数据搜索系统,热门电子元器件搜索
  Chinese  ▼
ALLDATASHEETCN.COM

X  

LM1972N 数据表(PDF) 8 Page - National Semiconductor (TI)

[Old version datasheet] Texas Instruments acquired National semiconductor.
部件名 LM1972N
功能描述  Pot 2-Channel 78dB Audio Attenuator with Mute
Download  11 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
制造商  NSC [National Semiconductor (TI)]
网页  http://www.national.com
标志 NSC - National Semiconductor (TI)

LM1972N 数据表(HTML) 8 Page - National Semiconductor (TI)

Back Button LM1972N Datasheet HTML 3Page - National Semiconductor (TI) LM1972N Datasheet HTML 4Page - National Semiconductor (TI) LM1972N Datasheet HTML 5Page - National Semiconductor (TI) LM1972N Datasheet HTML 6Page - National Semiconductor (TI) LM1972N Datasheet HTML 7Page - National Semiconductor (TI) LM1972N Datasheet HTML 8Page - National Semiconductor (TI) LM1972N Datasheet HTML 9Page - National Semiconductor (TI) LM1972N Datasheet HTML 10Page - National Semiconductor (TI) LM1972N Datasheet HTML 11Page - National Semiconductor (TI)  
Zoom Inzoom in Zoom Outzoom out
 8 / 11 page
background image
Application Information (Continued)
DAISY-CHAIN CAPABILITY
Since the µPot’s digital interface is essentially a shift register,
multiple µPots can be programmed utilizing the same data
and load/shift lines. As shown in
Figure 11, for an n-µPot
daisy-chain, there are 16n bits to be shifted and loaded for
the chain. The data loading sequence is the same for
n-µPots as it is for one µPot. First the LOAD/SHIFT line goes
low, then the data is clocked in sequentially while the preced-
ing data in each µPot is shifted out the DATA-OUT pin to the
next µPot in the chain or to ground if it is the last µPot in the
chain. Then the LOAD/SHIFT line goes high; latching the
data into each of their corresponding µPots. The data is then
decoded according to the address (channel selection) and
the appropriate tap switch controlling the attenuation level is
selected.
CROSSTALK MEASUREMENTS
The crosstalk of a µPot as shown in the Typical Perfor-
mance Characteristics section was obtained by placing a
signal on one channel and measuring the level at the output
of another channel of the same frequency. It is important to
be sure that the signal level being measured is of the same
frequency such that a true indication of crosstalk may be ob-
tained. Also, to ensure an accurate measurement, the mea-
sured channel’s input should be AC grounded througha1µF
capacitor.
CLICKS AND POPS
So, why is that output buffer needed anyway? There are
three answers to this question, all of which are important
from a system point of view.
The first reason to utilize a buffer/amplifier at the output of a
µPot is to ensure that there are no audible clicks or pops due
to attenuation step changes in the device. If an on-board bi-
polar op amp had been used for the output stage, its require-
ment of a finite amount of DC bias current for operation
would cause a DC voltage “pop” when the output impedance
of the µPot changes. Again, this phenomenon is due to the
fact that the output impedance of the µPot is changing with
step changes and a bipolar amplifier requires a finite amount
of DC bias current for its operation. As the impedance
changes, so does the DC bias current and thus there is a DC
voltage “pop”.
Secondly, the µPot has no drive capability, so any desired
gain
needs
to
be
accomplished
through
a
buffer/
non-inverting amplifer.
Third, the output of a µPot needs to see a high impedance to
prevent loading and subsequent linearity errors from ocur-
ring. A JFET input buffer provides a high input impedance to
the output of the µPot so that this does not occur.
Clicks and pops can be avoided by using a JFET input
buffer/amplifier such as an LF412ACN. The LF412 has a
high input impedance and exhibits both a low noise floor and
low THD+N throughout the audio spectrum which maintains
signal integrity and linearity for the system. The performance
of the system solution is entirely dependent upon the quality
and performance of the JFET input buffer/amplifier.
LOGARITHMIC GAIN AMPUFIER
The µPot is capable of being used in the feedback loop of an
amplifier, however, as stated previously, the output of the
µPot needs to see a high impedance in order to maintain its
high performance and linearity. Again, loading the output will
change the values of attenuation for the device. As shown in
Figure 10, a µPot used in the feedback loop creates a loga-
rithmic gain amplifier. In this configuration the attenuation
levels from
Table 1, now become gain levels with the largest
possible gain value being 78dB. For most applications 78dB
of gain will cause signal clipping to occur, however, because
of the µPot’s versatility the gain can be controlled through
programming such that the clipping level of the system is
never obtained. An important point to remember is that when
in mute mode the input is disconnected from the output. In
this configuration this will place the amplifier in its open loop
gain state, thus resulting in severe comparator action. Care
should be taken with the programming and design of this
type of circuit. To provide the best performance, a JFET input
amplifier should be used.
DS011978-11
FIGURE 9. µPot System Architecture
www.national.com
8


