Using the transfer functions and the equation for fc, the follo" />
參數(shù)資料
型號(hào)： MAX9742ETX+T
廠商： Maxim Integrated Products
文件頁數(shù)： 14/36頁
文件大?。?/td> 0K
描述： IC AMP AUDIO PWR 20.5W D 36TQFN
標(biāo)準(zhǔn)包裝： 2,500
類型： D 類
輸出類型： 2 通道（立體聲）
在某負(fù)載時(shí)最大輸出功率 x 通道數(shù)量： 20.5W x 2 @ 8 歐姆
電源電壓： 20 V ~ 40 V，±10 V ~ 20 V
特點(diǎn)： 消除爆音，差分輸入，靜音，短路和熱保護(hù)，關(guān)機(jī)
安裝類型： 表面貼裝
供應(yīng)商設(shè)備封裝： 36-TQFN 裸露焊盤（6x6）
封裝/外殼： 36-WFQFN 裸露焊盤
包裝： 帶卷 (TR)
Using the transfer functions and the equation for fc, the
following expressions for LF and CF can be derived:
Since the frequency response of the output filter is
dependent on the speaker resistance, it is best to opti-
mize the LC filter for a particular load resistance. To
calculate the component values of the LC filter for a
given speaker load resistance, first select an appropri-
ate cutoff frequency for the filter. The cutoff frequency
should be high enough so that upper audio frequency
band attenuation is kept to a minimum while providing
sufficient attenuation at the switching frequency (fSW) of
the MAX9742. Once the cutoff frequency is determined,
calculate CF using the DC resistance of the speaker
(RSPKR) and a damping ratio (ζ) equal to 0.707. Finally,
calculate LF using the resulting CF value.
When selecting CF, use capacitors with DC voltage rat-
ings greater than VDD.
When selecting LF, it is important to take into account
the DC resistance, current capabilities, and upper fre-
quency limitations of the inductor. Choosing an induc-
tor with minimum DC resistance minimizes I2R losses
due to the filter inductor and therefore preserves power
efficiency. The inductor current rating should be
greater than the maximum peak output current to pre-
vent the inductor from going into saturation. Output
inductor saturation introduces nonlinearities into the
output signal and therefore increases distortion. The
upper frequency limit of the inductor should also be
taken into account. The load connected to the output of
the half-bridge (LC filter and speaker) should remain
inductive at the switching frequency of the MAX9742. If
not, a significant amount of high-frequency energy is
dissipated in the resistive load, therefore, increasing
the supply current to excessive levels. To prevent this
from occurring, select an output inductor whose self-
resonant frequency is substantially higher than the
switching frequency of the MAX9742.
To minimize possible EMI radiation, place the LC filter
near the MAX9742 on the PCB.
Table 2 provides some suggested inductor manufac-
turers.
BTL LC Output Filter Design
When using the BTL configuration, optimize the output fil-
ter for fully differential operation (see Figure 9 and Table
3). Follow the design criteria provided for the single-
ended filter except use half the value of the BTL resis-
tance for the output filter calculations. This is because
each half-bridge output sees half of the BTL resistance.
For example, with a BTL resistance of 8 the ideal filter
component values are CF = 0.7F and LF = 22.5H for a
maximally flat differential filter response with an approxi-
mate cutoff frequency of 40kHz. Rounding to the nearest
standard component values yields CF = 0.68F and LF =
22H. Also connect ground-terminated Zobel networks
on each side of the speaker load (see the
Zobel Network
section). Ground terminating the Zobel networks pre-
vents excessive peaking in the common-mode frequen-
cy response of the filter.
C
1
4
f
R
L
1
4
f
C
F
C
SPKR
F
2
C
2
F
=
××
×
=
××
×
()
πζ
π
F
H
MAX9742
Single-/Dual-Supply, Stereo 16W,
Class D Amplifier with Differential Inputs
______________________________________________________________________________________
21
Table 1. Recommended LC Filter
Component Values for Various Speaker
Loads (fC = 40kHz)
DC RESISTANCE OF SPEAKER (
)LF (H)
CF (F)
4
22
0.68
6
33
0.47
8
47
0.33
Table 2. Suggested Inductor Manufacturers
MODEL
MANUFACTURER
DIMENSIONS
WEBSITE
DO3340P
Coilcraft
12.95mm x 9.4mm x 11.43mm
www.coilcraft.com
CDRH127
Sumida
12.3mm x 12.3mm x 8mm
www.sumida.com
11RHBP
Toko
11mm x 11mm x 13.75mm
www.tokoam.com
SLF12575
TDK
12.5mm x 12.5mm x 7.5mm
www.component.tdk.com
LF
CF
OUT_
RSPKR
SINGLE-ENDED OUTPUT FILTER
NOTE: AN OUTPUT-COUPLING CAPACITOR (COUT) IS NEEDED FOR SINGLE-SUPPLY,
SINGLE-ENDED OUTPUT CONFIGURATION.
Figure 8. Single-Ended LC Output Filter
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX9742EVKIT+ 功能描述:音頻放大器 Evaluation Kit for the MAX9742 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel
MAX9744ETH+ 功能描述:音頻放大器 Stereo 20W Class D Amplifier RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel
MAX9744ETH+T 功能描述:音頻放大器 Stereo 20W Class D Amplifier RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel
MAX9744EVCMAXQU+ 功能描述:音頻放大器 Evaluation Kit/Evaluation System for the MAX9744 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel
MAX9744EVKIT+ 功能描述:音頻放大器 Evaluation Kit/Evaluation System for the MAX9744 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel
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