LT6600-15
Very Low Noise, Differential
Amplifier and 15MHz Lowpass Filter
FEATURES
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DESCRIPTION
The LT
®
6600-15 combines a fully differential amplifier with a
4th order 15MHz lowpass filter approximating a Chebyshev
frequency response. Most differential amplifiers require
many precision external components to tailor gain and
bandwidth. In contrast, with the LT6600-15, two external
resistors program differential gain, and the filter’s 15MHz
cutoff frequency and passband ripple are internally set.
The LT6600-15 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 LT6600-15
integrates an antialiasing filter and a differential amplifier/
driver without compromising distortion or low noise perfor-
mance. At unity gain the measured in band signal-to-noise
ratio is an impressive 76dB. 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 LT6600-15 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.
The LT6600-15 is packaged in an SO-8 and is pin compat-
ible with stand alone differential amplifiers.
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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 15MHz
Cutoff
76dB S/N with 3V Supply and 2V
P-P
Output
Low Distortion, 2V
P-P
, 800Ω Load, V
S
= 3V
1MHz: 86dBc 2nd, 90dBc 3rd
10MHz: 63dBc 2nd, 69dBc 3rd
Fully Differential Inputs and Outputs
Compatible with Popular Differential Amplifier
Pinouts
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
LT6600-15
3V
0.1μF
R
IN
536Ω 1
7
0.01μF
V
IN
R
IN
536Ω
2
8
3
5.6pF
3V
V
+
D
OUT
V
CM
2.2μF
GAIN = 536Ω/R
IN
660015 TA01a
An 8192 Point FFT Spectrum
LTC2249
0
–10
–20
AMPLITUDE (dB)
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
0
10
20
FREQUENCY (MHz)
660015 TA01b
INPUT 10.7MHz
2V
P-P
f
SAMPLE
= 80MHz
–
V
MID
V
OCM
+
–
4
25Ω
5.6pF
5.6pF
+
A
IN
25Ω
5
+
6
–
V
–
30
40
660015fa
1
LT6600-15
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
LT6600CS8-15#PBF
LT6600IS8-15#PBF
LEAD BASED FINISH
LT6600CS8-15
LT6600IS8-15
TAPE AND REEL
LT6600CS8-15#TRPBF
LT6600IS8-15#TRPBF
TAPE AND REEL
LT6600CS8-15#TR
LT6600IS8-15#TR
PART MARKING
660015
600I15
PART MARKING
660015
600I15
PACKAGE DESCRIPTION
8-Lead Plastic SO
8-Lead Plastic SO
PACKAGE DESCRIPTION
8-Lead Plastic SO
8-Lead Plastic SO
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
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
= 536Ω, 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
= 1.5MHz (Gain Relative to 260kHz)
V
IN
= 2V
P-P
, f
IN
= 7.5MHz (Gain Relative to 260kHz)
V
IN
= 2V
P-P
, f
IN
= 12MHz (Gain Relative to 260kHz)
V
IN
= 2V
P-P
, f
IN
= 15MHz (Gain Relative to 260kHz)
V
IN
= 2V
P-P
, f
IN
= 45MHz (Gain Relative to 260kHz)
V
IN
= 2V
P-P
, f
IN
= 75MHz (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
= 1.5MHz (Gain Relative to 260kHz)
V
IN
= 2V
P-P
, f
IN
= 7.5MHz (Gain Relative to 260kHz)
V
IN
= 2V
P-P
, f
IN
= 12MHz (Gain Relative to 260kHz)
V
IN
= 2V
P-P
, f
IN
