LT1993CUD-2#TRPBF [Linear]
LT1993-2 - 800MHz Low Distortion, Low Noise Differential Amplifier ADC Driver (Av = 2V/V); Package: QFN; Pins: 16; Temperature Range: 0°C to 70°C;
| 型号： | LT1993CUD-2#TRPBF |
| 厂家： | 
Linear |
| 描述： | LT1993-2 - 800MHz Low Distortion, Low Noise Differential Amplifier ADC Driver (Av = 2V/V); Package: QFN; Pins: 16; Temperature Range: 0°C to 70°C 驱动器 放大器 功率放大器 |
| 文件： | 总20页 (文件大小：663K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT1993-2
800MHz Low Distortion, Low
Noise Differential Amplifier/
ADC Driver (A = 2V/V)
V
U
DESCRIPTIO
FEATURES
■
800MHz –3dB Bandwidth
The LT®1993-2 is a low distortion, low noise Differential
Amplifier/ADC driver for use in applications from DC to
800MHz. The LT1993-2 has been designed for ease of
use, with minimal support circuitry required. Exception-
ally low input-referred noise and low distortion products
(with either single-ended or differential inputs) make the
LT1993-2 an excellent solution for driving high speed 12-
bit and 14-bit ADCs. In addition to the normal unfiltered
outputs (+OUT and –OUT), the LT1993-2 has a built-in
175MHz differential low pass filter and an additional pair
of filtered outputs (+OUTFILTERED, –OUTFILTERED) to
reduce external filtering components when driving high
speedADCs.Theoutputcommonmodevoltageiseasilyset
■
Fixed Gain of 2V/V (6dB)
■
Low Distortion:
38dBm OIP3, –70dBc HD3 (70MHz, 2V
51dBm OIP3, –94dBc HD3 (10MHz, 2V
)
)
P-P
P-P
■
Low Noise: 12.3dB NF, e = 3.8nV/√Hz (70MHz)
n
■
■
■
■
■
■
Differential Inputs and Outputs
Additional Filtered Outputs
Adjustable Output Common Mode Voltage
DC- or AC-Coupled Operation
Minimal Support Circuitry Required
Small 0.75mm Tall 16-Lead 3 × 3 QFN Package
U
via the V
pin, eliminating either an output transformer
OCM
APPLICATIO S
or AC-coupling capacitors in many applications.
■
Differential ADC Driver for:
The LT1993-2 is designed to meet the demanding require-
ments of communications transceiver applications. It can
be used as a differential ADC driver, a general-purpose
differential gain block, or in any other application requir-
ing differential drive. The LT1993-2 can be used in data
acquisition systems required to function at frequencies
down to DC.
Imaging
Communications
■
Differential Driver/Receiver
■
Single Ended to Differential Conversion
■
Differential to Single Ended Conversion
■
Level Shifting
IF Sampling Receivers
SAW Filter Interfacing/Buffering
■
The LT1993-2 operates on a 5V supply and consumes
100mA. It comes in a compact 16-lead 3 × 3 QFN package
and operates over a –40°C to 85°C temperature range.
■
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
U
TYPICAL APPLICATIO
4-Tone WCDMA Waveform,
LT1993-2 Driving LTC2255 14-Bit
ADC at 92.16Msps
4-Channel WCDMA Receive Channel
0
32768 POINT FFT
–10
–20
TONE CENTER FREQUENCIES
AT 62.5MHz, 67.5MHz,
72.5MHz, 77.5MHz
1:4
Z-RATIO
0.1µF
70MHz
IF IN
–INB
–INA
12.2Ω
–30
–OUT
AIN–
LTC2255
–40
–OUTFILTERED
–50
82nH 52.3pF
LT1993-2
0.1µF
ADC
–60
+OUTFILTERED
+INB
AIN+
–70
+OUT
OCM
MINI-CIRCUITS
TCM4-19
12.2Ω
+INA
V
–80
LTC2255 125Msps
14-BIT ADC SAMPLING
AT 92.16Msps
ENABLE
–90
–100
–110
–120
2.2V
19932 TA01a
0
5
10 15 20 25 30 35 40 45
FREQUENCY (MHz)
19932 TA01b
19932fa
1
LT1993-2
W W U W
U
W
U
ABSOLUTE AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
(Note 1)
TOP VIEW
Total Supply Voltage (V /V /V
EEA EEB EEC
Input Current (+INA, –INA, +INB, –INB,
to
CCA CCB CCC
/V /V ) ...................................................5.5V
V
16 15 14 13
V
1
2
3
4
12
V
EEC
CCC
V
OCM
11 ENABLE
V
, ENABLE)................................................ 10mA
OCM
17
V
V
V
10
9
CCA
CCB
EEB
Output Current (Continuous) (Note 6)
V
EEA
+OUT, –OUT (DC) .......................................... 100mA
(AC) .......................................... 100mA
5
6
7
8
+OUTFILTERED, –OUTFILTERED (DC)............. 15mA
(AC) ............. 45mA
Output Short Circuit Duration (Note 2) ............ Indefinite
Operating Temperature Range (Note 3) ... –40°C to 85°C
Specified Temperature Range (Note 4) .... –40°C to 85°C
Storage Temperature Range................... –65°C to 125°C
Junction Temperature ........................................... 125°C
Lead Temperature Range (Soldering 10 sec) ........ 300°C
UD PACKAGE
16-LEAD (3mm × 3mm) PLASTIC QFN
T
= 125°C, θ = 68°C/W, θ = 4.2°C/W
JMAX
JA
JC
EXPOSED PAD IS V (PIN 17) MUST BE SOLDERED TO THE PCB
EE
ORDER PART NUMBER
UD PART MARKING*
LBJG
LT1993CUD-2
LT1993IUD-2
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
*The temperature grade is identified by a label on the shipping container.
DC ELECTRICAL CHARACTERISTICS
The
CCA
●
denotes the specifications which apply over the full operating
= V = 5V, V = V = V = 0V, ENABLE = 0.8V, +INA
temperature range, otherwise specifications are at T = 25°C. V
= V
A
CCB
CCC
EEA
EEB
EEC
shorted to +INB (+IN), –INA shorted to –INB (–IN), V
= 2.2V, Input common mode voltage = 2.2V, no R
unless otherwise noted.
