- 您现在的位置：买卖IC网 > PDF目录373943 > AD8327ARU (ANALOG DEVICES INC) 5 V CATV Line Driver Coarse Step Output Power Control PDF资料下载
参数资料
| 型号： | AD8327ARU |
| 厂商： | ANALOG DEVICES INC |
| 元件分类： | 通用总线功能 |
| 英文描述： | 5 V CATV Line Driver Coarse Step Output Power Control |
| 中文描述： | LINE DRIVER, PDSO20 |
| 封装： | TSSOP-20 |
| 文件页数： | 8/20页 |
| 文件大小： | 307K |
| 代理商： | AD8327ARU |
REV. 0
AD8327
–8–
APPLICATIONS
General Application
The AD8327 is primarily intended for use as the upstream power
amplifier (PA), also known as a line driver, in DOCSIS (Data
Over Cable Service Interface Specification) certified cable
modems and CATV set-top boxes. The upstream signal is either
a QPSK or QAM signal generated by a DSP, a dedicated QPSK/
QAM modulator, or a DAC.
In all cases the signal must be low-pass filtered before being
applied to the PA in order to filter out-of-band noise and higher
order harmonics from the amplified signal. Due to the varying
distances between the cable modem and the headend, the
upstream PA must be capable of varying the output power by
applying gain or attenuation. The varying output power of the
AD8327 ensures that the signal from the cable modem will have
the proper level once it arrives at the headend. The upstream
signal path commonly includes a diplexer and cable splitters.
The AD8327 has been designed to overcome losses associated
with these passive components in the upstream cable path.
Circuit Description
The AD8327 is composed of three analog functions in the power-
up or forward mode. The input amplifier (preamp) can be used
single-ended or differentially. If the input is used in the differen-
tial configuration, it is imperative that the input signals be 180
degrees out of phase and of equal amplitude. The preamp stage
drives a DAC, which provides the AD8327’s attenuation (eight
bits or 48.16 dB). The signals in the preamp and DAC gain
blocks are differential to improve the PSRR and linearity.
A differential current is fed from the DAC into the output stage,
which amplifies these currents to the appropriate levels necessary to
drive a 75
load. The output stage maintains 75
output
impedance, eliminating the need for external matching resistors.
SPI Programming and Gain Adjustment
The AD8327 is controlled through a serial peripheral interface
(SPI) of three digital data lines: CLK, DATEN, and SDATA.
Changing the gain requires eight bits of data to be streamed into
the SDATA port. The sequence of loading the SDATA register
begins on the falling edge of the DATEN pin, which activates
the CLK line. With the CLK line activated, data on the SDATA
line is clocked into the serial shift register, Most Significant Bit
(MSB) first, on the rising edge of the CLK pulses. The 8-bit
data word is latched into the attenuator core on the rising edge
of the DATEN line. This provides control over the changes in
the output signal level. The serial interface timing for the AD8327
is shown in Figures 2 and 3. The programmable gain range of
the AD8327 is –18.16 dB to +30 dB with steps of 6.02 dB per
major carry. This provides a total gain range of 48.16 dB.
The AD8327 was characterized with a TOKO transformer
(TOKO#617DB-A0070) on the input, and the stated gain
values account for the losses due to the transformer. Table I
shows the possible gain states.
Input Bias, Impedance, and Termination
The V
IN+
and V
IN–
inputs have a dc bias level of V
CC
/2, therefore
the input signal should be ac-coupled using 0.1
μ
F capacitors as
seen in the typical application circuit (see Figure 4). The differ-
ential input impedance of the AD8327 is approximately 1.6 k
,
while the single-ended input impedance is 800
.
Table I. Gain States
Decimal Code
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Gain
0
1
2
4
8
16
32
64
128
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
–18.16
–12.14
–6.12
–0.10
5.92
11.94
17.96
23.98
30
相关PDF资料 |
PDF描述 |
|---|---|
| AD8332ARU-REEL | Ultralow Noise VGAs with Preamplifier and Programmable RIN |
| AD8332ARU-REEL7 | Ultralow Noise VGAs with Preamplifier and Programmable RIN |
| AD8331 | Ultralow Noise VGAs with Preamplifier and Programmable RIN |
| AD8331-EVAL | Ultralow Noise VGAs with Preamplifier and Programmable RIN |
| AD8331ARQ | Ultralow Noise VGAs with Preamplifier and Programmable RIN |
相关代理商/技术参数 |
参数描述 |
|---|---|
| AD8327ARU-REEL | 功能描述:IC LN DVR CATV COARS-STP 20TSSOP RoHS:否 类别:集成电路 (IC) >> 线性 - 视频处理 系列:- 产品变化通告:Product Discontinuation 07/Mar/2011 标准包装:3,000 系列:OMNITUNE™ 类型:调谐器 应用:移动电话，手机，视频显示器 安装类型:表面贴装 封装/外壳:65-WFBGA 供应商设备封装:PG-WFSGA-65 包装:带卷 (TR) 其它名称:SP000365064 |
| AD8327ARUZ | 制造商:Analog Devices 功能描述:SP Amp Line Driver Amp Single 5.25V 20-Pin TSSOP Tube 制造商:Rochester Electronics LLC 功能描述:TSSOP COARSE STEP CATV LINE DRIVER - Bulk |
| AD8327ARUZ-REEL | 制造商:Analog Devices 功能描述:SP Amp Line Driver Amp Single 5.25V 20-Pin TSSOP T/R |
| AD8327-EVAL | 制造商:Analog Devices 功能描述:Evaluation Kit For 5 V CATV Line Driver Coarse Step Output Power Control |
| AD8328 | 制造商:AD 制造商全称:Analog Devices 功能描述:5 V Upstream Cable Line Driver |
发布紧急采购，3分钟左右您将得到回复。