Analog Devices AD8331 2 c Datasheet

Ultralow Noise VGAs with
FEATURES
Ultralow noise preamplifier
Voltage noise = 0.74 nV/√Hz
Current noise = 2.5 pA/√Hz 3 dB bandwidth: 120 MHz Low power: 125 mW/channel Wide gain range with programmable postamp
–4.5 dB to +43.5 dB
+7.5 dB to +55.5 dB Low output-referred noise: 48 nV/√Hz typical Active input impedance matching Optimized for 10-/12-bit ADCs Selectable output clamping level Single 5 V supply operation Available in space-saving chip scale package
APPLICATIONS
Ultrasound and sonar time-gain control High performance AGC systems I/Q signal processing High speed dual ADC driver
GENERAL DESCRIPTION
The AD8331/AD8332 are single- and dual-channel ultralow noise, linear-in-dB, variable gain amplifiers. Although optimized for ultrasound systems, they are usable as low noise variable gain elements at frequencies up to 120 MHz.
Each channel consists of an ultralow noise preamplifier (LNA), an X-AMP® VGA with 48 dB of gain range, and a selectable gain postamplifier with adjustable output limiting. The LNA gain is 19 dB with a single-ended input and differential outputs capable of accurate, programmable active input impedance matching by selecting an external feedback resistor. Active impedance control optimizes noise performance for applications that benefit from input matching.
The 48 dB gain range of the VGA makes these devices suitable for a variety of applications. Excellent bandwidth uniformity is maintained across the entire range. The gain control interface provides precise linear-in-dB scaling of 50 dB/V for control voltages between 40 mV and 1 V. Factory trim ensures excellent part-to-part and channel-to-channel gain matching. Differential signal paths lead to superb second and third order distortion performance and low crosstalk.
Preamplifier and Programmable R
IN
AD8331/AD8332
FUNCTIONAL BLOCK DIAGRAM
VPSV
VIN1VIP1LOP1LON1
[(–48 to 0) + 21] dB
+
+
VIN2VIP2LOP2LON2
COMM
VGA 1
BIAS AND
INTERPOLATOR
VGA 2
ENB
V
MID
VPS1
COM1
INH1
LMD1
LMD2
INH2
VPS2
COM2
25 24 22 21 15 20 9 19
26
23
+19dB
+
27
LNA 1 –
28
BIAS
(V
)
MID
1
LNA 2
+
2
3
6
4 5 7 8 14 18 11
Figure 1. AD8332 Shown 28-Lead TSSOP
50
40
30
)
20
B d
( N
I
10
A G
0
–10
–20
100k
V
= 1V
GAIN
0.8V
0.6V
0.4V
0.2V
0V
1M 1G100M10M
FREQUENCY (Hz)
Figure 2. Frequency Response vs. Gain
The VGA’s low output-referred noise is advantageous in driving high speed differential ADCs. The gain of the postamplifier may be pin selected to 3.5 dB or 15.5 dB to optimize gain range and output noise for 12-bit or 10-bit converter applications. The output may be limited to a user-selected clamping level, preventing input overload to a subsequent ADC. An external resistor adjusts the clamping level.
The operating temperature range is –40°C to +85°. The AD8331 is available in a 20-lead QSOP package, and the AD8332 in 28-lead TSSOP and 32-lead LFCSP packages. They require a single 5 V supply, and the quiescent power consumption is 125 mW/ch. A power-down (enable) pin is provided.
3.5dB/15.5dB
POST AMP1
POST AMP2
CLAMP
RCLMP
GAIN
INT
HILOVCM2VCM1
VOH1
17
16
VOL1
10
GAIN
13
VOL2
12
VOH2
03199-B-001
03199-C-002
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. Specifications subject to change without notice. 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: 781.326.8703 © 2003 Analog Devices, Inc. All rights reserved.
AD8331/AD8332
TABLE OF CONTENTS
REVISION HISTORY.................................................................. 2
AD8331, AD8332—Specifications.................................................. 3
Absolute Maximum Ratings............................................................ 6
ESD CAUTION ............................................................................ 6
AD8331, AD8332—Typical Performance Characteristics .......... 7
Test Circuits..................................................................................... 15
Theory of Operation...................................................................... 17
Overview...................................................................................... 17
Low Noise Amplifier (LNA)...................................................... 17
Variable Gain Amplifier............................................................. 19
Postamplifier............................................................................... 21
Applications..................................................................................... 22
LNA – External Components................................................... 22
Driving ADCs ............................................................................. 24
Overload...................................................................................... 24
Optional Input Overload Protection. ...................................... 25
Layout, Grounding, And Bypassing......................................... 25
Multiple Input Matching........................................................... 25
Disabling the LNA...................................................................... 25
Measurement Considerations................................................... 26
Ultrasound TGC Application ................................................... 26
Pin Configuration and Function Descriptions........................... 30
AD8331........................................................................................ 30
AD8332........................................................................................ 31
Outline Dimensions....................................................................... 32
Ordering Guide .......................................................................... 32

REVISION HISTORY

Revision C
11/03—Data Sheet Changed from REV. B to REV. C
Addition of New Part...........................................................Universal
Changes to Figures ...............................................................Universal
Updated Outline Dimensions..........................................................32
5/03—Data Sheet Changed from REV. A to REV. B
Edits to Ordering Guide....................................................................32
Edits to Ultrasound TGC Application section................................25
Added Figure 71, Figure 72, and Figure 73......................................26
Updated Outline Dimensions............................................................31
2/03—Data Sheet Changed from REV. 0 to REV. A
Edits to Ordering Guide.....................................................................32
Rev. C | Page 2 of 32
AD8331/AD8332

AD8331, AD8332—SPECIFICATIONS

Table 1. TA = 25°C, VS = 5 V, RL = 500 Ω, RS = RIN = 50 Ω, RFB = 280 Ω, CSH = 22 pF, f = 10 MHz, R
pin floating, –4.5 dB to +43.5 dB gain (HILO = LO), and differential output voltage, unless otherwise specified.
V
CM
Parameter Conditions Min Typ Max Unit
LNA CHARACTERISTICS
Gain
Single-Ended Input to Differential Output
Input to Output (Single-Ended) 13 dB
Input Voltage Range AC-Coupled ±275 mV
R
Input Resistance
280 Ω 50
FB =
R
= 412 Ω 75
FB
R
562 Ω 100
FB =
R
1.13 kΩ 200
FB =
R
6 kΩ
FB =
Input Capacitance 13 pF Output Impedance Single-Ended, Either Output 5 Ω –3 dB Small Signal Bandwidth V
= 0.2 V p-p 130 MHz
OUT
Slew Rate 650 V/µs Input Voltage Noise
= 0 Ω, HI or LO Gain,
R
S
= ∞, f = 5 MHz
R
FB
Input Current Noise RFB = ∞, HI or LO Gain, f = 5 MHz 2.5 pA/√Hz Noise Figure f = 10 MHz, LOP Output
Active Termination Match RS = RIN = 50 Ω 3.7 dB Unterminated RS = 50 Ω, RFB = ∞ 2.5 dB
Harmonic Distortion @ LOP1 or LOP2
HD2 –56 dBc HD3
= 0.5 V p-p,
V
OUT
Single-Ended, f = 10 MHz
Output Short-Circuit Current Pins LON, LOP 165 mA
LNA + VGA CHARACTERISTICS
–3 dB Small Signal Bandwidth V –3 dB Large Signal Bandwidth V
= 0.2 V p-p 120 MHz
OUT
= 2 V p-p 110 MHz
OUT
LO Gain 300 V/µs Slew Rate HI Gain 1200 V/µs
Input Voltage Noise
Noise Figure V
Active Termination Match
= 0 Ω, HI or LO Gain,
R
S
R
= ∞, f = 5 MHz
FB
= 1.0 V
GAIN
RS = RIN = 50 Ω, f = 10 MHz, Measured
R
= RIN = 200 Ω,
S
f = 5 MHz, Simulated
Unterminated
RS = 50 Ω, RFB = ∞, f = 10 MHz, Measured
R
= 200 Ω, RFB = ∞,
S
f = 5 MHz, Simulated V
= 0.5 V, LO Gain 48 nV/√Hz Output-Referred Noise
GAIN
V
= 0.5 V, HI Gain 178 nV/√Hz
GAIN
Output Impedance, Postamplifier DC to 1 MHz 1 Ω Output Signal Range, Postamplifier
≥ 500 Ω,
R
L
Unclamped, Either Pin
Differential 4.5 V p-p
Output Offset Voltage
Differential –50 ±5 +50 mV
V
GAIN
= 0.5 V
Common-Mode
Output Short-Circuit Current 45 mA
= ∞, CL = 1 pF,
CLMP
19 dB
0.74 nV/√Hz
–70 dBc
0.82 nV/√Hz
4.15 dB
2.0 dB
2.5 dB
1.0 dB
V
± 1.125 V
CM
–125 –25 +100 mV
Rev. C | Page 3 of 32
AD8331/AD8332
Parameter Conditions Min Typ Max Unit
Harmonic Distortion V
HD2 –88 dBc HD3 HD2 –68 dBc
HD3 Input 1 dB Compression Point V Two-Tone Intermodulation
Distortion (IMD3)
Channel-to-Channel Crosstalk (AD8332) Overload Recovery
Group Delay Variation 5 MHz < f < 50 MHz, Full Gain Range ±2 ns
ACCURACY
Absolute Gain Error2
Gain Law Conformance3 0.1 V < V Channel-to-Channel Gain Matching 0.1 V < V
GAIN CONTROL INTERFACE (Pin GAIN)
Gain Scaling Factor 0.10 V < V
Input Voltage (V
) Range 0 to 1.0 V
GAIN
Input Impedance 10 MΩ Response Time 48 dB Gain Change to 90% Full Scale 750 ns
COMMON-MODE INTERFACE (Pin VCMn)
Input Resistance Current Limited to ±1 mA 30 Ω Output CM Offset Voltage VCM = 2.5 V –125 –25 +100 mV Voltage Range
= 0.5 V, V
GAIN
f = 1 MHz
f = 10 MHz
= 0.25 V, V
GAIN
V
= 0.72 V, V
GAIN
= 0.5 V, V
V
GAIN
V
= 0.5 V, V
GAIN
V
= 0.5 V, V
GAIN
V
= 0.5 V, V
GAIN
= 1.0 V,
V
GAIN
= 50 mV p-p/1 V p-p,
V
IN
= 1 V p-p
OUT
–85 dBc
–65 dBc
= 1 V p-p, f = 1 MHz–10 MHz 7 dBm1
OUT
= 1 V p-p, f = 1 MHz –80 dBc
OUT
= 1 V p-p, f = 10 MHz –72 dBc
OUT
= 1 V p-p, f = 1 MHz 38 dBm Output Third Order Intercept
OUT
= 1 V p-p, f = 10 MHz 33 dBm
OUT
= 1 V p-p, f = 1 MHz –84 dB
OUT
5 ns
f = 10 MHz
0.05 V < V
0.10 V < V
0.95 V < V
< 0.10 V –1 +0.5 +2 dB
GAIN
< 0.95 V –1 ±0.3 +1 dB
GAIN
< 1.0 V –2 –1 +1 dB
GAIN
< 0.95 V ±0.2 dB
GAIN
< 0.95 V ±0.1 dB
GAIN
< 0.95 V 50 dB/V
GAIN
LO Gain –4.5 to +43.5 dB Gain Range HI Gain +7.5 to +55.5 dB
V
= 2.0 V p-p 1.5 to 3.5 V
OUT
ENABLE INTERFACE (Pins ENB, ENBL, ENBV)
Logic Level to Enable Power 2.25 5 V Logic Level to Disable Power 0 1.0 V Input Resistance
Pin ENB 25 kΩ Pin ENBL 40 kΩ Pin ENBV 70 kΩ V
= 30 mV p-p 300 µs Power-Up Response Time
INH
V
= 150 mV p-p 4 ms
INH
HILO GAIN RANGE INTERFACE (Pin HILO)
Logic Level to Select HI Gain Range 2.25 5 V Logic Level to Select LO Gain Range 0 1.0 V Input Resistance 50 kΩ
1
All dBm values are referred to 50 Ω, unless otherwise noted.
2
Conformance to theoretical gain expression (see Equation 1).
3
Conformance to best fit dB linear curve.
Rev. C | Page 4 of 32
AD8331/AD8332
Parameter Conditions Min Typ Max Unit
OUTPUT CLAMP INTERFACE (Pin RCLMP; HI or LO Gain)
Accuracy
HILO = LO R HILO = HI R
MODE INTERFACE (Pin MODE)
Logic Level for Positive Gain Slope 0 1.0 V Logic Level for Negative Gain Slope 2.25 5 V Input Resistance 200 kΩ
POWER SUPPLY (Pins VPS1, VPS2, VPSV, VPSL, VPOS)
Supply Voltage 4.5 5.0 5.5 V Quiescent Current per Channel 25 mA Power Dissipation per channel No Signal 125 mW Disable Current AD8332 (VGA and LNA) 300 600 µA AD8331 (VGA and LNA) 240 400 µA AD8332 (ENBL) Each Channel 12 mA AD8332 (ENBV) Each Channel 13 mA AD8331 (ENBL) 11 mA AD8331 (ENBV) 14 mA PSRR V
= 2.74 kΩ, V
CLMP
= 2.21 kΩ, V
CLMP
= 1 V p-p (Clamped) ±50 mV
OUT
= 1 V p-p (Clamped) ±75 mV
OUT
= 0, f = 100 kHz –68 dB
GAIN
Rev. C | Page 5 of 32
AD8331/AD8332