OCM
CONDITIONS
Input/Output Characteristics (+INA, +INB, –INA, –INB, +OUT, –OUT, +OUTFILTERED, –OUTFILTERED)
LOAD
SYMBOL
PARAMETER
MIN
TYP
MAX
UNITS
●
●
●
GDIFF
Gain
Differential (+OUT, –OUT), V
=
0.8V Differential
5.8
6.08
0.25
6.3
dB
IN
V
V
V
Single-Ended +OUT, –OUT, +OUTFILTERED,
0.35
0.5
V
V
SWINGMIN
SWINGMAX
SWINGDIFF
OUT
–OUTFILTERED. V 2.2V Differential
=
IN
Single-Ended +OUT, –OUT, +OUTFILTERED,
–OUTFILTERED. V 2.2V Differential
3.6
3.5
3.75
7
V
V
=
IN
Output Voltage Swing
Differential (+OUT, –OUT), V
Differential
=
2.2V
6.5
6
V
V
IN
P-P
P-P
●
●
I
Output Current Drive
Input Offset Voltage
(Note 5)
40
45
1
mA
V
OS
–6.5
–10
6.5
10
mV
mV
●
●
●
●
●
TCV
Input Offset Voltage Drift
T
to T
MAX
2.5
µV/°C
V
OS
VRMIN
VRMAX
MIN
I
I
Input Voltage Range, MIN
Input Voltage Range, MAX
Differential Input Resistance
Differential Input Capacitance
Common Mode Rejection Ratio
Single-Ended
Single-Ended
–0.1
240
5.1
V
Ω
R
INDIFF
170
200
1
C
INDIFF
pF
●
CMRR
Input Common Mode –0.1V to 5.1V
45
70
dB
19932fa
2
LT1993-2
DC ELECTRICAL CHARACTERISTICS
The
CCA
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T = 25°C. V
= V
= V
= 5V, V = V = V = 0V, ENABLE = 0.8V, +INA
CCC EEA EEB EEC
A
CCB
shorted to +INB (+IN), –INA shorted to –INB (–IN), V
= 2.2V, Input common mode voltage = 2.2V, no R
unless otherwise noted.
OCM
LOAD
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
0.3
0.8
MAX
UNITS
Ω
R
Output Resistance
Output Capacitance
OUTDIFF
OUTDIFF
C
pF
Common Mode Voltage Control (V
Pin)
OCM
GCM
Common Mode Gain
Differential (+OUT, –OUT), V
Differential (+OUT, –OUT), V
= 1.1V to 3.6V
= 1.3V to 3.4V
0.9
0.9
1
1.1
1.1
V/V
V/V
OCM
OCM
●
●
V
V
V
Output Common Mode Voltage
Adjustment Range, MIN
Measured Single-Ended at +OUT and –OUT
1.1
1.3
V
V
OCMMIN
Output Common Mode Voltage
Adjustment Range, MAX
Measured Single-Ended at +OUT and –OUT
3.6
3.4
V
V
OCMMAX
●
●
●
●
Output Common Mode Offset Voltage
Measured from V
to Average of +OUT and –OUT
–30
4
5
3
1
30
15
mV
µA
OSCM
OCM
I
V
V
V
Input Bias Current
Input Resistance
Input Capacitance
BIASCM
OCM
OCM
OCM
R
0.8
MΩ
pF
INCM
C
INCM
ENABLE Pin
●
●
●
●
V
ENABLE Input Low Voltage
ENABLE Input High Voltage
ENABLE Input Low Current
ENABLE Input High Current
0.8
V
V
IL
V
2
IH
I
IL
I
IH
ENABLE = 0.8V
ENABLE = 2V
0.5
3
µA
µA
1
Power Supply
●
●
●
●
V
Operating Range
4
5
5.5
112
500
V
mA
µA
S
I
I
Supply Current
ENABLE = 0.8V
ENABLE = 2V
4V to 5.5V
88
100
250
90
S
Supply Current (Disabled)
Power Supply Rejection Ratio
SDISABLED
PSRR
55
dB
AC ELECTRICAL CHARACTERISTICS
T = 25°C, V
= V
= V
= 5V, V = V = V = 0V,
A
CCA
CCB
CCC EEA EEB EEC
ENABLE = 0.8V, +INA shorted to +INB (+IN), –INA shorted to –INB (–IN), V
unless otherwise noted.
= 2.2V, Input common mode voltage = 2.2V, no R
LOAD
OCM
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Input/Output Characteristics
–3dBBW
0.1dBBW
0.5dBBW
SR
–3dB Bandwidth
200mV Differential (+OUT, –OUT)
500
800
50
MHz
MHz
MHz
V/µs
ns
P-P
Bandwidth for 0.1dB Flatness
Bandwidth for 0.5dB Flatness
Slew Rate
200mV Differential (+OUT, –OUT)
P-P
200mV Differential (+OUT, –OUT)
100
1100
4
P-P
3.2V Differential (+OUT, –OUT)
P-P
t
1% Settling Time
1% Settling for a 1V Differential Step
s1%
P-P
(+OUT, –OUT)
t
t
Turn-On Time
Turn-Off Time
40
ns
ns
ON
250
OFF
Common Mode Voltage Control (V
Pin)
OCM
–3dBBW
Common Mode Small-Signal –3dB
Bandwidth
0.1V at V , Measured Single-Ended at +OUT
OCM
300
500
MHz
CM
P-P
and –OUT
SR
CM
Common Mode Slew Rate
1.3V to 3.4V Step at V
V/µs
OCM
19932fa
3
LT1993-2
AC ELECTRICAL CHARACTERISTICS
T = 25°C, V
= V
= V
= 5V, V = V = V = 0V,
CCC EEA EEB EEC
A
CCA
CCB
ENABLE = 0.8V, +INA shorted to +INB (+IN), –INA shorted to –INB (–IN), V
unless otherwise noted.
= 2.2V, Input common mode voltage = 2.2V, no R
OCM
LOAD
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Noise/Harmonic Performance Input/output Characteristics
1kHz Signal
Second/Third Harmonic Distortion
2V Differential (+OUTFILTERED, –OUTFILTERED)
–100
–100
–100
–91
dBc
dBc
dBc
dBc
dBc
dBc
dBc
P-P
2V Differential (+OUT, –OUT)
P-P
2V Differential (+OUT, –OUT), R = 100Ω
P-P
L
3.2V Differential (+OUTFILTERED, –OUTFILTERED)
P-P
3.2V Differential (+OUT, –OUT)
–91
P-P
3.2V Differential (+OUT, –OUT), R = 100Ω
–91
P-P
L
Third-Order IMD
2V Differential Composite (+OUTFILTERED,
–102
P-P
–OUTFILTERED), f1 = 0.95kHz, f2 = 1.05kHz
2V Differential Composite (+OUT, –OUT),
L
–102
–93
54
dBc
dBc
P-P
R = 100Ω, f1 = 0.95kHz, f2 = 1.05kHz
3.2V Differential Composite (+OUTFILTERED,
P-P
–OUTFILTERED), f1 = 0.95kHz, f2 = 1.05kHz
OIP3
Output Third-Order Intercept
Differential (+OUTFILTERED, –OUTFILTERED),
f1 = 0.95kHz, f2 = 1.05kHz
dBm
1k
e
n1k
Input Referred Noise Voltage Density
1dB Compression Point
3.5
nV/√Hz
dBm
R = 100Ω
L
22.7
10MHz Signal
Second/Third Harmonic Distortion
2V Differential (+OUTFILTERED, –OUTFILTERED)
–94
–94
–86
–85
–85
–77
–96
dBc
dBc
dBc
dBc
dBc
dBc
dBc
P-P
2V Differential (+OUT, –OUT)
P-P
2V Differential (+OUT, –OUT), R = 100Ω
P-P
L
3.2V Differential (+OUTFILTERED, –OUTFILTERED)
P-P
3.2V Differential (+OUT, –OUT)
P-P
3.2V Differential (+OUT, –OUT), R = 100Ω
P-P
L
Third-Order IMD
2V Differential Composite (+OUTFILTERED,
P-P
–OUTFILTERED), f1 = 9.5MHz, f2 = 10.5MHz
2V Differential Composite (+OUT, –OUT),
L
–96
–87
51
dBc
dBc
P-P
R = 100Ω, f1 = 9.5MHz, f2 = 10.5MHz
3.2V Differential Composite (+OUTFILTERED,
P-P
–OUTFILTERED), f1 = 9.5MHz, f2 = 10.5MHz
OIP3
NF
Output Third-Order Intercept
Differential (+OUTFILTERED, –OUTFILTERED),
f1 = 9.5MHz, f2 = 10.5MHz
dBm
10M
Noise Figure
Measured Using DC800A Demo Board
11.3
3.5
dB
nV/√Hz
dBm
e
Input Referred Noise Voltage Density
1dB Compression Point
n10M
R = 100Ω
L
22.6
50MHz Signal
Second/Third Harmonic Distortion
2V Differential (+OUTFILTERED, –OUTFILTERED)
–77
–77
–74
–68
–65
dBc
dBc
dBc
dBc
P-P
2V Differential (+OUT, –OUT)
P-P
2V Differential (+OUT, –OUT), R = 100Ω
P-P
L
3.2V Differential (+OUTFILTERED, –OUTFILTERED)
P-P
3.2V Differential (+OUT, –OUT)
dBc
P-P
19932fa
4
LT1993-2
AC ELECTRICAL CHARACTERISTICS
T = 25°C, V
= V
= V
= 5V, V = V = V = 0V,
A
CCA
CCB
CCC EEA EEB EEC
ENABLE = 0.8V, +INA shorted to +INB (+IN), –INA shorted to –INB (–IN), V
unless otherwise noted.
