AD8320ARP [ADI]

Serial Digital Controlled Variable Gain Line Driver; 串行数字控制可变增益线路驱动器
AD8320ARP
型号: AD8320ARP
厂家: ADI    ADI
描述:

Serial Digital Controlled Variable Gain Line Driver
串行数字控制可变增益线路驱动器

驱动器 电信集成电路 电信电路 光电二极管
文件: 总20页 (文件大小:584K)
中文:  中文翻译
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Serial Digital Controlled  
Variable Gain Line Driver  
a
AD8320  
FEATURES  
8-Bit Serial Gain Control  
FUNCTIO NAL BLO CK D IAGRAM  
V/ V/ LSB Linear Gain Response  
36 dB Gain Range  
؎0.20 dB Gain Accuracy  
VCC  
GND  
PWR AMP  
AD8320  
REFERENCE  
Upper Bandw idth: 150 MHz  
VOUT  
22 dBm 1 dB Com pression Point (75 )  
Drives Low Distortion Signals into 75 Load:  
–57 dBc SFDR at 42 MHz and 12 dBm Out  
–46 dBc SFDR at 42 MHz and 18 dBm Out  
Single Supply Operation from 5 V to 12 V  
Maintains 75 Output Im pedance  
Pow er-Up and Pow er-Dow n Condition  
Supports SPI Input Control Standard  
VREF  
VIN  
REVERSE  
AMP  
INV.  
BUF.  
ATTENUATOR CORE  
DATA LATCH  
POWER-  
DOWN/  
SWITCH  
INTER.  
PD  
DATA SHIFT REGISTER  
APPLICATIONS  
Coaxial Cable Driver  
DATEN CLK  
SDATA  
HFC Cable Telephony System s  
HFC High Speed Data Modem s  
Interactive Set-Top Boxes  
PC Plug-In Modem s  
Interfaces w ith AD9853 I2C Controlled Digital Modulator  
High Perform ance Digitally Controlled Variable Gain  
Block  
D ESCRIP TIO N  
results in low glitch output during power-down and power-up  
transitions, eliminating the need for an external switch.  
T he 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). T he AD8320 provides linear gain response.  
T he 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.  
T he 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. T he AD8320 has a 220 input impedance and ac-  
cepts a single-ended input signal with a specified analog input  
level of up to 0.310 V p-p. T he output is specified for driving a  
75 load, such as coaxial cable, although the AD8320 is ca-  
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).  
؊20  
؊30  
P
= 18dBm  
O
؊40  
؊50  
؊60  
P
= 12dBm  
O
P
= 8dBm  
O
A key performance and cost advantage of the AD8320 results  
from the ability to maintain a constant 75 output impedance  
during power-up and power-down conditions. T his eliminates  
the need for external 75 back-termination, resulting in twice  
the effective output voltage when compared to a standard opera-  
tional amplifier. Additionally, the on-chip 75 termination  
؊70  
؊80  
P
= 4dBm  
O
10  
FREQUENCY – MHz  
100  
1
Figure 1. Worst Harm onic Distortion vs. Frequency for  
Various Output Levels at VCC = 12 V  
REV. 0  
Inform ation furnished by Analog Devices is believed to be accurate and  
reliable. However, no responsibility is assum ed by Analog Devices for its  
use, nor for any infringem ents of patents or other rights of third parties  
which m ay result from its use. No license is granted by im plication or  
otherwise under any patent or patent rights of Analog Devices.  
One Technology Way, P.O. Box 9106, Norw ood, MA 02062-9106, U.S.A.  
Tel: 781/ 329-4700  
Fax: 781/ 326-8703  
World Wide Web Site: http:/ / w w w .analog.com  
© Analog Devices, Inc., 1998  
(@ V = 12 V, T = +25؇C, V = 0.310 V p-p, R = 75 , R = 75 unless  
CC  
A
IN  
L
S
otherwise noted)  
AD8320–SPECIFICATIONS  
P aram eter  
Conditions  
Min  
Typ  
Max  
Units  
INPUT CHARACT ERIST ICS  
Full-Scale Input Voltage  
Max Gain, POUT = 18 dBm, VCC = 12 V  
Max Gain, POUT = 12 dBm, VCC = 5 V  
0.310  
0.155  
220  
V p-p  
V p-p  
Input Resistance  
Input Capacitance  
2.0  
pF  
GAIN CONT ROL INT ERFACE  
Gain Range  
36  
dB  
Full Scale (Max) Gain  
Gain Offset (Min) Gain  
Gain Scaling Factor  
26 (20)  
–10.0 (0.316)  
0.077  
dB (V/V)  
dB (V/V)  
V/V/LSB  
OUT PUT CHARACT ERIST ICS  
Bandwidth (–3 dB)  
Bandwidth Roll-Off  
All Gain Codes  
F = 65 MHz  
F = 65 MHz  
150  
0.7  
0
MHz  
dB  
dB  
Bandwidth Peaking  
Output Offset Voltage  
Output Offset Drift  
Output Noise Spectral Density  
All Gain Codes  
±40  
±0.25  
73  
mV  
Full T emperature Range  
Max. Gain, Frequency = 10 MHz  
Min. Gain, Frequency = 10 MHz  
PD = 0, Frequency = 10 MHz  
VCC = 12 V  
VCC = 5 V  
Power Up and Power Down  
Max Gain, VIN = 500 mV p-p  
mV/°C  
nV/Hz  
nV/Hz  
nV/Hz  
dBm  
dBm  
53  
4.5  
22.5  
16  
75  
40  
1 dB Compression Point  
Output Impedance  
Overload Recovery  
65  
85  
ns  
OVERALL PERFORMANCE  
Worst Harmonic Distortion  
F = 42 MHz, POUT = 12 dBm, VCC = 12 V  
F = 42 MHz, POUT = 12 dBm, VCC = 5 V  
F = 42 MHz, POUT = 18 dBm, VCC = 12 V  
F = 65 MHz, POUT = 12 dBm, VCC = 12 V  
F = 65 MHz, POUT = 12 dBm, VCC = 5 V  
F = 65 MHz, POUT = 18 dBm, VCC = 12 V  
F = 42 MHz, POUT = 18 dBm, VCC = 12 V  
F = 42 MHz, POUT = 12 dBm, VCC = 5 V  
F = 65 MHz, POUT = 18 dBm, VCC = 12 V  
F = 65 MHz, POUT = 12 dBm, VCC = 5 V  
F = 10 MHz  
–57.0  
–43.0  
–46.0  
–57.0  
–42.5  
