max9742 Maxim Integrated Products, Inc., max9742 Datasheet - Page 28

• Manufacturer Part Number: max9742
• Description: Max9742 Single-/dual-supply, Stereo 16w, Class D Amplifier With Differential Inputs
• Manufacturer: Maxim Integrated Products, Inc.

Single-/Dual-Supply, Stereo 16W,
Class D Amplifier with Differential Inputs
If low THD+N performance is needed at low-output pow-
ers, replace the feedback resistor (R
with the T-network shown in Figure 15. The T-network
provides additional attenuation of audio band noise,
therefore, providing improved THD+N performance at
lower output powers. Use the following expressions to
select R
where A
mize CMRR and minimize gain mismatch between
channels, use the closest 1% tolerance resistor values
available for R
See the THD+N vs. Output Power With and Without
T-Network plot in the Typical Operating Characteristics
for a comparison of the THD+N performance with and
without the optional T-network.
Figure 15. Optional T-Network for Minimizing THD+N at Low Output Powers
28
R
IN1
______________________________________________________________________________________
=
IN1
V
R
is the desired voltage gain in V/V. To maxi-
, R
F1a
IN2
A
IN1
+
V
T-Network for Low THD Performance
, R
R
, R
R
F1b
F2
F1a
IN2
at Low Output Powers (Optional)
R
=
IN1
, R
R
, R
=
F1a
F1b
=
121
F1a
AUDIO INPUT
AUDIO INPUT
R
IN2
+
, and R
NEGATIVE
k
POSITIVE
, R
R
Ω
A
R
R
F1b
V
F2
IN1
A
( )
F1b
+
Ω
=
V
= R
R
= R
562
F1a
( )
F1a
, and R
F2
Ω
IN2
R
F1
+ R
IN1
C
+ R
C
:
k
IN
IN
) in each channel
Ω
F1b
F1b
= 688kΩ
=
R
R
F2
IN1
IN2
681kΩ
683k
.
R
A
F2
TO MID
V
Ω
( )
C
150pF
Ω
FB_1
121kΩ
R
IN_-
IN_+
F1a
In applications where the output can be driven to clip-
ping, a pair of diodes around the feedback capacitor
helps reduce distortion. Clipping is most likely to hap-
pen when driving high-impedance speakers with lower
supply voltages, for example, 8Ω loads with a 24V sin-
gle supply. Diodes such as BAV99, a dual series silicon
switching diode, are a good choice. Connect these
diodes around the feedback capacitor as shown in
Figure 16.
Figure 16. Connection of Output Limiting Diodes
C
150pF
FB_1
MAX9742
C
10pF
FB_2
562kΩ
R
F1b
FB_
Output Limiting Diodes (Optional)
TO IN_-
TO CLASS D
MODULATOR
TO OUT_
C
FB_
TO FB_