ABSOLUTE MAXIMUM RATINGS

Table 2. Absolute Maximum Ratings
Parameter Rating
Voltage
Supply Voltage (VPSn, VPSV, VPSL, VPOS) 5.5 V Input Voltage (INHn) VS + 200 mV ENB, ENBL, ENBV, HILO Voltage VS + 200 mV GAIN Voltage 2.5 V
Power Dissipation
RU-28 Package (AD8332)4 0.96 W CP-32 Package (AD8332)5 1.97 W RQ-20 Package (AD8331)4 0.78 W
Temperature
Operating Temperature –40°C to +85°C Storage Temperature –65°C to +150°C Lead Temperature (Soldering 60 sec) 300°C
θJA
RU-28 Package (AD8332)4 68°C/W CP-32 Package (AD8332)5 33°C/W RQ-20 Package (AD8331)4 83°C/W
θJC
RU-28 Package (AD8332)4 14°C/W CP-32 Package (AD8332)5 33°C/W RQ-20 Package (AD8331)4 n/a
4
Four-Layer JEDEC Board (2S2P).
5
Exposed pad soldered to board, nine thermal vias in pad — JEDEC 4-Layer
Board J-STD-51-9.
Stresses above those listed under the Absolute Maximum Ratings may cause permanent damage to the device. This 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.

ESD CAUTION

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 this product 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.
Rev. C | Page 6 of 32
AD8331/AD8332