–43.0  
34  
–52.0  
–39.0  
–42.0  
–52.0  
–39.0  
–40.0  
dBc  
dBc  
dBc  
dBc  
dBc  
dBc  
dBm  
dBm  
dBm  
dBm  
dB  
3rd Order Intercept  
32  
32.5  
28.5  
±0.1  
±0.2  
Full-Scale (Max Gain) Accuracy  
Gain Offset (Min Gain) Accuracy  
Gain Accuracy  
F = 10 MHz  
F = 10 MHz, All Gain Codes  
dB  
dB  
–0.75 ±0.2  
0.75  
Gain Drift  
Full T emperature Range  
VCC = +5 V to 12 V  
±0.5  
35  
mdB/°C  
mdB/V  
Gain Variation w/Supply  
Output Settling to 1 mV  
Gain Change @ TDATEN = 1  
Input Change  
Min to Max Gain, VIN = 0.31 V p-p  
Max Gain, VIN = 0 V to 0.31 V p-p  
30  
25  
ns  
ns  
POWER CONT ROL  
Power-Down Settling T ime to 1 mV  
Power-Up Settling T ime to 1 mV  
Power-Down Pedestal Offset  
Spectral Output Leakage  
Max Gain, VIN = 0  
Max Gain, VIN = 0  
Max Gain, VIN = 0  
F (PD) = 400 Hz @ 15% Duty Cycle  
5 MHz F 65 MHz  
PD = 0  
45  
65  
±30  
–70  
ns  
ns  
mV  
dBm  
Maximum Reverse Power  
5
dBm  
POWER SUPPLY  
Specified Operating Range  
Quiescent Current  
Power Down  
Power Up, VCC = +12 V  
Power Down, VCC =+12 V  
+5  
80  
25  
97  
32  
+12  
85  
30  
105  
37  
V
PD = 1, VCC = +5 V  
PD = 0, VCC = +5 V  
PD = 1, VCC = +12 V  
PD = 0, VCC = +12 V  
mA  
mA  
mA  
mA  
–2–  
REV. 0  
AD8320  
LOGIC INPUTS (TTL/CMOS Logic) (DATEN, CLK, SDATA, 5 V V 12 V; Full Temperature Range)  
CC  
P aram eter  
Min  
Typ  
Max  
Units  
Logic “1” Voltage  
Logic “0” Voltage  
Logic “1” Current (VINH = 5 V) CLK, SDAT A, DATEN  
Logic “0” Current (VINL = 0 V) CLK, SDAT A, DATEN  
Logic “1” Current (VINH = 5 V) PD  
Logic “0” Current (VINL = 0 V) PD  
2.1  
0
0
–450  
0
–320  
5.0  
0.8  
20  
–75  
190  
–70  
V
V
nA  
nA  
µA  
µA  
(Full Temperature Range, V Supply Range, T = T = 4 ns, FCLK = 8 MHz unless otherwise noted.)  
TIMING REQUIREMENTS  
P aram eter  
CC  
R
F
Min  
Typ  
Max  
Units  
Clock Pulse Width (TWH  
Clock Period (TC)  
Setup T ime SDAT A vs. Clock (TDS  
Setup T ime DATEN vs. Clock (TES  
Hold T ime SDAT A vs. Clock (TDH  
)
12.0  
32.0  
6.5  
17.0  
5.0  
ns  
ns  
ns  
ns  
ns  
ns  
ns  
)
)
)
)
Hold T ime DATEN vs. Clock (TEH  
Input Rise and Fall T imes, SDAT A, DATEN, Clock (TR, T F)  
3.0  
10  
T
DS  
VALID DATA WORD G1  
VALID DATA WORD G2  
SDATA  
CLK  
MSB. . . .LSB  
T
C
T
WH  
EH  
T
T
ES  
8 CLOCK CYCLES  
DATEN  
PD  
GAIN TRANSFER (G1)  
GAIN TRANSFER (G2)  
T
OFF  
T
GS  
T
ON  
ANALOG  
OUTPUT  
PEDESTAL  
SIGNAL AMPLITUDE (p-p)  
Figure 2. Serial Interface Tim ing  
VALID DATA BIT  
MSB-1  
MSB  
MSB-2  
T
T
DH  
DS  
CLK  
Figure 3.  
–3–  
REV. 0  
AD8320  
ABSO LUTE MAXIMUM RATINGS*  
Supply Voltage +VS  
P IN CO NFIGURATIO N  
Pins 7, 8, 9, 17, 20 . . . . . . . . . . . . . . . . . . . –0.8 V to +13 V  
Input Voltages  
Pins 19 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±3 V  
Pins 1, 2, 3, 6 . . . . . . . . . . . . . . . . . . . . . . . . –0.8 V to +5 V  
Internal Power Dissipation  
Small Outline (RP) . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 W  
Operating T emperature Range . . . . . . . . . . . –40°C to +85°C  
Storage T emperature Range . . . . . . . . . . . . –65°C to +150°C  
Lead T emperature, Soldering 60 seconds . . . . . . . . . . +300°C  
1
2
20 VCC  
SDATA  
CLK  
19  
18  
17  
16  
15  
14  
13  
12  
11  
VIN  
3
VREF  
VCC  
GND  
GND  
BYP  
GND  
GND  
GND  
DATEN  
GND  
4
5
VOCM  
AD8320  
TOP VIEW  
(Not to Scale)  
6
PD  
VCC  
VCC  
VCC  
VOUT  
7
8
*Stresses above those listed under Absolute Maximum Ratings may cause perma-  
nent damage to the device. T his is a stress rating only; functional operation of the  
device at these or any other conditions above those indicated in the operational  
section of this specification is not implied. Exposure to absolute maximum rating  
conditions for extended periods may affect device reliability.  
9
10  
O RD ERING GUID E  
P ackage D escription  
Model  
Tem perature Range  
P ackage O ption  
RP-20  
JA  
AD8320ARP  
AD8320-EB  
–40°C to +85°C  
20-Lead Thermally Enhanced Power SOIC*  
Evaluation Board  
53°C/W  
*Shipped in tubes (38 pieces/tube) and dry packed per J-ST D-020.  
CAUTIO N  
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. T herefore, proper ESD  
precautions are recommended to avoid performance degradation or loss of functionality.  
WARNING!  
ESD SENSITIVE DEVICE  
P IN FUNCTIO N D ESCRIP TIO NS  
P in  
Function  
D escription  
1
SDAT A  
Serial Data Input. T his digital input allows for an 8-bit serial (gain) word to be loaded into the internal  
register with the MSB (most significant bit) first.  
2
3
CLK  
Clock Input. T he clock port controls the serial attenuator data transfer rate to the 8-bit master-slave  
register. A Logic 0 to 1 transition latches the data bit and a 1 to 0 transfers the data bit to the slave.  
T his requires the input serial data word to be valid at or before this clock transition.  
