ADA4939-1 Datasheet PDF - Analog Devices

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ADA4939-1
Analog Devices

Part Number ADA4939-1
Description (ADA4939-1/-2) Ultralow Distortion Differential ADC Driver
Page 24 Pages


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Extremely low harmonic distortion
−102 dBc HD2 @ 10 MHz
−83 dBc HD2 @ 70 MHz
−77 dBc HD2 @ 100 MHz
−101 dBc HD3 @ 10 MHz
−97 dBc HD3 @ 70 MHz
−91 dBc HD3 @ 100 MHz
Low input voltage noise: 2.3 nV/√Hz
High speed
−3 dB bandwidth of 1.4 GHz, G = 2
Slew rate: 6800 V/μs, 25% to 75%
Fast overdrive recovery of <1 ns
±0.5 mV typical offset voltage
Externally adjustable gain
Stable for differential gains ≥2
Differential-to-differential or single-ended-to-differential
operation
Adjustable output common-mode voltage
Single-supply operation: 3.3 V to 5 V
APPLICATIONS
ADC drivers
Single-ended-to-differential converters
IF and baseband gain blocks
Differential buffers
Line drivers
GENERAL DESCRIPTION
The ADA4939 is a low noise, ultralow distortion, high speed
differential amplifier. It is an ideal choice for driving high
performance ADCs with resolutions up to 16 bits from dc to
100 MHz. The output common-mode voltage is user adjustable
by means of an internal common-mode feedback loop, allowing
the ADA4939 output to match the input of the ADC. The internal
feedback loop also provides exceptional output balance as well as
suppression of even-order harmonic distortion products.
With the ADA4939, differential gain configurations are easily
realized with a simple external feedback network of four resistors
that determine the closed-loop gain of the amplifier.
The ADA4939 is fabricated using Analog Devices, Inc., proprietary
silicon-germanium (SiGe), complementary bipolar process,
enabling it to achieve very low levels of distortion with an input
voltage noise of only 2.3 nV/√Hz. The low dc offset and excellent
dynamic performance of the ADA4939 make it well suited for a
wide variety of data acquisition and signal processing applications.
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties 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.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
Ultralow Distortion
Differential ADC Driver
ADA4939-1/ADA4939-2
FUNCTIONAL BLOCK DIAGRAMS
–FB 1
+IN 2
–IN 3
+FB 4
ADA4939-1
12 PD
11 –OUT
10 +OUT
9 VOCM
Figure 1. ADA4939-1
–IN1 1
+FB1 2
+VS1 3
+VS1 4
–FB2 5
+IN2 6
ADA4939-2
18 +OUT1
17 VOCM1
16
15
––VVSS22
14 PD2
13 –OUT2
Figure 2. ADA4939-2
–60
VOUT, dm = 2V p-p
–65 HD2
–70 HD3
–75
–80
–85
–90
–95
–100
–105
–110
1
10
FREQUENCY (MHz)
100
Figure 3. Harmonic Distortion vs. Frequency
The ADA4939 is available in a Pb-free, 3 mm × 3 mm 16-lead
LFCSP (ADA4939-1, single) or a Pb-free, 4 mm × 4 mm 24-lead
LFCSP (ADA4939-2, dual). The pinout has been optimized to
facilitate PCB layout and minimize distortion. The ADA4939-1
and the ADA4939-2 are specified to operate over the −40°C to
+105°C temperature range; both operate on supplies between
3.3 V and 5 V.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2008 Analog Devices, Inc. All rights reserved.



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ADA4939-1/ADA4939-2
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications....................................................................................... 1
General Description ......................................................................... 1
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Functional Block Diagrams............................................................. 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
5 V Operation ............................................................................... 3
3.3 V Operation ............................................................................ 5
Absolute Maximum Ratings............................................................ 7
Thermal Resistance ...................................................................... 7
Maximum Power Dissipation ..................................................... 7
ESD Caution.................................................................................. 7
Pin Configurations and Function Descriptions ........................... 8
Typical Performance Characteristics ............................................. 9
Test Circuits..................................................................................... 15
Operational Description................................................................ 16
Definition of Terms.................................................................... 16
REVISION HISTORY
5/08—Revision 0: Initial Version
Theory of Operation ...................................................................... 17
Analyzing an Application Circuit ............................................ 17
Setting the Closed-Loop Gain .................................................. 17
Stable for Gains ≥2 ..................................................................... 17
Estimating the Output Noise Voltage ...................................... 17
Impact of Mismatches in the Feedback Networks................. 18
Calculating the Input Impedance for an Application Circuit
....................................................................................................... 19
Input Common-Mode Voltage Range ..................................... 21
Input and Output Capacitive AC-Coupling ........................... 21
Minimum RG Value of 50 Ω ...................................................... 21
Setting the Output Common-Mode Voltage .......................... 21
Layout, Grounding, and Bypassing.............................................. 22
High Performance ADC Driving ................................................. 23
Outline Dimensions ....................................................................... 24
Ordering Guide .......................................................................... 24
Rev. 0 | Page 2 of 24