= 2.2V, Input common mode voltage = 2.2V, no R
OCM
LOAD
SYMBOL
PARAMETER
CONDITIONS
3.2V Differential (+OUT, –OUT), R = 100Ω
MIN
TYP
–65
–84
MAX
UNITS
dBc
dBc
P-P
L
Third-Order IMD
2V Differential Composite (+OUTFILTERED,
P-P
–OUTFILTERED), f1 = 49.5MHz, f2 = 50.5MHz
2V Differential Composite (+OUT, –OUT),
L
–88
–75
45
dBc
dBc
P-P
R = 100Ω, f1 = 49.5MHz, f2 = 50.5MHz
3.2V Differential Composite (+OUTFILTERED,
P-P
–OUTFILTERED), f1 = 49.5MHz, f2 = 50.5MHz
OIP3
NF
Output Third-Order Intercept
Differential (+OUTFILTERED, –OUTFILTERED),
f1 = 49.5MHz, f2 = 50.5MHz
dBm
50M
Noise Figure
Measured Using DC800A Demo Board
11.8
3.65
19.7
dB
nV/√Hz
dBm
e
Input Referred Noise Voltage Density
1dB Compression Point
n50M
R = 100Ω
L
70MHz Signal
Second/Third Harmonic Distortion
Third-Order IMD
2V Differential (+OUTFILTERED, –OUTFILTERED)
–70
–61
–61
–70
dBc
dBc
dBc
dBc
P-P
2V Differential (+OUT, –OUT)
P-P
2V Differential (+OUT, –OUT), R = 100Ω
P-P
L
2V Differential Composite (+OUTFILTERED,
P-P
–OUTFILTERED), f1 = 69.5MHz, f2 = 70.5MHz
2V Differential Composite (+OUT, –OUT),
L
–72
38
dBc
P-P
R = 100Ω, f1 = 69.5MHz, f2 = 70.5MHz
OIP3
NF
Output Third-Order Intercept
Differential (+OUTFILTERED, –OUTFILTERED),
f1 = 69.5MHz, f2 = 70.5MHz
dBm
70M
Noise Figure
Measured Using DC800A Demo Board
12.3
3.8
dB
nV/√Hz
dBm
e
Input Referred Noise Voltage Density
1dB Compression Point
n70M
R = 100Ω
L
18.5
100MHz Signal
Second/Third Harmonic Distortion
Third-Order IMD
2V Differential (+OUTFILTERED, –OUTFILTERED)
–56
–54
–51
–58
dBc
dBc
dBc
dBc
P-P
2V Differential (+OUT, –OUT)
P-P
2V Differential (+OUT, –OUT), R = 100Ω
P-P
L
2V Differential Composite (+OUTFILTERED,
P-P
–OUTFILTERED), f1 = 99.5MHz, f2 = 100.5MHz
2V Differential Composite (+OUT, –OUT),
L
–59
32
dBc
P-P
R = 100Ω, f1 = 99.5MHz, f2 = 100.5MHz
OIP3
NF
Output Third-Order Intercept
Differential (+OUTFILTERED, –OUTFILTERED),
f1 = 99.5MHz, f2 = 100.5MHz
dBm
100M
Noise Figure
Measured Using DC800A Demo Board
12.8
4.1
dB
nV/√Hz
dBm
e
Input Referred Noise Voltage Density
1dB Compression Point
n100M
R = 100Ω
L
17.8
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: As long as output current and junction temperature are kept below
the Absolute Maximum Ratings, no damage to the part will occur.
0°C to 70°C. It is designed, characterized and expected to meet specified
performance from –40°C and 85°C but is not tested or QA sampled
at these temperatures. The LT1993I-2 is guaranteed to meet specified
performance from –40°C to 85°C.
Note 5: This parameter is pulse tested.
Note 3: The LT1993C-2 is guaranteed functional over the operating
temperature range of –40°C to 85°C.
Note 4: The LT1993C-2 is guaranteed to meet specified performance from
Note 6: This parameter is guaranteed to meet specified performance
through design and characterization. It has not been tested.