= 15MHz (Gain Relative to 260kHz)
V
IN
= 2V
P-P
, f
IN
= 45MHz (Gain Relative to 260kHz)
V
IN
= 2V
P-P
, f
IN
= 75MHz (Gain Relative to 260kHz)
Filter Gain, V
S
= ±5V
Filter Gain, R
IN
= 133Ω
V
IN
= 2V
P-P
, f
IN
= DC to 260kHz
V
OUT
= 2V
P-P
, f
IN
= DC to 260kHz, V
S
= 3V
V
OUT
= 2V
P-P
, f
IN
= DC to 260kHz, V
S
= 5V
V
OUT
= 2V
P-P
, f
IN
= DC to 260kHz, V
S
= ±5V
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ELECTRICAL CHARACTERISTICS
MIN
– 0.5
–0.1
–0.3
–0.3
– 0.7
TYP
0.1
0
0
0.2
0
– 29
–46
MAX
0.5
0.1
0.4
1.0
1.0
–25
0.5
0.1
0.3
0.9
0.9
–25
0.4
12.5
12.5
12.4
UNITS
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
660015fa
– 0.5
– 0.1
–0.4
–0.4
–0.8
0
0
0
0.1
0
– 29
– 46
– 0.6
11.5
11.5
11.4
–0.1
12.0
12.0
11.9
2
LT6600-15
ELECTRICAL CHARACTERISTICS
PARAMETER
Filter Gain Temperature Coefficient (Note 2)
Noise
Distortion (Note 4)
CONDITIONS
f
IN
= 250kHz, V
IN
= 2V
P-P
Noise BW = 10kHz to 15MHz
1MHz, 2V
P-P
, R
L
= 800Ω, V
S
= 3V
10MHz, 2V
P-P
, R
L
= 800Ω, V
S
= 3V
Differential Output Swing
Input Bias Current
Input Referred Differential Offset
Measured Between Pins 4 and 5
Average of Pin 1 and Pin 8
R
IN
= 536Ω
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
= 5V
V
S
= 3V
V
OCM
= V
MID
= V
S
/2
V
S
= 5V
V
S
= 3V
V
S
= 3V, V
S
= 5V
V
S
= 3V
V
S
= 5V
V
S
= ±5V
2nd Harmonic
3rd Harmonic
2nd Harmonic
3rd Harmonic
V
S
= 5V
V
S
= 3V
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
l
l
●
●
●
●
●
l
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
= 536Ω, and R
LOAD
= 1k.
MIN
TYP
780
109
86
90
63
69
3.80
3.75
– 90
4.75
4.50
– 35
±5
±10
±10
±5
±5
±5
10
Differential Input = 500mV
P-P
,
R
IN
= 133Ω
Differential Input = 2V
P-P
,
Pin 7 at Mid-Supply
Common Mode Voltage at Pin 2
0.0
0.0
–2.5
1.0
1.5
–1.0
–35
–40
–55
2.45
4.3
–10
–10
5
0
–10
64
2.50
1.50
5.7
–2
–2
35
38
3
39
44
45
48
11
2.55
7.7
1.5
3.0
1.0
1.5
3.0
2.0
40
40
35
±25
±30
±35
±15
±17
±20
MAX
UNITS
ppm/C
μV
RMS
dBc
dBc
dBc
dBc
V
P-P DIFF
V
P-P DIFF
μA
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
mA
V
R
IN
= 133Ω
Differential Offset Drift
Input Common Mode Voltage (Note 3)
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
Power Supply Voltage
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
≥ 100Ω.
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-15 is guaranteed functional over the operating
temperature range –40°C to 85°C.
Note 7:
The LT6600C-15 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-15 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.
660015fa
3
LT6600-15
TYPICAL PERFORMANCE CHARACTERISTICS
Amplitude Response
10
0
–10
GAIN (dB)
–20
–30
–40
–50
V
S
= 5V
GAIN = 1
T
A
= 25°C
1
10
FREQUENCY (MHz)
100
66005 G01
Passband Gain and Phase
1
0
–1
–2
GAIN (dB)
–3
–4
–5
–6
–7
–8
–9
0
5
15
10
FREQUENCY (MHz)
20
25
660015 G02
Passband Gain and Delay
V
S
= 5V
GAIN = 1
T
A
= 25°C
225
180
135
90
PHASE (DEG)
1
0
–1
–2
GAIN (dB)
–3
–4
–5
–6
–7
–8
–9
0
5
15
10
FREQUENCY (MHz)
20
25
660015 G03