AD8331, AD8332—TYPICAL PERFORMANCE CHARACTERISTICS

TA = 25°C, VS = 5 V, RL = 500 Ω, RS = RIN = 50 Ω, RFB = 280 Ω, CSH = 22 pF, f = 10 MHz, R –4.5 dB to +43.5 dB gain (HILO = LO), and differential signal voltage, unless otherwise specified.
60
50
40
)
30
B d
( N
I A
20
G
10
0
MODE = LO
HILO = HI
HILO = LO
MODE = HI (AC PACKAGE ONLY)
50
SAMPLE SIZE = 80 UNITS V
GAIN
40
S T
30
I N U
F O
%
20
10
= ∞, CL = 1 pF, VCM = 2.5 V,
CLMP
= 0.5V
–10
0 0.2
Figure 3. Gain vs. V
2.0
1.5
1.0
0.5
0
–0.5
GAIN ERROR (dB)
–1.0
–1.5
–2.0
00.2
and MODE (MODE Available on AC Package)
GAIN
–40°C
Figure 4. Absolute Gain Error vs. V
2.0
1.5
1.0
0.5
0
–0.5
GAIN ERROR (dB)
–1.0
–1.5
–2.0
1MHz
30MHz
0 0.2
Figure 5. Absolute Gain Error vs. V
0.60.4 1.00.8 1.1
V
(V)
GAIN
+25°C
+85°C
0.60.4
V
(V)
GAIN
at Three Temperatures
GAIN
10MHz
70MHz
0.60.4
V
(V)
GAIN
at Various Frequencies
GAIN
1.00.8 1.1
1.00.8 1.1
03199-C-003
03199-C-004
03199-C-005
0
–0.1
GAIN ERROR (dB)
Figure 6. Gain Error Histogram
25
SAMPLE SIZE = 50 UNITS
20
= 0.2V
V
GAIN
15 10
5 0
25
% OF UNITS
V
= 0.7V
GAIN
20 15 10
5 0
–0.05
–0.03
–0.01
0.01
–0.11
–0.17
–0.15
–0.13
–0.09
–0.07
CHANNEL-TO-CHANNEL GAIN MATCH(dB)
Figure 7. Gain Match Histogram for V
) B d
( N
I A G
–10
–20
50
40
30
20
10
0
100k
V
= 1V
GAIN
0.8V
0.6V
0.4V
0.2V
0V
1M 1G100M10M
FREQUENCY (Hz)
0.03
0.05
0.07
GAIN
0.09
= 0.2 V and 0.7 V
Figure 8. Frequency Response for Various Values of V
0.11
0.13
0.15
0.40–0.3 –0.2 0.1–0.4–0.5 0.30.2 0.5
0.21
0.19
0.17
GAIN
03199-C-006
03199-C-007
03199-C-008
Rev. C | Page 7 of 32
AD8331/AD8332
GAIN (dB)
60
50
40
30
20
10
0
–10
V
GAIN
0.8V
0.2V
1M 1G100k 100M10M
= 1V
0.6V
0.4V
0V
FREQUENCY (Hz)
03199-C-009
0
V
= 1 V p-p
OUT
–10
–20
–30
) B d
(
–40
K L A T S
–50
S
V
= 1V
–60
–70
–80
–90
GAIN
0.9V
0.7V
0.5V
1M100k 100M10M
FREQUENCY (Hz)
0.4V
03199-C-012
O R C
Figure 9. Frequency Response for Various Values of V
30
V
=0.5V
GAIN
20
10
0
–10
GAIN (dB)
–20
–30
–40
100k
RIN=RS=50Ω,75Ω,100
RIN=RS=1k
RIN=RS= 500
R
=200
IN=RS
1M 1G
FREQUENCY (Hz)
, HILO = HI
GAIN
100M10M
03199-C-010
Figure 10. Frequency Response for Various Matched Source Impedances
30
V
= 0.5V
GAIN
R
=
FB
20
10
)
0
B d
( N
I A
–10
G
–20
–30
–40
1M 1G100k 100M10M
FREQUENCY (Hz)
Figure 11. Frequency Response, Untermin ated, R
= 50 Ω
S
03199-C-011
Figure 12. Channel-to-Channel Crosstalk vs.
Frequency for Various Values of V
50
1µF COUPLING
0.1µF COUPLING
1M100k 100M10M
FREQUENCY(Hz)
45
40
35
30
25 20
GROUP DELAY (ns)
15
10
5
0
GAIN
Figure 13. Group Delay vs. Frequ ency
OFFSET VOLTAGE (mV)
–10
–20
–10
–20
20
10
0
20
10
0
HI GAIN
T=+25°C
LO GAIN
T = –40°C
T = –40°C
T = –40°C
T=+85°C
V
(V)
GAIN
T=+25°C
T=+25°C
T = –40°C
T=+85°C
T=+85°C
Figure 14. Representative Differential Output Offset Voltage vs. V
Temperatures
1.10.40.20 0.30.1 0.90.70.5 0.80.6 1.0
at Three
GAIN
03199-C-013
03199-C-014
Rev. C | Page 8 of 32
AD8331/AD8332
35
SAMPLE SIZE = 100
0.2V < V
30
GAIN
< 0.7V
25
20
15
% TOTAL
10
5
0
GAIN SCALING FACTOR
Figure 15. Gain Scaling Factor Histogram
100
SINGLE ENDED, PIN VOH OR VOL R
=
L
)
(
10
E C N A D E P M
I T
U P
1
T U O
25j
RIN = 75Ω,
= 412
R
FB
RIN = 100Ω,
= 549
R
FB
17
–25j
RIN = 200Ω,
= 1.1k
R
FB
0
03199-B-015
50.5
50.449.6 49.7 49.8 49.9 50.0 50.1 50.2 50.3
Figure 18. Smith Chart, S11 vs. Frequency, 0.1 MHz to 200 MHz
20
15
10
5
) B d
(
0
N
I A G
–5
50j
R
= 50
IN
RFB = 270
RIN = 6kΩ,
=
R
FB
–50j
for Va rious Values of R
RIN = 1k
RIN = 500
,
FB
100j
f = 100kHz
–100j
RIN = 50Ω, 75Ω, AND 100
RIN = 200
RIN = 200
03199-B-018
0.1 100k 1M
10k
)
(
1k
E C N A D E P M
I T
U
100
P N
I
10
FREQUENCY (Hz)
10M 100M
Figure 16. Output Impedance vs. Frequency
RFB = , CSH = 0pF
R
= 6.65k, CSH = 0pF
FB
= 3.01k, CSH = 0pF
R
FB
= 1.1k, CSH = 1.2pF
R
FB
R
= 549, CSH = 8.2pF
FB
R
= 412, CSH = 12pF
FB
R
= 270, CSH = 22pF
FB
1M100k 100M10M
FREQUENCY (Hz)
Figure 17. LNA Input Impedance vs. Frequency for
Various Values of R
and CSH
FB
03199-C-016
03199-C-017
–10
–15
–20
100k
10M
FREQUENCY (Hz)
100M1M
1G
Figure 19. LNA Frequency Response,
IN
100M1M
1G
) B d
( N
I A G
–10
–15
–20
20
15
10
–5
100k
5
0
Single-Ended, for Various Values of R
RFB =
10M
FREQUENCY (Hz)
Figure 20. LNA Frequency Response, Unterminated, Single-Ended
03199-C-019
03199-C-020
Rev. C | Page 9 of 32
AD8331/AD8332
500
)
z H
400
/ V n
( E
S
I
300
O N
D E R R E
200
F E R
­T U P T
100
U O
1.6
1.4
)
1.2
z H / V
1.0
n
( E
S
I
0.8
O N
T U
0.6
P N
I
0.4
0.2
100
f = 10MHz
HILO = HI
HILO = LO
0
0 0.4
0.2 0.8 V
GAIN
(V)
Figure 21. Output-Referred Noise vs. V
RS = 0, RFB = , V HILO = LO OR HI
0
= 1V
GAIN
1M 10M
FREQUENCY (Hz)
Figure 22. Short-Circuit Input-Referred Noise vs. Frequency
RS = 0, RFB = , HILO = LO OR HI, f = 10MHz
GAIN
1.00 RS = 0, RFB = ,
0.95
V
= 1V, f = 10MHz
GAIN
0.90
)
0.85
z H /
0.80
V n
( E
0.75
S
I O N
0.70
T U P
0.65
N
I
0.60
0.55
03199-C-021
1.00.6
03199-C-022
100M100k
0.50
10–30–50 –10 705030
TEMPERATURE (°C)
Figure 24. Short-Circuit Input-Referred Noise vs. Temperature
10
f = 5MHz, R
)
z H / V n
( E
S
I
1.0
O N
T U P N
I
0.1 110
7
6
=∞, V
FB
RS = THERMAL NOISE ALONE
= 1V
GAIN
SOURCE RESISTANCE (
100 1k
Figure 25. Input-Referred Noise vs. R
INCLUDES NOISE OF VGA
)
S
90
03199-C-025
03199-C-024
)
z H
10
/ V n
( E
S
I O N T U P
1
N
I
0.1 0 0.4
0.2 0.8 V
GAIN
(V)
Figure 23. Short-Circuit Input-Referred Noise vs. V
GAIN
03199-C-023
1.00.6
Rev. C | Page 10 of 32
5
) B d
( E
4
R U G
I F
3
E S
I O N
2
1
0
R
IN
SIMULATION
10050 1k
Figure 26. Noise Figure vs. R
= 50
75 100 200
R
=
FB
SOURCE RESISTANCE ()
for Variou s Value s of RIN
S
03199-C-026
AD8331/AD8332
50
f = 10MHz, R
45
40
35
) B d
(
30
E R U
25
G
I F
E
20
S
I
HILO = LO, R
O N
15
10
5
0
0 0.2
0.1 0.50.3 0.90.7
= 50
S
HILO = LO, RIN= 50
=
FB
HILO = HI, R
Figure 27. Noise Figure vs. V
30
25
) B
20
d
( E
R U
15
G
I F
E S
I O
10
N
5
HILO = LO, R
=
FB
HILO = HI, R
=
FB
HILO = HI, RIN= 50
0.60.4
V
(V)
GAIN
HILO = HI, R
HILO = LO, R
IN
= 50
03199-C-027
1.00.8 1.1
GAIN
=
FB
= 50
IN
–30
f = 10MHz
= 1V p-p
V
OUT
–40
) c B d
–50
( N
O
I T R
–60
O T S
I D
–70
C
I N O M
–80
R A H
–90
–100
HILO = LO, HD3
HILO = HI, HD2
200 8000 600400 1.0k 2.0k1.8k1.6k1.4k1.2k
Figure 30. Harmonic Distortion vs. R
–40
f = 10MHz
= 1V p-p
V
OUT
–50
) c B d
( N
–60
O
I T R
O T
–70
S
I D
C
I N
–80
O M R A H
–90
HILO = LO, HD3
HILO = HI,
HD3
HILO = LO, HD2
R
LOAD
()
HILO = HI, HD3
HILO = HI, HD2
HILO = LO, HD2
03199-C-030
LOAD
f = 10MHz, R
0
10 20
15 30 5040
S
= 50
3525
GAIN (dB)
Figure 28. Noise Figure vs. Gain
0
G = 30dB
–10
V
=1V
OUT
P-P
–20 –30
–40
HARMONIC DISTORTION (dBc)
–100
–50
–60
–70
–80 –90
HILO = LO, HD2
HILO = HI, HD2
FREQUENCY(Hz)
Figure 29. Harmonic Distortion vs. Frequency
HILO = LO, HD3
HILO = HI, HD3
5545 60
100M1M 10M
03199-C-028
03199-C-029
–100
–40
–50
) c B d
( N
–60
O
I T R
O T
–70
S
I D
C
I N
–80
O M R A H
–90
–100
10 40 5003020
C
LOAD
Figure 31. Harmonic Distortion vs. C
f = 10MHz GAIN = 30 dB
HILO = LO, HD3
14032
V
(V p-p)
OUT
(pF)
HILO = HI, HD3
HILO = HI, HD2
LOAD
HILO = LO, HD2
Figure 32. Harmonic Distortion vs. Differential Output Voltage
03199-C-031
03199-C-032
Rev. C | Page 11 of 32
AD8331/AD8332
0
V
= 1V p-p
OUT
–20
INPUT RANGE LIMITED WHEN HILO = LO
–40
–60
–80
DISTORTION (dBc)
–100
–120
DISTORTION (dBc)
–100
–120
) m
B d
( R
E W O
P T
U P N
I
HILO = HI,
HD3
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Figure 33. Harmonic Distortion vs. V
0
= 1V p-p
V
OUT
–20
INPUT RANG E
–40
–60
–80
LIMITED WHEN
HILO = LO
HILO = HI,
HD2
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
0
Figure 34. Harmonic Distortion vs. V
10
5
f = 10MHz
0
–5
–10
–15
–20
–25
–30
0 0.30.1
HILO = HI
Figure 35. Input 1 dB Compression vs. V
HILO = LO,
HD2
V
HILO = HI,
HD3
V
0.40.2 V
(V)
GAIN
HILO = LO,
HD2
(V)
GAIN
(V)
GAIN
HILO = LO,
HD3
GAIN
GAIN
HILO = HI,
HD2
, f = 1 MHz
HILO = LO,
HD3
, f = 10 MHz
HILO = LO
GAIN
0.90.70.5 0.80.6 1.0
03199-C-033
03199-C-034
03199-C-035
0
V
= 1V p-p COMPOSITE (f1+ f2)
OUT
G = 30dB
–10
–20
–30
)
c B
–40
d
( 3 D
–50
M
I
–60
–70
–80
–90
1M
10M
FREQUENCY (Hz)
Figure 36. IMD3 vs. Frequen cy
40
HILO = HI,
1MHz
35
) m
B d
( 3
P
I T
U P T U O
30
HILO = HI,
25
10MHz
20
15
= 1V p-p COMPOSITE (f1 + f2)
V
OUT
10
5
0
0.1 0.40 0.30.2
HILO = LO,
10MHz
V
GAIN
HILO = LO,
1MHz
(V)
Figure 37. Output Third Order Intercept vs. V
2mV
100
90
10
0
50mV
Figure 38. Small Signal Pulse Response, G = 30 dB,
Top: Input, Bottom: Output Voltage, HILO = HI or LO
10ns
GAIN
03199-C-036
100M
03199-C-037
1.00.90.80.70.60.5
03199-C-038
Rev. C | Page 12 of 32
AD8331/AD8332
5
20mV
100
90
10
0
500mV
Figure 39. Large Signal Pulse Response, G = 30 dB,
HILO = HI or LO, Top: Input, Bottom: Output Voltage
(V)
V
OUT
2
G = 30dB
1
INPUT
0
–1
C
C
= 50pF
L
= 0pF
L
10ns
03199-C-039
4
) p
3
­p
V
(
T U O
V
2
1
0
010 3020 5040
HILO = HI
HILO = LO
R
CLMP
(kΩ)
Figure 42. Clamp Level vs. R
4
G = 40dB
3
2
1
) V
(
T
0
U O
V
–1
–2
R
= 48.1k R
CLMP
R
= 7.15k R
CLMP
CLMP
CLMP
= 2.67k
03199-C-042
CLMP
= 16.5k
INPUT IS NOT TO SCALE
–2
10–10–30 0–20
TIME (ns)
Figure 40. Large Signal Pulse Response for
Various Capacitive Loads, C
500mV
200mV
Figure 41. Pin GAIN Transient Response,
, Bottom: Output Voltage
Top : V
GAIN
604020 5030–40
= 0 pF, 10 pF, 20 pF, 50 pF
L
400ns
8070
03199-B-041
03199-C-040
–3
–4
–10 200
10
TIME (ns)
Figure 43. Clamp Level Pulse Response
200mV
100
90
10
0
Figure 44. LNA Overdrive Recovery, V
1 V p-p Burst, V
= 0.27 V, VGA Output Shown
GAIN
30
100ns
0.05 V p-p to
INH
6040 50
03199-B-044
03199-C-043
Rev. C | Page 13 of 32
AD8331/AD8332
50mV
100
90
10
0
Figure 45. VGA Overdrive Recovery, V
V
= 1 V, VGA Output Shown Attenuated 24 dB
GAIN
50mV
100 90
10
0
Figure 46. VGA Overdrive Recovery, V
V
= 1 V, VGA Output Shown Attenuated 24 dB
GAIN
2V
100ns
4 mV p-p to 70 mV p-p Burst,
INH
100ns
4 mV p-p to 275 mV p-p Burst,
INH
2V
1V
03199-B-045
1ms
03199-B-048
Figure 48. Enable Response, Large Signal,
, Bottom: V
Top : V
ENB
0
–10
–20
VPSV, V
–30
) B d
(
–40
R R S P
–50
–60
–70
–80
03199-B-046
= 0.5V
GAIN
1M100k 100M10M
, V
= 150 mV p-p
OUT
INH
VPS1, V
FREQUENCY (Hz)
= 0.5V
GAIN
VPS1, V
GAIN
= 0V
03199-C-049
Figure 49. PSRR v s. Frequency (No By pass Capacito r)
60
= 0.5V
V
GAIN
55
50
45
AD8332
200mV
Figure 47. Enable Response, Top: V
, Bottom: V
ENB
OUT
, V
1ms
= 30 mV p-p
INH
03199-B-047
Rev. C | Page 14 of 32
40
35
30
QUIESCENT SUPPLY CURRENT (mA)
25
20
–40
–20
TEMPERATURE (°C)
AD8331
400
20
Figure 50. Quiescent Supply Current vs. Temperature
1008060
03199-C-050
AD8331/AD8332