19932fa
5
LT1993-2
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Frequency Response
= 400Ω
Frequency Response vs C
LOAD
,
Frequency Response
R = 100Ω
LOAD
LOAD
R
LOAD
R
= 400Ω
12
9
21
18
15
12
9
12
9
V
= 100mV
P-P
IN
UNFILTERED OUTPUTS
UNFILTERED OUTPUTS
FILTERED OUTPUTS
UNFILTERED OUTPUTS
FILTERED OUTPUTS
6
6
3
3
0
0
–3
–6
–9
–12
6
–3
–6
–9
–12
V
= 100mV
V
= 100mV
IN P-P
IN
P-P
LOAD
=
UNFILTERED: R
FILTERED: R
= 400Ω
UNFILTERED: R
FILTERED: R
= 100Ω
LOAD
=
3
0pF
2pF
5pF
10pF
LOAD
LOAD
350Ω (EXTERNAL) +
50Ω (EXTERNAL) +
0
50Ω (INTERNAL, FILTERED
50Ω (INTERNAL, FILTERED
OUTPUTS)
OUTPUTS)
–3
1
10
100
1000
10000
1
10
100
1000
10000
1
10
100
1000
10000
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
19932 G01
19932 G03
19932 G02
Third Order Intermodulation
Distortion vs Frequency
Third Order Intermodulation
Distortion vs Frequency
Third Order Intermodulation
Distortion vs Frequency
Differential Input, No R
Differential Input, R
= 400Ω
Differential Input, R
= 100Ω
LOAD
LOAD
LOAD
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
2 TONES, 2V COMPOSITE
P-P
2 TONES, 2V COMPOSITE
P-P
2 TONES, 2V COMPOSITE
P-P
1MHz TONE SPACING
1MHz TONE SPACING
1MHz TONE SPACING
FILTERED OUTPUTS
FILTERED OUTPUTS
FILTERED OUTPUTS
UNFILTERED OUTPUTS
UNFILTERED OUTPUTS
UNFILTERED OUTPUTS
0
20
40
60
80 100 120 140
0
20
40
60
80 100 120 140
0
20
40
60
80 100 120 140
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
19932 G06
19932 G04
19932 G05
Output Third Order Intercept vs
Frequency, Differential Input,
Output Third Order Intercept vs
Frequency, Differential Input,
LOAD
Output Third Order Intercept vs
Frequency, Differential Input,
LOAD
No R
R
= 400Ω
R
= 100Ω
LOAD
60
55
50
45
40
35
30
25
20
60
55
50
45
40
35
30
25
20
60
55
50
45
40
35
30
25
20
2 TONES, 2V COMPOSITE
P-P
2 TONES, 2V COMPOSITE
P-P
2 TONES, 2V COMPOSITE
P-P
1MHz TONE SPACING
1MHz TONE SPACING
1MHz TONE SPACING
UNFILTERED OUTPUTS
UNFILTERED OUTPUTS
UNFILTERED OUTPUTS
FILTERED OUTPUTS
FILTERED OUTPUTS
FILTERED OUTPUTS
0
20
40
60
80 100 120 140
0
20
40
60
80 100 120 140
0
20
40
60
80 100 120 140
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
19932 G09
19932 G07
19932 G08
19932fa
6
LT1993-2
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Distortion (Filtered) vs Frequency
Distortion (Filtered) vs Frequency
Distortion (Filtered) vs Frequency
Differential Input, R
= 400Ω
Differential Input, R
= 100Ω
Differential Input, No R
LOAD
LOAD
LOAD
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
FILTERED OUTPUTS
FILTERED OUTPUTS
FILTERED OUTPUTS
V
= 2V
V
= 2V
P-P
OUT
V
= 2V
P-P
P-P
OUT
OUT
HD3
HD2
HD3
HD2
HD3
HD2
1
10
100
1000
1
10
100
1000
1
10
100
1000
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
19932 G11
19932 G12
19932 G10
Distortion (Unfiltered) vs
Frequency, Differential Input,
No R
Distortion (Unfiltered) vs
Frequency, Differential Input,
= 400Ω
Distortion (Unfiltered) vs
Frequency, Differential Input,
R = 100Ω
R
LOAD
LOAD
UNFILTERED OUTPUTS
LOAD
UNFILTERED OUTPUTS
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
UNFILTERED OUTPUTS
V
= 2V
V
= 2V
V
= 2V
P-P
OUT
P-P
P-P
OUT
OUT
HD3
HD2
HD3
HD2
HD3
HD2
1
10
100
1000
1
10
100
1000
1
10
100
1000
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
19932 G13
19932 G14
19932 G15
Distortion vs Output Amplitude
70MHz Differential Input,
Distortion vs Output Amplitude
70MHz Differential Input,
LOAD
Distortion vs Output Amplitude
70MHz Differential Input,
LOAD
No R
R
= 400Ω
R
= 100Ω
LOAD
–50
–55
–60
–65
–70
–75
–80
–85
–90
–95
–100
–50
–55
–60
–65
–70
–75
–80
–85
–90
–95
–100
–50
–55
–60
–65
–70
–75
–80
HD3 UNFILTERED OUTPUTS
HD3 FILTERED OUTPUTS
HD3 UNFILTERED OUTPUTS
HD2 UNFILTERED OUTPUTS
HD3 UNFILTERED OUTPUTS
HD2 UNFILTERED OUTPUTS
HD2 FILTERED OUTPUTS
HD3 FILTERED OUTPUTS
–85 HD2 UNFILTERED OUTPUTS
HD2 FILTERED OUTPUTS
HD3 FILTERED OUTPUTS
–90
HD2 FILTERED OUTPUTS
11
–95
–100
–1
1
3
5
7
9
11
–1
1
3
5
7
9
11
–1
1
3
5
7
9
OUTPUT AMPLITUDE (dBm)
OUTPUT AMPLITUDE (dBm)
OUTPUT AMPLITUDE (dBm)
19932 G16
19932 G17
19932 G18
19932fa
7
LT1993-2
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Distortion (Filtered) vs Frequency
Distortion (Filtered) vs Frequency
Distortion (Filtered) vs Frequency
Single-Ended Input, No R
Single-Ended Input, R
= 400Ω
Single-Ended Input, R
= 100Ω
LOAD
LOAD
LOAD
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
FILTERED OUTPUTS
FILTERED OUTPUTS
FILTERED OUTPUTS
V
= 2V
V
= 2V
V
= 2V
P-P
OUT
P-P
P-P
OUT
OUT
HD3
HD2
HD3
HD2
HD3
HD2
1
10
100
1000
1
10
100
1000
1
10
100
1000
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
19932 G19
19932 G20
19932 G21
Distortion (Unfiltered) vs
Frequency, Single-Ended Input,
No R
Distortion (Unfiltered) vs
Frequency, Single-Ended Input,
= 400Ω
Distortion (Unfiltered) vs
Frequency, Single-Ended Input,
R = 100Ω
R
LOAD
LOAD
UNFILTERED OUTPUTS
LOAD
UNFILTERED OUTPUTS
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
UNFILTERED OUTPUTS
V
= 2V
V
= 2V
V
= 2V
P-P
OUT
P-P
P-P
OUT
OUT
HD3
HD2
HD3
HD2
HD3
HD2
1
10
100
1000
1
10
100
1000
1
10
100
1000
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
19932 G22
