參數(shù)資料
型號(hào)： LM4931
廠商： National Semiconductor Corporation
英文描述： Audio Subsystem with Mono High Efficiency Loudspeaker and Stereo Headphone Amplifiers
中文描述： 與單聲道音頻子系統(tǒng)高效揚(yáng)聲器和立體聲耳機(jī)放大器
文件頁(yè)數(shù)： 45/47頁(yè)
文件大小： 1640K
代理商： LM4931
Application Information
(Continued)
PLL must also be configured to match the incoming fre-
quency and provide the correct output for all the parts of the
subsystem.
The first register,
PLL_M (05h)
, sets the PLL input divider.
Bits 4:0 of this register are used to set the divider from 4 to
31. It is also possible to bypass the divider (M =1) by setting
PLL_M to 0001b. Setting PLL_M to 0010b gives a divide by
2. Setting PLL_M to 0011b gives a default divider of 4 (as
does setting to 0100b). Values above that are identical to
their base 10 integer values. Bits 7:5 programs the modulus
bits of the PLL feedback divider.
The second PLL register,
PLL_N (06h)
, sets the PLL feed-
back divider. Bits 6:0 are used to set the PLL feedback
divider from divide by 4 to divide by 127. Values set from 0 to
3 are rounded to 4. This register also may be used to alter
the speed of the VCO. Setting bit 7 (FAST_VCO) tunes the
VCO operation for frequencies up to 100MHz. Normally it is
tuned for outputs around 50MHz.
The final PLL register,
PLL_P (07h)
, sets the PLL output
divider. Bits 3:0 set this from divide by 4 to divide by 15.
Inputs of 0 to 3 are rounded to 4. It is also recommended that
P = 4 to keep the VCO around its nominal operating fre-
quency (50MHz if PLL_N bit 7 is clear). The divider modulus
may be set by bits 5:4. Additionally, the dither level for the
PLL is controlled in this register in bits 7:6.
The
Audio Clock Requirements
table details how different
clock values may be generated for a given input clock.
PLL Loop Filter
The LM4931 demoboard features an onboard second and
third order PLL loop filter. Jumpers (S6-S9) configure the
demoboard to select between the second and third order
PLL loop filters. Reference values for the loop filters are
given in the
LM4931 Demo Board Bill of Materials
section.
For a more detailed discussion on how to optimize a second
and third order PLL loop filter, please refer to
Note 20
.
Note 20:
http://www.national.com/appinfo/wireless/files/
DeansBook_4_01.pdf.
ANALOG INPUTS AND OUTPUTS
The LM4931 features a high-efficiency class D mono BTL
output for connection to an 8
external speaker. This output
can provide up to 1.1W of power into an 8 ohms load with a
5V analog supply. A single-ended stereo headphone output
is also featured, providing up to 26mW of power per channel
into 32
with a 5V analog supply. The MIC Jack input (JP1)
provides for a low level analog input. Pin 3 provides the
power to the MIC and the positive input of the LM4931. Gain
for the MIC preamp is set in the
MIC_GAIN (02h)
register.
HIGH EFFICIENCY CLASS D AMPLIFIER FUNCTION
The class D mono output signals generated by the LM4931
consist of two, BTL connected, output signals that pulse
momentarily from near ground potential to VDD. The two
outputs can pulse independently with the exception that they
both may never pulse simultaneously as this would result in
zero volts across the BTL load. The minimum width of each
pulse is approximately 160ns. However, pulses on the same
output can occur sequentially, in which case they are con-
catenated and appear as a single wider pulse to achieve an
effective 100% duty cycle. This results in maximum audio
output power for a given supply voltage and load impedance.
The LM4931 can achieve much higher efficiencies than
class AB amplifiers while maintaining acceptable THD per-
formance. The short (160ns) drive pulses emitted at the
LM4931 outputs means that good efficiency can be obtained
with minimal load inductance. The typical transducer load on
an audio amplifier is quite reactive (inductive). For this rea-
son, the load can act as it’s own filter, so to speak. This
"filter-less" switching amplifier/transducer load combination
is much more attractive economically due to savings in
board space and external component cost by eliminating the
need for a filter.
CLASS D POWER DISSIPATION AND EFFICIENCY
In general terms, efficiency is considered to be the ratio of
useful work output divided by the total energy required to
produce it with the difference being the power dissipated,
typically, in the IC. The key here is “useful” work. For audio
systems, the energy delivered in the audible bands is con-
sidered useful including the distortion products of the input
signal.
Sub-sonic
(DC)
and
(
>
22kHz) are not useful. The difference between the power
flowing from the power supply and the audio band power
being transduced is dissipated in the LM4931 and in the
transducer load. The amount of power dissipation in the
LM4931 is very low. This is because the ON resistance of the
switches used to form the output waveforms is typically less
than 0.25
. This leaves only the transducer load as a po-
tential "sink" for the small excess of input power over audio
band output power. The LM4931 dissipates only a fraction of
the excess power requiring no additional PCB area or cop-
per plane to act as a heat sink.
super-sonic
components
DUAL MICROPHONE SUPPORT
The LM4931 can be configured to accept two separate
microphone inputs when used in conjunction with the
LMS4684. The LMS4684 is a dual SPDT analog switch that
will allow the MIC_P and MIC_N inputs of the LM4931 to
switch between a differential handset microphone and a
single-ended handsfree microphone. The MIC DETECT
block shown in Figure 16 can be implemented with a micro-
phone jack’s mechanical control pin to set the voltage at the
IN1 and IN2 pins of the LMS4684. The voltage applied at the
IN1 and IN2 pins sets the position of the switch. For a more
detailed discussion on the operation of the analog switch,
please refer to the LMS4684 datasheet.
L
www.national.com
45
相關(guān)PDF資料
PDF描述
LM4960 Piezoelectric Speaker Driver
LM4960SQ Piezoelectric Speaker Driver
LM4961 Ceramic Speaker Driver
LM4961LQ Ceramic Speaker Driver
LM4970 Audio Synchronized Color LED Driver
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LM4931_06 制造商:NSC 制造商全稱(chēng):National Semiconductor 功能描述:Audio Subsystem with Mono High Efficiency Loudsperker and Stereo Headphone Amplifiers
LM4931ITL/NOPB 功能描述:音頻放大器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類(lèi)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
LM4931ITLBD 功能描述:BOARD EVALUATION LM4931ITL RoHS:否 類(lèi)別:編程器，開(kāi)發(fā)系統(tǒng) >> 評(píng)估板 - 音頻放大器 系列:Boomer® 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:1 系列:-
LM49321 制造商:NSC 制造商全稱(chēng):National Semiconductor 功能描述:Audio Sub-System with Stereo DAC, Mono Class AB Loudspeaker Amplifier, OCL/SE Stereo Headphone Output and RF Suppression
LM49321RL 制造商:NSC 制造商全稱(chēng):National Semiconductor 功能描述:Audio Sub-System with Stereo DAC, Mono Class AB Loudspeaker Amplifier, OCL/SE Stereo Headphone Output and RF Suppression
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。

采購(gòu)需求

(若只采購(gòu)一條型號(hào)，填寫(xiě)一行即可)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

*型號(hào) *數(shù)量 廠商 批號(hào) 封裝
添加更多采購(gòu)

我的聯(lián)系方式

*
*
*