apa2071 Anpec Electronics Corporation, apa2071 Datasheet - Page 16

• Manufacturer Part Number: apa2071
• Description: Stereo 3.1w Non-inverting Audio Power Amplifier With Dc Volume Control
• Manufacturer: Anpec Electronics Corporation

The APA2071 has an internal stereo volume control whose
setting is the function of the DC voltage applied to the
VOLUME input pin. The APA2071 volume control consists
of 32 steps that are individually selected by a variable DC
voltage level on the VOLUME control pin. The range of
the steps, controlled by the DC voltage, are from 18dB
to -80dB. Each gain step corresponds to a specific input
voltage range, as shown in table. To minimize the effect of
noise on the volume control pin, which can affect the se-
lected gain level, hysteresis and clock delay are
implemented. The amount of hysteresis corresponds to
half of the step width, as shown in volume control graph.
APA2071
In Figure 2, input SE/BTL operates as below:
When the phonejack plug is inserted, the 1k
disconnected and the SE/BTL input is pulled high to en-
able the SE mode. Meanwhile, the OUTN amplifier is shut
down which turns the speaker to be mute. The OUTP
amplifier then drives through the output capacitor into the
headphone jack. When there is no headphone plugged
into the system, the contact pin of the headphone jack is
connected from the signal pin, and the voltage divider is
set up by resistors 100k
pulled low the SE/BTL pin, enabling the BTL function.
DC Volume Control Function
SE/BTL Mode Selection Function (Cont.)
Copyright
Rev. A.1 - Aug., 2008
Function Description (Cont.)
-10
-20
-30
-40
-50
-60
-70
-80
Figure 3: Gain setting vs. VOLUME pin voltage
20
10
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
0
APA2071 DC Volume Control Curve (BTL)
ANPEC Electronics Corp.
DC Volume (V)
Backward
and 1k . Resistor 1k
Forward
resistor is
then is
16
For the highest accuracy, the voltage shown in the ‘ rec-
ommended voltage’ column of the table is used to select
a desired gain. This recommended voltage is exactly half-
way between the two nearest transitions. The gain levels
are 32 steps from 18dB to -40dB in BTL mode, and the
last step at -80dB as mute mode.
Shutdown Function
In order to reduce power consumption while not in using,
the APA2071 contains a shutdown pin to externally turn
off the amplifier bias circuitry. This shutdown feature
turns the amplifier off when a logic low is placed on the
SHUTDOWN pin. The trigger point between a logic high
and logic low level is typically 2.0V. It would be better to
switch between ground and the supply V
maximum device performance.
By switching the SHUTDOWN pin to low, the amplifier
enters a low-current state, I
down mode. On normal operation, SHUTDOWN pin is
pulled to high level to keep the IC out of the shutdown
mode. The SHUTDOWN pin should be tied to a defi-
nite voltage to avoid unwanted state changes.
Thermal Protection
The thermal protection circuit limits the junction tempera-
ture of the APA2071. When the junction temperature ex-
ceeds T
amplifier, allowing the devices to cool. The thermal sen-
sor allows the amplifier to start-up after the junction tem-
perature down about 125
designed with a 25
during continuous thermal overload conditions, which is
increasing lifetime of the IC.
Over-Current Protection
The APA2071 monitors the output current. When the cur-
rent exceeds the current-limit threshold, the APA2071 turns
off the output to prevent the IC from damages in over-
current or short-circuit condition. When the over-current
occurs in power amplifier, the output buffer’ s current will
be foldbacked to a low setting level, and it will release
when over-current situation is no long existence. On the
contrary, if the over-current period is long enough and the
IC’ s junction temperature reaches the thermal protection
threshold, the IC will enter thermal protection mode.
J
= +150
o
o
C, a thermal sensor turns off the
C hysteresis to lower the average T
o
C. The thermal protection is
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<1 A. APA2071 is in shut-
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