Table 4. suggested capacitor manufacturers – Rainbow Electronics MAX9755 User Manual

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MAX9750/MAX9751/MAX9755

2.6W Stereo Audio Power Amplifiers and

DirectDrive Headphone Amplifiers

______________________________________________________________________________________

maximum power dissipation for a given V

and load is

given by the following equation:

If the power dissipation for a given application exceeds
the maximum allowed for a given package, either reduce
V

, increase load impedance, decrease the ambient

temperature, or add heatsinking to the device. Large
output, supply, and ground PC board traces improve the
maximum power dissipation in the package.

Thermal-overload protection limits total power dissipa-
tion in these devices. When the junction temperature
exceeds +160°C, the thermal-protection circuitry dis-
ables the amplifier output stage. The amplifiers are
enabled once the junction temperature cools by 15°C.
This results in a pulsing output under continuous ther-
mal-overload conditions as the device heats and cools.

Output Power (Headphone Amplifier)

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

. In typical stereo audio applications,

the left and right signals have differences in both magni-
tude and phase, subsequently leading to an increase in
the maximum attainable output power. Figure 10 shows
the two extreme cases for in and out of phase. In reality,
the available power lies between these extremes.

Power Supplies

The MAX9750/MAX9751/MAX9755 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

. PV

ranges from 4.5V to 5.5V. The

headphone amplifiers are powered from HPV

and

. HPV

is the positive supply of the headphone

amplifiers and ranges from 3V to 5.5V. V

is the nega-

tive supply of the headphone amplifiers. Connect V

CPV

. The charge pump is powered by CPV

CPV

ranges from 3V to 5.5V and should be the same

potential as HPV

. The charge pump inverts the volt-

age at CPV

, and the resulting voltage appears at

CPV

. The remainder of the device is powered by V

Component Selection

Input Filtering

The input capacitor (C

), in conjunction with the ampli-

fier input resistance (R

), forms a highpass filter that

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:

is the amplifier’s internal input resistance value

given in the Electrical Characteristics. Choose C

such

that f

-3dB

is well below the lowest frequency of interest.

Setting f

-3dB

too high affects the amplifier’s low-fre-

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 Capacitor

BIAS is the output of the internally generated DC bias
voltage. The BIAS bypass capacitor, C

BIAS

, improves

PSRR and THD+N by reducing power supply and other
noise sources at the common-mode bias node, and
also generates the clickless/popless, startup/shutdown
DC bias waveforms for the speaker amplifiers. Bypass
BIAS with a 1µF capacitor to GND.

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. Table 4
lists suggested manufacturers.

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, which leads to a loss
of output voltage. Increasing the value of C1 improves
load regulation and reduces the charge-pump output

R C

IN IN

−

2π

DISS MAX

(

)

SUPPLIER

PHONE

FAX

WEBSITE

Taiyo Yuden

800-348-2496

847-925-0899

www.t-yuden.com

TDK

807-803-6100

847-390-4405

www.component.tdk.com

Table 4. Suggested Capacitor Manufacturers