Datasheet

The capacitive nature of the piezoelectric speaker may
cause the MAX9711 to become unstable. A simple induc-
tor/resistor network in series with the speaker isolates the
speaker capacitance from the driver and ensures that the
device output sees a resistive load of about 10Ω at high
frequency, thereby maintaining stability (Figure 3).
Layout and Grounding
Good PC board layout is essential for optimizing perfor-
mance. Use large traces for the power-supply inputs and
amplifier outputs to minimize losses due to parasitic
trace resistance and route heat away from the device.
Good grounding improves audio performance,
minimizes crosstalk between channels, and prevents any
digital switching noise from coupling into the audio
signal.
The MAX9710/MAX9711 thin QFN package features an
exposed thermal pad on the underside. This pad low-
ers the thermal resistance of the package by providing
a direct-heat conduction path from the die to the print-
ed circuit board. Connect the exposed pad to the
ground plane using multiple vias, if required. For opti-
mum performance, connect to the ground planes as
shown in Figure 4.
MAX9710/MAX9711
3W Mono/Stereo BTL Audio Power Amplifiers
with Shutdown
_______________________________________________________________________________________ 9
TOTAL HARMONIC DISTORTI0N PLUS NOISE
vs. FREQUENCY
FREQUENCY (Hz)
THD+N (%)
1010.1
0.01
0.1
1
10
0.001
0.01 100
V
OUT
= 8V
P-P
Figure 2. MAX9711 Piezoelectric Speaker Driver THD+N vs.
Frequency
MAX9711
IN
OUT+
OUT-
2
4
12
*PIEZOELECTRIC
SPEAKER.
*
AUDIO
INPUT
1μF
15kΩ
15kΩ
10Ω
100μH
Figure 3. Isolation Network for Driving a Piezoelectric Speaker
MAX9710
PGND
PV
DD
AUDIO SIGNAL
GND
V
DD
5V
FOR OPTIMUM PERFORMANCE,
AUDIO GND SHOULD HAVE A
STAR CONNECTION TO THE HIGH
CURRENT, AMPLIFIER PGND AT
A SINGLE POINT, PIN 6.
Figure 4. MAX9710 Audio Ground Connection