TEST CIRCUITS

NETWORK ANALYZER
5050
INOUT
1.8nF
270
FB*
22pF
0.1µF
0.1µF
INH
LMD
120nH
*FERRITE BEAD
Figure 51. Gain and Bandwidth Measurements
1.8nF
270
DUT
0.1µF
0.1µF
237
237
28
28
1:1
03199-C-051
OSCILLOSCOPE
50
120nH
50
FB*
49
0.1µF
22pF
*FERRITE BEAD
LMD
0.1µF
Figure 52. Transient Measurements
ABG
FB*
0.1µF
120nH
1
22pF
Figure 53. Used for Noise Measurements
INH
0.1µF
INH
LMD
DUT
0.1µF
0.1µF
DUT
237
237
28
28
0.1µF
0.1µF
1:1
IN
1:1
*FERRITE BEAD
50
IN
SPECTRUM ANALYZER
50
03199-C-052
03199-C-053
Rev. C | Page 15 of 32
AD8331/AD8332
1.8nF
270
DUT
0.1µF
0.1µF
237
28
237
28
FB*
120nH
22pF
50
*FERRITE BEAD
0.1µF
0.1µF
INH
LMD
1:1
SPECTRUM ANALYZER
50
IN
03199-C-054
Figure 54. Distortion
NETWORK ANALYZER
FB*
120nH
0.1µF
22pF
*FERRITE BEAD
50
1.8nF
INH
LMD
0.1µF
270
DUT
50
0.1µF
0.1µF
INOUT
50
237
50
03199-C-055
237
28
28
1:1
Figure 55. S11 Measurements
Rev. C | Page 16 of 32
AD8331/AD8332
(
)
(
(
)
(
(
)
(
)

THEORY OF OPERATION

OVERVIEW

The following discussion applies to all part numbers. Figure 56 and Figure 1 are functional block diagrams of the AD8331 and AD8332, respectively.
GAIN
INT
17
COMM
VIN
8
7
AD8331
G = –48dB to 0dB
BIAS AND
INTERPOLATOR
19
ENBL
VPOS
VCM
14
11
V
VGA
+21dB
18
ENBV RCLMP
HILO
19
3.5dB/
15.5dB
MID
15
POST AMP1
CLAMP
12
VOH
VOL
16
9
MODE
03199-C-056
LON LOP VIP
4 5
3
VPSL
6
COML
2
INH
LMD
GAIN
LNA
1
LNA BIAS
)
(V
MID
10
20
COMM
Figure 56. Functional Block Diagram — AD8331
Each channel contains an LNA that provides user-adjustable input impedance termination, a differential X-AMP VGA, and a programmable gain postamplifier with adjustable output voltage limiting. Figure 57 shows a simplified block diagram.
60
50
40
30
MODE = LO
20
GAIN (dB)
10
0
–10
00.2
MODE = HI
(WHERE AVAILABLE)
HILO = HI
HILO = LO
0.60.4
V
(V)
GAIN
Figure 58. Gain Control Characteristics
When MODE is set high, (where available):
GAIN
or
GAIN
03199-C-058
1.00.8 1.1
3=,545+×50=)( LOHILOdB.VVdBdBGAIN
()
()
()
4=,557+×50=)( HIHILOdB.VVdBdBGAIN
()
VIN
VIP
GAIN
*SHARED BETWEEN CHANNELS
X-AMP VGA POSTAMP
[(–48 to 0) + 21] dB
A
B
A
N
I
S
D
N
R
I
T
O
E
L
A
P
T
O
R
*
VCM
V
MID
3.5dB/15.5dB
VOH
VOL
RCLMP
CLAMP*
HILO
LMD
PREAMPLIFIER
+INH
BIAS (V
)
MID
LON
19dB
LNA
LOP
INTERFACE*
GAIN
Figure 57. Simplified Block Diagram
The linear-in-dB gain control interface is trimmed for slope and absolute accuracy. The overall gain range is 48 dB, extending from –4.5 dB to +43.5 dB or from +7.5 dB to +55.5 dB, depending on the setting of the HILO pin. The slope of the gain control interface is 50 dB/V, and the gain control range is 40 mV to 1 V, leading to the following expressions for gain:
GAIN
()
=×=
)
1,56 50)( LOHILOdB.VVdBdBGAIN
or
GAIN
()
=+×=
)
2,55 50)( HIHILOdB.VVdBdBGAIN
The gain characteristics are shown in Figure 58.
The LNA converts a single-ended input to a differential output with a voltage gain of 19 dB. When only one output is used, the gain is 13 dB. The inverting output is used for active input impedance termination. Each of the LNA outputs is capacitively coupled to a VGA input. The VGA consists of an attenuator with a range of 48 dB followed by an amplifier with 21 dB of gain, for a net gain range of –27 dB to +21 dB. The X-AMP gain-interpolation technique results in low gain error and uniform bandwidth, and differential signal paths minimize
03199-B-057
distortion.
The final stage is a logic programmable amplifier with gains of
3.5 dB or 15.5 dB. The LO and HI gain modes are optimized for 12-bit and 10-bit A/D converter applications, in terms of output-referred noise and absolute gain range. Output voltage limiting may be programmed by the user.

LOW NOISE AMPLIFIER (LNA)

Good noise performance relies on a proprietary ultralow noise preamplifier at the beginning of the signal chain, which minimizes the noise contribution in the following VGA. Active impedance control optimizes noise performance for applications that benefit from input matching.
Rev. C | Page 17 of 32
AD8331/AD8332
A simplified schematic of the LNA is shown in Figure 59. INH is capacitively coupled to the source. An on-chip bias generator centers the output dc levels at 2.5 V and the input voltages at
3.25 V. A capacitor C capacitor C
is connected from the LMD pin to ground.
INH
of the same value as the input coupling
LMD
C
FB
R
FB
LOP
VPOS
LON
is needed in series with RFB, since the dc levels at Pins LON
C
FB
and INH are unequal. Expressions for choosing R R
and for choosing CFB are found in the Applications section.
IN
C
and the ferrite bead enhance stability at higher frequencies
SH
in terms of
FB
where the loop gain declines and prevents peaking. Frequency response plots of the LNA are shown in Figure 19 and Figure 20. The bandwidth is approximately 130 MHz for matched input impedances of 50 Ω to 200 Ω and declines at higher source impedances. The unterminated bandwidth (R
= ∞) is
FB
approximately 80 MHz.
I
C
INH
R
S
INH
C
SH
Figure 59. Simplified LNA Schematic
Q1
I
I
0
0
Q2
I
0
0
LMD
C
LMD
The LNA supports differential output voltages as high as 5 V p-p with positive and negative excursions of ±1.25 V, about a common-mode voltage of 2.5 V. Since the differential gain magnitude is 9, the maximum input signal before saturation is ± 275 mV or 550 mV p-p. Overload protection ensures quick recovery time from large input voltages. Since the inputs are capacitively coupled to a bias voltage near midsupply, very large inputs can be handled without interacting with the ESD protection.
Low value feedback resistors and the current-driving capability of the output stage allow the LNA to achieve a low input­referred voltage noise of 0.74 nV/√Hz. This is achieved with a modest current consumption of 10 mA per channel (50 mW). On-chip resistor matching results in precise gains of 4.5 per side (9 differential), critical for accurate impedance control. The use of a fully differential topology and negative feedback minimizes distortion. Low HD2 is particularly important in second harmonic ultrasound imaging applications. Differential signaling enables smaller swings at each output, further reducing third order distortion.

Active Impedance Matching

The LNA supports active impedance matching through an external shunt feedback resistor from Pin LON to Pin INH. The input resistance R
is given by Equation 5, where A is the
IN
single-ended gain of 4.5, and 6 kΩ is the unterminated input impedance.
Each output can drive external loads as low as 100 Ω in addition to the 100 Ω input impedance of the VGA (200 Ω differential). Capacitive loading up to 10 pF is permissible. All loads should be ac-coupled. Typically, Pin LOP output is used as a single­ended driver for auxiliary circuits, such as those used for Doppler mode ultrasound imaging, and Pin LON drives R
.
FB
Alternatively, a differential external circuit can be driven from
03199-C-059
the two outputs, in addition to the active feedback termination. In both cases, important stability considerations discussed in the Applications section should be carefully observed.
The impedance at each LNA output is 5 Ω. A 0.4 dB reduction in open-circuit gain results when driving the VGA, and 0.8 dB with an additional 100 Ω load at the output. The differential gain of the LNA is 6 dB higher. If the load is less than 200 Ω on either side, a compensating load is recommended on the opposite output.

LNA Noise

The input-referred voltage noise sets an important limit on system performance. The short-circuit input voltage noise of the LNA is 0.74 nV/√Hz or 0.82 nV/√Hz (at maximum gain), including the VGA noise. The open-circuit current noise is
2.5 pA/√Hz. These measurements, taken without a feedback resistor, provide the basis for calculating the input noise and noise figure performance of the configurations in Figure 60. Figure 61 and Figure 62 are simulations extracted from these results, and the 4.1 dB NF measurement with the input actively matched to a 50 Ω source. Unterminated (R
= ∞) operation
FB
exhibits the lowest equivalent input noise and noise figure. Figure 61 shows the noise figure versus source resistance, rising at low R source noise, and again at high R
, where the LNA voltage noise is large compared to the
S
due to current noise. The
S
VGA’s input-referred voltage noise of 2.7 nV/√Hz is included in all of the curves.
×Ω6
R
R
FB
=
IN
+1
A
=Ω6
k
Rk
FB
+Ω33
Rk
5
()
FB
Rev. C | Page 18 of 32
AD8331/AD8332
V
IN
V
IN
ACTIVE IMPEDANCE MATCH –RS = R
V
IN
UNTERMINATED
R
S
+ –
RESISTIVE TERMINATION
R
S
+ –
R
S
+ –
RIN=
Figure 60. Input Configurations
7
6
5
) B d
( E
4
R U G
I F
3
E S
I O N
2
1
SIMULATION
0
10050 1k
Figure 61. Noise Figure vs. R
Active Matched, and Unterminated Inputs
7
INCLUDES NOISE OF VGA
6
5
4
IGURE (dB)
3
NOISE F
2
1
SIMULATION
0
10050 1k
Figure 62. Noise Figure vs. R
R
IN
V
OUT
R
IN
R
IN
1 + 4.5
R
S
R
R
FB
V
OUT
FB
IN
V
OUT
03199-C-060
INCLUDES NOISE OF VGA
RESISTIVE TERMINATION
ACTIVE IMPEDANCE MATCH
= RIN)
(R
S
UNTERMINATED
R
()
S
for Resistive,
S
RIN = 50
70
100
200
RFB =
RS(Ω)
for Various Fixed Values of RIN, Actively Matched
S
03199-C-061
03199-C-081
The primary purpose of input impedance matching is to improve the system transient response. With resistive termination, the input noise increases due to the thermal noise of the matching resistor and the increased contribution of the LNA’s input voltage noise generator. With active impedance matching, however, the contributions of both are smaller than they would be for resistive termination by a factor of 1/(1 +
LNA Gain). Figure 61 shows their relative noise figure (NF)
performance. In this graph, the input impedance has been swept with R
to preserve the match at each point. The noise figures
S
for a source impedance of 50 Ω are 7.1 dB, 4.1 dB, and 2.5 dB, respectively, for the resistive, active, and unterminated configurations. The noise figures for 200 Ω are 4.6 dB, 2.0 dB, and 1.0 dB, respectively.
Figure 62 is a plot of the NF versus R
for various values of RIN,
S
which is helpful for design purposes. The plateau in the NF for actively matched inputs mitigates source impedance variations. For comparison purposes, a preamp with a gain of 19 dB and noise spectral density of a 1.0 nV/√Hz, combined with a VGA with 3.75 nV/√Hz, would yield a noise figure degradation of approximately 1.5 dB (for most input impedances), significantly worse than the AD8332 performance.
The equivalent input noise of the LNA is the same for single­ended and differential output applications. The LNA noise figure improves to 3.5 dB at 50 Ω without VGA noise, but this is exclusive of noise contributions from other external circuits connected to LOP. A series output resistor is usually recommended for stability purposes, when driving external circuits on a separate board (see the Applications section). In low noise applications, a ferrite bead is even more desirable.

