LT6600-5
Very Low Noise, Differential
Amplifier and 5MHz Lowpass Filter
FEATURES
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DESCRIPTION
The LT
®
6600-5 combines a fully differential amplifier with a
4th order 5MHz lowpass filter approximating a Chebyshev
frequency response. Most differential amplifiers require
many precision external components to tailor gain and
bandwidth. In contrast, with the LT6600-5, two external
resistors program differential gain, and the filter’s 5MHz
cutoff frequency and passband ripple are internally set.
The LT6600-5 also provides the necessary level shifting
to set its output common mode voltage to accommodate
the reference voltage requirements of A/Ds.
Using a proprietary internal architecture, the LT6600-5
integrates an antialiasing filter and a differential ampli-
fier/driver without compromising distortion or low noise
performance. At unity gain the measured in band sig-
nal-to-noise ratio is an impressive 82dB. At higher gains
the input referred noise decreases so the part can process
smaller input differential signals without significantly
degrading the output signal-to-noise ratio.
The LT6600-5 also features low voltage operation. The
differential design provides outstanding performance for
a 2V
P-P
signal level while the part operates with a single
3V supply.
For similar devices with other cutoff frequencies, refer to
the LT6600-20, LT6600-10 and LT6600-2.5.
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Programmable Differential Gain via Two External
Resistors
Adjustable Output Common Mode Voltage
Operates and Specified with 3V, 5V, ±5V Supplies
0.5dB Ripple 4th Order Lowpass Filter with 5MHz
Cutoff
82dB S/N with 3V Supply and 2V
P-P
Output
Low Distortion, 2V
P-P
, 800Ω Load
1MHz: 93dBc 2nd, 96dBc 3rd
Fully Differential Inputs and Outputs
Compatible with Popular Differential Amplifier
Pinouts
Available in an SO-8 Package
APPLICATIONS
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High Speed ADC Antialiasing and DAC Smoothing in
Networking or Cellular Base Station Applications
High Speed Test and Measurement Equipment
Medical Imaging
Drop-in Replacement for Differential Amplifiers
L,
LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Dual, Matched, 5MHz Lowpass Filter
3V 0.1μF
R
IN
0.01μF
I
IN
30
1
7
2
8
R
IN
V
OCM
(1V-1.5V)
R
IN
0.01μF
Q
IN
1
7
2
8
R
IN
3
5MHz Phase Distribution
(50 Units)
– +
+ –
6
4
Q
OUT
PERCENTAGE OF UNITS (%)
25
20
15
10
5
I
OUT
0
5
–135 –134.5 –134 –133.5 –133 –132.5 –132 –131.5
5MHz PHASE (DEG)
66005 TA01
LT6600-5
5
GAIN =
3V 0.1μF
3
806Ω
R
IN
– +
+ –
6
4
LT6600-5
66005fa
1
LT6600-5
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
IN
–
1
V
OCM
2
V
+
3
OUT
+
4
8
7
6
5
IN
+
V
MID
V
–
OUT
–
Total Supply Voltage .................................................11V
Input Voltage (Note 8)...............................................±V
S
Input Current (Note 8)..........................................±10mA
Operating Temperature Range (Note 6).... –40°C to 85°C
Specified Temperature Range (Note 7) .... –40°C to 85°C
Junction Temperature ........................................... 150°C
Storage Temperature Range...................– 65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 150°C,
θ
JA
= 100°C/W
ORDER INFORMATION
LEAD FREE FINISH
LT6600CS8-5#PBF
LT6600IS8-5#PBF
LEAD BASED FINISH
LT6600CS8-5
LT6600IS8-5
TAPE AND REEL
LT6600CS8-5#TRPBF
LT6600IS8-5#TRPBF
TAPE AND REEL
LT6600CS8-5#TR
LT6600IS8-5#TR
PART MARKING
66005
6600I5
PART MARKING
66005
6600I5
PACKAGE DESCRIPTION
8-Lead Plastic SO
8-Lead Plastic SO
PACKAGE DESCRIPTION
8-Lead Plastic SO
8-Lead Plastic SO
SPECIFIED TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
SPECIFIED TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. Unless otherwise specified V
S
= 5V (V
+
= 5V, V
–
= 0V), R
IN
= 806Ω, and R
LOAD
= 1k.
