apa4838 Anpec Electronics Corporation, apa4838 Datasheet - Page 22

• Manufacturer Part Number: apa4838
• Description: Stereo 2.8w Audio Power Amplifier With Dc Volume Control And Selectable Gain
• Manufacturer: Anpec Electronics Corporation

APA4838
Application Descriptions (Cont.)
PCBEEP Detect Circuitry
If the amplifier in the mute mode, it will out of mute
mode whenever PCBEEP mode enable. The
APA4838’s shutdown mode must be deactivated
before a system alert signal is applied to Beep In pin.
The APA4838 will return to previous setting when it
is out of PCBEEP mode. The Beep In pin should be
tied to a ground when not used to avoid unwanted
state changes.
Mode Function
The APA4838’s Mode function has 2 states controlled
by the voltage applied to the Mode pin. By applying
0V to the Mode pin, forces the APA4838 to fixed gain
amplifier and internal volume control block will be dis-
able and internal first amplifier output signal (Dock)
to power amplifier directly. When Mode pin goes to
high level, which uses the internal DC controlled vol-
ume control is selected. This mode sets the amplifier’s
gain according to the DC voltage applied to the DC
Vol control pin. Do not let the Mode pin float when it
does not used.
Internal and External Gain Selection
APA4838 provides external gain setting for base
boost function or internal feedback gain setting which
is decided by Gain Select control input. If Gain Se-
lect pin goes high level, the gain setting will be de-
fined by Gain1 and Gain2 pin. When Gain Select pin
tied to low level, APA4835 power amplifier gain set-
ting as unit gain by internal resistor.
Copyright
Rev. A.1 - Apr., 2003
ANPEC Electronics Corp.
(Cont.)
22
Internal and External Gain Selection (Cont.)
Figure3: Bass Boost gain setting configuration
In some cases a designer may want to improve the
low frequency response of the bridged amplifier or
incorporate a bass boost feature. Refer to the Figure,
a resistor, R
be placed in series with the feedback resistor of the
bridged amplifier as seen in Figure.
The bridged-amplifier low frequency differential gain
is:
Using the component values shown in Figure (R
20k ,R
6dB pole is created at 120Hz. Assuming R
the low frequency differential gain is 4. The input (C
and output (C
for a low frequency response that covers the range
of frequencies affected by the desired bass-boost
operation.
Fc=
Fc=
Am plifier output signal
2 R
2x(R
Volum e Control
LF
1
LF
= 20k , and C
R
F2
C
12
+R
LF
LF
, and a capacitor, C
O
LF
) capacitor values must be selected
R
)
I2
LF
R
= 0.068µF), a first-order, -
F2
OP1
C
R
www.anpec.com.tw
LF
LF
LF
, in parallel, can
-Out
12
= 20k ,
F2
(8)
(9)
=
i
)