VARIABLE GAIN AMPLIFIER

The differential X-AMP VGA provides precise input attenuation and interpolation. It has a low input-referred noise of 2.7 nV/√Hz and excellent gain linearity. A simplified block diagram is shown in Figure 63.
GAIN
g
VIP
VIN
GAIN INTERPOLATOR
m
6dB
R
(BOTH CHANNELS)
48dB
2R
Figure 63. Simplified VGA Schematic
POST-AMP
POST-AMP
03199-C-063
Rev. C | Page 19 of 32
AD8331/AD8332

X-AMP VGA

The input of the VGA is a differential R-2R ladder attenuator network, with 6 dB steps per stage and a net input impedance of 200 Ω differential. The ladder is driven by a fully differential input signal from the LNA and is not intended for single-ended operation. LNA outputs are ac-coupled to reduce offset and isolate their common-mode voltage. The VGA inputs are biased through the ladder’s center tap connection to VCM, which is typically set to 2.5 V and is bypassed externally to provide a clean ac ground.
The signal level at successive stages in the input attenuator falls from 0 dB to –48 dB, in 6 dB steps. The input stages of the X-AMP are distributed along the ladder, and a biasing interpolator, controlled by the gain interface, determines the input tap point. With overlapping bias currents, signals from successive taps merge to provide a smooth attenuation range from 0 dB to –48 dB. This circuit technique results in excellent, linear-in-dB gain law conformance and low distortion levels and deviates ±0.2 dB or less from ideal. The gain slope is monotonic with respect to the control voltage and is stable with variations in process, temperature, and supply.
The X-AMP inputs are part of a gain-of-12 feedback amplifier, which completes the VGA. Its bandwidth is 150 MHz. The input stage is designed to reduce feedthrough to the output and ensure excellent frequency response uniformity across gain setting (see Figure 8 and Figure 9).

Gain Control

Position along the VGA attenuator is controlled by a single­ended analog control voltage, V to 1.0 V. The gain control scaling is trimmed to a slope of 50 dB/V (20 mV/dB). Values of V
GAIN
minimum or maximum gain values. Both channels of the AD8332 are controlled from a single gain interface to preserve matching. Gain can be calculated using Equations 1 and 2.
Gain accuracy is very good since both the scaling factor and absolute gain are factory trimmed. The overall accuracy relative to the theoretical gain expression is ±1 dB for variations in temperature, process, supply voltage, interpolator gain ripple, trim errors, and tester limits. The gain error relative to a best-fit line for a given set of conditions is typically ±0.2 dB. Gain matching between channels is better than 0.1 dB (see Figure 7, which shows gain errors in the center of the control range). When V or > 0.95, gain errors are slightly greater.
The gain slope may be inverted, as shown in Figure 58 (avail­able in most versions). The gain drops with a slope of –50 dB/V across the gain control range from maximum to minimum gain. This slope is useful in applications, such as automatic gain control, where the control voltage is proportional to the measured output signal amplitude. The inverse gain mode is selected by setting the MODE pin HI.
, with an input range of 40 mV
GAIN
beyond the control range saturate to
< 0.1
GAIN
Gain control response time is less than 750 ns to settle within 10% of the final value for a change from minimum to max­imum gain.

VGA Noise

In a typical application, a VGA compresses a wide dynamic range input signal to within the input span of an ADC. While the input-referred noise of the LNA limits the minimum resolvable input signal, the output-referred noise, which depends primarily on the VGA, limits the maximum instantaneous dynamic range that can be processed at any one particular gain control voltage. This limit is set in accordance with the quantization noise floor of the ADC.
Output and input-referred noise as a function of V
GAIN
are plotted in Figure 21 and Figure 23 for the short-circuited input condition. The input noise voltage is simply equal to the output noise divided by the measured gain at each point in the control range.
The output-referred noise is flat over most of the gain range, since it is dominated by the fixed output-referred noise of the VGA. Values are 48 nV/√Hz in LO gain mode and 178 nV/√Hz in HI gain mode. At the high end of the gain control range, the noise of the LNA and source prevail. The input-referred noise reaches its minimum value near the maximum gain control voltage, where the input-referred contribution of the VGA becomes very small.
At lower gains, the input-referred noise, and thus noise figure, increases as the gain decreases. The instantaneous dynamic range of the system is not lost, however, since the input capacity increases with it. The contribution of the ADC noise floor has the same dependence as well. The important relationship is the magnitude of the VGA output noise floor relative to that of the ADC.
With its low output-referred noise levels, these devices ideally drive low-voltage ADCs. The converter noise floor drops 12 dB for every 2 bits of resolution and drops at lower input full-scale voltages and higher sampling rates. ADC quantization noise is discussed in the Applications section.
The preceding noise performance discussion applies to a differential VGA output signal. Although the LNA noise performance is the same in single-ended and differential applications, the VGA performance is not. The noise of the VGA is significantly higher in single-ended usage, since the contribution of its bias noise is designed to cancel in the differential signal. A transformer can be used with single-ended applications when low noise is desired.
Rev. C | Page 20 of 32
AD8331/AD8332
Gain control noise is a concern in very low noise applications. Thermal noise in the gain control interface can modulate the channel gain. The resultant noise is proportional to the output signal level and usually only evident when a large signal is present. Its effect is observable only in LO gain mode, where the noise floor is substantially lower. The gain interface includes an on-chip noise filter, which reduces this effect significantly at frequencies above 5 MHz. Care should be taken to minimize noise impinging at the GAIN input. An external RC filter may be used to remove V
source noise. The filter bandwidth
GAIN
should be sufficient to accommodate the desired control bandwidth.

Common-Mode Biasing

An internal bias network connected to a midsupply voltage establishes common-mode voltages in the VGA and postamp. An externally bypassed buffer maintains the voltage. The bypass capacitors form an important ac ground connection, since the VCM network makes a number of important connections internally, including the center tap of the VGA’s differential input attenuator, the feedback network of the VGA’s fixed gain amplifier, and the feedback network of the postamplifier in both gain settings. For best results, use a 1 nF and a 0.1 µF capacitor in parallel, with the 1 nF nearest to Pin VCM. Separate VCM pins are provided for each channel. For dc-coupling to a 3 V ADC, the output common-mode voltage is adjusted to 1.5 V by biasing the VCM pin.

POSTAMPLIFIER

The final stage has a selectable gain of 3.5 dB or 15.5 dB, set by the logic Pin HILO. These correspond to linear gains of 1.5 or 6. A simplified block diagram of the postamplifier is shown in Figure 64.
Separate feedback attenuators implement the two gain settings. These are selected in conjunction with an appropriately scaled input stage to maintain a constant 3 dB bandwidth between the two gain modes (~150 MHz). The slew rate is 1200 V/µs in HI gain mode and 300 V/µs in LO gain mode. The feedback networks for HI and LO gain modes are factory trimmed to adjust the absolute gains of each channel.

Noise

The topology of the postamplifier provides constant input­referred noise with the two gain settings and variable output­referred noise. The output-referred noise in HI gain mode increases (with gain) by four. This setting is recommended when driving converters with higher noise floors. The extra gain boosts the output signal levels and noise floor appropriately. When driving circuits with lower input noise floors, the LO gain mode optimizes the output dynamic range.
Gm2
+
VOH
Gm1
F2
VCM
F1
Gm2
Gm1
Figure 64. Postamplifier Block Diagram
VOL
03199-B-064
Although the quantization noise floor of an ADC depends on a number of factors, the 48 nV/√Hz and 178 nV/√Hz levels are well suited to the average requirements of most 12-bit and 10-bit converters, respectively. An additional technique, described in the Applications section, can extend the noise floor even lower for possible use with 14-bit ADCs.

Output Clamping

Outputs are internally limited to a level of 4.5 V p-p differential when operating at a 2.5 V common-mode voltage. The postamp implements an optional output clamp engaged through a resistor from R
to ground. Table shows a list of
CLMP
recommended resistor values.
Output clamping can be used for ADC input overload protection, if needed, or postamp overload protection when operating from a lower common-mode level, such as 1.5 V. The user should be aware that distortion products increase as output levels approach the clamping levels and should adjust the clamp resistor accordingly. Also, see the Applications section.
The accuracy of the clamping levels is approximately ±5% in LO or HI mode. Figure 65 illustrates the output characteristics for a few values of R
5.0
4.5
4.0
3.5
3.0
(V)
OL
2.5
, V
OH
2.0
V
1.5
1.0
0.5
0
–3 –2
.
CLMP
R
=
CLMP
8.8k
3.5k
R
= 1.86k
CLMP
Figure 65. Output Clamping Characteristics
0–1
V
(V)
INH
213
03199-C-065
Rev. C | Page 21 of 32
AD8331/AD8332

APPLICATIONS

LNA – EXTERNAL COMPONENTS

The LMD pin (connected to the bias circuitry) must be bypassed to ground, and signal source to the INH pin capacitively coupled using 2.2 nF to 0.1 μF capacitors (see Figure 66).
The unterminated input impedance of the LNA is 6 kΩ. The user may synthesize any LNA input resistance between 50 Ω and 6 kΩ. R from Table .
Table 3. LNA External Component Values for Common Source Impedances
R
(Ω) R
IN
50 280 22 75 412 12 100 562 8 200 1.13k 1.2 500 3.01k None 6k
When active input termination is used, a 0.1 µF capacitor (C required to isolate the input and output bias voltages of the LNA.
The shunt input capacitor, C frequencies where the active termination match is lost due to the HF gain roll-off of the LNA. Suggested values are shown in Table ; for unterminated applications, reduce the capacitor value by half.
When a long trace to Pin INH is unavoidable, or if both LNA outputs drive external circuits, a small ferrite bead (FB) in series with Pin INH preserves circuit stability with negligible effect on noise. The bead shown is 75 Ω at 100 MHz (Murata BLM21 or equivalent). Other values may prove useful.
Figure 67 shows the interconnection details of the LNA output. Capacitive coupling between LNA outputs and the VGA inputs is required because of differences in their dc levels and to eliminate the offset of the LNA. Capacitor values of 0.1 µF are recommended. There is 0.4 dB loss in gain between the LNA output and the VGA input due to the 5 Ω output resistance. Additional loading at the LOP and LON outputs will affect LNA gain.
is calculated according to Equation 6 or selected
FB
×Ω33
Rk
()
IN
=
R
FB
(Nearest STD 1% Value, Ω) C
FB
Ω6
Rk
()
6
()
IN
, reduces gain peaking at higher
SH
(pF)
SH
None
FB
) is
C
0.1µF
V
GAIN
1nF
0.1µF
1nF
1nF
+5V
LMD
0.1µF
1
LMD2
2
INH2
3
VPS2
4
LON2
5
LOP2
6
COM2
7
VIP2
8
VIN2
9
VCM2
10
GAIN
11
RCLMP
12
VOH2
13
VOL2
14
COMM
*
SEE TEXT
LMD1
INH1
VPS1
LON1
LOP1
COM1
VIP1
VIN1
VCM1
HILO
ENB
VOH1
VOL1
VPSV
28
27
26
25
24
23
22
21
20
19
18
17
16
15
1nF
FB
C
*
SH
1nF
C
*
FB
R
*
FB
LNA OUT
0.1µF
1nF
VGA OUT
VGA OUT
0.1µF
0.1µF
5V
5V
5V
* *
0.1µF
5V
0.1 F
LNA
SOURCE
Figure 66. Basic Connections for a Typical Channel (AD8332 Shown)
TO EXT
CIRCUIT
VIP
VCM
VIN
50
50
100
100
TO EXT
CIRCUIT
5
LON
LNA
C
SH
LOP
5
Figure 67. Interconnections of the LNA and VGA
Both LNA outputs are available for driving external circuits. Pin LOP should be used in those instances when a single-ended LNA output is required. The user should be aware of stray capacitance loading of the LNA outputs, in particular LON. The LNA can drive 100 Ω in parallel with 10 pF. If an LNA output is routed to a remote PC board, it will tolerate a load capacitance up to 100 pF with the addition of a 49.9 Ω series resistor or ferrite 75 Ω/100 MHz bead.
03199-C-066
03199-C-067
Rev. C | Page 22 of 32
AD8331/AD8332

