AD8320 Analog Devices, AD8320 Datasheet

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AD8320

Manufacturer Part Number
AD8320
Description
Manufacturer
Analog Devices
Datasheet

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a
DESCRIPTION
The AD8320 is a digitally controlled variable gain amplifier
optimized for coaxial line driving applications. An 8-bit serial
word determines the desired output gain over a 36 dB range
(256 gain levels). The AD8320 provides linear gain response.
The AD8320 is made up of a digitally controlled variable at-
tenuator of 0 dB to –36 dB, which is preceded by a low noise,
fixed gain buffer and followed by a low distortion high power
amplifier. The AD8320 has a 220
cepts a single-ended input signal with a specified analog input
level of up to 0.310 V p-p. The output is specified for driving a
75
pable of driving other loads. Distortion performance of –57 dBc
is achieved with an output level up to 12 dBm (3.1 V p-p) at
42 MHz, while –46 dBc distortion is achieved with an output
level up to 18 dBm (6.2 V p-p).
A key performance and cost advantage of the AD8320 results
from the ability to maintain a constant 75
during power-up and power-down conditions. This eliminates
the need for external 75
the effective output voltage when compared to a standard opera-
tional amplifier. Additionally, the on-chip 75
REV. 0
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
FEATURES
8-Bit Serial Gain Control
36 dB Gain Range
Upper Bandwidth: 150 MHz
22 dBm 1 dB Compression Point (75
Drives Low Distortion Signals into 75
Single Supply Operation from 5 V to 12 V
Maintains 75
Supports SPI Input Control Standard
APPLICATIONS
Coaxial Cable Driver
Interfaces with AD9853 I
High Performance Digitally Controlled Variable Gain
V/V/LSB Linear Gain Response
–57 dBc SFDR at 42 MHz and 12 dBm Out
–46 dBc SFDR at 42 MHz and 18 dBm Out
Power-Up and Power-Down Condition
HFC Cable Telephony Systems
HFC High Speed Data Modems
Interactive Set-Top Boxes
PC Plug-In Modems
Block
load, such as coaxial cable, although the AD8320 is ca-
0.20 dB Gain Accuracy
Output Impedance
back-termination, resulting in twice
2
C Controlled Digital Modulator
input impedance and ac-
output impedance
)
Load:
termination
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
Fax: 781/326-8703
results in low glitch output during power-down and power-up
transitions, eliminating the need for an external switch.
The AD8320 is packaged in a 20-lead SOIC and operates from
a single +5 V through +12 V supply and has an operational
temperature range of –40 C to +85 C.
VREF
VIN
Figure 1. Worst Harmonic Distortion vs. Frequency for
Various Output Levels at V
DATEN CLK
50
60
70
80
20
30
40
1
REFERENCE
INV.
BUF.
FUNCTIONAL BLOCK DIAGRAM
Variable Gain Line Driver
P
O
Serial Digital Controlled
= 8dBm
VCC
World Wide Web Site: http://www.analog.com
DATA SHIFT REGISTER
ATTENUATOR CORE
GND
AD8320
DATA LATCH
FREQUENCY – MHz
CC
10
= 12 V
P
O
© Analog Devices, Inc., 1998
P
= 4dBm
O
= 12dBm
P
SDATA
O
AD8320
= 18dBm
POWER-
SWITCH
DOWN/
INTER.
PWR AMP
REVERSE
AMP
100
VOUT
PD

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AD8320 Summary of contents

Page 1

... The AD8320 provides linear gain response. The AD8320 is made digitally controlled variable at- tenuator –36 dB, which is preceded by a low noise, fixed gain buffer and followed by a low distortion high power amplifier ...

Page 2

... AD8320–SPECIFICATIONS Parameter INPUT CHARACTERISTICS Full-Scale Input Voltage Input Resistance Input Capacitance GAIN CONTROL INTERFACE Gain Range Full Scale (Max) Gain Gain Offset (Min) Gain Gain Scaling Factor OUTPUT CHARACTERISTICS Bandwidth (–3 dB) Bandwidth Roll-Off Bandwidth Peaking Output Offset Voltage Output Offset Drift ...

Page 3

... GAIN TRANSFER (G1) T OFF T GS PEDESTAL Figure 2. Serial Interface Timing VALID DATA BIT MSB MSB CLK Figure 3. –3– AD8320 12 V; Full Temperature Range) Typ Max 5.0 0.8 20 –75 190 – ns MHz unless otherwise noted CLK Typ Max ...

Page 4

... ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD8320 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality ...