DATEN  
Data Enable Low Input. T his port controls the 8-bit parallel data latch and shift register. A Logic 0 to 1  
transition transfers the latched data to the attenuator core (updates the gain) and simultaneously inhib-  
its serial data transfer into the register. A 1 to 0 transition inhibits the data latch (holds the previous  
gain state) and simultaneously enables the register for serial data load.  
4, 11, 12,  
13, 15, 16  
GND  
Common External Ground Reference.  
5
VOCM  
VCC/2 Reference Pin. A dc output reference level that is equal to 1/2 of the supply voltage (VCC).  
T his port should be externally ac decoupled (0.1 µF cap).  
6
PD  
Power-Down Low Logic Input. A Logic 0 powers down (shuts off) the power amplifier disabling the  
output signal and enabling the reverse amplifier. A Logic 1 enables the output power amplifier and  
disables the reverse amplifier.  
7, 8, 9, 17, 20 VCC  
Common Positive External Supply Voltage.  
10  
14  
18  
VOUT  
Output Signal Port. DC biased to approximately VCC/2.  
Internal Bypass. T his pin must be externally ac decoupled (0.1 µF cap).  
BYP  
VREF  
Input Reference Voltage (typically 1.9 V at 27°C). T his port should be externally ac decoupled  
(0.1 µF cap).  
19  
VIN  
Analog Voltage Input Signal Port. DC biased to VREF voltage.  
–4–  
REV. 0  
Typical Performance Characteristics–AD8320  
0.6  
0.3  
0.3  
0.2  
0.45  
V
= 12V  
CC  
F = 10MHz  
T = +25؇C  
V
= 12V  
F = 10MHz  
CC  
0.30  
T = +25؇C  
T = +25؇C  
0.1  
0.15  
0
0
10MHz  
42MHz  
V
= 12V  
CC  
0
؊0.3  
؊0.6  
T = ؊40؇C  
T = +85؇C  
؊0.15  
؊0.1  
V
= 5V  
CC  
65MHz  
؊0.30  
؊0.45  
؊0.2  
؊0.3  
؊0.9  
؊1.2  
256  
0
64  
128  
192  
0
64  
128  
192  
256  
0
64  
128  
192  
256  
GAIN CONTROL – Decimal  
GAIN CONTROL – Decimal  
GAIN CONTROL – Decimal  
Figure 4. Gain Error vs. Gain Control  
at Various Tem peratures  
Figure 6. Gain Error vs. Gain Control  
at Different Supply Voltages  
Figure 5. Gain Error vs. Gain Control  
at Various Frequencies  
30  
؊20  
30  
255D  
255D  
170D  
V
= 5V  
V
= 12V  
CC  
CC  
MAX GAIN  
PD = 0V  
؊30  
؊40  
؊50  
؊60  
؊70  
؊80  
؊90  
170D  
85D  
20  
10  
0
20  
10  
85D  
0
V
= 5V, P = ؊14dBm  
IN  
CC  
01D  
00D  
01D  
00D  
؊10  
؊20  
؊10  
؊20  
V
= 12V, P = ؊8dBm  
IN  
CC  
؊100  
100k  
100k  
1M  
10M  
100M  
1G  
1M  
10M  
100M  
1G  
100k  
1M  
10M  
100M  
1G  
FREQUENCY – Hz  
FREQUENCY – Hz  
FREQUENCY – Hz  
Figure 9. Input Signal Feedthrough  
vs. Frequency  
Figure 7. AC Response  
Figure 8. AC Response  
90  
80  
75  
70  
65  
60  
80  
75  
70  
65  
60  
F = 10MHz  
F = 10MHz  
V
= 12V  
CC  
80  
MAX GAIN, V = 12V  
CC  
+85؇C  
70  
V
= 12V  
CC  
+25؇C  
MAX GAIN, V = 5V  
CC  
60  
MIN GAIN, V = 12V  
CC  
؊40؇C  
V
= 5V  
55  
50  
CC  
55  
50  
50  
MIN GAIN, V = 5V  
CC  
40  
30  
45  
40  
45  
40  
256  
128  
192  
10M  
1M  
FREQUENCY – Hz  
100M  
0
64  
100k  
256  
128  
192  
0
64  
GAIN CONTROL – Decimal  
GAIN CONTROL – Decimal  
Figure 10. Output Referred Noise vs.  
Gain Control at Various Tem peratures  
Figure 12. Output Referred Noise vs.  
Frequency  
Figure 11. Output Referred Noise vs.  
Gain Control at Different Supply  
Voltages  
REV. 0  
–5–  
AD8320  
؊30  
؊20  
؊30  
؊40  
؊50  
؊60  
؊20  
؊30  
؊40  
V
= 12V  
CC  
F = 65MHz, P = 18dBm  
O
؊40  
؊50  
؊60  
؊70  
P
= 12dBm  
F = 42MHz, P = 18dBm  
O
O
P
= 12dBm  
O
P
= 10dBm  
P
= 10dBm  
O
O
؊50  
؊60  
P
= 8dBm  
O
F = 42MHz, P = 12dBm  
O
؊80  
؊90  
؊70  
؊80  
؊70  
؊80  
P = 4dBm  
O
P
= 8dBm  
F = 65MHz, P = 12dBm  
O
O
P
= 4dBm  
O
0
64  
128  
192  
256  
1
10  
FREQUENCY – MHz  
100  
1
10  
FREQUENCY – MHz  
100  
GAIN CONTROL – Decimal  
Figure 13. Worst Harm onic Distor-  
tion vs. Gain Control  
Figure 14. Worst Harm onic Distor-  
tion vs. Frequency for Various Output  
Levels at VCC = 5 V  
Figure 15. Worst Harm onic Distor-  
tion vs. Frequency for Various Output  
Levels at VCC = 6 V  
؊20  
؊30  
؊20  
؊30  
40  
V
P
= 12V  
CC  
= 18dBm  
O
F = 42MHz  
N = 30  
P
= 18dBm  
O
30  
20  
P
= 18dBm  
O
؊40  
؊40  
؊50  
؊60  
P
O
= 12dBm  
P
= 12dBm  
؊50  
؊60  
O
P
= 8dBm  
P
= 8dBm  
O
O
10  
0
؊70  
؊80  
؊70  
؊80  
P
= 4dBm  
O
P
O
= 4dBm  
10  
FREQUENCY – MHz  
100  
1
1
10  
100  
؊47  
؊46  
؊45  
؊44  
؊43  
FREQUENCY – MHz  
HARMONIC DISTORTION – dBc  
Figure 17. Worst Harm onic Distor-  
tion vs. Frequency for Various Output  
Levels at VCC = 12 V  
Figure 16. Worst Harm onic Distor-  
tion vs. Frequency for Various Output  
Levels at VCC = 10 V  
Figure 18. Distribution of Worst Har-  
m onic Distortion  
40  
20  
30.0  
V
P
= 5V  
V
P
= 12V  
= 18dBm  
V
P
= 12V  
= 12dBm  
CC  
= 12dBm  
CC  
CC  
O
O
O
F = 65MHz  
N = 30  
F = 65MHz  
N = 30  
F = 42MHz  
N = 30  
30  
20  
15  
10  
22.5  
15.0  
10  
0
5
0
7.5  
0
؊45  
؊44  
؊43  
؊42  
؊41  
؊59  
؊58  
؊57  
؊56  
؊55  
؊44  
؊43  
؊42  
؊41  
؊40  
HARMONIC DISTORTION ؊ dBc  
HARMONIC DISTORTION ؊ dBc  
HARMONIC DISTORTION ؊ dBc  
Figure 19. Distribution of Worst Har-  
m onic Distortion  
Figure 20. Distribution of Worst Har-  
m onic Distortion  
Figure 21. Distribution of Worst Har-  
m onic Distortion  
–6–  
REV. 0  
AD8320  
45  
40  
؊35  
؊40  
؊45  
20  
0
V
= 12V  
F = 42MHz, V = 5V, P = 12dBm  
CC  
CC  
O
P
= 18dBm  
O
MAX GAIN  
= 12V  
V
CC  
P
= 12dBm  
O
–20  
–40  
35  
30  
F = 65MHz  
P = 18dBm  
O
V
= 12V  
CC  
؊50  
؊55  
F = 42MHz  
P
= 18dBm  
O
V
= 12V  
CC  
P
= 18dBm  
O
25  
20  
–60  
–80  
؊60  
؊65  
F = 65MHz, V = 12V, P = 12dBm  
CC  
O
0
25  
50  
75  
100  
؊50 ؊25  
1
10  
FREQUENCY – MHz  
100  
41.2  
41.6  
42.0  
42.4  
42.8  
TEMPERATURE ؊ ؇C  
FREQUENCY – MHz  
Figure 22. Harm onic Distortion vs.  