Gain Input

Pin GAIN is common to both channels of the AD8332. The input impedance is nominally 10 M and a bypass capacitor from 100 pF to1 nF is recommended.
Parallel connected devices may be driven by a common voltage source or DAC. Decoupling should take into account any bandwidth considerations of the drive waveform, using the total distributed capacitance.
If gain control noise in LO gain mode becomes a factor, maintaining ≤15 nV/√Hz noise at the GAIN pin will ensure satisfactory noise performance. Internal noise prevails below 15 nV/√Hz at the GAIN pin. Gain control noise is negligible in HI gain mode.

VCM Input

The common-mode voltage of Pins VCM, VOL, and VOH defaults to 2.5 Vdc. With output ac-coupled applications, the VCM pin will be unterminated; however, it must still be bypassed in close proximity for ac grounding of internal circuitry. The VGA outputs may be dc connected to a differential load, such as an ADC. Common-mode output voltage levels between 1.5 V and 3.5 V may be realized at Pins VOH and VOL by applying the desired voltage at Pin VCM. DC-coupled operation is not recommended when driving loads on a separate PC board.
The voltage on the VCM pin is sourced by an internal buffer with an output impedance of 30 Ω and a ±2 mA default output current (see Figure 68). If the VCM pin is driven from an external source, its output impedance should be <<30 Ω and its current drive capability should be >>2 mA. If the VCM pins of several devices are connected in parallel, the external buffer should be capable of overcoming their collective output currents. When a common-mode voltage other than 2.5 V is used, a voltage-limiting resistor, R
, is needed to protect
CLMP
against overload.
INTERNAL
2mA MAX
AC GROUNDING FOR INTERNAL CIRCUITRY
CIRCUITRY
V
CM
30
100pF
Figure 68. VCM Interface
RO << 30
0.1µF
NEW V
CM
03199-B-068

Logic Inputs—ENB, MODE, and HILO

The input impedance of all enable pins is nominally 25 kΩ and may be pulled up to 5 V (a pull-up resistor is recommended) or driven by any 3 V or 5 V logic families. The enable pins perform a power-down function, when disabled, the VGA outputs are near ground. Multiple devices may be driven from a common source. Consult the pin-function tables for circuit functions controlled by the enable pins.
Pin HILO is compatible with 3 V or 5 V CMOS logic families. It is either connected to ground or pulled up to 5 V, depending on the desired gain range and output noise.

Optional Output Voltage Limiting

The RCLMP pin provides the user with a means to limit the output voltage swing when used with loads that have no provisions for prevention of input overdrive. The peak-to-peak limited voltage is adjusted by a resistor to ground, and Table lists several voltage levels and the corresponding resistor value. Unconnected, the default limiting level is 4.5 V p-p.
Note that third harmonic distortion will increase as waveform amplitudes approach clipping. For lowest distortion, the clamp level should be set higher than the converter input span. A clamp level of 1.5 V p-p is recommended for a 1 V p-p linear output range, 2.7 V p-p for a 2 V p-p range, or 1 V p-p for a
0.5 V p-p operation. The best solution will be determined experimentally. Figure 69 shows third harmonic distortion as a function of the limiting level for a 2 V p-p output signal. A wider limiting level is desirable in HI gain mode.
–20
V
= 0.75V
GAIN
–30
–40
) c B d
(
–50
3 D H
–60
–70
–80
Figure 69. HD3 vs. Clamping Level for 2 V p-p Differential Input
2.0 3.51.5 3.02.5 4.0 4.5 CLAMP LIMIT LEVEL (V p-p)
HILO = LO
HILO = HI
5.0
03199-C-069
Rev. C | Page 23 of 32
AD8331/AD8332
Table 4. Clamp Resistor Values
Clamp Resistor Value (kΩ) Clamp Level
(V p-p)
0.5 1.21
1.0 2.74 2.21
1.5 4.75 4.02
2.0 7.5 6.49
2.5 11 9.53
3.0 16.9 14.7
3.5 26.7 23.2
4.0 49.9 39.2
4.4 100 73.2

Output Filtering and Series Resistor Requirements

To ensure stability at the high end of the gain control range, series resistors or ferrite beads are recommended for the outputs when driving large capacitive loads, or circuits on other boards,. These components can be part of the external noise filter.
Recommended resistor values are 84.5 Ω for LO gain mode and 100 Ω for HI gain mode (see Figure 66) and are placed near Pins VOH and VOL. Lower value resistors are permissible for applications with nearby loads or with gains less than 40 dB. Lower values are best selected empirically.
An antialiasing noise filter is typically used with an ADC. Filter requirements are application dependent.
When the ADC resides on a separate board, the majority of filter components should be placed nearby to suppress noise picked up between boards and mitigates charge kickback from the ADC inputs. Any series resistance beyond that required for output stability should be placed on the ADC board. Figure 70 shows a second order low-pass filter with a bandwidth of 20 MHz. The capacitor is chosen in conjunction with the 10 pF input capacitance of the ADC.
0
84.5
0
Figure 70. 20 MHz Second-Order Low-Pass Filter
HILO = LO HILO = HI
OPTIONAL
BACKPLANE
.
1
µ
F
.
1
µ
F
1
.
5
µ
H
158
15884.5
1
.
5
µ
H
18pF
ADC
The relative noise and distortion performance of the two gain modes can be compared in Figure 21 and Figure 27 through Figure 37. The 48 nV/√Hz noise floor of the LO gain mode is suited to converters with higher sampling rates or resolutions (such as 12 bits). Both gain modes can accommodate ADC full­scale voltages as high as 4 V p-p. Since distortion performance remains favorable for output voltages as high as 4 V p-p (see Figure 32), it is possible to lower the output-referred noise even further by using a resistive attenuator (or transformer) at the output. The circuit in Figure 71 has an output full-scale range of 2 V p-p, a gain range of –10.5 dB to +37.5 dB, and an output noise floor of 24 nV/√Hz, making it suitable for some 14-bit ADC applications.
HZ
187
2:1
187
2V p-p DIFF, 24n V/
HZ
374
LPF
ADC
AD6644
03199-C-071
4V p-p DIFF, 48n V/
VOH
VOL
Figure 71. Adjusting the Noise Floor for 14-Bit ADCs

OVERLOAD

These devices respond gracefully to large signals that overload its input stage and to normal signals that overload the VGA when the gain is set unexpectedly high. Each stage is designed for clean-limited overload waveforms and fast recovery when gain setting or input amplitude is reduced.
Signals larger than ±275 mV at the LNA input are clipped to 5 V p-p differential prior to the input of the VGA. Figure 44 shows the response to a 1 V p-p input burst. The symmetric overload waveform is important for applications, such as CW Doppler ultrasound, where the spectrum of the LNA outputs during overload is critical. The input stage is also designed to accommodate signals as high as ±2.5 V without triggering the slow-settling ESD input protection diodes.
Both stages of the VGA are susceptible to overload. Postamp limiting is more common and results in the clean-limited output characteristics found in Figure 45. Under more extreme conditions, the X-AMP will overload, causing the minor glitches evident in Figure 46. Recovery is fast in all cases. The graph in Figure 72 summarizes the combinations of input signal and gain that lead to the different types of overload.

DRIVING ADCS

The output drive will accommodate a wide range of ADCs. The noise floor requirements of the VGA will depend on a number of application factors, including bit resolution, sampling rate, full-scale voltage, and the bandwidth of the noise/antialias filter. The output noise floor and gain range can be adjusted by selecting HI or LO gain mode.
Rev. C | Page 24 of 32
AD8331/AD8332
43.5
–4.5
OVERLOAD
) B d
( IN
A G
1m
POSTAMP
X-AMP
OVERLOAD
15mV
25mV
LO GAIN
MODE
INPUT AMPLITUDE (V)
POSTAMP
OVERLOAD
4mV
56.5
29dB
)
24.5dB
B d
(
D A O L R E V
O A N L
.2750.110m
IN A G
7.5
1
1m 0.2750.110m 1
X-AMP
OVERLOAD
25mV
HI GAIN
MODE
INPUT AMPLITUDE (V)
41dB
24.5dB
D A O L R E V
O A N L
Figure 72. Overload Gain and Signal Conditions
The previously mentioned clamp interface controls the maximum output swing of the postamp and its overload response. When no R
resistor is provided, this level defaults
CLMP
to near 4.5 V p-p differential to protect outputs centered at a
2.5 V common mode. When other common-mode levels are set through the VCM pin, the value of R
should be chosen for
CLMP
graceful overload. A value of 8.3 kΩ or less is recommended for
1.5 V or 3.5 V common-mode levels (7.2 kΩ for HI gain mode). This limits the output swing to just above 2 V p-p diff.

OPTIONAL INPUT OVERLOAD PROTECTION.

Applications in which high transients are applied to the LNA input may benefit from the use of clamp diodes. A pair of back­to-back Schottky diodes can reduce these transients to manageable levels. Figure 73 illustrates how such a diode­protection scheme may be connected.

LAYOUT, GROUNDING, AND BYPASSING

Due to their excellent high frequency characteristics, these devices are sensitive to their PCB environment. Realizing expected performance requires attention to detail critical to good high speed board design.
A multilayer board with power and ground plane is recommended, and unused area in the signal layers should be filled with ground. The multiple power and ground pins provide robust power distribution to the device and must all be connected. The power supply pins should each be with multiple
03199-C-072
values of high frequency ceramic chip capacitors to maintain low impedance paths to ground over a wide frequency range. These should have capacitance values of 0.01 μF to 0.1 μF in parallel with 100 pF to 1 nF, and be placed as close as possible to the pins. The LNA power pins should be decoupled from the VGA using ferrite beads. Together with the decoupling capacitors, ferrite beads help eliminate undesired high frequencies without reducing the headroom, as do small value resistors.
Several critical LNA areas require special care. The LON and LOP output traces must be as short as possible before connecting to the coupling capacitors connected to Pins VIN and VIP. R
must be placed nearby the LON pin as well.
FB
Resistors must be placed as close as possible to the VGA output pins VOL and VOH to mitigate loading effects of connecting traces. Values are discussed in the section entitled Output Filtering and Series Resistor Requirements.
OPTIONAL SCHOTTKY OVERLOAD
CLAMP
231
BAS40-04
0.1µF
FB
C
R
SH
C
R
SH
2
FB
3
FB
4
INH
VPS
LON
COMM
ENBL
20
19
03199-C-072
Figure 73. Input Overload Clamping
When selecting overload protection, the important parameters are forward and reverse voltages and t BAS40 series shown in Figure 73 has a τ
(or τrr.). The Infineon
rr
of 100 ps and VF of
rr
310 mV at 1 mA. Many variations of these specifications can be found in vendor catalogs.
Signal traces must be short and direct to avoid parasitic effects. Wherever there are complementary signals, symmetrical layout should be employed to maintain waveform balance. PCB traces should be kept adjacent when running differential signals over a long distance.

