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| 型号： | MAX9770ETI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 4/22页 |
| 文件大小： | 0K |
| 描述： | IC AMP AUDIO 1.2W MONO D 28TQFN |
| 标准包装： | 2,500 |
| 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： | 1.2W x 1 @ 8 欧姆; 80mW x 2 @ 16 欧姆 |
| 电源电压： | 2.5 V ~ 5.5 V |
| 特点： | 消除爆音，输入多路复用器，静音，短路和热保护，关机 |
| 安装类型： | 表面贴装 |
| 供应商设备封装： | 28-TQFN-EP（5x5） |
| 封装/外壳： | 28-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
Operating Modes
The switching frequency of the charge pump is 1/2 the
switching frequency of the Class D amplifier, regard-
less of the operating mode. When SYNC is driven exter-
nally, the charge pump switches at 1/2 fSYNC. When
SYNC = VDD, the charge pump switches with a spread-
spectrum pattern.
Fixed-Frequency Modulation (FFM) Mode
The MAX9770 features two FFM modes. The FFM
modes are selected by setting SYNC = GND for a
1.1MHz switching frequency, and SYNC = unconnect-
ed for a 1.45MHz switching frequency. In FFM mode,
the frequency spectrum of the Class D output consists
of the fundamental switching frequency and its associ-
ated harmonics (see the Wideband Output Spectrum
(Speaker Mode) graph in the
Typical Operating
Characteristics). The MAX9770 allows the switching fre-
quency to be changed by +32% should the frequency
of one or more harmonics fall in a sensitive band. This
can be done during operation and does not affect
audio reproduction.
Spread-Spectrum Modulation (SSM) Mode
The MAX9770 features a unique spread-spectrum
mode that flattens the wideband spectral components,
improving EMI emissions radiated by the speaker and
cables by 5dB. Proprietary techniques ensure that the
cycle-to-cycle variation of the switching period does
not degrade audio reproduction or efficiency (see the
Typical Operating Characteristics). Select SSM mode
by setting SYNC = VDD. In SSM mode, the switching
frequency varies randomly by
±120kHz around the cen-
ter frequency (1.22MHz). The modulation scheme
remains the same, but the period of the sawtooth wave-
form changes from cycle-to-cycle (Figure 2). Instead of
a large amount of spectral energy present at multiples
of the switching frequency, the energy is now spread
over a bandwidth that increases with frequency. Above
a few MHz, the wideband spectrum looks like white
noise for EMI purposes (Figure 3).
External Clock Mode
The SYNC input allows the MAX9770 to be synchro-
nized to a system clock (allowing a fully synchronous
system), or allocating the spectral components of the
switching harmonics to insensitive frequency bands.
Applying an external clock of 800kHz to 2MHz to SYNC
synchronizes the switching frequency of both the Class
D and charge pump. The period of the SYNC clock can
be randomized, enabling the MAX9770 to be synchro-
nized to another spread-spectrum Class D amplifier
operating in SSM mode.
Filterless Modulation/Common-Mode Idle
The MAX9770 uses Maxim’s unique modulation scheme
that eliminates the LC filter required by traditional Class D
amplifiers, improving efficiency, reducing component
count, conserving board space and system cost.
Conventional Class D amplifiers output a 50% duty cycle
square wave when no signal is present. With no filter, the
square wave appears across the load as a DC voltage,
resulting in finite load current, increasing power con-
sumption. When no signal is present at the device input,
the outputs switch as shown in Figure 4. Because the
MAX9770 drives the speaker differentially, the two out-
puts cancel each other, resulting in no net idle mode volt-
age across the speaker, minimizing power consumption.
Efficiency
The efficiency of a Class D amplifier is attributed to the
region of operation of the output stage transistors. In a
Class D amplifier, the output transistors act as current-
steering switches and consume negligible additional
power. Any power loss associated with the Class D out-
put stage is mostly due to the I*R loss of the MOSFET
on-resistance, and quiescent current overhead.
The theoretical best efficiency of a linear amplifier is
78%; however, that efficiency is only exhibited at peak
output powers. Under normal operating levels (typical
music reproduction levels), efficiency falls below 30%,
whereas the MAX9770 still exhibits > 80% efficiencies
under the same conditions (Figure 5).
DirectDrive
Traditional single-supply headphone drivers have their
outputs biased about a nominal DC voltage (typically
half the supply) for maximum dynamic range. Large
coupling capacitors are needed to block this DC bias
from the headphone. Without these capacitors, a signif-
icant amount of DC current flows to the headphone,
resulting in unnecessary power dissipation and possi-
ble damage to both headphone and headphone driver.
MAX9770
1.2W, Low-EMI, Filterless, Mono Class D Amplifier
with Stereo DirectDrive Headphone Amplifiers
12
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相关代理商/技术参数 |
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| MAX9770EUI | 制造商:Rochester Electronics LLC 功能描述: |
| MAX9770EUI+ | 功能描述:音频放大器 1.2W Low-EMI Class D Amplifier RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel |
| MAX9770EUI+T | 功能描述:音频放大器 1.2W Low-EMI Class D Amplifier RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel |
| MAX9770EVKIT | 功能描述:音频 IC 开发工具 Programmers, Development Systems RoHS:否 制造商:Texas Instruments 产品:Evaluation Kits 类型:Audio Amplifiers 工具用于评估:TAS5614L 工作电源电压:12 V to 38 V |
| MAX9772EBA | 制造商:Maxim Integrated Products 功能描述:1.2WLOW-EMIFILTERLESSMONO CLASS - Rail/Tube |
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