

• Manufacturer Part Number: apa0712
• Description: 1.4w Mono Audio Low-voltage Audio Power Amplifier
• Manufacturer: Anpec Electronics Corporation

Application Descriptions (Cont.)
Input Capacitor, C
at V
level. Please note that it is important to confirm the
capacitor polarity in the application.
Effective Bypass Capacitor, C
As other power amplifiers, proper supply by- passing
is critical for low noise performance and high power
supply rejection.
The capacitors located on the bypass and power
supply pins should be as close to the device as
possible. The effect of a larger half supply bypass
capacitor will improve PSRR due to increased half-
supply stability. Typical application employ a 5V
regulator with 1.0 F and a 0.1 F bypass as supply
filtering. This does not eliminate the need for bypassing
the supply nodes of the APA0712. The selection of
bypass capacitors, especially C
upon desired PSRR requirements, click and pop
performance.
To avoid start-up pop noise occurred, the bypass
voltage should rise slower than the input bias voltage
and the relationship shown in equation (4) should be
maintained
The bypass capacitor is fed from an 80k
inside the amplifier. Bypass capacitor, C
1 F to 2.2 F ceramic or tantalum low-ESR capacitors
are recommended for the best THD+N and noise
performance. The bypass capacitance also effects to
the start up time. It is determined in the following
equation
Power Supply Decoupling, C
The APA0712 is a high-performance CMOS audio
Copyright
Rev. A.2 - Aug., 2007
APA0712
C
T
DD
start
B
/2, which is likely higher that the source DC
65
up
V
B
A
ANPEC Electronics Corp.
C
B
50mS
65
V
B
i
A
(Cont.)
50mS
2
(R
i
B
s
B
, is thus dependent
R
f
)C
i
B
, values of
resistor
(4)
(5)
14
amplifier that requires adequate power supply
decoupling to ensure the output total harmonic
distortion (THD+N) is as low as possible. Power sup-
ply decoupling also prevents the oscillations causing
by long lead length between the amplifier and the
speaker.
The optimum decoupling is achieved by using two
different type capacitors that target on different type
of noise on the power supply leads. For higher frequency
transients, spikes, or digital hash on the line, a good
low equivalent-series- resistance (ESR) ceramic
capacitor, typically 0.1 F placed as close as possible
to the device V
frequency noise signals, a large aluminum electrolytic
capacitor of 10 F or greater placed near the audio
power amplifier is recommended.
Optimizing Depop Circuitry
Circuitry has been included in the APA0712 to minimize
the amount of popping noise at power-up and when
coming out of shutdown mode. Popping occurs
whenever a voltage step is applied to the speaker. In
order to eliminate clicks and pops, all capacitors must
be fully discharged before turn-on.
Rapid on/off switching of the device or the shutdown
function will cause the click and pop circuitry. The
value of C
Bypass Capacitance). The bypass voltage rise up
should be slower than input bias voltage. Although the
bypass pin current source cannot be modified, the size
of C
and the amount of clicks and pops. By increasing the
value of C
tradeoff for using a larger bypass capacitor is to
increase the turn-on time for this device. There is a
linear relationship between the size of C
turn-on time.
In the most cases, choosing a small value of C
B
can be changed to alter the device turn-on time
i
B
will also affect turn-on pops (refer to Effective
, turn-on pop can be reduced. However, the
DD
lead works best. For filtering lower
www.anpec.com.tw
B
and the
i
in the