MULTIPLE INPUT MATCHING

Matching of multiple sources with dissimilar impedances can be accomplished as shown in the circuit of Figure 75. A relay and low supply voltage analog switch may be used to select between multiple sources and their associated feedback resistors. An ADG736 dual SPDT switch is shown in this example; however, multiple switches are also available and users are referred to the Analog Devices Selection Guide for switches and multiplexers.

DISABLING THE LNA

Where accessible, connection of the LNA enable pin to ground will power down the LNA, resulting in a current reduction of about half. In this mode, the LNA input and output pins may be left unconnected, however the power must be connected to all the supply pins for the disabling circuit to function. Figure 74 illustrates the connections using an AD8331 as an example.
Rev. C | Page 25 of 32
AD8331/AD8332
+5V
NC
NC
C
FB
0.018µF
1
LMD
AD8331
2
INH
3
VPS
COMM
ENBL
ENBV
20

MEASUREMENT CONSIDERATIONS

Figure 51 through Figure 55 show typical measurement
19
configurations and proper interface values for measurements with 50 Ω conditions.
18
+5V
Short-circuit input noise measurements are made using Figure 53. The input-referred noise level is determined by dividing the output noise by the numerical gain between Point A and Point B and accounting for the noise floor of the spectrum analyzer. The gain should be measured at each
NC
4
LON
COMM
17
frequency of interest and with low signal levels since a 50 Ω
NC
5
LOP
6
COML
VOL
VOH
16
VOUT
15
load is driven directly. The generator is removed when noise measurements are made.

ULTRASOUND TGC APPLICATION

The AD8332 ideally meets the requirements of medical and industrial ultrasound applications. The TGC amplifier is a key
0.1µF
VIN
0.1µF
7
VIP
8
VIN
14
VPOS +5V
13
HILO
HILO
subsystem in such applications, since it provides the means for echolocation of reflected ultrasound energy.
Figure 76 through Figure 78 are schematics of a dual, fully differential system using the AD8332 and AD9238 12-bit high speed ADC with conversion speeds as high as 65 MSPS. In this example, the VGA outputs are dc-coupled, using the reference
MODE
9
MODE
CLMP
12
R
CLMP
output of the ADC and a level shifter to center the common­mode output voltage to match that of the converter. Consult the data sheet of the converter to determine whether external CMV
GAIN
10
GAIN
VCM
11
VCM
biasing is required. AC coupling is recommended if the CMV of the VGA and ADC are widely disparate.
03199-C-074
Figure 74. Disabling the LNA
200
50
0.1µF
ADG736
SELECTR
18nF
INH
LMD
AD8332
1.13k
FB
280
LON
5
LNA
LOP
5
03199-C-075
Using the circuit shown, and a high speed ADC FIFO evaluation kit connected to a laptop PC, an FFT can be performed on the AD8332. With the on-board clock of 20 MHz, and minimal low-pass filtering, and both channels driven with a 1 MHz filtered sine wave, the THD is –75 dB, noise floor –93 dB and HD2 –83 dB.
Figure 75. Accommodating Multiple Sources
Rev. C | Page 26 of 32
AD8331/AD8332
V
TP3
+5V
(RED) TB1 +5V
TP4
(BLACK)
TB2
GND
VREF
R23 2k
OPTIONAL 4-POLE LOW-PASS
VIN+B
C66 SAT
–B
IN
L19
SAT
L20
SAT
3
2
+
L7
120nH FB
L6
120nH FB
7
4
C71 1nF
R22
1k
FILTER
C67 SAT
C46 1µF
AD8541
6
VCM
L17
SAT
L18
SAT
+5VGA
+5VLNA
0.1µF
VCM1
JP13
JP14
JP12
CFB2
18nF
RFB2
274
C51
0.1µF
TP2 GAIN
TP7 GND
R3
(R
CLMP
JP8
DC2H
C54
0.1µF
C55
0.1µF
JP7
DC2L
S3
E
)
IN2
C50
0.1µF
L12 120nH FB
C80
22PF
+5VLNA
C41
0.1µF
C83 1nF
C69
0.1µF
100
120nH FB
120nH FB
TP5
0.1µF
C48
0.1µF
R27
L11
L10
R26
100
C53
0.1µF
C68 1nF
C49
JP5
IN2
C74 1nF
C78 1nF
AD8332ARU
1
LMD2
2
INH2
3
VPS2
4
LON2
5
LOP2
6
COM2
7
VIP2
8
VIN2
9
VCM2
10
GAIN
11
CLMP
12
VOH2
13
VOL2
14
COM
+5VGA
C45
0.1µF
LMD1
INH1
VPS1
LON1
LOP1
COM1
VIP1
VIN1
VCM1
HILO
ENB
VOH1
VOL1
VPSV
C85
1nF
28
27
26
+5VLNA
25
24
23
22
21
20
C77 1nF
19
+5VGA
18
17
16
15
C70
0.1µF
JP6
IN1
ENABLE
JP16
DISABLE
120nH FB
120nF FB
22 PF
C42
0.1µF
C43
0.1µF
R24
100
L9
L8
R25
100
C79
VCM1
120nH FB
CFB1 18nF
RFB1 274
C59
0.1µF
0.1µF
0.1µF
L13
+5VGA
HI GAIN
JP10 LO GAIN
JP9
C58
C56
JP10
TP6
C60
0.1µF
OPTIONAL 4-POLE LOW-PASS
L1
SAT
JP17
L14
SAT
FILTER
SAT
C64 SAT
SAT
E
L15
L16
S1
IN1
VIN+A
C65 SAT
VIN–A
03199-C-076
Figure 76. Schematic, TGC, VGA Section
Rev. C | Page 27 of 32
AD8331/AD8332
ADP3339AKC-3.3
+5V
312
IN
OUT
OUT TAB
S2
EXT CLOCK
R17
49.9
+3.3VCLK
C86
0.1µF
V
DD
20MHz
GND
SG-636PCE
OUT
2
VR1
OE
U6
GND
+
14
3
C44
1µF
+
C63
0.1µF
C47 10µF
6.3V
120nH FB
120nH FB
120nH FB
120nH FB
+3.3VCLK
3
JP 4
2
EXT
1
INT
L5
L4
L3
L2
R18 499
R16 5k
R19 499
+3.3VCLK
C31
0.1µ
F
+3.3VADDIG
C30
0.1µ
F
+3.3VAVDD
C29
0.1µ
F
+3.3VDVDD
C1
0.1
µ
F
U5
74VHC04
U5
74VHC04
SPARES
10µF
R5
R20
R4
1.5k
C33
10µF
6.3V
+
C34
10µF
6.3V
1.5k1.5k
0.1µF
33
R6
33
R8
33
R7
33
C20
JP 11JP 3
R41
4.7k
C17
0.1µF
10µF
0.1µF
C39
C16
0.1µF
C32
0.1µF
C19 1nF
VIN+_A
V
IN
VREF
VIN–B
V
–_A
1.5k
C35
0.1µF
C36
0.1µF
C38
0.1µF
C37
0.1µF
+B
IN
R12
4.7k
ADCLK
ADCLK
74VHC04
4312
U5
74VHC04
U5
74VHC04
11
U5
74VHC04
TP 12
U5
TP 13
DATA
CLK
JP 1
3
1
2
8965
1213
10
Figure 77. Converter Schematic
+3.3VAVDD
C2
+
6.3V
C61
18pF
C18 1nF
C40
TP 9
+
C12 10µF
6.3V
C15 1nF
C62
18pF
R9
0
+3.3VADDIG
C52
10nF
C57
10nF
DNC
DNC
D0_B
D1_B
D2_B
D3_B
D4_B
D5_B
0.1µF
C26
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
C22
0.1µF
AGND
VIN+_A
VIN –_A
AGND
AVDD
REFT_A
REFB_A
VREF
SENSE
REFB_B
REFT_B
AVDD
AGND
VIN –_B
VIN+_B
AGND
AVDD
CLK_B
DCS
DFS
PDWN_B
OEB_B
DNC
DNC
D0_B
D1_B
D2_B
DRGND
DRVDD
D3_B
D4_B
D5_B
C24 1nF
C21 1nF
CLK_A
SHARED_REF
MUX_SELECT
PDWN_A
OEB_A
OTRA_A
D11_A(MSB)
D10_A
DRGND
DRVDD
U1 A/D CONVERTER AD9238
DRVDD
DRGND
OTRB_B
D11_B(MSB)
D10_B
AVDD
D9_A
D8_A
D7_A
D6_A
D5_A
D4_A
D3_A
D2_A
D1_A
D0_A
DNC
DNC
D9_B
D8_B
D7_B
D6_B
64
63
62
61
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
ADCLK
R10 0
4.7k
R15 0
R11 100
JP 2
SHARED
REF
Y
R14
+3.3VADDIG
OTR_A
D11_A
D10_A
D9_A
D8_A
C23
0.1µF
D7_A
D6_A
D5_A
D4_A
D3_A
D2_A
D1_A
D0_A
DNC
DNC
C13 1nF
OTR_B
D11_B
D10_B
D9_B
D8_B
D7_B
D6_B
N
+3.3VADDIG
C25 1nF
C14
0.1µF
C11
+
10µF
6.3V
03199-C-077
Rev. C | Page 28 of 32
AD8331/AD8332
VCC GND
Y1 Y2 Y3
Y4 Y5 Y6 Y7
Y8
20
10
C3
0.1µF
18 17 16
15 14 13 12
11
+
+3.3VDVDD
C28 10µF
6.3V
+3.3VDVDD
20
U7
VCC GND
Y1 Y2
Y3 Y4 Y5 Y6
Y7 Y8
10
C8
0.1µF
18 17
16 15 14 13
12 11
C10
0.1µF
+
C76 10µF
6.3V
OTR_A
D11_A
D10_A
D9_A D8_A D7_A
D6_A
D5_A D4_A
D3_A D2_A D1_A D0_A
DNC DNC
DATACLKA
22× 4
18
RP 9
7
2
6
3
54
18
22× 4
RP 10
7
2
6
3
54
8
22 × 4
1
RP 11
7
2
6
3
54
18
22× 4
RP 12
7
2
6
3
54
19
19
1
2 3 4
5 6 7 8
9
1
2 3
4 5 6 7 8
9
G1
74VHC541
G2 A1 A2 A3
A4 A5 A6 A7
A8
G1
74VHC541
G2 A1 A2
A3 A4 A5 A6
A7 A8
U10
R40 22
22× 4
18
RP 1
7
2
6
3
54
22× 4
18
RP2
7
2
6
3
54
18
22× 4
RP 3
7
2
6
3
54
18
22× 4
RP 4
7
2
6
3
54
2 4 6 8
10 12 14 16
18 20 22 24
26 25 28 27 30
34 36 38 40
SAM080UPM
1 3 5 7
9 11 13 15
17 19 21 23
29 3132 33
35 37 39
OTR_B
D11_B D10_B
D9_B D8_B D7_B
D6_B D5_B
D4_B
D3_B D2_B D1_B D0_B
DNC
DNC
18
22× 4
RP 13
7
2
6
3
54
22× 4
18
RP 14
7
2
6
3
54
18
22× 4
RP 15
7
2
6
3
54
22× 4
18
RP 16
7
2
6
3
54
DATACLK
19
19
1
2 3
4 5 6 7
8 9
1
2
3 4 5 6 7
8 9
G1
74VHC541
G2 A1
A2 A3 A4 A5
A6 A7 A8
G1
74VHC541
G2 A1
A2 A3 A4 A5
A6 A7 A8
U2
U3
20
VCC
10
GND
18
Y1
17
Y2
16
Y3
15
Y4
14
Y5
13
Y6
12
Y7
11
Y8
+3.3VDVDD
20
VCC
10
GND
18
Y1
17
Y2
16
Y3
15
Y4
14
Y5
13
Y6
12
Y7
11
Y8
+3.3VDVDD
++
C7
0.1µFC90.1µF
C4
0.1µFC50.1µFC60.1µF
C27 10µF
6.3V
+
C75 10µF
6.3V
Figure 78. Interface Schematic
22× 4
18
RP 5
7
2
6
3
54
22× 4
8
1
RP 6
7
2
6
3
54
22× 4
18
RP 7
7
2
6
3
54
18
22× 4
RP 8
7
2
6
3
54
R39 22
42 44
46
48 47
52 54 53
HEADER UP MALE NO SHROUDHEADER UP MALE NO SHROUD
56 55
58 60 62 64
66
68
70
72
74 76 78 80
SAM080UPM
41 43 45
4950 51
57 59 61 63
65 67 69 71
73 75 77 79
03199-B-078
Rev. C | Page 29 of 32
AD8331/AD8332