19932 G23
19932 G24
Distortion vs Output Amplitude
70MHz Single-Ended Input,
Distortion vs Output Amplitude
70MHz Single-Ended Input,
LOAD
Distortion vs Output Amplitude
70MHz Single-Ended Input,
LOAD
No R
R
= 400Ω
R
= 100Ω
LOAD
–50
–55
–60
–65
–70
–75
–80
–85
–90
–95
–100
–50
–55
–60
–65
–70
–75
–80
–85
–90
–95
–100
–50
–55
HD3 UNFILTERED OUTPUTS
HD3 UNFILTERED OUTPUTS
HD3 UNFILTERED OUTPUTS
–60 HD3 FILTERED OUTPUTS
HD3 FILTERED OUTPUTS
HD3 FILTERED OUTPUTS
–65
–70
–75
–80
HD2 UNFILTERED OUTPUTS
HD2 FILTERED OUTPUTS
–85
–90
HD2 UNFILTERED OUTPUTS
HD2 UNFILTERED OUTPUTS
HD2 FILTERED OUTPUTS
HD2 FILTERED OUTPUTS
–95
–100
–1
1
3
5
7
9
11
–1
1
3
5
7
9
11
–1
1
3
5
7
9
11
OUTPUT AMPLITUDE (dBm)
OUTPUT AMPLITUDE (dBm)
OUTPUT AMPLITUDE (dBm)
19932 G25
19932 G26
19932 G27
19932fa
8
LT1993-2
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Output 1dB Compression
vs Frequency
Input Referred Noise Voltage vs
Frequency
Noise Figure vs Frequency
25
20
15
10
5
12
10
8
30
25
20
15
10
5
UNFILTERED OUTPUTS
R
= 400Ω
LOAD
R
= 100Ω
LOAD
6
4
0
2
–5
–10
V
= 5V
CC
MEASURED USING DC800A DEMO BOARD
0
0
10
100
1000
1000
1000
10
100
1000
1
10
100
1000
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
19932 G28
19932 G29
19932 G30
Differential Input Impedance vs
Frequency
Differential Output Impedance vs
Frequency
Isolation vs Frequency
100
10
1
–40
–50
300
250
200
150
100
50
UNFILTERED OUTPUTS
UNFILTERED OUTPUTS
–60
IMPEDANCE MAGNITUDE
IMPEDANCE PHASE
–70
–80
–90
0
–100
–110
–50
–100
0.1
1
10
100
1000
1
10
100
1000
10000
1
10
100
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
19932 G32
19932 G33
19932 G31
Input Reflection Coefficient vs
Frequency
Output Reflection Coefficient vs
Frequency
PSRR, CMRR vs Frequency
0
–5
0
–5
100
90
80
70
60
50
40
30
20
10
0
MEASURED USING DC800A DEMO BOARD
MEASURED USING DC800A DEMO BOARD
UNFILTERED OUTPUTS
–10
–15
–20
–25
–30
–35
–40
–45
–50
–10
–15
–20
–25
–30
–35
–40
–45
–50
CMRR
PSRR
10
100
1000
10
100
1
10
100
1000
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
19932 G36
19932 G34
19932 G35
19932fa
9
LT1993-2
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Small-Signal Transient Response
Large-Signal Transient Response
Overdrive Recovery Time
2.28
2.26
2.24
2.22
2.20
2.18
2.16
2.14
2.12
3.0
2.8
2.6
2.4
2.2
2.0
1.8
1.6
1.4
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
R
= 100Ω PER OUTPUT
R
= 100Ω PER OUTPUT
LOAD
LOAD
+OUT
R
= 100Ω
LOAD
PER OUTPUT
–OUT
15 20
15 20
75 100
25 50
0
5
10
25 30 35 40 45 50
0
5
10
25 30 35 40 45 50
0
125 150 175 200 225 250
TIME (ns)
TIME (ns)
TIME (ns)
19932 G37
19932 G38
19932 G39
Distortion vs Output Common
Mode Voltage LT1993-2 Driving
LTC2249 14-Bit ADC
Turn-On Time
Turn-Off Time
–64
–66
–68
–70
–72
–74
–76
4
3
4
3
FILTERED OUTPUTS, NO R
LOAD
+OUT
–OUT
+OUT
V
= 70MHz 2V
OUT
P-P
2
2
–OUT
1
1
0
0
R
= 100Ω PER OUTPUT
LOAD
HD3
HD2
4
4
ENABLE
R
2
2
ENABLE
0
0
= 100Ω PER OUTPUT
LOAD
–2
–2
1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6
0
250
TIME (ns)
500
625
125
375
250
TIME (ns)
0
125
375
500
625
OUTPUT COMMON MODE VOLTAGE (V)
19932 G40
19932 G41
19932 G42
19932fa
10
LT1993-2
U W
TYPICAL PERFOR A CE CHARACTERISTICS
30MHz 8192 Point FFT, LT1993-2
Driving LTC2249 14-Bit ADC
50MHz 8192 Point FFT, LT1993-2
Driving LTC2249 14-Bit ADC
70MHz 8192 Point FFT, LT1993-2
Driving LTC2249 14-Bit ADC
0
–10
0
–10
0
–10
8192 POINT FFT
8192 POINT FFT
8192 POINT FFT
f
= 30MHz, –1dBFS
f
= 50MHz, –1dBFS
f
= 70MHz, –1dBFS
IN
IN
IN
FILTERED OUTPUTS
FILTERED OUTPUTS
FILTERED OUTPUTS
–20
–20
–20
–30
–30
–30
–40
–40
–40
–50
–50
–50
–60
–60
–60
–70
–70
–70
–80
–80
–80
–90
–90
–90
–100
–110
–120
–100
–110
–120
–100
–110
–120
25 30
10 15 20
FREQUENCY (MHz)
25 30
10 15 20
FREQUENCY (MHz)
25 30
10 15 20
FREQUENCY (MHz)
0
5
35 40
0
5
35 40
0
5
35 40
19932 G46
19932 G47
19932 G48
70MHz 2-Tone 32768 Point FFT,
LT1993-2 Driving LTC2249
14-Bit ADC
2-Tone WCDMA Waveform,
4-Tone WCDMA Waveform,
LT1993-2 Driving LTC2255 14-Bit
ADC at 92.16Msps
LT1993-2 Driving LTC2255 14-Bit
ADC at 92.16Msps
0
–10
0
–10
0
–10
32768 POINT FFT
TONE CENTER FREQUENCIES
AT 67.5MHz, 72.5MHz
32768 POINT FFT
32768 POINT FFT
TONE CENTER FREQUENCIES
AT 62.5MHz, 67.5MHz,
72.5MHz, 77.5MHz
TONE 1 AT 69.5MHz, –7dBFS
TONE 2 AT 70.5MHz, –7dBFS
FILTERED OUTPUTS
–20
–20
–20
–30
–30
–30
–40
–40
–40
–50
–50
–50
–60
–60
–60
–70
–70
–70
–80
–80
–80
–90
–90
–90
–100
–110
–120
–100
–110
–120
–100
–110
–120
0
5
10 15 20 25 30 35 40 45
0
5
10 15 20 25 30 35 40 45
25 30
10 15 20
FREQUENCY (MHz)
0
5
35 40
FREQUENCY (MHz)
FREQUENCY (MHz)
19932 G50
19932 G51
19932 G49
19932fa
11
LT1993-2
U
U
U
PI FU CTIO S
V
(Pin 2): This pin sets the output common mode
+OUTFILTERED, –OUTFILTERED (Pins 6, 7): Filtered
Outputs. These pins add a series 25Ω resistor from the
unfiltered outputs and three 12pF capacitors. Each output
OCM
voltage. Without additional biasing, both inputs bias to
this voltage as well. This input is high impedance.
has 12pF to V , plus an additional 12pF between each pin
EE
V
, V , V
(Pins 3, 10, 1): Positive Power Supply
CCA CCB CCC
(See the Block Diagram). This filter has a –3dB bandwidth
of 175MHz.