Tem perature  
Figure 23. Two-Tone Interm odula-  
tion Distortion  
Figure 24. Third Order Intercept vs.  
Frequency  
30  
V
= 5V  
CC  
MAX GAIN  
V
V
= 12V  
= 310mV p-p  
V
V
= 12V  
= 310mV p-p  
27  
24  
21  
CC  
CC  
C
= 0pF  
L
IN  
IN  
MAX GAIN  
F = 10MHz  
MIN GAIN  
F = 10MHz  
C
= 22pF  
L
C
= 100pF  
L
C
= 150pF  
L
18  
15  
1.2V  
12.5nsec  
12.5nsec  
20mV  
100k  
1M  
10M  
100M  
1G  
FREQUENCY – Hz  
Figure 26. Transient Response  
Figure 25. Transient Response  
Figure 27. AC Response for Various  
Capacitive Loads  
30  
V
= 12V  
CC  
MAX GAIN  
V
= 12V  
V
= 5V  
27  
24  
21  
CC  
CC  
C
= 0pF  
MAX GAIN  
F = 1MHz  
MAX GAIN  
F = 1MHz  
L
C
= 22pF  
C
= 22pF  
L
L
C
= 100pF  
L
C
= 100pF  
L
C
= 0pF  
C
= 0pF  
L
L
C
= 22pF  
L
C
= 150pF  
C
= 150pF  
L
L
C
= 100pF  
L
C
= 150pF  
L
18  
15  
500mV  
1V  
5nsec  
5nsec  
TIME – Seconds  
100k  
1M  
10M  
100M  
1G  
FREQUENCY – Hz  
Figure 29. AC Response for Various  
Capacitive Loads  
Figure 30. Transient Response for  
Various Capacitive Loads  
Figure 28. Transient Response for  
Various Capacitive Loads  
REV. 0  
–7–  
AD8320  
V
= 12V  
V
= 5V  
100mV  
1.25V  
5mV  
CC  
CC  
V
= 12V  
CC  
MAX GAIN  
= 0V p-p  
MAX GAIN  
= 0V p-p  
F = 40MHz  
MAX GAIN  
V
V
IN  
OUT  
V
IN  
V
V
OUT  
OUT  
CLK  
V
IN  
PD  
75nsec  
DATEN  
500mV  
5V  
20nsec  
5V  
250nsec  
Figure 33. Overload Recovery  
Figure 32. Clock Feedthrough  
Figure 31. Power-Up/Power-Down  
Glitch  
V
= 12V, F = 40MHz  
V
= 12V, F = 40MHz  
CC  
MIN TO MAX GAIN  
= .310V p-p  
2.50V  
V
2.50V  
V
= 12V  
2.00V  
V
CC  
CC  
MAX GAIN  
F = 40MHz  
MAX GAIN  
V
IN  
V
OUT  
OUT  
OUT  
V
V
IN  
IN  
DATEN  
5V  
1V  
20nsec  
20nsec  
250mV  
20nsec  
Figure 35. Output Settling Tim e Due  
to Input Change  
Figure 36. Output Settling Tim e Due  
to Gain Change  
Figure 34. Overload Recovery  
80  
90  
120  
V
= 5V  
V
= 5V, PD = 0  
CC  
CC  
R
= 115⍀  
V
= 12V, PD = 1  
= 5V, PD = 1  
T
CC  
V
= 5V, PD = 1  
100  
80  
60  
40  
20  
0
CC  
80  
70  
70  
V
V
CC  
60  
50  
40  
V
= 12V, PD = 1  
CC  
V
= 12V, PD = 0  
CC  
= 12V, PD = 0  
= 5V, PD = 0  
CC  
60  
50  
V
CC  
100k  
1M  
10M  
100M  
100k  
1M  
10M  
100M  
1G  
–50  
–25  
0
25  
50  
75  
100  
FREQUENCY – Hz  
FREQUENCY – Hz  
TEMPERATURE – ؇C  
Figure 38. Output Im pedance vs.  
Frequency  
Figure 37. Input Im pedance vs.  
Frequency  
Figure 39. Supply Current vs.  
Tem perature  
–8–  
REV. 0  
AD8320  
32  
24  
16  
8
O P ERATIO NAL D ESCRIP TIO N  
T he AD8320 is a digitally controlled variable gain power ampli-  
fier that is optimized for driving 75 cable. A multifunctional  
bipolar device on single silicon, it incorporates all the analog  
features necessary to accommodate reverse path (upstream) high  
speed (5 MH z to 65 MH z) cable data modem and cable tele-  
phony requirements. T he AD8320 has an overall gain range of  
36 dB (–10 dB to 26 dB) and is capable of greater than 100 MHz  
of operation at output signal levels exceeding 18 dBm. Overall,  
when considering the device’s wide gain range, low distortion,  
wide bandwidth and variable load drive, the device can be used  
in many variable gain block applications.  
