参数资料
型号: MAX9877EWP+TG45
厂商: Maxim Integrated Products
文件页数: 11/30页
文件大小: 0K
描述: IC AUDIO SUBSYSTEM 20-WLP
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: D 类
输出类型: 1-通道(单声道),带立体声耳机
在某负载时最大输出功率 x 通道数量: 825mW x 1 @ 4 欧姆; 53mW x 2 @ 16 欧姆
电源电压: 2.7 V ~ 5.25 V
特点: 消除爆音,I²C,输入多路复用器,短路和热保护,关机,音量控制
安装类型: 表面贴装
供应商设备封装: 20-WLP
封装/外壳: 20-WFBGA,WLBGA
包装: 带卷 (TR)
MAX9877
Low RF Susceptibility, Mono Audio
Subsystem with DirectDrive Headphone Amplifier
______________________________________________________________________________________
19
DirectDrive Headphone Amplifier
Traditional single-supply headphone amplifiers have
outputs biased at a nominal DC voltage (typically half
the supply). Large coupling capacitors are needed to
block this DC bias from the headphone. Without these
capacitors, a significant amount of DC current flows to
the headphone, resulting in unnecessary power dissi-
pation and possible damage to both the headphone
and headphone amplifier.
Maxim’s DirectDrive architecture uses a charge pump to
create an internal negative supply voltage. This allows
the headphone outputs of the MAX9877 to be biased at
GND while operating from a single supply (Figure 5).
Without a DC component, there is no need for the large
DC-blocking capacitors. Instead of two large (220F,
typ) capacitors, the MAX9877 charge pump requires
two small ceramic capacitors, conserving board space,
reducing cost, and improving the frequency response of
the headphone amplifier. See the Output Power vs.
Load Resistance graph in the
Typical Operating
Characteristics for details of the possible capacitor
sizes. There is a low DC voltage on the amplifier outputs
due to amplifier offset. However, the offset of the
MAX9877 is typically ±0.15mV, which, when combined
with a 32Ω load, results in less than 10A of DC current
flow to the headphones.
In addition to the cost and size disadvantages of the
DC-blocking capacitors required by conventional head-
phone amplifiers, these capacitors limit the amplifier’s
low-frequency response and can distort the audio sig-
nal. Previous attempts at eliminating the output-cou-
pling capacitors involved biasing the headphone return
(sleeve) to the DC bias voltage of the headphone
amplifiers. This method raises some issues:
FREQUENCY (MHz)
AMPLITUDE
(dB
μ
V/m)
160
140
120
100
80
60
10
15
20
25
30
35
40
TEST LIMIT
MAX9877 OUTPUT
TEST LIMIT
5
30
180
200
240
260
280
300
220
FREQUENCY (MHz)
AMPLITUDE
(dB
μ
V/m)
600
550
500
450
400
350
15
20
25
35
40
10
300
650
700
800
850
900
1000
950
750
Figure 4. EMI with 152mm of Speaker Cable
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