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參數(shù)資料
| 型號： | LM1972MNOPB |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 消費(fèi)家電 |
| 英文描述： | SPECIALTY CONSUMER CIRCUIT, PDSO20 |
| 封裝： | SOP-20 |
| 文件頁數(shù)： | 10/12頁 |
| 文件大小： | 406K |
| 代理商： | LM1972MNOPB |
MUTE FUNCTION
One major feature of a
μPot is its ability to mute the input
signal to an attenuation level of 104dB as shown in Figure 3.
This is accomplished internally by physically isolating the out-
put from the input while also grounding the output pin through
approximately 2 k
Ω.
The mute function is obtained during power-up of the device
or by sending any binary data of 01111111 and above (to
11111111) serially to the device. The device may be placed
into mute from a previous attenuation setting by sending any
of the above data. This allows the designer to place a mute
button onto his system which could cause a microcontroller
to send the appropriate data to a
μPot and thus mute any or
all channels. Since this function is achieved through software,
the designer has a great amount of flexibility in configuring the
system.
DC INPUTS
Although the
μPot was designed to be used as an attenuator
for signals within the audio spectrum, the device is capable of
tracking an input DC voltage. The device will track DC volt-
ages to a diode drop above each supply rail.
One point to remember about DC tracking is that with a buffer
at the output of the
μPot, the resolution of DC tracking will
depend upon the gain configuration of that output buffer and
its supply voltage. It should also be remembered that the out-
put buffer's supply voltage does not have to be the same as
the
μPot's supply voltage. This could allow for more resolution
when DC tracking.
SERIAL DATA FORMAT
The LM1972 uses a 3-wire serial communication format that
is easily controlled by a microcontroller. The timing for the 3-
wire set, comprised of DATA-IN, CLOCK, and LOAD/SHIFT
how the digital interface controls the tap switches which select
the appropriate attenuation level. As depicted in Figure 2, the
LOAD/SHIFT line is to go low at least 150 ns before the rising
edge of the first clock pulse and is to remain low throughout
the transmission of each set of 16 data bits. The serial data
is comprised of 8 bits for channel selection and 8 bits for at-
tenuation setting. For both address data and attenuation set-
ting data, the MSB is sent first and the 8 bits of address data
are to be sent before the 8 bits of attenuation data. Please
refer to Figure 7 to confirm the serial data format transfer pro-
cess.
TABLE 1. LM1972 Micropot Attenuator
Register Set Description
MSB:
LSB
Address Register (Byte 0)
0000 0000
Channel 1
0000 0001
Channel 2
0000 0010
Channel 3
Data Register (Byte 1)
Contents
Attenuation Level dB
0000 0000
0.0
0000 0001
0.5
0000 0010
1.0
0000 0011
1.5
: : : : :
: :
0001 1110
15.0
0001 1111
15.5
0010 0000
16.0
0010 0001
16.5
0010 0010
17.0
: : : : :
: :
0101 1110
47.0
0101 1111
47.5
0110 0000
48.0
0110 0001
49.0
0110 0010
50.0
: : : : :
: :
0111 1100
76.0
0111 1101
77.0
0111 1110
78.0
0111 1111
100.0 (Mute)
1000 0000
100.0 (Mute)
: : : : :
: :
1111 1110
100.0 (Mute)
1111 1111
100.0 (Mute)
1197810
FIGURE 7. Serial Data Format Transfer Process
μPot SYSTEM ARCHITECTURE
The
μPot's digital interface is essentially a shift register, where
serial data is shifted in, latched, and then decoded. As new
data is shifted into the DATA-IN pin, the previously latched
data is shifted out the DATA-OUT pin. Once the data is shifted
in, the LOAD/SHIFT line goes high, latching in the new data.
The data is then decoded and the appropriate switch is acti-
vated to set the desired attenuation level for the selected
channel. This process is continued each and every time an
attenuation change is made. Each channel is updated, only,
when that channel is selected for an attenuator change or the
system is powered down and then back up again. When the
μPot is powered up, each channel is placed into the muted
mode.
7
www.national.com
LM1972
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| LM1972MX | 功能描述:衰減器 -IC RoHS:否 制造商:Skyworks Solutions, Inc. 最大衰減:18 dB 容差: 阻抗: 功率額定值:30 dBm 安裝風(fēng)格:SMD/SMT 工作溫度范圍:- 40 C to + 85 C |
| LM1972MX/NOPB | 功能描述:有源衰減器 RoHS:否 制造商:TriQuint Semiconductor 通道數(shù)量: 最大頻率: 阻抗: 最大 VSWR: 位數(shù): 最大工作溫度: 最小工作溫度: |
| LM1972N | 功能描述:IC AUDIO ATTENUATOR 2CH 20-DIP RoHS:否 類別:集成電路 (IC) >> 線性 - 音頻處理 系列:- 其它有關(guān)文件:STA321 View All Specifications 標(biāo)準(zhǔn)包裝:1 系列:Sound Terminal™ 類型:音頻處理器 應(yīng)用:數(shù)字音頻 安裝類型:表面貼裝 封裝/外殼:64-LQFP 裸露焊盤 供應(yīng)商設(shè)備封裝:64-LQFP EP（10x10） 包裝:Digi-Reel® 其它名稱:497-11050-6 |
| LM1972N | 制造商:Texas Instruments 功能描述:AUDIO ATTENUATOR 78DB 1972 DIP20 |
| LM1972N/NOPB | 制造商:Texas Instruments 功能描述:Digital Attenuator 104dB Attenuation 20-Pin PDIP Rail |
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