參數(shù)資料
型號: MAX9705BETB+T
廠商: Maxim Integrated Products
文件頁數(shù): 4/18頁
文件大?。?/td> 0K
描述: IC AMP AUDIO PWR 2.3W D 10TDFN
產(chǎn)品培訓(xùn)模塊: Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
標(biāo)準(zhǔn)包裝: 1
類型: D 類
輸出類型: 1-通道(單聲道)
在某負(fù)載時最大輸出功率 x 通道數(shù)量: 2.3W x 1 @ 4 歐姆
電源電壓: 2.5 V ~ 5.5 V
特點(diǎn): 消除爆音,差分輸入,短路和熱保護(hù),關(guān)閉
安裝類型: 表面貼裝
供應(yīng)商設(shè)備封裝: 10-TDFN-EP(3x3)
封裝/外殼: 10-WFDFN 裸露焊盤
包裝: 標(biāo)準(zhǔn)包裝
產(chǎn)品目錄頁面: 1392 (CN2011-ZH PDF)
其它名稱: MAX9705BETB+TDKR
MAX9705
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
12
______________________________________________________________________________________
Click-and-Pop Suppression
The MAX9705 features comprehensive click-and-pop
suppression that eliminates audible transients on start-
up and shutdown. While in shutdown, the H-bridge is in
a high-impedance state. During startup or power-up,
the input amplifiers are muted and an internal loop sets
the modulator bias voltages to the correct levels, pre-
venting clicks and pops when the H-bridge is subse-
quently enabled. For 30ms following startup, a soft-start
function gradually unmutes the input amplifiers.
Applications Information
Filterless Operation
Traditional Class D amplifiers require an output filter to
recover the audio signal from the amplifier’s output. The
filters add cost, increase the solution size of the amplifi-
er, and can decrease efficiency and THD+N perfor-
mance. The traditional PWM scheme uses large
differential output swings (2 x VDD peak-to-peak) and
causes large ripple currents. Any parasitic resistance in
the filter components results in a loss of power, lower-
ing the efficiency.
The MAX9705 does not require an output filter. The
device relies on the inherent inductance of the speaker
coil and the natural filtering of both the speaker and the
human ear to recover the audio component of the
square-wave output. Eliminating the output filter results
in a smaller, less costly, more efficient solution.
Because the frequency of the MAX9705 output is well
beyond the bandwidth of most speakers, voice coil
movement due to the square-wave frequency is very
small. Although this movement is small, a speaker not
designed to handle the additional power can be dam-
aged. For optimum results, use a speaker with a series
inductance >10H. Typical 8
speakers exhibit series
inductances in the 20H to 100H range.
Power-Conversion Efficiency
Unlike a class AB amplifier, the output offset voltage of
a Class D amplifier does not noticeably increase quies-
cent-current draw when a load is applied. This is due to
the power conversion of the Class D amplifier. For exam-
ple, an 8mV DC offset across an 8
load results in 1mA
extra current consumption in a Class AB device. In the
Class D case, an 8mV offset into 8
equates to an addi-
tional power drain of 8W. Due to the high efficiency of
the Class D amplifier, this represents an additional quies-
cent-current draw of 8W/(VDD/100
η), which is on the
order of a few microamps.
Input Amplifier
Differential Input
The MAX9705 features a differential input structure,
making it compatible with many CODECs, and offering
improved noise immunity over a single-ended input
amplifier. In devices such as cellular phones, high-fre-
quency signals from the RF transmitter can be picked
up by the amplifier’s input traces. The signals appear at
the amplifier’s inputs as common-mode noise. A differ-
ential input amplifier amplifies the difference of the two
inputs; any signal common to both inputs is canceled.
Single-Ended Input
The MAX9705 can be configured as a single-ended
input amplifier by capacitively coupling either input to
GND and driving the other input (Figure 5).
Figure 3. MAX9705 Outputs with No Input Signal
VIN = 0V
OUT-
OUT+
VOUT+ - VOUT- = 0V
Figure 4. MAX9705 Efficiency vs. Class AB Efficiency
EFFICIENCY vs. OUTPUT POWER
OUTPUT POWER (W)
EFFICIENCY
(%)
0.8
0.6
0.4
0.2
10
20
30
40
50
60
70
80
90
100
0
01.0
VDD = 3.3V
fIN = 1kHz
RL = 8
CLASS AB
MAX9705
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