(Normally Tied to 5V). All three pins must be tied to the
same voltage. Bypass each pin with 1000pF and 0.1µF
capacitors as close to the package as possible. Split
ENABLE (Pin 11): This pin is a TTL logic input referenced
supplies are possible as long as the voltage between V
and V is 5V.
to the V pin. If low, the LT1993-2 is enabled and draws
CC
EEC
typically 100mA of supply current. If high, the LT1993-2
EE
is disabled and draws typically 250µA.
V
, V , V (Pins 4, 9, 12): Negative Power Supply
EEA EEB EEC
(Normally Tied to Ground). All three pins must be tied to
+INA, +INB (Pins 15, 16): Positive Inputs. These pins are
normally tied together. These inputs may be DC- or AC-
coupled. If the inputs are AC-coupled, they will self-bias
the same voltage. Split supplies are possible as long as
the voltage between V and V is 5V. If these pins are
CC
EE
nottiedtoground, bypasseachpinwith1000pFand0.1µF
to the voltage applied to the V
pin.
OCM
capacitors as close to the package as possible.
–INA, –INB (Pins 14, 13): Negative Inputs. These pins are
normally tied together. These inputs may be DC- or AC-
coupled. If the inputs are AC-coupled, they will self-bias
+OUT, –OUT (Pins 5, 8): Outputs (Unfiltered). These
pins are high bandwidth, low-impedance outputs. The DC
output voltage at these pins is set to the voltage applied
to the voltage applied to the V
pin.
OCM
at V
.
OCM
Exposed Pad (Pin 17): Tie the pad to V (Pin 12). If split
EEC
supplies are used, DO NOT tie the pad to ground.
19932fa
12
LT1993-2
W
BLOCK DIAGRA
200Ω
V
EEA
V
CCA
–INA
14
12pF
200Ω
200Ω
–
+
+OUT
5
6
A
–INB
13
+OUTFILTERED
25Ω
V
EEA
V
200Ω
CCC
V
OCM
2
+
–
C
12pF
V
EEC
200Ω
200Ω
25Ω
–OUTFILTERED
–OUT
V
CCB
+INA
16
7
8
+
–
B
+INB
15
200Ω
12pF
V
EEB
V
EEB
200Ω
BIAS
11
19932 BD
3
10
1
4
9
12
V
V
V
ENABLE
V
V
V
EEC
CCA
CCB
CCC
EEA
EEB
19932fa
13
LT1993-2
U
W U U
APPLICATIO S I FOR ATIO
Circuit Description
Input Impedance and Matching Networks
The LT1993-2 is a low-noise, low-distortion differential
amplifier/ADC driver with:
Because of the internal feedback network, calculation of
the LT1993-2’s input impedance is not straightforward
from examination of the block diagram. Furthermore, the
inputimpedancewhendrivendifferentiallyisdifferentthan
when driven single-ended. When driven differentially, the
LT1993-2’s input impedance is 200Ω (differential); when
driven single-ended, the input impedance is 133Ω.
• DC to 800MHz –3dB bandwidth
• Fixed gain of 2V/V (6dB) independent of R
LOAD
• 200Ω differential input impedance
• Low output impedance
For single-ended 50Ω applications, an 80.6Ω shunt
matching resistor to ground will result in the proper input
termination (Figure 1). For differential inputs there are
several termination options. If the input source is 50Ω
differential, then input matching can be accomplished by
either a 67Ω shunt resistor across the inputs (Figure 3),
or a 33Ω shunt resistor on each of the inputs to ground
(Figure2).IfadditionalACgainisdesired,a1:4impedance
ratiotransformer(liketheMini-CircuitsTCM4-19)canalso
be used to better match impedances and to provide an ad-
ditional 6dB of gain (Figure 4). With a 1:4 impedance ratio
transformer, idealmatchingimpedanceatthetransformer
output is 200Ω, so no termination resistors are required
to match the LT1993-2’s 200Ω input impedance.
• Built-in, user adjustable output filtering
• Requires minimal support circuitry
Referringtotheblockdiagram,theLT1993-2usesaclosed-
loop topology which incorporates 3 internal amplifiers.
Two of the amplifiers (A and B) are identical and drive
the differential outputs. The third amplifier (C) is used
to set the output common mode voltage. Gain and input
impedance are set by the 200Ω resistors in the internal
feedback network. Output impedance is low, determined
by the inherent output impedance of amplifiers A and B,
and further reduced by internal feedback.
The LT1993-2 also includes built-in single-pole output
filtering. The user has the choice of using the unfiltered
outputs, the filtered outputs (175MHz –3dB lowpass), or
modifying the filtered outputs to alter frequency response
by adding additional components. Many lowpass and
bandpass filters are easily implemented with just one or
two additional components.
13
–INB
–INA
8
5
–OUT
LT1993-2
+OUT
14
0.1µF
15
16
IF IN
+INB
+INA
The LT1993-2 has been designed to minimize the need
for external support components such as transformers or
AC-coupling capacitors. As an ADC driver, the LT1993-2
requires no external components except for power-supply
bypass capacitors. This allows DC-coupled operation for
applications that have frequency ranges including DC.
At the outputs, the common mode voltage is set via the
80.6Ω
SINGLE-ENDED
Z
= 50Ω
IN
19932 F01
Figure 1. Input Termination for Single-Ended 50Ω
Input Impedance
13
–INB
–
V
OCM
pin,allowingtheLT1993-2todriveADCsdirectly.No
IF IN
8
5
14
–OUT
LT1993-2
+OUT
–INA
outputAC-couplingcapacitorsortransformersareneeded.
At the inputs, signals can be differential or single-ended
with virtually no difference in performance. Furthermore,
DC levels at the inputs can be set independently of the
outputcommonmodevoltage.Theseinputcharacteristics
often eliminate the need for an input transformer and/or
AC-coupling capacitors.
33Ω
33Ω
Z
= 50Ω
IN
DIFFERENTIAL
15
16
+INB
+INA
+
IF IN
19932 F02
Figure 2. Input Termination for Differential 50Ω Input Impedance
19932fa
14
LT1993-2
U
W U U
APPLICATIO S I FOR ATIO
high impedance inputs of these differential ADCs. If the
filtered outputs are used, then cutoff frequency and the
type of filter can be tailored for the specific application if
needed.
13
–INB
–
IF IN
8
14
–OUT
LT1993-2
+OUT
–INA
Z
= 50Ω
DIFFERENTIAL
IN
67Ω
15
16
+INB
+INA
Wideband Applications
(Using the +OUT and –OUT Pins)
+
IF IN
5
19932 F02
In applications where the full bandwidth of the LT1993-2
is desired, the unfiltered output pins (+OUT and –OUT)
should be used. They have a low output impedance;
therefore, gain is unaffected by output load. Capacitance
in excess of 5pF placed directly on the unfiltered outputs
results in additional peaking and reduced performance.
When driving an ADC directly, a small series resistance
is recommended between the LT1993-2’s outputs and
the ADC inputs (Figure 5). This resistance helps eliminate
any resonances associated with bond wire inductances of
either the ADC inputs or the LT1993-2’s outputs. A value
between 10Ω and 25Ω gives excellent results.