PARAMETER
Filter Gain, V
S
= 3V
CONDITIONS
V
IN
= 2V
P-P
, f
IN
= DC to 260kHz
V
IN
= 2V
P-P
, f
IN
= 500k (Gain Relative to 260kHz)
V
IN
= 2V
P-P
, f
IN
= 2.5MHz (Gain Relative to 260kHz)
V
IN
= 2V
P-P
, f
IN
= 4MHz (Gain Relative to 260kHz)
V
IN
= 2V
P-P
, f
IN
= 5MHz (Gain Relative to 260kHz)
V
IN
= 2V
P-P
, f
IN
= 15MHz (Gain Relative to 260kHz)
V
IN
= 2V
P-P
, f
IN
= 25MHz (Gain Relative to 260kHz)
Filter Gain, V
S
= 5V
V
IN
= 2V
P-P
, f
IN
= DC to 260kHz
V
IN
= 2V
P-P
, f
IN
= 500k (Gain Relative to 260kHz)
V
IN
= 2V
P-P
, f
IN
= 2.5MHz (Gain Relative to 260kHz)
V
IN
= 2V
P-P
, f
IN
= 4MHz (Gain Relative to 260kHz)
V
IN
= 2V
P-P
, f
IN
= 5MHz (Gain Relative to 260kHz)
V
IN
= 2V
P-P
, f
IN
= 15MHz (Gain Relative to 260kHz)
V
IN
= 2V
P-P
, f
IN
= 25MHz (Gain Relative to 260kHz)
Filter Gain, V
S
= ±5V
V
IN
= 2V
P-P
, f
IN
= DC to 260kHz
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ELECTRICAL CHARACTERISTICS
MIN
– 0.5
–0.15
–0.4
– 0.7
–1.1
TYP
0
0
– 0.1
– 0.1
–0.2
– 28
–44
MAX
0.5
0.1
0.3
0.6
0.8
–25
0.5
0.1
0.3
0.6
0.8
–25
0.4
UNITS
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
66005fa
– 0.5
– 0.15
–0.4
– 0.7
– 1.1
0
0
– 0.1
–0.1
–0.2
– 28
– 44
– 0.6
–0.1
2
LT6600-5
ELECTRICAL CHARACTERISTICS
PARAMETER
Filter Gain, R
IN
= 229Ω
CONDITIONS
V
IN
= 2V
P-P
, f
IN
= DC to 260kHz
V
S
= 3V
V
S
= 5V
V
S
= ±5V
The
l
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. Unless otherwise specified V
S
= 5V (V
+
= 5V, V
–
= 0V), R
IN
= 806Ω, and R
LOAD
= 1k.
MIN
10.4
10.3
10.1
TYP
10.9
10.8
10.7
780
45
2nd Harmonic
3rd Harmonic
2nd Harmonic
3rd Harmonic
V
S
= 5V
V
S
= 3V
V
S
= 3V
V
S
= 5V
V
S
= ±5V
V
S
= 3V
V
S
= 5V
V
S
= ±5V
V
S
= 3V
V
S
= 5V
V
S
= ±5V
V
S
= 3V
V
S
= 5V
V
S
= ±5V
V
S
= 3V
V
S
= 5V
V
S
= ±5V
V
S
= 5
V
S
= 3
V
OCM
= V
MID
= V
S
/2
V
S
= 5
V
S
= 3
V
S
= 3V, V
S
= 5
V
S
= 3V, V
S
= 5
V
S
= ±5V
l
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MAX
11.5
11.4
11.3
UNITS
dB
dB
dB
ppm/C
μV
RMS
dBc
dBc
dBc
dBc
V
P-P DIFF
V
P-P DIFF
μA
Filter Gain Temperature Coefficient (Note 2) f
IN
= 260kHz, V
IN
= 2V
P-P
Noise
Distortion (Note 4)
Noise BW = 10kHz to 5MHz, R
IN
= 806Ω
1MHz, 2V
P-P
, R
L
= 800Ω
5MHz, 2V
P-P
, R
L
= 800Ω
Differential Output Swing
Input Bias Current
Input Referred Differential Offset
Measured Between Pins 4 and 5
Pin 7 Shorted to Pin 2
Average of Pin 1 and Pin 8
R
IN
= 806Ω
93
96
66
73
3.85
3.85
–70
4.8
4.8
–30
5
10
8
5
5
5
10
0.0
0.0
–2.5
1.0
1.5
–2.5
–25
–30
–55
2.46
4.3
–15
–10
5
0
–5
61
2.51
1.5
5.5
–3
–3
28
30
31
34
38
2.55
7.7
25
30
35
13
16
20
1.5
3.0
1.0
1.5
3.0
2.0
50
45
35
mV
mV
mV
mV
mV
mV
μV/°C
V
V
V
V
V
V
mV
mV
mV
dB
V
V
kΩ
μA
μA
mA
mA
mA
R
IN
= 229Ω
Differential Offset Drift
Input Common Mode Voltage (Note 3)
Differential Input = 500mV
P-P
,
R
IN
= 229Ω
Differential Output = 2V
P-P
,
Pin 7 at Midsupply
Output Common Mode Voltage (Note 5)
Output Common Mode Offset
(with Respect to Pin 2)
Common Mode Rejection Ratio
Voltage at V
MID
(Pin 7)
V
MID
Input Resistance
V
OCM
Bias Current
Power Supply Current
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
This is the temperature coefficient of the internal feedback
resistors assuming a temperature independent external resistor (R
IN
).