0
A
= 20 
؋
 LOG (0.316 + 0.077 
؋
 CODE)  
10  
V
–8  
T he digitally programmable gain is controlled by the three wire  
“SPI” compatible inputs. T hese inputs are called SDAT A  
(serial data input port), DATEN (data enable low input port)  
and CLK (clock input port). See Pin Function Descriptions and  
Functional Block diagram. T he AD8320 is programmed by an  
8-bit “attenuator” word. T hese eight bits determine the 256  
programmable gain settings. See attenuator core description  
below. T he gain is linear in V/V/LSB and can be described by  
the following equation:  
–16  
0
32  
64  
96  
128  
160  
192  
224  
256  
GAIN – Code – Decimal  
Figure 41. Log Gain vs. Gain Control  
T he attenuator core can be viewed as eight binarily weighted  
(differential in–differential out) transconductance (gm) stages  
with the “in phase” current outputs of all eight stages connected  
in parallel to their respective differential load resistors (not  
shown). T he core differential output signals are also 180 degrees  
out of phase and equal in amplitude. T he input stages are like-  
wise parallel, connected to the inverting input amplifier and  
buffer outputs as shown. Nine bits plus of accuracy is achieved  
for all gain settings over the specified frequency, supply voltage  
and temperature range. T he actual total core GM × RL attenua-  
tion is determined by which combination of binarily weighted  
gm stages are selected by the data latch. With 8 bits, 256 levels  
of attenuation can be programmed. T his results in a 36 dB  
attenuation range (0 dB to –36 dB). See gain equation above.  
AV = 0.316 + 0.077 × Code (RL = 75 )  
where code is the decimal equivalent of the 8-bit word. For ex-  
ample, if all 8 bits are at a logic “1,” the decimal equivalent is  
255 and AV equals 19.95 V/V or 26 dB. T he gain scaling factor  
is 0.077 V/V/LSB, with an offset of 0.316 V/V (–10.0 dB). Fig-  
ure 40 shows the linear gain versus decimal code and Figure 41  
shows the gain in dB versus decimal code. Note the nonlin-  
earity that results when viewed in dB versus code. T he dB step  
size increases as the attenuation increases (i.e., gain decreases)  
and reaches a maximum step size of approximately 1.9 dB (gain  
change between 01 and 00 decimal).  
VCC  
GND  
PWR AMP  
22  
20  
18  
AD8320  
REFERENCE  
VOUT  
VREF  
VIN  
A
= 0.316 + 0.077 
؋
 CODE  
REVERSE  
AMP  
V
INV.  
BUF.  
ATTENUATOR CORE  
16  
14  
12  
10  
POWER-UP  
DATA LATCH  
POWER–  
DOWN  
PD  
8
6
4
SWITCH  
INTER.  
DATA SHIFT REGISTER  
2
DATEN CLK  
SDATA  
POWER-DOWN  
0
Figure 42. Functional Block Diagram  
–2  
0
32  
64  
96  
128  
160  
192  
224  
256  
T o update the AD8320 gain, the following digital load sequence  
is required. T he attenuation setting is determined by the 8-bit  
word in the data latch. T his 8-bit word is serially loaded (MSB  
first) into the shift register at each rising edge of the clock. See  
Figure 43. During this data load time (T ), DATEN is low and  
the data latch is latched holding the previous (T – 1) data word  
keeping the attenuation level unchanged. After eight clock  
cycles the new data word is fully loaded and DATEN is  
switched high. T his enables the data latch (becomes transpar-  
ent) and the loaded register data is passed to the attenuator with  
the updated gain value. Also at this DATEN transition, the  
internal clock is disabled, thus inhibiting new serial input data.  
GAIN – Code – Decimal  
Figure 40. Linear Gain vs. Gain Control  
The AD8320 is composed of three analog functions in the power-  
up or forward mode (Figure 42). T he input inverter/buffer  
amplifier provides single-ended to differential output conver-  
sion. T he output signals are nominally 180 degrees out of phase  
and equal in amplitude with a differential voltage gain of 2 (6 dB).  
Maintaining close to 180 degrees and equal amplitude is re-  
quired for proper gain accuracy of the attenuator core over the  
specified operating frequency. T he input buffer/inverter also  
provides equal dc voltages to the core inputs via the internal  
reference. T his is required to ensure proper core linearity over  
the full specified power supply range (5 V to 12 V).  
REV. 0  
–9–  
AD8320  
T
DS  
VALID DATA WORD G1  
MSB. . . .LSB  
VALID DATA WORD G2  
SDATA  
CLK  
T
C
T
WH  
T
T
ES  
EH  
8 CLOCK CYCLES  
DATEN  
PD  
GAIN TRANSFER (G1)  
GAIN TRANSFER (G2)  
T
OFF  
T
GS  
T
ON  
ANALOG  
OUTPUT  
SIGNAL AMPLITUDE (p-p)  
PEDESTAL  
Figure 43. Serial Interface Tim ing  
T he power amplifier has two basic modes of operation; forward  
or power-up mode and reverse or power-down mode. In the  
power-up mode (PD = 1), the power amplifier stage is enabled  
and the differential output core signal is amplified by 20 dB.  
With a core attenuation range of 0 dB to –36 dB and 6 dB of  
input gain, the overall AD8320 gain range is 26 dB to –10 dB.  
In this mode, the single-ended output signal maintains a dc  
level of VCC/2. T his dc output level provides for optimum large  
signal linearity and allows for dc coupling the output if neces-  
sary. T he output stage is unique in that it maintains a dynamic  
output impedance of 75 . T his allows for a direct 75 cable  
connection and results in 6 dB of added load power versus using  
a series 75 back-termination resistor as required with tradi-  
tional low output impedance amplifiers. T he power amplifier  
will also drive lower or higher output loads, although the device’s  
gain (not gain range) will change accordingly (see Applications  
section).  
what is referred to as sleep and standby modes, and VCC supply  
switching via PFETS or equivalent, as described in the applica-  
tions section, would be required.  
AP P LICATIO NS  
T he AD8320 is primarily intended to be used as the return path  
(also called upstream path) line driver in cable modem and  
cable telephony applications. Data to be transmitted is modu-  
lated in either QPSK or QAM format. T his is done either in  
DSP or by a dedicated QPSK/QAM modulator such as the  
AD9853.  
T he amplifier receives its input signal either from the dedicated  
QPSK/QAM modulator or from a DAC. In both cases, the  
signal must be low-pass filtered before being applied to the line  
driving amplifier.  