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

AD8331

PIN 1
1
LMD
INH
VPSL
LON LOP
COML
VIP VIN
MODE
GAIN
IDENTIFIER
2 3 4 5
(Not to Scale)
6 7 8 9
10
AD8331
TOP VIEW
Figure 79. 20-Lead QSOP
Table 5. 20–Lead QSOP (RQ PACKAGE)
Pin No. Name Description
1 LMD LNA Signal Ground 2 INH LNA Input 3 VPSL LNA 5V Supply 4 LON LNA Inverting Output 5 LOP LNA Noninverting Output 6 COML LNA Ground 7 VIP VGA Noninverting Input 8 VIN VGA Inverting Input 9 MODE Gain Slope Logic Input 10 GAIN Gain Control Voltage 11 VCM Common-Mode Voltage 12 CLMP Output Clamping Level 13 HILO Gain Range Select (HI or LO) 14 VPOS VGA 5 V Supply 15 VOH Noninverting VGA Output 16 VOL Inverting VGA Output 17 COMM VGA Ground 18 ENBV VGA Enable 19 ENBL LNA Enable 20 COMM VGA Ground
20 19 18 17 16 15 14 13 12 11
COMM ENBL ENBV COMM VOL VOH VPOS HILO RCLMP VCM
03199-C-079
Rev. C | Page 30 of 32
AD8331/AD8332

AD8332

PIN 1
1
LMD2
INH2
VPS2
LON2
LOP2
COM2
VIP2 VIN2
VCM2
GAIN
RCLMP
VOH2
VOL2
COMM
IDENTIFIER
2 3 4 5 6
(Not to Scale)
7 8
9 10 11 12 13 14
AD8332
TOP VIEW
Figure 80. 28-Lead TSSOP
Table 6. 28–Lead TSSOP (AR PACKAGE)
Pin No. Name Description
1 LMD2 CH2 LNA Signal Ground 2 INH2 CH2 LNA Input 3 VPS2 CH2 Supply LNA 5 V 4 LON2 CH2 LNA Inverting Output 5 LOP2 CH2 LNA Noninverting Output 6 COM2 CH2 LNA Ground 7 VIP2 CH2 VGA Noninverting Input 8 VIN2 CH2 VGA Inverting Input 9 VCM2 CH2 Common-Mode Voltage 10 GAIN Gain Control Voltage 11 RCLMP Output Clamping Resistor 12 VOH2 CH2 Noninverting VGA Output 13 VOL2 CH2 Inverting VGA Output 14 COMM VGA Ground (Both Channels) 15 VPSV VGA Supply 5 V (Both Channels) 16 VOL1 CH1 Inverting VGA Output 17 VOH1 CH1 Noninverting VGA Output 18 ENB Enable—VGA/LNA 19 HILO VGA Gain Range Select (HI or LO) 20 VCM1 CH1 Common-Mode Voltage 21 VIN1 CH1 VGA Inverting Input 22 VIP1 CH1 VGA Noninverting Input 23 COM1 CH1 LNA Ground 24 LOP1 CH1 LNA Noninverting Output 25 LON1 CH1 LNA Inverting Output 26 VPS1 CH1 LNA Supply 5 V 27 INH1 CH1 LNA Input 28 LMD1 CH1 LNA Signal Ground
28
LMD1
27
INH1
26
VPS1
25
LON1
24
LOP1
23
COM1
22
VIP1
21
VIN1
20
VCM1
19
HILO
18
ENB
17
VOH1
16
VOL1
15
VPSV
03199-B-081
Table 7. 32–Lead LFCSP (AC PACKAGE)
LON1
VPS1
INH1
LMD1
LMD2
INH2 VPS2 LON2
VIP1
VIN1
VCM1
COM1
LOP1
1 2 3 4 5 6 7 8
LOP2
3132
PIN 1 INDICATOR
(Not to Scale)
10
COM2
2930
28
AD8332
TOP VIEW
1211
VIP2
VIN2
HILO
ENBL
252627
14139
15 16
GAIN
VCM2
MODE
Figure 81. 32-Lead LFCSP
ENBV
24 23 22 21 20 19 18 17
RCLMP
COMM
VOH1 VOL1 VPSV NC VOL2 VOH2 COMM
03199-C-082
Pin No. Name Description
1 LON1 CH1 LNA Inverting Output 2 VPS1 CH1 LNA Supply 5 V 3 INH1 CH1 LNA Input 4 LMD1 CH1 LNA Signal Ground 5 LMD2 CH2 LNA Signal Ground 6 INH2 CH2 LNA Input 7 VPS2 CH2 LNA Supply 5 V 8 LON2 CH2 LNA Inverting Output 9 LOP2 CH2 LNA Noninverting Output 10 COM2 CH2 LNA Ground 11 VIP2 CH2 VGA Noninverting Input 12 VIN2 CH2 VGA Inverting Input 13 VCM2 CH2 Common-Mode Voltage 14 MODE Gain Slope Logic Input 15 GAIN Gain Control Voltage 16 RCLMP Output Clamping Level Input 17 COMM VGA Ground 18 VOH2 CH2 Noninverting VGA Output 19 VOL2 CH2 Inverting VGA Output 20 NC Not Connected 21 VPSV VGA Supply 5 V 22 VOL1 CH1 Inverting VGA Output 23 VOH1 CH1 Noninverting VGA Output 24 COMM VGA Ground 25 ENBV VGA Enable 26 ENBL LNA Enable 27 HILO VGA Gain Range Select (HI or LO) 28 VCM1 CH1 Common-Mode Voltage 29 VIN1 CH1 VGA Inverting Input 30 VIP1 CH1 VGA Noninverting Input 31 COM1 CH1 LNA Ground 32 LOP1 CH1 LNA Noninverting Output
Rev. C | Page 31 of 32
AD8331/AD8332
C
Y

OUTLINE DIMENSIONS

9.80
9.70
9.60
28
PIN 1
0.15
0.05
COPLANARITY
0.10
0.65 BSC
0.30
0.19
COMPLIANT TO JEDEC STANDARDS MO-153AE
Figure 82. 28-Lead Thin Shrink Small Outline Package [TSSOP] (RU-28)
Dimensions shown in millimeters
5.00
BSC SQ
PIN 1
1.00
0.85
0.80
12° MAX
SEATING PLANE
INDICATOR
TOP
VIEW
4.75
BSC SQ
0.80 MAX
0.65 TYP
0.30
0.20 REF
0.23
0.18
COMPLIANT TO JEDEC STANDARDS MO-220-VHHD-2
Figure 83. 32-Lead Frame Chip Scale Package [LFCSP] (CP-32)
Dimensions shown in millimeters
1.20 MAX
SEATING
PLANE
0.60 MAX
0.05 MAX
0.02 NOM
15
4.50
4.40
4.30
141
0.20
0.09
0.50
BSC
0.50
0.40
0.30
COPLANARITY
0.08
6.40 BSC
0.60 MAX
25
24
17
16
BOTTOM
VIEW
8° 0°
32
1
8
9
3.50 REF
0.75
0.60
0.45
PIN 1 INDICATOR
3.25
3.10 SQ
2.95
0.25MIN
0.341 BSC
20 11
1
PIN 1
0.065
0.049
0.010
0.004
OPLANARIT
0.004 COMPLIANT TO JEDEC STANDARDS MO-137AD
Figure 84. 20 Lead Shrink Outline [QSOP] (RQ-20)
0.025 BSC
0.012
0.008
0.069
0.053
10
SEATING PLANE
0.154 BSC
0.236 BSC
0.010
0.006
8° 0°
0.050
0.016
Dimensions shown in millimeters

ORDERING GUIDE

AD8331/AD8332 Models
AD8331ARQ –40°C to +85°C Shrink Small Outline Package 150 mil Body, 25 mil pitch RQ-20 AD8331ARQ-REEL –40°C to +85°C Shrink Small Outline Package 150 mil Body, 25 mil pitch RQ-20 AD8331ARQ-REEL7 –40°C to +85°C Shrink Small Outline Package 150 mil Body, 25 mil pitch RQ-20 AD8331-EVAL Evaluation Board with AD8331ARQ AD8332ARU –40°C to +85°C Thin Shrink Small Outline Package (TSSOP) RU-28 AD8332ARU-REEL –40°C to +85°C Thin Shrink Small Outline Package (TSSOP) RU-28 AD8332ARU-REEL7 –40°C to +85°C Thin Shrink Small Outline Package (TSSOP) RU-28 AD8332ACP-REEL –40°C to +85°C Lead Frame Chip Scale Package (LFCSP) CP-32 AD8332ACP-REEL7 –40°C to +85°C Lead Frame Chip Scale Package (LFCSP) CP-32 AD8332-EVAL Evaluation Board with AD8332ARU
© 2003 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. C03199-0-11/03(C)
Temperature Range Package Description
Rev. C | Page 32 of 32
Package Outline
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