Note 3:
The input common mode voltage is the average of the voltages
applied to the external resistors (R
IN
). Specification guaranteed for
R
IN
≥ 229Ω.
Note 4:
Distortion is measured differentially using a differential stimulus.
The input common mode voltage, the voltage at Pin 2, and the voltage at
Pin 7 are equal to one half of the total power supply voltage.
Note 5:
Output common mode voltage is the average of the voltages at
Pins 4 and 5. The output common mode voltage is equal to the voltage
applied to Pin 2.
Note 6:
The LT6600C is guaranteed functional over the operating
temperature range –40°C to 85°C.
Note 7:
The LT6600C is guaranteed to meet 0°C to 70°C specifications and
is designed, characterized and expected to meet the extended temperature
limits, but is not tested at –40°C and 85°C. The LT6600I is guaranteed to
meet specified performance from –40°C to 85°C.
Note 8:
The inputs are protected by back-to-back diodes. If the differential
input voltage exceeds 1.4V, the input current should be limited to less than
10mA.
66005fa
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LT6600-5
TYPICAL PERFORMANCE CHARACTERISTICS
Amplitude Response
10
0
–10
–20
GAIN (dB)
GAIN (dB)
–30
–40
–50
–60
–70
–80
0.1
1
10
FREQUENCY (MHz)
100
66005 G01
Passband Gain and Delay
1
V
S
= 5V
GAIN = 1
T
A
= 25°C
0
–1
–2
–3
–4
–5
–6
–7
–8 GAIN = 1
T
A
= 25°C
–9
0 1 2
DELAY
GAIN
120
110
100
90
DELAY (ns)
GAIN (dB)
80
70
60
50
40
30
3 4 5 6 7
FREQUENCY (MHz)
8
9
20
10
13
12
11
10
9
8
7
6
5
Passband Gain and Delay
120
GAIN
110
100
90
DELAY
80
70
60
50
40
30
20
8
9
10
DELAY (ns)
4 GAIN = 4
T
A
= 25°C
3
0 1 2 3 4 5 6 7
FREQUENCY (MHz)
66005 G02
66005 G03
Output Impedance vs Frequency
100
V
S
= 5V
GAIN = 1
T
A
= 25°C
90
80
70
CMRR (dB)
Common Mode Rejection Ratio
V
S
= 5V
GAIN = 1
V
IN
= 1V
P-P
T
A
= 25°C
PSRR (dB)
80
70
60
50
40
30
20
40
10
0.1
1
10
FREQUENCY (MHz)
100
66005 G05
Power Supply Rejection Ratio
OUTPUT IMPEDANCE (Ω)
10
60
50
1
0.1
0.1
1
10
FREQUENCY (MHz)
100
66005 G04
30
0.01
0
0.01
V
S
= 3V
V
IN
= 200mV
P-P
T
A
= 25°C
V+ TO DIFFOUT
0.1
1
10
FREQUENCY (MHz)
100
66005 G06
Distortion vs Frequency
–50
–60
DISTORTION (dB)
–70
–80
–90
DIFFERENTIAL INPUT,
2ND HARMONIC
DIFFERENTIAL INPUT,
3RD HARMONIC
SINGLE-ENDED INPUT,
2ND HARMONIC
SINGLE-ENDED INPUT,
3RD HARMONIC
–50
–60
DISTORTION (dB)
–70
–80
–90
Distortion vs Frequency
DIFFERENTIAL INPUT,
2ND HARMONIC
DIFFERENTIAL INPUT,
3RD HARMONIC
SINGLE-ENDED INPUT,
2ND HARMONIC
SINGLE-ENDED INPUT,
3RD HARMONIC
–40
Distortion vs Signal Level
V
S
= 3V
R
L
= 800Ω
–50 T = 25°C
A
–60
–70
–80
–90
3RD HARMONIC,
5MHz INPUT
2ND HARMONIC,
