apa3002 Anpec Electronics Corporation, apa3002 Datasheet - Page 22

• Manufacturer Part Number: apa3002
• Description: 12w Stereo Class-d Audio Power Amplifier
• Manufacturer: Anpec Electronics Corporation

Application Information (Cont.)
DC Volume
Three pins, VOLUME, VARMAX, and VARDIFF, determine
the VAROUT’ s gain. The figure 4 shows the VAROUT vol-
ume control flow. All the values are DC voltage, and the
V
table “VAROUT VOLUME Control Table”.
VARMAX
The VARMAX limits the maximum gain of VAROUT chan-
nels to avoid the un-comfortable listening of headphone.
VARDIFF
To avoid the uncomfortable listening when headphone is
plugging, the VARDIFF sets the different gain between
the Class-D and VAROUT channels. At initial (V
the difference gain between the Class-D and VAROUT is
16dB. W hen voltage of VARDIFF is increasing, the
VAROUT’ s gain decreases.
MODE Operation
The mode controls the output mode of the APA3002, a
logic “HIGH” will disable the Class-D outputs; a logic
“LOW” will enable the Class-D outputs. This pin can con-
nect to the switch on the headphone jack to disable the
Class-D outputs when headphone plug is inserted. The
“Typical Application Circuit “ shows an example for this
application.
MODE_OUT Operation
The MODE_OUT is the inverting output of MODE, and it
controls the external headphone amplifier’ s SD pin (like
the APA4801) for switching the Speaker mode or
headphone.
Copyright
Rev. A.6 - Sep., 2009
V
V
APA3002
VOLUME
VARDIFF
AROUT
+
(V)
(V)
-
channel gain can be determined by consulting the
-
Figure 4. VAROUT Volume Control Flow
V
V
VOLUME
VARDIFF
ANPEC Electronics Corp.
-
VAROUT s VOLUME(V) = V
V
VARMAX
Is V
VARMAX
NO
(V)
V
VARDIFF
>(V
VOLUME
)
VARMAX
-
YES
(V)
VAROUT s VOLUME(V) =
V
VOLUME
(V)-V
VARDIFF
VARDIFF
=0V),
(V)
22
LDO Operation
The 5VLOD terminal is the output of an internal-gener-
ated 5V power supply that is used for oscillator, pream-
plifier and DC volume control circuitry. The regulator can
be powered the external headphone amplifier like the
APA4801, or other circuitry, up to the current limit of 5VLDO
pin (on specification table). With 10 F & 0.1 F capacitors
connected to the terminal are recommended if powered
by the APA4801; however, if there is no other larger loading,
1 F and 0.1 F are sufficient enough.
Shutdown Function
In order to reduce power consumption when not in use,
the APA3002 contains a shutdown function to externally
turn off the amplifier bias circuitry. This shutdown feature
turns the amplifier off when logic low is placed on the SD
pin for the APA3002. The trigger point between a logic
high and logic low level is typically 1.2V. It will be the best
to switch between ground and the supply voltage V
provide maximum device performance. By switching the
SD pin to low level, the amplifier enters a low-consump-
tion-current state, I
mode. Under normal operating, APA3002’ s SD pin should
pull to a high level to keep the IC out of the shutdown
mode. The SD pin should be tied to a definite voltage to
avoid unwanted state change.
Thermal Pad Consideration
The thermal pad must be connected to the ground. The
package with thermal pad of the APA3002 requires spe-
cial attention on thermal design. If the thermal design
issues are not properly addressed, the APA3002 will go
into thermal shutdown. The thermal pad on the bottom of
the APA3002 should be soldered down to a copper pad
on the circuit board. Heat can be conducted away from
the thermal pad through the copper plane to ambient. If
the copper plane is not on the top surface of the circuit
board, 10 to 16 vias of 15 mil or smaller in diameter should
be used to thermally couple the thermal pad to the bot-
tom plane. For good thermal conduction, the vias must
be plated through and solder filled. The copper plane
used to conduct heat away from the thermal pad should
DD
for the APA3002 is in shutdown
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to