max9710etpt Maxim Integrated Products, Inc., max9710etpt Datasheet - Page 9

• Manufacturer Part Number: max9710etpt
• Description: 3w Mono/stereo Btl Audio Power Amplifiers With Shutdown
• Manufacturer: Maxim Integrated Products, Inc.

Figure 2. MAX9711 Piezoelectric Speaker Driver THD+N vs.
Frequency
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).
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 and TSSOP-EP
packages feature exposed thermal pads on their
undersides. This pad lowers the thermal resistance of
the package by providing a direct-heat conduction
path from the die to the printed circuit board. Connect
the exposed pad to the ground plane using multiple
vias, if required. For optimum performance, connect to
the ground planes as shown in Figure 4.
3W Mono/Stereo BTL Audio Power Amplifiers
0.001
0.01
0.1
10
1
TOTAL HARMONIC DISTORTI0N PLUS NOISE
0.01
_______________________________________________________________________________________
0.1
vs. FREQUENCY
FREQUENCY (Hz)
Layout and Grounding
1
V
10
OUT
= 8V
P-P
100
Figure 3. Isolation Network for Driving a Piezoelectric Speaker
Figure 4. MAX9710 Audio Ground Connection
AUDIO
INPUT
5V
1µF
AUDIO SIGNAL
PGND
GND
15kΩ
PV
DD
2
MAX9710
IN
with Shutdown
V
DD
15kΩ
MAX9711
FOR OPTIMUM PERFORMANCE,
AUDIO GND SHOULD HAVE A
STAR CONNECTION TO THE HIGH
CURRENT, AMPLIFIER PGND AT
ONE POINT ONLY. THIS IS DIFFERENT
FOR THE TWO AVAILABLE PACKAGES:
TSSOP-EP: PIN 3
THIN QFN: PIN 6
OUT+
OUT-
4
12
*
SPEAKER.
PIEZOELECTRIC
100µH
10Ω
*
9