MAX9779ETI+ Maxim Integrated Products, MAX9779ETI+ Datasheet - Page 14

• Manufacturer Part Number: MAX9779ETI+
• Description: IC AMP AUDIO PWR 2.6W AB 28TQFN
• Manufacturer: Maxim Integrated Products
• Series: DirectDrive™r
• Type: Class ABr

Specifications of MAX9779ETI+

• Output Type: 2-Channel (Stereo) with Stereo Headphones
• Max Output Power X Channels @ Load: 2.6W x 2 @ 3 Ohm; 110mW x 2 @ 16 Ohm
• Voltage - Supply: 4.5 V ~ 5.5 V
• Features: Depop, Short-Circuit and Thermal Protection, Shutdown
• Mounting Type: Surface Mount
• Package / Case: 28-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

2.6W Stereo Audio Power Amplifier and
DirectDrive Headphone Amplifier
Figure 7. Total Harmonic Distortion Plus Noise vs. Output Power
with Inputs In/Out of Phase (Headphone Mode)
For 8Ω applications, the worst-case power dissipation
occurs when the output power is 1.1W/channel, resulting
in a power dissipation of approximately 1W. In this case,
the TQFN package can be used without violating the
maximum power dissipation or exceeding the thermal
protection threshold. For 4Ω applications, the TQFN
package may require heatsinking or forced air cooling to
prevent the device from reaching its thermal limit. The
more thermally efficient TQFN package is suggested for
speaker loads less than 8Ω.
The increase in power delivered by the BTL configura-
tion directly results in an increase in internal power dis-
sipation over the single-ended configuration. The
maximum power dissipation for a given V
given by the following equation:
If the power dissipation for a given application exceeds
the maximum allowed for a given package, either reduce
V
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.
14
DD
, increase load impedance, decrease the ambient
______________________________________________________________________________________
0.001
1000
0.01
100
0.1
10
1
Output Power (Speaker Amplifier)
0
V
R
A
DD
L
V
= 16Ω
= 3dB
P
= 5V
25
DISS MAX
OUTPUTS IN PHASE
OUTPUT POWER (mW)
50
(
OUTPUTS 180° OUT OF PHASE
75
)
=
2
π
100
V
2
DD
R
L
2
125
DD
150
and load is
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
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 7 shows
the two extreme cases for in and out of phase. In reality,
the available power lies between these extremes.
The MAX9779 has different supplies for each portion of
the device, allowing for the optimum combination of
headroom, power dissipation, and noise immunity. The
speaker amplifiers are powered from PV
ranges from 4.5V to 5.5V. The headphone amplifiers are
powered from HPV
supply of the headphone amplifiers and ranges from 3V
to 5.5V. V
amplifiers. Connect V
powered by CPV
should be the same potential as HPV
pump inverts the voltage at CPV
voltage appears at CPV
is powered by V
The input capacitor (C
fier input resistance (R
removes the DC bias from an incoming signal (see the
Block Diagram). 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
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.
IN
is the amplifier’s internal input resistance value
-3dB
Output Power (Headphone Amplifier)
-3dB
is well below the lowest frequency of interest.
SS
is the negative supply of the headphone
too high affects the amplifier’s low-fre-
SS
DD
DD
f
−
. In typical stereo audio applications,
3
.
DD
. CPV
dB
SS
IN
=
and V
IN
SS
), in conjunction with the ampli-
to CPV
2π
DD
), forms a highpass filter that
. The remainder of the device
R C
Component Selection
ranges from 3V to 5.5V and
IN IN
1
SS
SS
. HPV
. The charge pump is
DD
Power Supplies
, and the resulting
DD
DD
Input Filtering
is the positive
. The charge
DD
. PV
IN
such
DD