MAX9768EVKIT+ Maxim Integrated Products, MAX9768EVKIT+ Datasheet - Page 21

• Manufacturer Part Number: MAX9768EVKIT+
• Description: EVALUATION KIT FOR MAX9768
• Manufacturer: Maxim Integrated Products

Specifications of MAX9768EVKIT+

• Amplifier Type: Class D
• Output Type: 1-Channel (Mono)
• Max Output Power X Channels @ Load: 10W x 1 @ 8 Ohm
• Voltage - Supply: 4.5 V ~ 14 V
• Operating Temperature: -40°C ~ 85°C
• Board Type: Fully Populated
• Utilized Ic / Part: MAX9768
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Table 8. Suggested Values for LC filter
Some applications will use the MAX9768 with a full
inductor-/capacitor-based (LC) output filter. This is
common for longer speaker lead lengths, and to gain
increased margin to EMC limits. Select the PWM output
mode and use fixed-frequency modulation mode for
best audio performance. See Figure 8 for the correct
connections of these components.
The component selection is based on the load imped-
ance of the speaker. Table 8 lists suggested values for
a variety of load impedances.
Inductors L3 and L4, and capacitor C15 form the pri-
mary output filter. In addition to these primary filter
components, other components in the filter improve its
functionality. Capacitors C13 and C14, plus resistors
R6 and R7, form a Zobel at the output. A Zobel corrects
the output loading to compensate for the rising imped-
ance of the loudspeaker. Without a Zobel, the filter will
have a peak in its response near the cutoff frequency.
Capacitors C11 and C12 provide additional high-fre-
quency bypass to reduce radiated emissions.
Figure
8. Output Filter for PWM Mode
R
L
12
6
8
(Ω)
Inductor-Based Output Filters
______________________________________________________________________________________
L3, L4 (µH)
MAX9768
15
22
33
14, 18
1, 2
15
4
BOOT_+
OUT_+
OUT_-
BOOT_-
Amplifier with Volume Control
C15 (µF)
0.33
0.22
0.1
C1
0.1μF
C2
0.1μF
10W Mono Class D Speaker
L4
L3
C11
C12
External feedback resistors set the gain of the
MAX9768. The output stage has an internal 20dB gain
in addition to the externally set gain. Set the maximum
gain by using resistors R
Choose R
the actual gain of the amplifier is dependent on the vol-
ume level setting. For example, with the volume control
set to +9.5dB, the amplifier gain would be 9.5dB +
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 MAX9768 to be configured as a
summing amplifier, a filter, or an equalizer, for example.
C11, C12 (µF)
0.01
0.01
0.01
C13
C14
F
C15
between 10kΩ and 50kΩ. Please note that
A
V
F
R6
R7
= −
= R
R6, R7 (Ω)
10
IN
F
7.5
10
15
⎛
⎜
⎝
.
and R
R
R
IN
F
⎞
⎟
⎠
Gain-Setting Resistors
IN
V V
/
(Figure 9 ) as follows:
Adjustable Gain
R
L
C13, C14 (µF)
0.68
0.47
0.33
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