GAIN
GAIN
V
S
= 5V
GAIN = 1
T
A
= 25°C
50
45
40
35
DELAY (ns)
PHASE
45
0
–45
–90
–135
–180
–225
DELAY
30
25
20
15
10
5
0
–60
0.1
Passband Gain and Delay
14
12
10
8
GAIN (dB)
6
4
2
0
–2
–4
–6
0
5
15
10
FREQUENCY (MHz)
20
25
660015 G04
Output Impedance
V
S
= 5V
GAIN = 4
T
A
= 25°C
50
45
OUTPUT IMPEDANCE (Ω)
40
35
DELAY (ns)
100
V
S
= 5V
GAIN = 1
T
A
= 25°C
80
75
70
65
CMRR (dB)
60
55
50
45
40
35
0.1
0.1
30
1
10
FREQUENCY (MHz)
100
660015 G05
Common Mode Rejection Ratio
V
IN
= 1V
P-P
V
S
= 5V
GAIN = 1
T
A
= 25°C
GAIN
10
DELAY
30
25
20
15
10
5
0
1
0.1
1
10
FREQUENCY (MHz)
100
660015 G06
Power Supply Rejection Ratio
80
70
60
DISTORTION (dB)
PSRR (dB)
50
40
30
20
10
V
S
= 3V
V
IN
= 200mV
P-P
T
A
= 25°C
V
+
TO DIFFOUT
1
10
FREQUENCY (MHz)
100
600015 G07
Distortion vs Frequency
–50
–60
–70
–80
–90
V
IN
= 2V
P-P
V
S
= 3V
R
L
= 800Ω AT
EACH OUTPUT
GAIN = 1
T
A
= 25°C
–40
Distortion vs Signal Level
3RD HARMONIC
V
S
= 3V
10MHz INPUT
R
L
= 800Ω AT
–50 EACH OUTPUT
GAIN = 1
–60 T
A
= 25°C
2ND
HARMONIC
10MHz INPUT
2ND
HARMONIC
1MHz INPUT
0
1
2
3
3RD
HARMONIC
1MHz INPUT
DISTORTION (dB)
100
660015 G08
–70
–80
–90
–100
–110
0.1
1
10
FREQUENCY (MHz)
–100
–110
0
0.1
4
5
660015 G09
INPUT LEVEL (V
P-P
)
DIFFERENTIAL INPUT, 2ND HARMONIC
DIFFERENTIAL INPUT, 3RD HARMONIC
SINGLE-ENDED INPUT, 2ND HARMONIC
SINGLE-ENDED INPUT, 3RD HARMONIC
660015fa
4
LT6600-15
TYPICAL PERFORMANCE CHARACTERISTICS
Distortion vs Signal Level
–40
V
S
= ±5V
R
L
= 800Ω AT EACH OUTPUT
–50 GAIN = 1
T
A
= 25°C
–60
2ND HARMONIC,
10MHz INPUT
–70
–80
–90
–100
–110
0
1
3RD
HARMONIC,
10MHz INPUT
2ND HARMONIC,
1MHz INPUT
3RD HARMONIC,
1MHz INPUT
2
3
4
5
660015 G10
Distortion
vs Input Common Mode Level
–40
DISTORTION COMPONENT (dB)
–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
GAIN = 1
R
L
= 800Ω AT EACH
OUTPUT
T
A
= 25°C
2V
P-P
1MHz INPUT
–40
DISTORTION COMPONENT (dB)
–50
–60
–70
–80
–90
Distortion
vs Input Common Mode Level
2ND HARMONIC,
V
S
= 3V
3RD HARMONIC,
V
S
= 3V
2ND HARMONIC,
V
S
= 5V
3RD HARMONIC,
V
S
= 5V
DISTORTION (dB)
–100
–110
–2
–1
0
1
2
–3
3
INPUT COMMON MODE VOTLAGE RELATIVE TO PIN 7 (V)
66002 G11
–100
GAIN = 4, R
L
= 800Ω AT EACH OUTPUT
T
A
= 25°C, 500mV
P-P
1MHz INPUT
INPUT LEVEL (V
P-P
)
–3
3
–2
–1
0
1
2
INPUT COMMON MODE VOTLAGE RELATIVE TO PIN 7 (V)
660015 G12
Distortion
vs Output Common Mode
–40
DISTORTION COMPONENT (dB)
–50
–60
–70
–80
–90
–100
–110
–1.5 –1 –0.5
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
2V
P-P
1MHz INPUT
GAIN = 1,
R
L
= 800Ω AT EACH OUTPUT
T
A
= 25°C
0
2.5
0.5 1 1.5 2
VOLTAGE PIN 2 TO PIN 7 (V)
660015 G13
Total Supply Current
vs Total Supply Voltage
50
TOTAL SUPPLY CURRENT (mA)
45
40
35
T
A
= –40°C
30
25
20
2
10
4
6
8
TOTAL SUPPLY VOLTAGE (V)
12
660015 G14
Transient Response
OUT
–
200mV/DIV
T
A
= 85°C
T
A
= 25°C
OUT
+
200mV/DIV
IN
–
IN
+
500mV/DIV
100ns/DIV
DIFFERENTIAL GAIN = 1
SINGLE-ENDED INPUT
DIFFERENTAL OUTPUT
660015 G15
660015fa
5
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