5MHz INPUT
3RD HARMONIC,
1MHz INPUT
–100
–110
V
S
= 3V, V
IN
= 2V
P-P
R
L
= 800Ω, T
A
= 25°C
0.1
1
FREQUENCY (MHz)
10
66005 G07
–100
–110
V
S
= ±5V, V
IN
= 2V
P-P
R
L
= 800Ω, T
A
= 25°C
0.1
1
FREQUENCY (MHz)
10
66005 G08
DISTORTION (dB)
–100
–110
0
1
2ND HARMONIC,
1MHz INPUT
2
3
INPUT LEVEL (V
P-P
)
4
5
66005 G09
66005fa
4
LT6600-5
TYPICAL PERFORMANCE CHARACTERISTICS
Distortion vs Signal Level
–40
DISTORTION COMPONENT (dB)
–50
DISTORTION (dB)
–60
–70
–80
–90
–100
–110
0
3RD HARMONIC
1MHz INPUT
2ND HARMONIC
1MHz INPUT
V
S
= ±5V
R
L
= 800Ω, T
A
= 25°C
1
2
3
4
5
66005 G10
Distortion vs Input Common Mode
–40
–50
–60
–70
–80
–90
2ND HARMONIC,
V
S
= 3V
3RD HARMONIC,
V
S
= 3V
2ND HARMONIC,
V
S
= 5V
3RD HARMONIC,
V
S
= 5V
–40
DISTORTION COMPONENT (dB)
–50
–60
–70
–80
–90
Distortion vs Input Common Mode
2ND HARMONIC,
V
S
= 3V
3RD HARMONIC,
V
S
= 3V
2ND HARMONIC,
V
S
= 5V
3RD HARMONIC,
V
S
= 5V
3RD HARMONIC
5MHz INPUT
2ND HARMONIC
5MHz INPUT
INPUT LEVEL (V
P-P
)
–100 GAIN = 1, PIN 7 = V
S
/2
2V
P-P
1MHz INPUT
R
L
= 800Ω, T
A
= 25°C
–110
–1
0
1
2
3
–3
–2
INPUT COMMON MODE VOLTAGE
RELATIVE TO PIN 7 (V)
66005 G11
–100 GAIN = 4, PIN 7 = V
S
/2
2V
P-P
1MHz INPUT
R
L
= 800Ω, T
A
= 25°C
–110
2
3
–3
–1
0
1
–2
INPUT COMMON MODE VOLTAGE
RELATIVE TO PIN 7 (V)
66005 G12
Power Supply Current
vs Power Supply Voltage
36
POWER SUPPLY CURRENT (mA)
34
32
30
28
26
24
22
20
2
6
10
8
4
TOTAL SUPPLY VOLTAGE (V)
12
66005 G13
Transient Response, Differential
Gain = 1, Single-Ended Input,
Differential Output
20
OUT
–
200mV/DIV
0
OUTPUT LEVEL (dBV)
–20
–40
–60
–80
Distortion vs Temperature
1dB PASSBAND GAIN
COMPRESSION POINTS
1MHz T
A
= 25°C
1MHz T
A
= 85°C
3RD HARMONIC
T
A
= 85°C
3RD HARMONIC
T
A
= 25°C
T
A
= 85°C
OUT
+
200mV/DIV
T
A
= 25°C
T
A
= –40°C
IN
–
500mV/DIV
IN
+
100ns/DIV
66005 G14
–100
–120
0
1
2ND HARMONIC
T
A
= 85°C
2ND HARMONIC
T
A
= 25°C
4
3
5
2
1MHz INPUT LEVEL (V
P-P
)
6
7
66005 G15
Distortion
vs Output Common Mode
–40
DISTORTION COMPONENT (dB)
GAIN = 4
PIN 7 = V
S
/2
–50 T
A
= 25°C
0.5V
P-P
1MHz INPUT
–60 R
L
= 800Ω
–70
–80
–90
2ND HARMONIC, V
S
= 3V
3RD HARMONIC, V
S
= 3V
2ND HARMONIC, V
S
= 5V
3RD HARMONIC, V
S
= 5V
2ND HARMONIC, V
S
= ±5V
3RD HARMONIC, V
S
= ±5V
45
40
NOISE DENSITY (nV/√Hz)
35
30
25
20
15
10
5
2.5
Input Referred Noise
INTEGRATED NOISE, GAIN = 1X
INTEGRATED NOISE, GAIN = 4X
NOISE DENSITY, GAIN = 1X
NOISE DENSITY, GAIN = 4X
90
80
70
60
50
40
30
20
10
0.1
FREQUENCY (MHz)
66005 G17
INTEGRATED NOISE (μV)
–100
–110
–1.5 –1.0 –0.5
0 0.5 1.0 1.5 2.0
VOLTAGE PIN 2 TO PIN 7 (V)
0
0.01
10
0
100
66005 G16
66005fa
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