MAX9787ETI+T Maxim Integrated Products, MAX9787ETI+T Datasheet - Page 10

• Manufacturer Part Number: MAX9787ETI+T
• Description: IC AMP AUDIO PWR 2.2W AB 28TQFN
• Manufacturer: Maxim Integrated Products
• Type: Class ABr

Specifications of MAX9787ETI+T

• Output Type: 2-Channel (Stereo)
• Max Output Power X Channels @ Load: 2.2W x 2 @ 3 Ohm
• Voltage - Supply: 4.5 V ~ 5.5 V
• Features: Depop, Short-Circuit and Thermal Protection, Shutdown, Volume Control
• Mounting Type: Surface Mount
• Package / Case: 28-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX9787 features speaker amplifiers designed to
drive a load differentially, a configuration referred to as
bridge-tied load (BTL). The BTL configuration (Figure 5)
offers advantages over the single-ended configuration,
where one side of the load is connected to ground.
Driving the load differentially doubles the output volt-
age compared to a single-ended amplifier under similar
conditions. Thus, the device’s differential gain is twice
the closed-loop gain of the input amplifier. The effective
gain is given by:
Substituting 2 x V
yields four times the output power due to double the
output voltage:
Since the differential outputs are biased at midsupply,
there is no net DC voltage across the load. This elimi-
nates the need for DC-blocking capacitors required for
single-ended amplifiers. These capacitors can be large
and expensive, can consume board space, and can
degrade low-frequency performance.
2.2W Stereo Audio Power Amplifier
with Analog Volume Control
Figure 5. Bridge-Tied Load Configuration
10
______________________________________________________________________________________
Applications Information
+1
-1
OUT(P-P)
P
V
OUT
RMS
A
VD
BTL Speaker Amplifiers
=
=
= ×
V
2
V
into the following equation
RMS
OUT P P
R
2 2
L
R
R
IN
F
2
(
−
)
V
2 x V
V
OUT(P-P)
OUT(P-P)
OUT(P-P)
Under normal operating conditions, the MAX9787 can dis-
sipate a significant amount of power. The maximum power
dissipation for each package is given in the Absolute
Maximum Ratings under Continuous Power Dissipation, or
can be calculated by the following equation:
where T
and θ
as specified in the Absolute Maximum Ratings section.
For example, θ
optimum power dissipation, the exposed paddle of the
package should be connected to the ground plane
(see the Layout and Grounding section).
For 8Ω applications, the worst-case power dissipation
occurs when the output power is 1.1W/channel, result-
ing in a power dissipation of about 1W. In this case, the
TQFN packages can be used without violating the max-
imum power dissipation or exceeding the thermal pro-
tection threshold.
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.
If the power dissipation for a given application exceeds
the maximum allowed for a given package, either
reduce V
ambient temperature, or add heatsinking to the device.
Large output, supply, and ground PCB traces improve
the maximum power dissipation in the package.
Figure 6. Total Harmonic Distortion Plus Noise vs. Output Power
with Inputs In/Out of Phase
JA
J(MAX)
is the reciprocal of the derating factor in
Power Dissipation and Heat Sinking
DD
0.001
1000
0.01
100
0.1
10
P
, increase load impedance, decrease the
1
DISSPKG MAX
is +150°C, T
0
JA
V
R
A
DD
L
V
of the TQFN package is +42
= 16Ω
= 3dB
= 5V
25
OUTPUTS IN PHASE
(
OUTPUT POWER (mW)
50
OUTPUTS 180° OUT OF PHASE
)
A
=
is the ambient temperature,
75
T
J MAX
(
100
θ
JA
)
−
125
Output Power
T
A
150
o
C/W. For
o
C/W