Page 5

... 256 0 64 128 192 GAIN CONTROL – Decimal Figure 10. Output Referred Noise vs. Gain Control at Various Temperatures REV. 0 Typical Performance Characteristics–AD8320 0 12V 10MHz 0.3 42MHz 0.6 65MHz 0.9 1 128 192 256 GAIN CONTROL – Decimal Figure 5 ...

Page 6

... AD8320 12V 65MHz 18dBm 42MHz 18dBm 42MHz 12dBm 65MHz 12dBm 128 192 256 GAIN CONTROL – Decimal Figure 13. Worst Harmonic Distor- tion vs. Gain Control 18dBm 12dBm 8dBm 4dBm ...

Page 7

... 22pF 100pF 150pF 100k 1M 10M 100M 1G FREQUENCY – Hz Figure 29. AC Response for Various Capacitive Loads –7– AD8320 12V 12dBm 18dBm 100 FREQUENCY – MHz Figure 24. Third Order Intercept vs. Frequency 30 V ...

Page 8

... AD8320 100mV V = 12V CC MAX GAIN p OUT 75nsec Figure 31. Power-Up/Power-Down Glitch 2.50V V = 12V 40MHz MAX GAIN V OUT 20nsec Figure 34. Overload Recovery 115 100k 1M 10M 100M 1G FREQUENCY – Hz Figure 37. Input Impedance vs. ...

Page 9

... GAIN – Code – Decimal Figure 40. Linear Gain vs. Gain Control The AD8320 is composed of three analog functions in the power forward mode (Figure 42). The input inverter/buffer amplifier provides single-ended to differential output conver- sion. The output signals are nominally 180 degrees out of phase and equal in amplitude with a differential voltage gain dB) ...

Page 10

... With a core attenuation range –36 dB and input gain, the overall AD8320 gain range –10 dB. In this mode, the single-ended output signal maintains a dc level of VCC/2. This dc output level provides for optimum large signal linearity and allows for dc coupling the output if neces- sary ...

Page 11

... Varying the Gain The gain of the AD8320 can be varied over a range of 36 dB, from – +26 dB, by varying the 8-bit gain setting word. VCC +5V TO +12V ...

Page 12

... AD8320. TTL or CMOS logic can be used to drive the two voltages driving the RF switch (V1 and V2). Before the AD8320 is turned back on again, the gain needs to be set to a known level. This can be done by holding the PD pin of the AD8320 low after POWER-DOWN has gone high. While PD is held low, the 8-bit serial data stream can be clocked into the AD8320 ...

Page 13

... In order that the same gain control word can be used for both the AD603 and the AD8320, the serial data stream is converted to the parallel format of the AD7801 DAC using a serial-to- parallel shift register. The rising edge of the enable pulse simul- taneously updates both amplifiers ...

Page 14

... Code LOAD where Code is the decimal equivalent of the 8-bit word. Evaluation Board A two layer evaluation board for the AD8320 is available (part number AD8320-EB). This board has been carefully laid out VCC 0.1 F TP2 VREF C12 ...

Page 15

... However, some laptop computers use the PRN port. Figure 56 shows the main screen of the control software. Using the slider, you can set any gain in the AD8320’ range. The gain is displayed on-screen in dB and V/V. The 8-bit gain setting byte is also displayed, in binary, hexadecimal and decimal. ...

Page 16

... AD8320 Figure 53. Evaluation Board Layout (Component Side) –16– REV. 0 ...

Page 17

... PIN CENTRONICS Figure 55. Interconnection Between AD8320EB and PC Printer Port REV. 0 Figure 54. Evaluation Board Layout (Solder Side SIGNAL D-SUB-25 DATEN DATA 5 CLK 6 DGND EVALUATION BOARD –17– AD8320 D-SUB 25 PIN (MALE) 1 DATEN 14 PD SDATA CLK GND 25 13 36-PIN CENTRONICS ...

Page 18

... AD8320 Figure 56. Screen Display of Windows-Based Control Software –18– REV. 0 ...

Page 19

... STANDOFF REV. 0 OUTLINE DIMENSIONS Dimensions shown in inches and (mm). (RP-20) 0.5118 (13.00) 0.4961 (12.60 0.1890 (4.80) 0.4193 (10.65) HEAT SINK 0.1791 (4.55) 0.3937 (10.00 PIN 1 0.3340 (8.61) 0.1043 (2.65) 0.3287 (8.35) 0.0926 (2.35 0.0500 0.0201 (0.51) SEATING 0.0500 (1.27) (1.27) 0.0130 (0.33) PLANE BSC 0.0057 (0.40) –19– AD8320 0.0295 (0.75 0.0098 (0.25) ...

Page 20

–20– ...

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