AA4838
Agamem Microelectronics Inc.
PRELIMINARY
AUDIO POWER AMPLIFIER
as a "line-out," unity-gain amplifier. Mode 1, which uses the internal DC controlled volume
control is selected by applying VDD to the MODE pin. This mode sets the amplifier’s gain
according to the DC voltage applied to the DC VOL CONTROL pin. Unanticipated gain
behavior can be prevented by connecting the MODE pin to VDD or ground. Note: Do not let
the mode pin float.
• MUTE FUNCTION
The AA4838 mutes the amplifier and DOCK outputs when VDD is applied to the MUTE pin.
Even while muted, the AA4838 will amplify a system alert (beep) signal whose magnitude
satisfies the BEEP DETECT circuitry. Applying 0V to the MUTE pin returns the AA4838 to
normal, unmuted operation. Prevent unanticipated mute behavior by connecting the MUTE
pin to VDD or ground. Do not let the mute pain float.
• HP SENSE FUNCTION (HEAD PHONE IN)
Applying a voltage between 4V and VDD to the AA4838’s HP-IN headphone control pin turns
off the amps that drive the Left out "+" and Right out "+" pins. This action mutes a
ridged-connected load. Quiescent current consumption is reduced when the IC is in this
single-ended mode. Figure 3 shows the implementation of the AA4838’s head- phone control
function. With no headphones connected to the headphone jack, the R1-R2 voltage divider
sets the voltage applied to the HP SENSE pin at approximately 50mV. This 50mV puts the
AA4838 into bridged mode operation. The output coupling capacitor blocks the amplifier’s half
supply DC voltage, protecting the headphones. The HP-IN threshold is set at 4V. While the
AA4838 operates in bridged mode, the DC potential across the load is essentially 0V.
Therefore, even in an ideal situation, the output swing cannot cause a false single-ended
trigger. Connecting headphones to the headphone jack disconnects the head phone jack
contact pin from R2 and allows R1 to pull the HP Sense pin up to VDD through R4. This
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©Copyright Agamem Microelectronics Inc.
www.agamem.com.tw
2008/8/26
AGAMEM MICROELECTRONICS INCOPERATION RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE
TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. AGAMEM DOES NOT ASSUME ANY
LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCTS OR CIRCUIT DESRIBED HEREIN; NEITHER
DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS.
AGAMEM [ AGAMEM MICROELECTRONIC INC. ]