Figure 3. Alternate Input Termination for Differential
50Ω Input Impedance
13
–INB
–INA
8
5
–OUT
LT1993-2
+OUT
14
0.1µF
Z
= 50Ω
DIFFERENTIAL
IN
15
16
+INB
+INA
1:4 TRANSFORMER
(MINI-CIRCUITS TCM4-19)
19932 F04
Figure 4. Input Termination for Differential 50Ω Input Impedance
with 6dB Additional Gain
Single-Ended to Differential Operation
10Ω TO 25Ω
8
–OUT
The LT1993-2’s performance with single-ended inputs is
comparable to its performance with differential inputs.
This excellent single-ended performance is largely due
to the internal topology of the LT1993-2. Referring to
the block diagram, if the +INA and +INB pins are driven
with a single-ended signal (while –INA and –INB are tied
to AC ground), then the +OUT and –OUT pins are driven
differentially without any voltage swing needed from
amplifier C. Single-ended to differential conversion using
more conventional topologies suffers from performance
limitations due to the common mode amplifier.
LT1993-2
+OUT
ADC
10Ω TO 25Ω
5
19932 F05
Figure 5. Adding Small Series R at LT1993-2 Output
Filtered Applications
(Using the +OUTFILTERED and –OUTFILTERED Pins)
Filtering at the output of the LT1993-2 is often desired to
provide either anti-aliasing or improved signal to noise
ratio. To simplify this filtering, the LT1993-2 includes an
additional pair of differential outputs (+OUTFILTERED
and –OUTFILTERED) which incorporate an internal low-
pass filter network with a –3dB bandwidth of 175MHz
(Figure 6). These pins each have an output impedance
Driving ADCs
The LT1993-2 has been specifically designed to interface
directly with high speed Analog to Digital Converters
(ADCs). In general, these ADCs have differential inputs,
with an input impedance of 1k or higher. In addition, there
isgenerallysomeformoflowpassorbandpassfilteringjust
prior to the ADC to limit input noise at the ADC, thereby
improving system signal to noise ratio. Both the unfiltered
and filtered outputs of the LT1993-2 can easily drive the
of 25Ω. Internal capacitances are 12pF to V on each
EE
filtered output, plus an additional 12pF capacitor con-
nected differentially between the two filtered outputs. This
resistor/capacitor combination creates filtered outputs
19932fa
15
LT1993-2
U
W U U
APPLICATIO S I FOR ATIO
that look like a series 25Ω resistor with a 36pF capacitor
shunting each filtered output to AC ground, giving a –3dB
bandwidth of 175MHz.
it will appear at each filtered output as a single-ended
capacitance of twice the value. To halve the filter band-
width, for example, two 36pF capacitors could be added
(one from each filtered output to ground). Alternatively
one 18pF capacitor could be added between the filtered
outputs, again halving the filter bandwidth. Combinations
of capacitors could be used as well; a three capacitor
solution of 12pF from each filtered output to ground plus
a 12pF capacitor between the filtered outputs would also
halve the filter bandwidth (Figure 8).
LT1993-2
8
–OUT
V
EE
12pF
12pF
25Ω
25Ω
7
6
–OUTFILTERED
+OUTFILTERED
FILTERED OUTPUT
(175MHz)
12pF
LT1993-2
V
EE
8
–OUT
5
V
+OUT
EE
19932 F06
12pF
25Ω
25Ω
Figure 6. LT1993-2 Internal Filter Topology –3dB BW ≈175MHz
12pF
7
–OUTFILTERED
FILTERED OUTPUT
(87.5MHz)
12pF
12pF
The filter cutoff frequency is easily modified with just a
fewexternalcomponents.Toincreasethecutofffrequency,
simplyadd2equalvalueresistors, onebetween+OUTand
+OUTFILTEREDandtheotherbetween–OUTand–OUTFIL-
TERED (Figure 7). These resistors are in parallel with the
internal 25Ω resistor, lowering the overall resistance and
increasingfilterbandwidth.Todoublethefilterbandwidth,
for example, add two external 25Ω resistors to lower
the series resistance to 12.5Ω. The 36pF of capacitance
remains unchanged, so filter bandwidth doubles.
+OUTFILTERED
6
5
12pF
12pF
V
EE
+OUT
19932 F08
Figure 8. LT1993-2 Internal Filter Topology Modified for
1/2x Filter Bandwidth (3 External Capacitors)
Bandpass filtering is also easily implemented with just a
few external components. An additional 120pF and 39nH,
each added differentially between +OUTFILTERED and
–OUTFILTERED creates a bandpass filter with a 71MHz
center frequency, –3dB points of 55MHz and 87MHz, and
1.6dB of insertion loss (Figure 9).
LT1993-2
8
–OUT
25Ω
V
EE
12pF
12pF
25Ω
25Ω
7
6
–OUTFILTERED
FILTERED OUTPUT
(350MHz)
LT1993-2
12pF
8
–OUT
V
EE
+OUTFILTERED
12pF
25Ω
25Ω
25Ω
7
–OUTFILTERED
39nH
V
EE
5
+OUT
FILTERED OUTPUT
(71MHz BANDPASS,
–3dB @ 55MHz/87MHz)
19932 F07
12pF
120pF
Figure 7. LT1993-2 Internal Filter Topology Modified for
2x Filter Bandwidth (2 External Resistors)
+OUTFILTERED
6
5
12pF
To decrease filter bandwidth, add two external capacitors,
one from +OUTFILTERED to ground, and the other from
–OUTFILTERED to ground. A single differential capacitor
connected between +OUTFILTERED and –OUTFILTERED
can also be used, but since it is being driven differentially
V
EE
+OUT
19932 F09
Figure 9. LT1993-2 Output Filter Topology Modified for Bandpass
Filtering (1 External Inductor, 1 External Capacitor)
19932fa
16
LT1993-2
U
W U U
APPLICATIO S I FOR ATIO
Output Common Mode Adjustment
ADCs because of the input voltage range constraints of
the ADC.
TheLT1993-2’soutputcommonmodevoltageissetbythe
V
pin. It is a high-impedance input, capable of setting
OCM
Large Output Voltage Swings
the output common mode voltage anywhere in a range
from 1.1V to 3.6V. Bandwidth of the V pin is typically
The LT1993-2 has been designed to provide the 3.2V
P-P
OCM
output swing needed by the LTC1748 family of 14-bit
low-noise ADCs. This additional output swing improves
system SNR by up to 4dB. Typical performance curves
and AC specifications have been included for these ap-
plications.
300MHz, so for applications where the V
pin is tied to
OCM
a DC bias voltage, a 0.1µF capacitor at this pin is recom-
mended. For best distortion performance, the voltage at
the V
pin should be between 1.8V and 2.6V.
OCM
When interfacing with most ADCs, there is generally a
output pin that is at about half of the supply voltage
V
OCM
Input Bias Voltage and Bias Current
of the ADC. For 5V ADCs such as the LTC17XX family, this
output pin should be connected directly (with the
The input pins of the LT1993-2 are internally biased to
V
OCM
the voltage applied to the V
pin. No external biasing
OCM
addition of a 0.1µF capacitor) to the input V
pin of the
OCM
resistors are needed, even for AC-coupled operation. The
input bias current is determined by the voltage difference
LT1993-2. For 3V ADCs such as the LTC22XX families,
the LT1993-2 will function properly using the 1.65V from
betweentheinputcommonmodevoltageandtheV
pin
OCM
the ADC’s V reference pin, but improved Spurious Free
CM
(which sets the output common mode voltage). At both
the positive and negative inputs, any voltage difference is
imposed across 200Ω, generating an input bias current.