CENTRAL  
OFFICE  
SUBSCRIBER  
TO MODEM  
RECEIVE  
In the power-down mode (PD = 0), the power amplifier is turned  
off and a “reverse” amplifier (the inner triangle in Figure 42) is  
enabled. During this 1 to 0 transition, the output power amplifier’s  
input stage is also disabled, resulting in no forward output signal  
(S21 is 0), although the attenuator core and input amplifier/  
buffer signals are not affected (S11 0). T he function of the  
reverse amplifier is to maintain 75 and VCC/2 at the output  
port (VOUT ) during power-down. T his is required to minimize  
line reflections (S22 0) and ensures proper filter operation for  
any forward mode device sharing the same bus (i.e., in a multi-  
plexed configuration). (See Applications section.) In the time  
domain, as PD switches states, a transitional glitch and pedestal  
offset results. (See Figures 31 and 43.) T he powered down  
supply current drops to 32 mA versus 97 mA (VCC = 12 V) in  
power-up mode.  
CIRCUITRY  
DIPLEXER  
75⍀  
7TH ORDER  
ELLIPTIC  
LOW PASS  
FILTER  
AD9853  
AD8320  
Figure 44. Block Diagram of Cable Modem s Upstream  
Driver Section  
T he amplifier drives the line through a diplexer. T he insertion  
loss of a diplexer is typically –3 dB. As a result, the line driver  
must deliver a power level roughly 3 dB greater than required by  
the applicable cable modem standard so that diplexer losses are  
canceled out.  
Because the distance to the central office varies from subscriber  
to subscriber, signals from different subscribers will be attenu-  
ated by differing amounts. As a result, the line driver is required  
to vary its gain so that all signals arriving at the central office  
have the same amplitude.  
Generally, using the power-down low input (PD) for switching  
allows for multiple devices to be multiplexed via splitters (N-1  
off, 1 on) and reduces overall total power consumption as re-  
quired for cable data applications. For cable telephony, the  
power-down current generally needs to be much lower during  
–10–  
REV. 0  
AD8320  
Basic Connection  
T he timing diagram for AD8320s serial interface is shown in  
Figure 43.  
Figure 45 shows the basic schematic for operating the AD8320.  
Because the amplifier operates from a single supply, the input  
signal must be ac-coupled using a 0.1 µF capacitor. T he input  
pin has a bias level of about 1.9 V. T his bias level is available on  
the VREF pin (Pin 18) and can be used to externally bias signals  
if dc-coupling is desired. Under all conditions, a 0.1 µF decoupling  
capacitor must be connected to the VREF pin. If the VREF volt-  
age is to be used externally, it should be buffered first.  
T he write cycle to the device is initiated by the falling edge of  
DATEN. T his is followed by eight clock pulses that clock in the  
control word. Because the clock signal is level triggered, data is  
effectively clocked on the falling edge of CLK.  
After the control word has been clocked in, the DATEN line  
goes back high, allowing the gain to be updated (this takes  
about 30 ns).  
T he VIN pin of the AD8320 (Pin 19) has an input impedance  
of 220 . T ypically, in video applications, 75 termination is  
favored. As a result, an external shunt resistance (R1) to ground  
of 115 is required to create an overall input impedance of  
75 . If 50 termination is required, a 64.9 shunt resistor  
should be used. Note, to avoid dc loading of the VIN pin, the  
ac-coupling capacitor should be placed between the input pin  
and the shunt resistor as shown in Figure 45.  
T he relationship between gain and control word is given by the  
equation:  
Gain (V/V) = 0.077 × Code + 0.316  
where code is the decimal equivalent of the gain control word  
(0 to 255).  
T he gain in dB is given by the equation:  
On the output side, the VOUT pin also has a dc bias level. In  
this case the bias level is midway between the supply voltage and  
ground. T he output signal must therefore be ac-coupled before  
being applied to the load. T he dc bias voltage is available on the  
VOCM pin (Pin 5) and can be used in dc-coupled applications.  
T his node must be decoupled to ground using a 0.1 µF capaci-  
tor. If the VOCM voltage is to be used externally, it should be  
buffered.  
Gain (dB) = 20 log10 (0.077 × Code + 0.316)  
T he digital interface also contains an asynchronous power-down  
mode. T he normally high PD line can be pulled low at any time.  
T his turns off the output signal after 45 ns, and reduces the  
quiescent current to between 25 mA and 32 mA (depending  
upon the power supply voltage). In this mode, the programmed  
gain is maintained.  
Clock Line Feedthr ough  
Since the AD8320 has a dynamic output impedance of 75 , no  
external back termination resistor is required. If the output  
signal is being evaluated on 50 test equipment such as a spec-  
trum analyzer, a 75 to 50 adapter (commonly called a pad)  
should be used to maintain a properly matched circuit.  
Clock feedthrough results in a 5 mV p-p signal appearing super-  
imposed on the output signal (see Figure 32). If this impinges  
upon the dynamic range of the application, the clock signal  
should be noncontinuous, i.e., should only be turned on for  
eight cycles during programming.  
Var ying the Gain  
T he gain of the AD8320 can be varied over a range of 36 dB,  
from –10 dB to +26 dB, by varying the 8-bit gain setting word.  
P ower Supply and D ecoupling  
T he AD8320 should be powered with a good quality (i.e., low  
noise) single supply of between +5 V and +12 V. In order to  
achieve an output power level of +18 dBm (6.2 V p-p) into  
VCC  
+5V TO +12V  
C3  
0.1F  
C7  
10F  
C5  
0.1F  
C4  
0.1F  
C2  
0.1F  
C11  
0.1F  
C6  
0.1F  
VCC  
VCC  
VCC  
VCC  
GND  
BYP  
VCC  
C10  
0.1F  
VOUT  
AD8320  
REFERENCE  
C12  
0.1F  
TO DIPLEXER  
RIN = 75⍀  
C1  
0.1F  
VREF  
VIN  
VOCM  
ATTENUATOR CORE  
DATA LATCH  
C8  
0.1F  
INPUT  
R1*  
115⍀  
POWER-  
DOWN  
/
PD  
*FOR A 75INPUT  
IMPEDANCE  
SWITCH  
INTER.  
DATA SHIFT REGISTER  
SDATA GND GND GND GND GND  
CLK  
DATEN  
CLK  
SDATA  
DATEN  
PD  
Figure 45. Basic Connection  
–11–  
REV. 0  
AD8320  
75 , a supply voltage of at least +10 V is required. T o achieve  
a signal level of +12 dBm (about 3.1 V p-p) into 75 , a mini-  
mum supply level of +5 V is required. However, for the lowest  
possible distortion, the power supply voltage should be raised as  
high as possible. In varying the power supply from +5 V to  
+12 V, the quiescent current increases from 80 mA to 97 mA.  
A HEXFET power MOSFET (International Rectifier part num-  
ber IRLML5103) is used to turn on and off the current to the  
supply pins of the AD8320. Under normal operating conditions,  
the gate (labeled POWER-DOWN) should be grounded. Pull-  
ing the gate to within 2 V of the supply will open the switch and  
reduce the current to the amplifier to zero.  
