max9722beue Maxim Integrated Products, Inc., max9722beue Datasheet - Page 12

• Manufacturer Part Number: max9722beue
• Description: 5v, Differential Input, Directdrive, 130mw Stereo Headphone Amplifiers With Shutdown Products
• Manufacturer: Maxim Integrated Products, Inc.

The input capacitor (C
resistor (R
bias from an incoming signal (see the Typical Application
Circuit). The AC-coupling capacitor allows the device 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
interest. For the MAX9722B, use the value of R
in the DC Electrical Characteristics table. Setting f
high affects the device’s low-frequency response. Use
capacitors whose dielectrics have low-voltage coeffi-
cients, such as tantalum or aluminum electrolytic.
Capacitors with high-voltage coefficients, such as ceram-
ics, can result in increased distortion at low frequencies.
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 perfor-
mance over the extended temperature range, select
capacitors with an X7R dielectric. Table 1 lists suggested
manufacturers.
The value of the flying capacitor (C1) affects the charge
pump’s load regulation and output resistance. A C1 value
that is too small degrades the device’s ability to provide
sufficient current drive, which leads to a loss of output
voltage. Increasing the value of C1 improves load regula-
tion and reduces the charge-pump output resistance to
an extent. See the Output Power vs. Charge-Pump
Capacitance and Load Resistance graph in the Typical
Operating Characteristics. Above 1µF, the on-resistance
of the switches and the ESR of C1 and C2 dominate.
The hold capacitor value and ESR directly affect the rip-
ple at PV
ripple. Likewise, decreasing the ESR of C2 reduces both
ripple and output resistance. Lower capacitance values
5V, Differential Input, DirectDrive, 130mW
Stereo Headphone Amplifiers with Shutdown
Table
12
Murata
Taiyo Yuden
TDK
______________________________________________________________________________________
1. Suggested Capacitor Manufacturers
SS
SUPPLIER
IN
IN
. Increasing the value of C2 reduces output
), forms a highpass filter that removes the DC
so f
-3dB
f
-3
dB
Charge-Pump Capacitor Selection
is well below the lowest frequency of
IN
=
), in conjunction with the input
2
π
Component Selection
R C
IN IN
1
Flying Capacitor (C1)
Hold Capacitor (C2)
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800-348-2496
847-803-6100
PHONE
Input Filtering
IN
as given
-3dB
too
can be used in systems with low maximum output power
levels. See the Output Power vs. Charge-Pump
Capacitance and Load Resistance graph in the Typical
Operating Characteristics.
The power-supply bypass capacitor (C3) lowers the
output impedance of the power supply and reduces the
impact of the MAX9722A/MAX9722Bs’ charge-pump
switching transients. Bypass PV
value as C1, and place it physically close to the PV
and PGND pins.
The gain of the MAX9722B is internally set at -2V/V. All
gain-setting resistors are integrated into the device,
reducing external component count. The internally set
gain, in combination with DirectDrive, results in a head-
phone amplifier that requires only five tiny 1µF capaci-
tors to complete the amplifier circuit: two for the charge
pump, two for audio input coupling, and one for power-
supply bypassing (see the Typical Application Circuit).
The gain of the MAX9722A amplifier is set externally as
shown in Figure 7, the gain is:
Choose feedback resistor values of 10kΩ. Values other
than 10kΩ increase output offset voltage due to the input
bias current, which, in turn, increases the amount of DC
current flow to the load.
Figure 7. Gain Setting for the MAX9722A
AUDIO
AUDIO
INPUT
RIGHT
INPUT
LEFT
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847-925-0899
847-390-4405
R
R
FAX
IN
IN
INL-
INL+
INR+
INR-
Power-Supply Bypass Capacitor
A
V
= -R
MAX9722A
R
R
F
F
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F
/R
OUTL
OUTR
IN
DD
with C3, the same
WEBSITE
Amplifier Gain
DD