max9758etjt Maxim Integrated Products, Inc., max9758etjt Datasheet - Page 22

• Manufacturer Part Number: max9758etjt
• Description: 2.3w Stereo Speaker Amplifiers And Directdrive Headphone Amplifiers With Automatic Level Control
• Manufacturer: Maxim Integrated Products, Inc.

The headphone amplifiers have been specified for the
worst-case scenario—when both inputs are in phase.
Under this condition, the drivers simultaneously draw
current from the charge pump, leading to a slight loss
in headroom of V
tions, the left and right signals have differences in both
magnitude and phase, subsequently leading to an
increase in the maximum attainable output power.
Figure 14 shows the two extreme cases for in and out
of phase. In reality, the available power lies between
these extremes.
The MAX9756/MAX9757/MAX9758 have different sup-
plies for each portion of the device, allowing for the opti-
mum combination of headroom and power dissipation
and noise immunity. The speaker amplifiers are pow-
ered from PV
headphone amplifiers are powered from HPV
V
amplifiers and ranges from 3V to 5.5V. V
tive supply of the headphone amplifiers. Connect V
CPV
CPV
potential as HPV
age at CPV
CPV
The input capacitor (C
fier input resistance (R
removes the DC bias from an incoming signal (see the
Typical Application Circuit). 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:
R
given in the Electrical Characteristics. Choose C
that f
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
Table 6. Suggested Capacitor Manufacturers
22
Taiyo Yuden
TDK
SS
IN
. HPV
DD
SS
is the amplifier’s internal input resistance value
SS
______________________________________________________________________________________
-3dB
. The remainder of the device is powered by V
. The charge pump is powered by CPV
SUPPLIER
ranges from 3V to 5.5V and should be the same
Output Power (Headphone Amplifier)
DD
is well below the lowest frequency of interest.
DD
DD
is the positive supply of the headphone
, and the resulting voltage appears at
. PV
DD
SS
f
. The charge pump inverts the volt-
−
3
DD
. In typical stereo audio applica-
dB
IN
IN
), in conjunction with the ampli-
ranges from 4.5V to 5.5V. The
=
), forms a highpass filter that
2π
Component Selection
R C
800-384-2496
807-803-6100
IN IN
1
PHONE
Power Supplies
Input Filtering
SS
is the nega-
DD
IN
SS
such
and
DD
DD
to
.
.
800-925-0899
847-390-4405
FAX
Setting f
quency response. Use capacitors with low-voltage
coefficient dielectrics, such as tantalum or aluminum
electrolytic. Capacitors with high-voltage coefficients,
such as ceramics, may result in increased distortion at
low frequencies.
BIAS is the output of the internally generated DC bias
voltage. The BIAS bypass capacitor, C
PSRR and THD+N by reducing power supply and other
noise sources at the common-mode bias node, and
also generates the startup/shutdown DC bias wave-
forms for the speaker amplifiers. Bypass BIAS with a
1µF capacitor to GND.
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. Table 6
lists suggested manufacturers.
Figure 14. Total Harmonic Distortion Plus Noise vs. Output
Power with Inputs In/Out of Phase (Headphone Mode)
-3dB
0.001
0.01
100
0.1
10
1
0
too high affects the amplifier’s low-fre-
www.t-yuden.com
www.component.tdk.com
HPV
R
L
20 40
= 16Ω
DD
Charge-Pump Capacitor Selection
OUTPUTS IN PHASE
= 5V
OUTPUT POWER (mW)
60 80
OUTPUTS 180° OUT OF PHASE
100 120
WEBSITE
140
160
BIAS Capacitor
180
BIAS
200
, improves