MAX9713(2004) 데이터 시트보기 (PDF) - Maxim Integrated
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MAX9713 Datasheet PDF : 18 Pages
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6W, Filterless, Spread-Spectrum
Mono/Stereo Class D Amplifiers
Table 2. Gain Settings
GAIN (dB)
13.0
16.1
19.1
22.1
13.0
16.1
19.1
22.1
DIFF INPUT
(VRMS)
1.27
0.89
0.63
0.45
0.78
0.54
0.39
0.27
RL (Ω)
16
16
16
16
8
8
8
8
POUT
at 10%
THD+N (W)
8
8
8
8
6
6
6
6
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.
Gain Selection
Table 2 shows the suggested gain settings to attain a
maximum output power from a given peak input voltage
and given load.
Output Offset
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/(VDD/100 ✕ η),
which is on the order of a few microamps.
Input Amplifier
Differential Input
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
0.47µF
SINGLE-ENDED
AUDIO INPUT
0.47µF
IN+
MAX9713/
IN- MAX9714
Figure 5. Single-Ended Input
difference of the two inputs, any signal common to both
inputs is canceled.
Single-Ended Input
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).
Component Selection
Input Filter
An input capacitor, CIN, in conjunction with the input
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:
f
-3dB
=
1
2πRINCIN
Choose CIN so f-3dB is well below the lowest frequency
of interest. Setting f-3dB too high affects the low-fre-
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.
Charge-Pump Capacitor Selection
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.
Flying Capacitor (C1)
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-
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