Datasheet
MAX9742
Single-/Dual-Supply, Stereo 16W,
Class D Amplifier with Differential Inputs
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Detailed Description
The MAX9742 is a two-channel, single-ended Class D
stereo amplifier capable of providing 16W of output
power on each channel into 4Ω loads in single- or dual-
supply operation. The amplifier can also provide 32W
of output power in a mono bridge-tied-load (BTL) con-
figuration. The device offers Class AB audio perfor-
mance with Class D efficiency.
The differential input architecture reduces common-
mode noise pickup. The device can also be configured
for single-ended input signals.
The connection of external feedback components
allows custom gain settings.
Class D Operation and Efficiency
Class D amplifiers are switch-mode devices capable of
significantly higher power efficiencies in comparison to
linear amplifiers. The output stage of the MAX9742 con-
sists of a half-bridge speaker driver (see Figure 2). The
high efficiency of a Class D amplifier is attributed to the
region of operation of the output stage transistors. In a
Class D amplifier, the output transistors act as current-
steering switches by switching the output between V
DD
and V
SS
(ground for single-supply operation). Any
power loss associated with the Class D output stage is
mostly due to the I
2
R loss of the MOSFET on-resistance
and quiescent current overhead. The theoretical best
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Pin Description (continued)
PIN NAME FUNCTION
24 BOOTR Right-Channel Bootstrap Capacitor. Connect a 0.1µF capacitor between BOOTR and OUTR.
25, 26 OUTR Right Speaker Output
29, 30,
34, 35
V
DD
Positive Power-Supply Input. Bypass V
DD
to LGND with a 0.1µF plus additional bulk capacitance. See
the Supply Pumping Effects section.
31, 32, 33 V
SS
Negative Power-Supply Input. For dual-supply operation, connect to negative power-supply voltage
and bypass V
SS
to LGND with a 0.1µF plus additional bulk capacitance. For single-supply operation,
connect to LGND.
EP EP
Exposed Paddle. EP is internally connected to device substrate. Connect EP to V
SS
through a large
section of copper to maximize power dissipation.
OUTL
OUTR
C
F
L
F
R
L
AUX-0025
FILTER
AUDIO
ANALYZER
SINGLE-ENDED CONFIGURATION
BTL CONFIGURATION
MAX9742
C
F
L
F
R
L
OUTL
+
-
+
-
+
-
+
-
+
-
+
-
OUTR
C
F
L
F
R
L
AUX-0025
FILTER
AUDIO
ANALYZER
MAX9742
C
F
L
F
NOTE: SINGLE-ENDED CONFIGURATION IS AC-COUPLED IN SINGLE-SUPPLY MODE.
Figure 1. Test Circuits for Single-Ended and BTL Configurations
Test Circuits