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ADA4939-1/ADA4939-2
SPECIFICATIONS
5 V OPERATION
TA = 25°C, +VS = 5 V, −VS = 0 V, VOCM = +VS/2, RF = 402 Ω, RG = 200 Ω, RT = 60.4 Ω (when used), RL, dm = 1 kΩ, unless otherwise noted.
All specifications refer to single-ended input and differential outputs, unless otherwise noted. Refer to Figure 42 for signal definitions.
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±DIN to VOUT, dm Performance
Table 1.
Parameter
DYNAMIC PERFORMANCE
−3 dB Small Signal Bandwidth
Bandwidth for 0.1 dB Flatness
Large Signal Bandwidth
Slew Rate
Overdrive Recovery Time
NOISE/HARMONIC PERFORMANCE
Second Harmonic
Third Harmonic
IMD
Voltage Noise (RTI)
Input Current Noise
Crosstalk
INPUT CHARACTERISTICS
Offset Voltage
Input Bias Current
Input Offset Current
Input Resistance
Input Capacitance
Input Common-Mode Voltage
CMRR
OUTPUT CHARACTERISTICS
Output Voltage Swing
Linear Output Current
Output Balance Error
Conditions
VOUT, dm = 0.1 V p-p
VOUT, dm = 0.1 V p-p, ADA4939-1
VOUT, dm = 0.1 V p-p, ADA4939-2
VOUT, dm = 2 V p-p
VOUT, dm = 2 V p-p, 25% to 75%
VIN = 0 V to 1.5 V step, G = 3.16
See Figure 41 for distortion test circuit
VOUT, dm = 2 V p-p, 10 MHz
VOUT, dm = 2 V p-p, 70 MHz
VOUT, dm = 2 V p-p, 100 MHz
VOUT, dm = 2 V p-p, 10 MHz
VOUT, dm = 2 V p-p, 70 MHz
VOUT, dm = 2 V p-p, 100 MHz
f1 = 70 MHz, f2 = 70.1 MHz, VOUT, dm = 2 V p-p
f1 = 140 MHz, f2 = 140.1 MHz, VOUT, dm = 2 V p-p
f = 100 kHz
f = 100 kHz
f = 100 MHz, ADA4939-2
VOS, dm = VOUT, dm/2, VDIN+ = VDIN− = 2.5 V
TMIN to TMAX variation
TMIN to TMAX variation
Differential
Common mode
∆VOUT, dm/∆VIN, cm, ∆VIN, cm = ±1 V
Maximum ∆VOUT; single-ended output, RF = RG = 10 kΩ
∆VOUT, cm/∆VOUT, dm, ∆VOUT, dm = 1 V, 10 MHz,
see Figure 40 for test circuit
Min Typ Max Unit
1400
300
90
1400
6800
<1
MHz
MHz
MHz
MHz
V/μs
ns
−102
−83
−77
−101
−97
−91
−95
−89
2.3
6
−80
dBc
dBc
dBc
dBc
dBc
dBc
dBc
dBc
nV/√Hz
pA/√Hz
dB
−3.4
−26
−11.2
1.1
±0.5
±2.0
−10
±0.5
+0.5
180
450
1
−83
+2.8
+2.2
+11.2
3.9
−77
mV
μV/°C
μA
μA/°C
μA
pF
V
dB
0.9 4.1 V
100 mA
−64 dB
Rev. 0 | Page 3 of 24



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ADA4939-1/ADA4939-2
VOCM to VOUT, cm Performance
Table 2.
Parameter
VOCM DYNAMIC PERFORMANCE
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Slew Rate
Input Voltage Noise (RTI)
VOCM INPUT CHARACTERISTICS
Input Voltage Range
Input Resistance
Input Offset Voltage
VOCM CMRR
Gain
General Performance
Table 3.
Parameter
POWER SUPPLY
Operating Range
Quiescent Current per Amplifier
Power Supply Rejection Ratio
POWER-DOWN (PD)
PD Input Voltage
Turn-Off Time
Turn-On Time
PD Pin Bias Current per Amplifier
Enabled
Disabled
OPERATING TEMPERATURE RANGE
Conditions
VIN = 1.5 V to 3.5 V, 25% to 75%
f = 100 kHz
VOS, cm = VOUT, cm, VDIN+ = VDIN− = +VS/2
ΔVOUT, dm/ΔVOCM, ΔVOCM = ±1 V
ΔVOUT, cm/ΔVOCM, ΔVOCM = ±1 V
Conditions
TMIN to TMAX variation
Powered down
ΔVOUT, dm/ΔVS, ΔVS = 1 V
Powered down
Enabled
PD = 5 V
PD = 0 V
Min Typ
Max Unit
670
2500
7.5
MHz
V/μs
nV/√Hz
1.3
8.3 9.7
−3.7 ±0.5
−90
0.97 0.98
3.5 V
11.5 kΩ
+3.7 mV
−73 dB
0.99 V/V
Min Typ
3.0
35.1 36.5
16
0.26 0.32
−90
≤1
≥2
500
100
30
−200
−40
Max
5.25
37.7
0.38
−80
+105
Unit
V
mA
μA/°C
mA
dB
V
V
ns
ns
μA
μA
°C
Rev. 0 | Page 4 of 24



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