MAX9744ETH+T Maxim Integrated Products, MAX9744ETH+T Datasheet - Page 22

• Manufacturer Part Number: MAX9744ETH+T
• Description: IC AMP AUDIO PWR 22.5W D 44TQFN
• Manufacturer: Maxim Integrated Products
• Type: Class Dr

Specifications of MAX9744ETH+T

• Output Type: 2-Channel (Stereo)
• Max Output Power X Channels @ Load: 22.5W x 2 @ 4 Ohm
• Voltage - Supply: 4.5 V ~ 14 V
• Features: Depop, Mute, Short-Circuit and Thermal Protection, Shutdown, Volume Control
• Mounting Type: Surface Mount
• Package / Case: 44-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

20W Stereo Class D Speaker Amplifier
with Volume Control
External feedback resistors set the gain of the
MAX9744. The output stage has an internal 20dB gain
in addition to the externally set input stage gain. Set the
maximum gain by using resistors R
as follows:
Choose R
actual gain of the amplifier is dependent on the volume
level setting. For example, with the volume set to
+9.5dB, the amplifier gain would be 9.5dB plus 20dB,
assuming R
The input amplifier can be configured into a variety of
circuits. The FB terminal is an actual operational ampli-
fier output, allowing the MAX9744 to be configured as a
summing amplifier, a filter, or an equalizer, for example.
An input capacitor (C
impedance of the MAX9744 form a highpass filter that
removes the DC bias from an incoming signal. The AC-
coupling capacitor allows the amplifier to automatically
bias the signal to an optimum DC level. Assuming zero
source impedance, the -3dB point of the highpass filter
is given by:
Figure 9. Setting Gain
22
AUDIO
INPUT
______________________________________________________________________________________
C
IN
R
F
IN
IN
between 10kΩ and 50kΩ. Note that the
= R
F
R
A
F
.
V
f
−
3
=
FB
dB
IN
IN
−
30
) in conjunction with the input
=
9.5dB (max)
CONTROL
VOLUME
⎛
⎝ ⎜
2π
Component Selection
R
R
R C
MAX9744
IN
F
IN IN
1
Gain-Setting Resistors
⎞
⎠ ⎟
V V
F
/
and R
Input Capacitor
BOOT+
OUT+
OUT-
BOOT-
IN
(Figure 9)
Choose C
cy of interest. Use capacitors whose dielectrics have
low-voltage coefficients, such as tantalum or aluminum
electrolytic. Capacitors with high-voltage coefficients,
such as ceramics, may result in increased distortion at
low frequencies.
The input amplifier can accept DC-coupled inputs that
are biased to the amplifier’s bias voltage. DC-coupling
eliminates input-coupling capacitors, reducing compo-
nent count to potentially one external component. In this
configuration the highpass filtering effect of the capacitors
is lost, allowing low-frequency signals to be amplified.
The MAX9744 features separate supplies for each por-
tion of the device, allowing for the optimum combination
of headroom power dissipation and noise immunity. The
speaker amplifier is powered from PVDD and can range
from 4.5V to 14V. The remainder of the device is pow-
ered by V
other so sequencing is not necessary. Power may be
supplied by separate sources or derived from a single
higher source using a linear regulator (Figure 10).
BIAS is the output of the internally generated DC bias
voltage. The BIAS bypass capacitor, C
PSRR and THD+N by reducing power supply and other
noise sources at the common-mode bias node, and
also generates the clickless/popless, startup/shutdown,
DC bias waveforms for the speaker amplifiers. Bypass
BIAS with a 2.2µF capacitor to GND.
Figure 10. Using a Linear Regulator to Produce 3.3V from a
Higher Power Supply
1μF
SHDN
IN
DD
that f
. Power supplies are independent of each
MAX1615
-3dB
GND
IN
is well below the lowest frequen-
4.5V TO 14.5V
OUT
3.3V
V
DD
Power Supplies
DC-Coupled Input
MAX9744
BIAS Capacitor
BIAS
PV
GND
DD
, improves
1μF