max9722beue Maxim Integrated Products, Inc., max9722beue Datasheet - Page 11

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

The MAX9722A/MAX9722B feature shutdown control
allowing audio signals to be shut down or muted.
Driving SHDN low disables the amplifiers and the
charge pump, sets the amplifier output impedance to
10kΩ, and reduces the supply current. In shutdown
mode, the supply current is reduced to 0.1µA. The
charge pump is enabled once SHDN is driven high.
Under normal operating conditions, linear power ampli-
fiers can dissipate a significant amount of power. The
maximum power dissipation for each package is given
in the Absolute Maximum Ratings section under
Continuous Power Dissipation or can be calculated by
the following equation:
where T
ture, and θ
°C/W as specified in the Absolute Maximum Ratings
section. For example, θ
+63.8°C/W, and 99.3°C/W for the TSSOP package.
The MAX9722A/MAX9722B have two power dissipation
sources: the charge pump and two amplifiers. If power
dissipation for a given application exceeds the maxi-
mum allowed for a particular package, either reduce
SV
temperature, or add heatsinking to the device. Large
output, supply, and ground traces improve the maxi-
mum power dissipation in the package.
Thermal-overload protection limits total power dissipa-
tion in the MAX9722A/MAX9722B. When the junction
temperature exceeds +145°C, the thermal-protection
circuitry disables the amplifier output stage. The ampli-
fiers are enabled once the junction temperature cools
by 5°C. This results in a pulsing output under continu-
ous thermal-overload conditions.
The device has been specified for the worst-case sce-
nario—when both inputs are in-phase. Under this con-
dition, the amplifiers simultaneously draw current from
the charge pump, leading to a slight loss in SV
room. In typical stereo audio applications, the left and
right signals have differences in both magnitude and
phase, subsequently leading to an increase in the max-
DD
, increase load impedance, decrease the ambient
Stereo Headphone Amplifiers with Shutdown
J(MAX)
JA
P
DISSPKG MAX
is the reciprocal of the derating factor in
5V, Differential Input, DirectDrive, 130mW
is +145°C, T
Applications Information
______________________________________________________________________________________
(
JA
)
of the thin QFN package is
=
A
T
is the ambient tempera-
J MAX
Power Dissipation
(
θ
JA
)
- T
Output Power
A
Shutdown
SS
head-
imum attainable output power. Figure 6 shows the two
extreme cases for in- and out-of-phase. In reality, the
available power lies between these extremes.
An additional benefit of the MAX9722A/MAX9722B is
the internally generated, negative supply voltage
(PV
output level. PV
other devices within a design limit current drawn from
PV
amplifier operation. A typical application is a negative
supply to adjust the contrast of LCD modules.
PV
ed voltage. The charge-pump output impedance must be
taken into account when powering other devices from
PV
in the Typical Operating Characteristics . For best results,
use 1µF charge-pump capacitors.
The MAX9722A/MAX9722B feature an UVLO function
that prevents the device from operating if the supply
voltage is less than 2.2V (typ). This feature ensures
proper operation during brownout conditions and pre-
vents deep battery discharge. Once the supply voltage
reaches the UVLO threshold, the MAX9722A/
MAX9722B charge pump is turned on and the ampli-
fiers are powered.
Figure 6. Distortion Contributed by DC-Blocking Capacitors
SS
SS
SS
SS
. The charge-pump output impedance plot appears
is roughly proportional to PV
). This voltage provides the ground-referenced
to 5mA; exceeding this affects the headphone
160
140
120
100
80
60
40
20
0
2.4
OUTPUT POWER vs. SUPPLY VOLTAGE
f
R
THD+N = 10%
IN
L
SS
= 1kHz
= 32Ω
2.6
can, however, be used to power
2.8
SUPPLY VOLTAGE (V)
Powering Other Circuits
from a Negative Supply
3.0
3.2
OUT OF PHASE
IN PHASE
INPUTS 180°
INPUTS
DD
3.4
and is not a regulat-
3.6
3.8
4.0
UVLO
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