Careful attention must be paid to decoupling the power supply  
pins. A 10 µF capacitor, located fairly close to the device, is  
required to provide good decoupling for lower frequency signals.  
In addition, five 0.1 µF decoupling capacitors should be located  
close to each of the five power supply pins (7, 8, 9, 17 and 20).  
A 0.1 µF capacitor must also be connected to the pin labeled  
BYP (Pin 14), to provide decoupling to an internal node of the  
device. All six ground pins should be connected to a low imped-  
ance ground plane.  
In cable modem and cable telephony applications the modem  
must always present an output impedance of 75 to the line.  
T his forces the line driver to always present a 75 impedance  
to the diplexer. In this application, a single pole double throw  
RF switch (AS103, Alpha Semiconductor) is used to switch in  
an external 75 impedance when the AD8320 is turned off.  
T his resistor then mimics the dynamic output impedance of the  
AD8320. T T L or CMOS logic can be used to drive the two  
voltages driving the RF switch (V1 and V2).  
Alter native P ower -D own Mode  
Before the AD8320 is turned back on again, the gain needs to  
be set to a known level. T his 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. During this time the quiescent current will in-  
crease to 32 mA. However, this time period can be as small as  
about 1 µs. In this mode the output settles about 45 ns after the  
rising edge of PD.  
As previously mentioned, the AD8320 can be put into a low  
power sleep mode by pulling the PD pin low. If lower power  
consumption is required during power-down mode, an alternative  
scheme can be used as shown in Figure 46.  
VCC+12V  
POWER-  
S
DOWN  
G
IRLML5103  
Alternatively, if DATEN is held low as the AD8320 is powered  
on, the device will power up in minimum gain. In this mode, the  
output settles after about 200 µs. Note that for both cases, the  
capacitor on VOCM has been reduced from 0.1 µF to 0.01 µF  
to facilitate a faster turn-on time. All other capacitors in the  
circuit should be connected as shown in Figure 45.  
0.1F  
D
VOUT  
J1  
PD  
VDD  
+5V  
AS103  
(SEETEXT)  
J2  
VCC  
PD  
DATEN  
CLK  
0.1F  
0.1F  
75⍀  
VOUT  
VOCM  
J3  
AD8320*  
0.1F  
SDATA  
GND  
75⍀  
14  
0.1F  
V2  
V1  
0.01F  
V2  
V1  
*ADDITIONAL PINS AND DECOUPLING CAPACITORS  
OMITTED FOR CLARITY  
10–12V  
POWER-  
DOWN  
0V  
3–5V  
V1  
V2  
0V  
3–5V  
0V  
PD  
DATEN  
0V  
CLK  
SDATA  
OUTPUT  
97mA  
97mA  
32mA  
QUIESCENT  
CURRENT  
0mA  
Figure 46. Alternative Power-Down Mode with Tim ing  
–12–  
REV. 0  
AD8320  
TO MODEM  
RECEIVE  
CHANNEL  
58dBmV  
DIPLEXER  
75⍀  
+5V  
+12V  
AD603*  
VIN  
VIN  
VPOS  
AD8320*  
VOUT  
11dBmV  
0.1F  
220⍀  
75⍀  
100⍀  
FBDK  
61dBmV  
؉5V  
20pF  
41dBmV  
220⍀  
VNEG  
GNEG  
GPOS  
COMM  
–5V  
PD  
VDD  
REFIN  
CLR  
+0.5V  
1.5⍀  
1k⍀  
AD7801*  
*ADDITIONAL PINS AND  
DECOUPLING CAPACITORS  
OMITTED FOR CLARITY  
DGND  
AGND  
CS WR LDAC D0–D7  
8
D0–D7  
74HCT164*  
CLK  
A
B
DATA  
CLK  
ENABLE  
PD  
Figure 47. Enhanced Dynam ic Range Circuit  
Enhanced D ynam ic Range Application  
T he AD8320 can be combined with the AD603 to give addi-  
tional dynamic range as shown in Figure 47. T he AD603 is a  
voltage controlled variable gain amplifier. The gain of the AD603 is  
determined by the difference in voltage between the GPOS and  
GNEG pins. T his differential voltage has a range of ±0.5 V. In  
this example, the voltage on GNEG is tied to +0.5 V. As the  
voltage on GPOS is varied from 0 V to 1 V, the gain of the AD603  
changes from –10 dB to +30 dB with a slope of 25 mV/dB (i.e.,  
linear in dB). T he gain control voltage is supplied by the AD7801  
DAC. T he output voltage of the DAC (0 V to +2.5 V) is divided  
down to fit the 0 V to 1 V range of the AD603 using a resistor  
attenuator network.  
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. T he rising edge of the enable pulse simul-  
taneously updates both amplifiers.  
Figure 48. Output Spectrum of Enhanced Dynam ic Range  
Circuit (Output Level = 61 dBm V, Frequency = 42 MHz)  
60  
50  
As the control word is varied from 00Dec to 255Dec, the gain of  
the signal chain varies from –26 dB to +50 dB (there is 6 dB of  
attenuation between AD603 and AD8320). In practice, this  
circuit is not usable at the lower end of the gain range due to the  
small input signal (11 dBmV or about 10 mV p-p). Figure 48  
shows the spectrum of the output signal at a frequency of  
42 MHz and an output level of 61 dBmV (3.1 V p-p, max gain).  
AD8320/AD603  
40  
30  
AD8320  
20  
10  
AD603  
0
T he gain vs. code transfer function of the two amplifiers along  
with the overall gain is shown in Figure 49. T he overall gain  
transfer function combines a linear in dB transfer function with  
a linear in Volts/Volt transfer function. It is clear from Figure 49  
that the overall gain transfer function can be considered to be  
approximately linear in dB over the top 50 dB of its range.  
–10  
–20  
–30  
0
21 41 61 81 101 121 141 161 181 201 221 241  
GAIN CONTROL WORD – Decimal  
Figure 49. Gain Transfer Function of Enhanced Dynam ic  
Range Circuit  
REV. 0  
–13–  
AD8320  
Var ying Gain by Var ying Load Im pedance  
and tested to demonstrate the specified high speed performance  
of the device. Figure 51 shows the schematic of the evaluation  
board. T he silkscreen for the component side layer is shown in  
Figure 52. T he layout of the board is shown in Figure 53 and  
Figure 54.  
As already mentioned, the AD8320 has a dynamic output im-  
pedance of 75 . T he specified gain range assumes that the  
output is terminated with a 75 load impedance. Varying the  
load impedance allows the gain to be varied, up to a maximum  
of twice the specified gain (for RL  
= ϱ). T he variation in gain  
T he evaluation board package includes a fully populated board  
with BNC-type connectors along with Windows®-based soft-  
ware for controlling the board from a PC’s printer port via a  
standard printer cable.  
with load resistance is shown in Figure 50 for the case of a gain  
control word of 255Dec (i.e., max gain).  
