AD8321 Datasheet PDF - Analog Devices
| Part Number | AD8321 | |
| Description | Gain Programmable CATV Line Driver | |
| Manufacturers | Analog Devices | |
| Logo |  |
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a
FEATURES
Linear in dB Gain Response Over >53 dB Range
Drives Low Distortion >11 dBm Signal into 75 � Load:
–53 dBc SFDR at 42 MHz
Very Low Output Noise Level
Maintains Constant 75 � Output Impedance
Power-Up and Power-Down Condition
No Line Transformer Required
Upper Bandwidth: 235 MHz (Min Gain)
9 V Single Supply Operation
Power-Down Functionality
Supports SPI Interface
Low Cost
APPLICATIONS
Gain Programmable Line Driver
HFC High Speed Data Modems
Interactive CATV Set-Top Boxes
CATV Plant Test Equipment
General Purpose IF Variable Gain Block
Gain Programmable
CATV Line Driver
AD8321
FUNCTIONAL BLOCK DIAGRAM
VCC
GND
VIN+
VIN–
AD8321
INV ATTENUATOR CORE
PWR
AMP
REVERSE
AMP
VOUT
DATADASTHAIFLTARTECGHISTER
DATA SHIFT REGISTER
POWER-
DOWN/
SWITCH
INTER
PD
DATEN CLK
SDATA
DESCRIPTION
The AD8321 is a low cost digitally controlled variable gain
amplifier optimized for coaxial line driving applications such as
cable modems that are designed to the DOCSIS* (upstream)
standard. An 8-bit serial word determines the desired output gain
over a 53.4 dB range, resulting in gain changes of 0.75 dB/LSB.
The AD8321 comprises a digitally controlled variable attenuator
of 0 dB to –53.4 dB, which is preceded by a low noise, fixed
gain buffer and followed by a low distortion high power ampli
fier. The AD8321 accepts a differential or single-ended input
signal. The output is specified for driving a 75 W load, such as
coaxial cable, although the AD8321 is capable of driving other
loads. Performance of –53 dBc is achieved with an output level
up to 11 dBm at 42 MHz bandwidth using a 9 V supply.
A key performance and cost advantage of the AD8321 results
from the ability to maintain a constant 75 W output impedance
during power-up and power-down conditions. This eliminates
the need for external 75 W termination, resulting in twice the
effective output voltage when compared to a standard opera
tional amplifier, thus eliminating the need for a transformer.
*Data-Over-Cable Service Interface Specifications
The AD8321 is packaged in a low cost 20-lead SOIC, operates
from a single +9 V supply, and has an operational temperature
range of –40∞C to +85∞C.
–40
fO = 42MHz
VIN = 137mV p-p
(PIN = –15dBm)
–50 (POUT = 11dBm @
MAX GAIN)
–60
HD3
–70
HD2
–80
–90
0
8 16 24 32 40 48 56 64 72
GAIN CONTROL – Decimal
Figure 1. Harmonic Distortion vs. Gain Control
REV. A
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/461-3113 © 2005 Analog Devices, Inc. All rights reserved.
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0.6
0.3
0
–0.3
f = 10MHz
f = 42MHz
–0.6
–0.9
f = 65MHz
–1.2 0
8 16 24 32 40 48 56 64 72
GAIN CONTROL – Decimal
Figure 4. Gain Error vs. Gain Control
Typical Performance Characteristics–AD8321
30
20 71D
10
0 46D
–10
23D
–20
–30
00D
–40
0.1
1 10 100
FREQUENCY – MHz
Figure 5. AC Response
1000
70
f = 10MHz
PD =1
60
50
40
30
20
10
0 8 16 24 32 40 48 56 64 72
GAIN CONTROL – Decimal
Figure 6. Output Referred Noise vs.
Gain Control
70
60
MAX GAIN
(71D)
50
PD = 1
40
30
MIN GAIN
(00D)
20
10
1 10 100
FREQUENCY – MHz
Figure 7. Output Referred Noise vs.
Frequency
–30
fO = 65MHz
VIN = 0.137V p-p
–40 (PIN = –15dBm)
(POUT = 11dBm @
MAX GAIN)
–50
HD3
–60
HD2
–70
–80 0
8 16 24 32 40 48 56 64 72
GAIN CONTROL – Decimal
Figure 8. Harmonic Distortion vs.
Gain Control
–47
PIN = –14dBm
(POUT = 12dBm @
MAX GAIN)
–50
PIN = –13dBm
(POUT = 13dBm @
MAX GAIN)
–53
PIN = –15dBm
(POUT = 11dBm @
MAX GAIN)
–56
–59
5
PIN = –17dBm
(POUT = 9dBm @
MAX GAIN)
15 25 35 45 55 65
FUNDAMENTAL FREQUENCY – MHz
Figure 9. Second Order Harmonic
Distortion vs. Frequency for Various
Input Levels
–47
PIN = –13dBm
(POUT = 13dBm @
MAX GAIN)
–50
PIN = –14dBm
(POUT = 12dBm @
MAX GAIN)
–53
–56
–59
5
PIN = –15dBm
(POUT = 11dBm @
MAX GAIN)
PIN = –17dBm
(POUT = 9dBm @
MAX GAIN)
15 25 35 45 55 65
FUNDAMENTAL FREQUENCY – MHz
Figure 10. Third Order Harmonic
Distortion vs. Frequency for Various
Input Levels
20
POUT = 11dBm
MAX GAIN
0
–20
–40
–60
–80
41.0
41.4 41.8 42.2 42.6
FREQUENCY – MHz
43.0
Figure 11. Two-Tone Intermodula-
tion Distortion
30
29
POUT = 11dBm
MAX GAIN
28
27
26
25
24
23
22
5
15 25 35 45 55
FREQUENCY – MHz
65
Figure 12. Third Order Intercept vs.
Frequency
REV. A
–5–
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Part DetailsOn this page, you can learn information such as the schematic, equivalent, pinout, replacement, circuit, and manual for AD8321 electronic component. |
| Information | Total 20 Pages | |
| Link URL | [ Copy URL to Clipboard ] | |
| Download | [ AD8321.PDF Datasheet ] | |
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