参数资料
型号: MAX9722BETE+
厂商: Maxim Integrated Products
文件页数: 3/21页
文件大小: 0K
描述: IC AMP AUDIO .13W STER AB 16TQFN
产品培训模块: Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
标准包装: 100
系列: DirectDrive®
类型: AB 类
输出类型: 耳机,2-通道(立体声)
在某负载时最大输出功率 x 通道数量: 130mW x 2 @ 32 欧姆
电源电压: 2.4 V ~ 5.5 V
特点: 消除爆音,差分输入,短路和热保护,关闭
安装类型: 表面贴装
供应商设备封装: 16-TQFN-EP(3x3)
封装/外壳: 16-WFQFN 裸露焊盘
包装: 管件
Shutdown
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
10k
Ω, and reduces the supply current. In shutdown
mode, the supply current is reduced to 0.1A. The
charge pump is enabled once SHDN is driven high.
Applications Information
Power Dissipation
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 TJ(MAX) is +145°C, TA is the ambient tempera-
ture, and
θJA is the reciprocal of the derating factor in
°C/W as specified in the Absolute Maximum Ratings
section. For example,
θJA of the thin QFN package is
+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
SVDD, increase load impedance, decrease the ambient
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.
Output Power
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 SVSS head-
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-
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.
Powering Other Circuits
from a Negative Supply
An additional benefit of the MAX9722A/MAX9722B is
the internally generated, negative supply voltage
(PVSS). This voltage provides the ground-referenced
output level. PVSS can, however, be used to power
other devices within a design limit current drawn from
PVSS to 5mA; exceeding this affects the headphone
amplifier operation. A typical application is a negative
supply to adjust the contrast of LCD modules.
PVSS is roughly proportional to PVDD and is not a regulat-
ed voltage. The charge-pump output impedance must be
taken into account when powering other devices from
PVSS. The charge-pump output impedance plot appears
in the Typical Operating Characteristics. For best results,
use 1F charge-pump capacitors.
UVLO
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.
P
T
DISSPKG MAX
J MAX
JA
()
=
-TA
θ
MAX9722A/MAX9722B
5V, Differential Input, DirectDrive, 130mW
Stereo Headphone Amplifiers with Shutdown
______________________________________________________________________________________
11
OUTPUT POWER vs. SUPPLY VOLTAGE
MAX9722
fig06
SUPPLY VOLTAGE (V)
OUTPUT
POWER
(mW)
3.8
3.6
2.6
2.8
3.0
3.2
3.4
20
40
60
80
100
120
140
160
0
2.4
4.0
fIN = 1kHz
RL = 32
Ω
THD+N = 10%
INPUTS
IN PHASE
INPUTS 180
°
OUT OF PHASE
Figure 6. Output Power vs. Supply Voltage With Inputs In/Out
of Phase
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