Dynamic Range (SFDR) and distortion performance can
beachievedbylevel-shiftingtheLTC22XX’sV reference
CM
voltage up to at least 1.8V. This can be accomplished as
For example, if the inputs are tied to 2.5V with the V
OCM
shown in Figure 10 by using a resistor divider between
pin at 2.2V, then a total input bias current of 1.5mA will
flowintotheLT1993-2’s+INAand+INBpins.Furthermore,
an additional input bias current totaling 1.5mA will flow
into the –INA and –INB inputs.
the LTC22XX’s V output pin and V and then bypass-
CM
CC
ing the LT1993-2’s V
pin with a 0.1µF capacitor. For a
OCM
commonmodevoltageabove1.9V,ACcouplingcapacitors
are recommended between the LT1993-2 and LTC22XX
Application (Demo) Boards
3V
11k
TheDC800ADemoBoardhasbeencreatedforstand-alone
evaluation of the LT1993-2 with either single-ended or
differential input and output signals. As shown, it accepts
a single-ended input and produces a single-ended output
so that the LT1993-2 can be evaluated using standard
laboratory test equipment. For more information on this
Demo Board, please refer to the Demo Board section of
this data sheet.
1.9V
0.1µF
4.02k
2
13
14
31 1.5V
–INB
–INA
V
V
OCM
CM
10Ω
10Ω
6
7
1
2
+
–
+OUTFILTERED
LT1993-2
AIN
AIN
0.1µF
LTC22xx
–OUTFILTERED
15
16
+INB
+INA
IF IN
There are also additional demo boards available that
combine the LT1993-2 with a variety of different Linear
Technology ADCs. Please contact the factory for more
information on these demo boards.
80.6Ω
19932 F10
Figure 10. Level Shifting 3V ADC V Voltage for
Improved SFDR
CM
19932fa
17
LT1993-2
U
TYPICAL APPLICATIO
19932fa
18
LT1993-2
U
PACKAGE DESCRIPTIO
UD Package
16-Lead Plastic QFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1691)
0.70 0.05
3.50 0.05
2.10 0.05
1.45 0.05
(4 SIDES)
PACKAGE OUTLINE
0.25 0.05
0.50 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
BOTTOM VIEW—EXPOSED PAD
PIN 1 NOTCH R = 0.20 TYP
OR 0.25 × 45° CHAMFER
R = 0.115
TYP
0.75 0.05
3.00 0.10
(4 SIDES)
15 16
PIN 1
TOP MARK
(NOTE 6)
0.40 0.10
1
2
1.45 0.10
(4-SIDES)
(UD16) QFN 0904
0.200 REF
0.25 0.05
0.50 BSC
0.00 – 0.05
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WEED-2)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON THE TOP AND BOTTOM OF PACKAGE
19932fa
InformationfurnishedbyLinearTechnologyCorporationisbelievedtobeaccurateandreliable.However,
no responsibility is assumed for its use. Linear Technology Corporation makes no representation that
the interconnection of its circuits as described herein will not infringe on existing patent rights.
19
LT1993-2
U
TYPICAL APPLICATIO
Demo Circuit DC800A Schematic
(AC Test Circuit)
R18
0Ω
R17
0Ω
V
CC
V
CC
GND
V
CC
2
1
2
1
1
SW1
3
TP1
ENABLE
C17
1000pF
C18
0.01µF
R16
0Ω
2
1
1
2
R2
R4
[1]
R14
C11
[1]
12
11
10
9
C2
0.1µF
C4
0Ω
0Ω
R6
R10
R12
0.1µF
V
ENABLE
V
V
EEC
CCB EEB
–OUT
0Ω
24.9Ω
75Ω
13
14
15
16
8
–INB
1
2
1
2
J1
–IN
R8
[1]
J4
–OUT
T1
T2
C21
0.1µF
7
6
5
1:4 Z-RATIO
1:4 Z-RATIO
5
4
1
3
–INA
+INB
+INA
–OUTFILTERED
+OUTFILTERED
+OUT
3
1
4
5
2
1
2
2
L1
[1]
C8
[1]
R15
[1]
R7
[1]
+6dB
LT1993-2
+10.8dB
+6dB
1
2
MINI-
MINI-
0dB
0dB
J2
+IN
J5
+OUT
C1
0.1µF
C3
0.1µF
CIRCUITS
TCM 4-19
CIRCUITS
TCM 4-19
R9
24.9Ω
R11
75Ω
R5
0Ω
1
2
1
2
V
CCC
V
OCM
V
V
CCA
EEA
1
2
2
R1
1Ω
R3
[1]
R13
[1]
C16
[1]
C22
0.1µF
1
2
3
4
V
CC
V
CC
1
2
1
2
1
2
1
2
1
C10
0.01µF
C9
1000pF
C12
1000pF
C13
0.01µF
V
CC
R19
14k
J3
V
OCM
2
1
C7
0.01µF
R20
11k
C5
0.1µF
J6
TEST IN
T3
T4
J7
1:4
4:1
TEST OUT
4
5
5
1
3
3
2
1
2
R22
C19, 0.1µF
C20, 0.1µF
2
R21
[1]
C6
[1]
0.1µF
1
2
1
2
MINI-
CIRCUITS
TCM 4-19
MINI-
CIRCUITS
TCM 4-19
4
1
1
2
TP2
CC
V
CC
V
NOTES: UNLESS OTHERWISE SPECIFIED,
[1] DO NOT STUFF.
1
1
2
2
1
C14
4.7µF
C15
1µF
1
TP3
GND
19932 TA02
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
A = 4V/V, NF = 14.5dB, OIP3 = 40dBm at 70MHz
LT1993-4
900MHz Differential Amplifier/ADC Driver
700MHz Differential Amplifier/ADC Driver
V
LT1993-10
LT5514
A = 10V/V, NF = 12.7dB, OIP3 = 40dBm at 70MHz
V
Ultralow Distortion IF Amplifier/ADC Driver Digitally Controlled Gain Output IP3 47dBm at 100MHz
LT6600-2.5
Very Low Noise Differential Amplifier and
2.5MHz Lowpass Filter
86dB S/N with 3V Supply, SO-8 Package
82dB S/N with 3V Supply, SO-8 Package
82dB S/N with 3V Supply, SO-8 Package
76dB S/N with 3V Supply, SO-8 Package
LT6600-5
LT6600-10
LT6600-20
Very Low Noise Differential Amplifier and
5MHz Lowpass Filter
Very Low Noise Differential Amplifier and
10MHz Lowpass Filter
Very Low Noise Differential Amplifier and
20MHz Lowpass Filter
19932fa
LT/LT 1005 REV A • PRINTED IN USA
20 LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
●
●
© LINEAR TECHNOLOGY CORPORATION 2005
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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