MAX9713ETJ MAXIM [Maxim Integrated Products], MAX9713ETJ Datasheet - Page 10

• Manufacturer Part Number: MAX9713ETJ
• Description: 6W, Filterless, Spread-Spectrum Mono/Stereo Class D Amplifiers
• Manufacturer: MAXIM [Maxim Integrated Products]

is very small. Although this movement is small, a speak-
er not designed to handle the additional power can be
damaged. For optimum results, use a speaker with a
series inductance > 30µH. Typical 8Ω speakers exhibit
series inductances in the range of 30µH to 100µH.
Optimum efficiency is achieved with speaker induc-
tances > 60µH.
Table 2 shows the suggested gain settings to attain a
maximum output power from a given peak input voltage
and given load.
Unlike a class AB amplifier, the output offset voltage of
class D amplifiers does not noticeably increase quies-
cent current draw when a load is applied. This is due to
the power conversion of the class D amplifier. For
example, an 8mV DC offset across an 8Ω load results
in 1mA extra current consumption in a class AB device.
In the class D case, an 8mV offset into 8Ω equates
to an additional power drain of 8µW. Due to the high
efficiency of the class D amplifier, this represents an
additional quiescent current draw of: 8µW/(V
which is on the order of a few microamps.
The MAX9713/MAX9714 feature a differential input struc-
ture, making them compatible with many CODECs, and
offering improved noise immunity over a single-ended
input amplifier. In devices such as PCs, noisy digital sig-
nals can be picked up by the amplifier’s input traces.
The signals appear at the amplifiers’ inputs as common-
mode noise. A differential input amplifier amplifies the
6W, Filterless, Spread-Spectrum
Mono/Stereo Class D Amplifiers
Table 2. Gain Settings
10
GAIN (dB)
13.0
16.1
19.1
22.1
13.0
16.1
19.1
22.1
______________________________________________________________________________________
DIFF INPUT
(V
1.27
0.89
0.63
0.45
0.78
0.54
0.39
0.27
RMS
)
R
L
16
16
16
16
8
8
8
8
Input Amplifier
( )
Gain Selection
Differential Input
Output Offset
DD
THD+N (W)
at 10%
/100
P
OUT
8
8
8
8
6
6
6
6
η),
difference of the two inputs, any signal common to both
inputs is canceled.
The MAX9713/MAX9714 can be configured as single-
ended input amplifiers by capacitively coupling either
input to GND and driving the other input (Figure 5).
An input capacitor, C
impedance of the MAX9713/MAX9714, forms a high-
pass 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 impedance, the -3dB point of the highpass
filter is given by:
Choose C
of interest. Setting f
quency response of the amplifier. 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.
Use capacitors with an ESR less than 100mΩ for opti-
mum performance. Low-ESR ceramic capacitors mini-
mize the output resistance of the charge pump. For
best performance over the extended temperature
range, select capacitors with an X7R dielectric.
The value of the flying capacitor (C1) affects the load
regulation and output resistance of the charge pump. A
C1 value that is too small degrades the device’s ability to
provide sufficient current drive. Increasing the value of
C1 improves load regulation and reduces the charge-
pump output resistance to an extent. Above 1µF, the on-
Figure 5. Single-Ended Input
IN
SINGLE-ENDED
Charge-Pump Capacitor Selection
so f
AUDIO INPUT
-3dB
0.47µF
f
- 3dB
-3dB
is well below the lowest frequency
IN
0.47µF
, in conjunction with the input
=
too high affects the low-fre-
2
Component Selection
π
R C
IN+
IN-
IN IN
1
Flying Capacitor (C1)
MAX9713/
MAX9714
Single-Ended Input
Input Filter