apa0715xa Anpec Electronics Corporation, apa0715xa Datasheet - Page 16

• Manufacturer Part Number: apa0715xa
• Description: 3w Mono Fully Differential Audio Power Amplifier
• Manufacturer: Anpec Electronics Corporation

Application Information
Input Resistance (R
The gain for the APA0715 is set by the external input re-
sistors (R
R
recommended. For the performance of a fully differential
amplifier, it’ s better to select matching input resistors R
and R
recommended. If the input resistors are not matched, the
CMRR and PSRR performance are worse than using
matching devices.
Input Capacitor (C
When the APA0715 is driven by a differential input source,
the input capacitor may not be required.
In the single-ended input application, an input capacitor,
C
nal to the proper DC level for optimum operation. In this
case, C
with the corner frequency determined in the following
equation:
The value of C
directly affects the low frequency performance of the circuit.
Consider the example where R
cation that calls for a flat bass response down to 100Hz.
The equation is reconfigured as below:
When the input resistance variation is considered, the C
is 0.16 F. Therefore, a value in the range of 0.22 F to
0.47 F would be chosen. A further consideration for this
capacitor is the leakage path from the input source through
the input network (R
This leakage current creates a DC offset voltage at the
input of the amplifier. The offset reduces useful
headroom, especially in high gain applications. For this
reason, a low-leakage tantalum or ceramic capacitor is
the best choice. When polarized capacitors are used, the
positive side of the capacitor should face the amplifier
Copyright
Rev. A.1 - Dec., 2008
APA0715
i
i
, is required to allow the amplifier to bias the input sig-
and R
F
C
A
C(highpass
V
i
i2
i
and the input resistance R
. Therefore, 1% tolerance resistors are
f
2
R
i
R
) and external feedback resistors (R
should range from 1k
f
i
R
1
)
i
ANPEC Electronics Corp.
F
i
c
must be considered carefully because it
2
i
R
)
1
i
i
i
C
) and Feedback Resistance (R
+ R
i
f
, C
i
) to the load.
i
is 10k
i
to 100k . R
form a high-pass filter
and the specifi-
f
).
i
is 10k
(1)
(2)
(3)
f
)
i1
i
16
input in most applications because the DC level of the
amplifiers’ inputs are held at V
important to confirm the capacitor polarity in the application.
Effective Bypass Capacitor (C
The BYPASS pin sets the V
voltage divider. Adding capacitors at this pin to filter the
noise and regulator the mid-supply rail will increase the
PSRR and noise performance.
The capacitors should be as close to the device as
possible. The effect of a larger bypass capacitor will im-
prove PSRR due to increased supply stability.
The bypass capacitance also affects to the start time. The
large capacitors will increase the start time when device
in shutdown.
Optimizing Depop Circuitry
Circuitry has been included in the APA0715 to minimize
the amount of popping noise at power-up and when com-
ing out of shutdown mode. Popping occurs whenever a
voltage step is applied to the speaker. In order to elimi-
nate clicks and pops, all capacitors must be fully dis-
charged before turn-on. Rapid on/off switching of the de-
vice or the shutdown function will cause the click and pop
circuitry.
The value of C
voltage ramp up should be slower than input bias voltage.
Although the BYPASS pin current source cannot be
modified, the size of C
device turn-on time and the amount of clicks and pops.
By increasing the value of C
reduced. However, the 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
and the turn-on time.
A high gain amplifier intensifies the problem as the small
delta in voltage is multiplied by the gain. Hence, it is ad-
vantageous to use low-gain configurations.
Power Supply Decoupling Capacitor (C
The APA0715 is a high-performance CMOS audio ampli-
fier that requires adequate power supply decoupling to
ensure the output total harmonic distortion (THD+N) is
i
will also affect turn-on pops. The bypass
BYPASS
DD
can be changed to alter the
/2 for internal reference by
BYPASS
DD
BYPASS
/2. Please note that it is
, turn-on pop can be
)
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s
)
BYPASS