Detailed Description of Hardware
The MAX9768 is a mono, switch-mode (Class D) audio
power amplifier. The EV kit is designed to be driven by
the lineout or headphone jack of a CD player, or direct-
ly connected to any audio source. A thumbwheel
potentiometer mounted on-board is provided to control
the volume. The volume can also be controlled by the
I
2
C interface.
The EV kit has an on-board LDO (MAX1726) to power
the input buffers and the volume-control circuitry.
Preamplifier Gain Configuration
The preamplifier gain stage of the MAX9768 EV kit is
configured to 0dB. To avoid clipping at the amplifier
input stage, ensure input signals are ≤ 1V
RMS
. If input
signals are ≥ 1V
RMS
, attenuate the input signal at the
preamplifier gain stage to avoid clipping at the pream-
plifier output. The preamplifier gain stage is defined as:
A
V (preamplifier)
= -R3 / R2
where R2 is in the 10kΩ to 40kΩ range.
Define the preamplifier gain such that the output of the
preamplifier is ≤ 1V
RMS
(i.e., V
IN
x A
V (preamplifier)
≤
1V
RMS
). Once the preamplifier gain is fixed, use the
amplifier’s volume-control block to set the clipping lev-
els at the output of the Class D amplifier.
Power Supplies
The power supply is applied on PV
DD
and PGND binding
posts. V
DD
is generated either by the on-board MAX1726
or by an external 3.3V power supply applied between the
V
DD
pad and PGND. See Table 2 for JU7 setting.
Volume Control
Jumpers JU3, JU4, JU5, and JU8 select which volume-
control mode is used. See Table 3 for details.
Shutdown Mode
Jumper JU2 sets the amplifier in normal operation or
shutdown mode. See Table 4 for details.
Mute Control
Jumper JU1 controls the MUTE pin state. See Table 5
for details.
Evaluate: MAX9768
MAX9768 Evaluation Kit/Evaluation System
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