max9742 Maxim Integrated Products, Inc., max9742 Datasheet - Page 19

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

Since each half-bridge output stage is only capable of
driving loads as small as 4Ω and each half-bridge sees
half of the differential load resistance when configured
for BTL, only use the BTL configuration with loads
greater than or equal to 8Ω. The MAX9742 may be ther-
mally limited when using the BTL configuration with
high supply voltages due to the decreased load resis-
tance seen by each half bridge. For optimum perfor-
mance, the PCB should be thermally optimized to
achieve the continuous output powers required for the
application (see the Thermal Considerations section).
Figure 7. Input Signal Source and Load Connections for BTL Operation
DIFFERENTIAL
AUDIO INPUT
Class D Amplifier with Differential Inputs
C
C
C
C
IN
IN
IN
IN
______________________________________________________________________________________
R
R
R
R
MID
IN1
IN2
IN2
IN1
C
C
F
F
R
R
F2
F2
A
R
V_BTL
IN1
= R
= 2 ×
IN2
INL-
INL+
INR+
INR-
, R
R
F1
R
Single-/Dual-Supply, Stereo 16W,
IN_
F_
= R
C
C
FBL
FBR
MAX9742
F2
FBL
FBR
AND GATE DRIVE
AND GATE DRIVE
R
R
MODULATOR
MODULATOR
F1
F1
CLASS D
CLASS D
To maximize dynamic range, an external feedback
capacitor (C
for the Class D modulator. The feedback capacitor con-
figures the input amplifier stage as an integrator whose
output is equal to an error signal consisting of the sum
of the integrated input audio and PWM output signals.
The integrator provides a noise-shaping function for the
closed-loop response of the amplifier.
V
V
V
V
DD
SS
DD
SS
OUTL
OUTR
FB_
) is needed to generate an error signal
L
L
F
F
C
C
F
F
C
C
R
R
ZBL
ZBL
ZBL
ZBL
Feedback Capacitor (C
Component Selection
V
V
DD
DD
/2
/2
0V
V
V
OUT_P-P
OUT_P-P
2 x V
OUT_P-P
FB_
19
)