apa2070 Anpec Electronics Corporation, apa2070 Datasheet - Page 18

• Manufacturer Part Number: apa2070
• Description: Stereo 2.6w Audio Power Amplifier With Dc Volume Control
• Manufacturer: Anpec Electronics Corporation

The bypass capacitance also affects the start-up time.
It is determined in the following equation:
APA2070
Effective Bypass Capacitor (C
To avoid start-up pop noise, the bypass voltage should
rise slower than the input bias voltage and the relation-
ship shown in equation should be maintained.
The capacitor is fed from a 150k
the amplifier and the 150k is the maximum input resis-
tance of (R
2.2 F to 10 F ceramic or tantalum low-ESR capacitors
are recommended for the best TH D+N and noise
performance.
Output Coupling Capacitor (C
In the typical single-supply SE configuration, an output
coupling capacitor (C
the output of the amplifier thus preventing DC currents in
the load. As with the input coupling capacitor, the output
coupling capacitor and impedance of the load form a high-
pass filter governed by the equation.
For example, a 330 F capacitor with an 8 speaker would
attenuate low frequencies below 60.6Hz. The main
disadvantage, from a performance standpoint, is the load
impedance is typically small, which drives the low-fre-
quency corner higher degrading the bass response.
Large values of C
into the load.
Power Supply Decoupling Capacitor (C
The APA2070 is a high-performance CMOS audio ampli-
fier that requires adequate power supply decoupling to
ensure the output total harmonic distortion (THD+N) is
as low as possible. Power supply decoupling also pre-
vents the oscillations caused by long lead length between
the amplifier and the speaker. The optimum decoupling
is achieved by using two different type capacitors that tar-
get on different types of noise on the power supply leads.
Copyright
Rev. A.2 - Aug., 2008
Application Information (Cont.)
T
F
(
C
start
C
(
highpass
BYPASS
up
i
+R
5X(C
)
ANPEC Electronics Corp.
1
X150k
F
). Bypass capacitor, C
2
C
BYPASS
R
are required to pass low frequencies
1
L
C
C
) is required to block the DC bias at
)
C
X150k
C
i
C
X150k
BYPASS
)
1
)
) (Cont.)
resistor inside of
BYPASS
S
)
, values of
(
(
(
7)
8)
9)
18
For higher frequency transients, spikes, or digital hash
on the line, a good low equivalent-series-resistance
(ESR) ceramic capacitor, typically 0.1 F, is placed as close
as possible to the device V
lower-frequency noise signals, it is recommended to
place a large aluminum electrolytic capacitor of 10 F or
greater near the audio power amplifier
Optimizing Depop Circuitry
Circuitry has been included in the APA2070 to minimize the
amount of popping noise at power-up and when coming
out of shutdown mode. Popping occurs whenever a volt-
age 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
Effective Bypass Capacitance). The bypass voltage ramp
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 relation-
ship between the size of C
SE configuration, the output coupling capacitor (C
particular concern.
This capacitor discharges through the internal 10k
resistors. Depending on the size of C
can be relatively large. To reduce transients in SE mode,
an external 1k
internal 10k
is an increase in quiescent current. In the most cases,
choosing a small value of C
1 F, C
resistor should be placed in parallel with the internal
10k
popless turn-on.
A high gain amplifier intensifies the problem as the small
delta in voltage is multiplied by the gain, so it is advanta-
geous to use low-gain configurations.
BYPASS
BYPASS
resistor should produce a virtually clickless and
BYPASS
can be changed to alter the device turn-on time
, turn-on pop can be reduced. However, the
being equal to 4.7 F and an external 1k
resistor. The tradeoff for using this resistor
i
resistor can be placed in parallel with the
will also affect turn-on pops (Refer to
DD
BYPASS
lead works best. For filtering
i
in the range of 0.33 F to
and the turn-on time. In a
www.anpec.com.tw
C
, the time constant
C
), is of