类似零件编号 - LM1972N

制造商部件名数据表功能描述
logo
Texas Instruments
LM1972 TI1-LM1972 Datasheet
1,016Kb / 21P
[Old version datasheet]   LM1972 關Pot 2-Channel 78dB Audio Attenuator with Mute
LM1972 TI1-LM1972 Datasheet
1Mb / 22P
[Old version datasheet]   2-Channel 78dB Audio Attenuator
LM1972M TI1-LM1972M Datasheet
1,016Kb / 21P
[Old version datasheet]   LM1972 關Pot 2-Channel 78dB Audio Attenuator with Mute
LM1972M TI1-LM1972M Datasheet
1Mb / 22P
[Old version datasheet]   2-Channel 78dB Audio Attenuator
LM1972M/NOPB TI1-LM1972M/NOPB Datasheet
1Mb / 22P
[Old version datasheet]   2-Channel 78dB Audio Attenuator
More results

类似说明 - LM1972N

制造商部件名数据表功能描述
logo
Texas Instruments
LM1972 TI1-LM1972_14 Datasheet
1,016Kb / 21P
[Old version datasheet]   LM1972 關Pot 2-Channel 78dB Audio Attenuator with Mute
LM1972 TI1-LM1972_16 Datasheet
1Mb / 22P
[Old version datasheet]   2-Channel 78dB Audio Attenuator
logo
National Semiconductor ...
LM1973 NSC-LM1973 Datasheet
305Kb / 11P
   關Pot??-Channel 76dB Audio Attenuator with Mute
logo
Texas Instruments
LM1973 TI1-LM1973_14 Datasheet
1,010Kb / 20P
[Old version datasheet]   LM1973 關Pot 3-Channel 76dB Audio Attenuator with Mute
logo
National Semiconductor ...
LM1971 NSC-LM1971 Datasheet
248Kb / 11P
   LM1971 Overture??Audio Attenuator Series Digitally Controlled 62 dB Audio Attenuator with/Mute
logo
Eutech Microelectronics...
EUA5202 EUTECH-EUA5202 Datasheet
680Kb / 23P
   2-W Stereo Audio Power Amplifier with Mute
logo
Unisonic Technologies
PA3202 UTC-PA3202_09 Datasheet
362Kb / 11P
   2-W STEREO AUDIO POWER AMPLIFIER WITH MUTE
PA3202 UTC-PA3202 Datasheet
311Kb / 11P
   2-W STEREO AUDIO POWER AMPLIFIER WITH MUTE
PA6021 UTC-PA6021_15 Datasheet
274Kb / 6P
   2-W STEREO AUDIO POWER AMPLIFIER WITH MUTE
PA0202 UTC-PA0202 Datasheet
230Kb / 11P
   2-W STEREO AUDIO POWER AMPLIFIER WITH MUTE
More results


Html Pages

1 2 3 4 5 6 7 8 9 10 11


数据表 下载

Go To PDF Page


链接网址




隐私政策
ALLDATASHEETCN.COM
ALLDATASHEET是否为您带来帮助?  [ DONATE ] 

关于 Alldatasheet   |   广告服务   |   联系我们   |   隐私政策   |   链接交换   |   制造商名单
All Rights Reserved©Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz
Family Site : ic2ic.com  |   icmetro.com