32  
30  
28  
26  
24  
22  
20  
A prototyping area is provided to allow for additional circuitry  
on the board. The single supply and ground to the board are  
brought over to this area and are available on two strips. T here  
are also two extra strips available on the prototyping area which  
can be used for additional power supplies.  
T he board should be powered with a good quality (i.e., low  
noise) single supply of between +5 V and +12 V. Extensive  
decoupling is provided on the board. A 10 µF capacitor, located  
fairly close to the device, provides good decoupling for lower  
frequency signals. In addition, and more importantly, five  
0.1 µF decoupling capacitors are located close to each of the  
five power supply pins (7, 8, 9, 17 and 20).  
0
100  
1000  
10000  
Contr olling the Evaluation Boar d fr om a P C  
R
⍀  
LOAD  
T he evaluation board ships with Windows-based control soft-  
ware. A standard printer cable can be used to connect the  
evaluation board to a PC’s printer port (also called parallel  
port). T he cable length should be kept to less than about 5 feet.  
T he wiring of a standard printer cable, with respect to the sig-  
nal lines that are used in this application, is shown in Figure 55.  
Although the software controls the evaluation board via the  
PCs parallel port, the AD8320 digital interface is serial. T hree  
of the parallel port’s eight bits (and one digital ground line) are  
used to implement this serial interface. A fourth bit is used to  
control the PD pin.  
Figure 50. Gain vs. RLOAD (Gain Control Word = 255Dec)  
T he gain can be described by the following equation:  
2 RLOAD  
AV = 20 log10  
0.316 +0.077 × Code  
(
)
RLOAD +75  
where Code is the decimal equivalent of the 8-bit word.  
Evaluation Boar d  
A two layer evaluation board for the AD8320 is available (part  
number AD8320-EB). T his board has been carefully laid out  
VCC  
C7  
C3  
0.1F  
C6  
0.1F  
C5  
0.1F  
C4  
0.1F  
C2  
0.1F  
C11  
0.1F  
10F  
TP2  
TP4  
VCC  
VCC  
VCC  
VCC  
GND  
BYP  
VCC  
VREF  
C10  
0.1F  
OUTPUT  
VOCM  
VOUT  
AD8320  
C12  
0.1F  
REFERENCE  
TP3  
TP1  
C1  
0.1F  
VREF  
VIN  
ATTENUATOR CORE  
DATA LATCH  
C8  
0.1F  
VOCM  
R1  
115⍀  
INPUT  
POWER-  
DOWN  
/
PD  
SWITCH  
INTER  
DATA SHIFT REGISTER  
SDATA  
GND GNDGND GNDGND  
CLK  
DATEN  
R4  
0
C9  
OPTIONAL  
3
5
2
16, 19-30, 33  
6
36-PIN CENTRONICS CONNECTOR  
Figure 51. Evaluation Board Schem atic  
All trademarks are the property of their respective holders.  
–14–  
REV. 0  
AD8320  
T he control software requires Windows 3.1 or later to operate.  
T o install the software, insert the disk labeled “Disk # 1 of 2” in  
the PC and run the file called SETUP.EXE. Additional installa-  
tion instructions will be given on-screen. Before beginning installa-  
tion, it is important to close any other Windows applications  
that are running.  
can power down or reset the device simply by clicking the  
appropriate buttons. T he software also offers one volatile stor-  
age location that can be used to store a particular gain. T his  
functions in the same way as the memory on a pocket calculator.  
O ver shoot on P C P r inter P or ts’ D ata Lines  
T he data lines on some printer ports have excessive overshoot.  
Overshoot on the pin used as the serial clock (Pin 6 on the D-  
Sub-25 connector) can cause communication problems. T his  
overshoot can be eliminated by applying mild filtering to the  
CLK line on the evaluation board. T his can be done by putting  
a small series resistor on the CLK line, combined with a  
capacitor to ground. Pads are provided (C9, R4) on the com-  
ponent side of the evaluation board to allow easy insertion of  
these devices. Determining the size of these values will take  
some experimentation. Depending upon the overshoot from the  
printer port, this capacitor may need to be as large as 0.01 µF,  
while the resistor is typically in the 50 to 100 range.  
When you launch the installed control software from Windows,  
you will be asked to select the printer port you are using. Most  
modern PCs have only one printer port, usually called LPT 1.  
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 AD8320s 36 dB range.  
T he gain is displayed on-screen in dB and V/V. T he 8-bit gain  
setting byte is also displayed, in binary, hexadecimal and decimal.  
Each time the slider is moved, the software automatically sends  
and latches the required 8-bit data stream to the AD8320. You  
Figure 52. Evaluation Board Silkscreen (Com ponent Side)  
REV. 0  
–15–  
AD8320  
Figure 53. Evaluation Board Layout (Com ponent Side)  
–16–  
REV. 0  
AD8320  
Figure 54. Evaluation Board Layout (Solder Side)  
36 PIN CENTRONICS  
D-SUB 25 PIN (MALE)  
1
1
19  
DATEN  
14  
PD  
SDATA  
CLK  
GND  
25  
13  
SIGNAL  
D-SUB-25  
2
36-PIN CENTRONICS  
3
DATEN  
PD  
3
5
1
DATA  
CLK  
5
6
2
DGND  
25  
16, 19–30, 33  
36  
18  
EVALUATION BOARD  
PC  
Figure 55. Interconnection Between AD8320EB and PC Printer Port  
REV. 0  
–17–  
AD8320  
Figure 56. Screen Display of Windows-Based Control Software  
–18–  
REV. 0  
AD8320  
O UTLINE D IMENSIO NS  
D imensions shown in inches and (mm).  
20-Lead Ther m ally Enhanced P ower Sm all O utline P ackage  
(RP -20)  
0.5118 (13.00)  
0.4961 (12.60)  
20  
11  
0.1890 (4.80) 0.4193 (10.65)  
0.1791 (4.55) 0.3937 (10.00)  
HEAT  
SINK  
0.2992 (7.60)  
0.2914 (7.40)  
1
10  
PIN 1  
0.3340 (8.61)  
0.3287 (8.35)  
0.1043 (2.65)  
0.0926 (2.35)  
8°  
0°  
0.0500  
(1.27)  
BSC  
0.0201 (0.51)  
0.0118 (0.30)  
0.0295 (0.75)  
0.0098 (0.25)  
SEATING  
PLANE  
0.0500 (1.27)  
0.0057 (0.40)  
x 45°  
0.0130 (0.33)  
0.0040 (0.10)  
STANDOFF  
REV. 0  
–19–  
–20–  

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