参数资料
型号: MAX9722BEUE+T
厂商: Maxim Integrated Products
文件页数: 4/21页
文件大小: 0K
描述: IC AMP AUDIO .13W STER 16TSSOP
产品培训模块: Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
标准包装: 2,500
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-TSSOP
封装/外壳: 16-TSSOP(0.173",4.40mm 宽)
包装: 带卷 (TR)
MAX9722A/MAX9722B
Component Selection
Input Filtering
The input capacitor (CIN), in conjunction with the input
resistor (RIN), forms a highpass filter that removes the DC
bias from an incoming signal (see the Typical Application
Circuit). The AC-coupling capacitor allows the device to
bias the signal to an optimum DC level. Assuming zero
source impedance, the -3dB point of the highpass filter is
given by:
Choose CIN so f-3dB is well below the lowest frequency of
interest. For the MAX9722B, use the value of RIN as given
in the Electrical Characteristics table. Setting f-3dB too
high affects the device’s low-frequency response. Use
capacitors whose dielectrics have low-voltage coeffi-
cients, such as tantalum or aluminum electrolytic.
Capacitors with high-voltage coefficients, such as ceram-
ics, can result in increased distortion at low frequencies.
Charge-Pump Capacitor Selection
Use capacitors with an ESR less than 100m
Ω for optimum
performance. Low-ESR ceramic capacitors minimize the
output resistance of the charge pump. For best perfor-
mance over the extended temperature range, select
capacitors with an X7R dielectric. Table 1 lists suggested
manufacturers.
Flying Capacitor (C1)
The value of the flying capacitor (C1) affects the charge
pump’s load regulation and output resistance. 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 regula-
tion and reduces the charge-pump output resistance to
an extent. See the Output Power vs. Load Resistance
graph in the Typical Operating Characteristics. Above
1F, the on-resistance of the switches and the ESR of C1
and C2 dominate.
Hold Capacitor (C2)
The hold capacitor value and ESR directly affect the rip-
ple at PVSS. Increasing the value of C2 reduces output
ripple. Likewise, decreasing the ESR of C2 reduces both
ripple and output resistance. Lower capacitance values
can be used in systems with low maximum output power
levels. See the Output Power vs. Load Resistance graph
in the Typical Operating Characteristics.
Power-Supply Bypass Capacitor
The power-supply bypass capacitor (C3) lowers the
output impedance of the power supply and reduces the
impact of the MAX9722A/MAX9722Bs’ charge-pump
switching transients. Bypass PVDD with C3, the same
value as C1, and place it physically close to the PVDD
and PGND pins.
Amplifier Gain
The gain of the MAX9722B is internally set at -2V/V. All
gain-setting resistors are integrated into the device,
reducing external component count. The internally set
gain, in combination with DirectDrive, results in a head-
phone amplifier that requires only five tiny 1F capaci-
tors to complete the amplifier circuit: two for the charge
pump, two for audio input coupling, and one for power-
supply bypassing (see the Typical Application Circuit).
The gain of the MAX9722A amplifier is set externally as
shown in Figure 7, the gain is:
AV = -RF/RIN
Choose feedback resistor values of 10k
Ω. Values other
than 10k
Ω increase output offset voltage due to the input
bias current, which, in turn, increases the amount of DC
current flow to the load.
f
RC
dB
IN IN
-3
1
2
=
π
5V, Differential Input, DirectDrive, 130mW
Stereo Headphone Amplifiers with Shutdown
12
______________________________________________________________________________________
Table 1. Suggested Capacitor Manufacturers
SUPPLIER
PHONE
FAX
WEBSITE
Murata
770-436-1300
770-436-3030
www.murata.com
Taiyo Yuden
800-348-2496
847-925-0899
www.t-yuden.com
TDK
847-803-6100
847-390-4405
www.component.tdk.com
LEFT
AUDIO
INPUT
RIGHT
AUDIO
INPUT
OUTL
INL-
INL+
INR+
INR-
OUTR
RIN
RF
RIN
MAX9722A
Figure 7. Gain Setting for the MAX9722A
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