max9708etntd Maxim Integrated Products, Inc., max9708etntd Datasheet - Page 14

• Manufacturer Part Number: max9708etntd
• Description: Max9708 20w/40w, Filterless, Spread-spectrum, Mono/stereo, Class D Amplifier
• Manufacturer: Maxim Integrated Products, Inc.

20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
The supply voltage range for the MAX9708 is from 10V
to 18V to achieve high-output power. An internal linear
regulator reduces this voltage to 6.3V for use with
small-signal and digital circuitry that does not require a
high-voltage supply. Bypass a 0.01µF capacitor from
REG to GND.
All of the digital logic inputs and output have an
absolute maximum rating of +12V. If the MAX9708 is
operating with a supply voltage between 10V and 12V,
digital inputs can be connected to PV
PV
outputs must connected to a digital system supply
lower than 12V.
The MAX9708 features a differential input structure,
making them compatible with many CODECs, and
offering improved noise immunity over a single-ended
input amplifier. In devices such as flat-panel displays,
noisy digital signals can be picked up by the amplifier’s
inputs. These signals appear at the amplifiers’ inputs as
common-mode noise. A differential input amplifier
amplifies only the difference of the two inputs, while any
signal common to both inputs is attenuated.
The MAX9708 can be configured as a single-ended
input amplifier by capacitively coupling either input to
GND and driving the other input (Figure 4).
An input capacitor, C
impedance of the MAX9708, forms a highpass filter that
removes the DC bias from an incoming signal. The AC-
coupling capacitor allows the amplifier to bias the signal
to an optimum DC level. Assuming zero-source imped-
ance, the -3dB point of the highpass filter is given by:
14
DD
______________________________________________________________________________________
and V
DD
Applications Information
are greater than 12V, digital inputs and
f
−
3
dB
IN
=
, in conjunction with the input
Linear Regulator (REG)
2 π
Component Selection
R
IN
1
C
Single-Ended Input
IN
Input Amplifier
Differential Input
Logic Inputs
DD
Input Filter
or V
DD
. If
Choose C
quency of interest. Setting f
low-frequency response of the amplifier. Use capaci-
tors with dielectrics that 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 MAX9708 does not require an output filter.
However, output filtering can be used if a design is fail-
ing radiated emissions due to board layout or cable
length, or the circuit is near EMI-sensitive devices.
Refer to the MAX9708 Evaluation Kit for suggested filter
topologies. The tuning and component selection of the
filter should be optimized for the load. A purely resistor
load (8Ω) used for lab testing will require different com-
ponents than a real, complex load-speaker load.
The MAX9708 has an internal charge-pump converter
that produces a voltage level for internal circuitry. It
requires a flying capacitor (C1) and a holding capacitor
(C2). Use capacitors with an ESR less than 100mΩ for
optimum performance. Low-ESR ceramic capacitors
minimize the output resistance of the charge pump. For
best performance over the extended temperature
range, select capacitors with an X7R dielectric. The
capacitors’ voltage rating must be greater than 36V.
Figure 4. Single-Ended Input Connections
IN
so that f
1µF
1µF
Charge-Pump Capacitor Selection
-3dB
is well below the lowest fre-
INR+
INR-
MAX9708
-3dB
too high affects the
Output Filter