LINER LT6604CUFF-2.5-PBF

LT6604-2.5
Dual Very Low Noise,
Differential Amplifier and
2.5MHz Lowpass Filter
FEATURES
DESCRIPTION
n
The LT®6604-2.5 consists of two matched, fully differential
amplifiers, each with a 4th order, 2.5MHz lowpass filter. The
fixed frequency lowpass filter approximates a Chebyshev
response. By integrating a filter and a differential amplifier, distortion and noise are made exceptionally low. At
unity gain, the measured in-band signal-to-noise ratio is
an impressive 86dB. At higher gains, the input referred
noise decreases, allowing the part to process smaller
input differential signals without significantly degrading
the signal-to-noise ratio.
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Dual Differential Amplifier with 2.5MHz Lowpass Filters
4th Order Filters
Approximates Chebyshev Response
Guaranteed Phase and Gain Matching
Resistor-Programmable Differential Gain
>86dB Signal-to-Noise (3V Supply, 1VRMS Output)
Low Distortion (1MHz, 1VRMS Output, 800Ω Load)
HD2: 92dBc
HD3: 88dBc
Specified for Operation with 3V, 5V and ±5V Supplies
Fully Differential Inputs and Outputs
Adjustable Output Common Mode Voltage
Small 4mm × 7mm × 0.75mm QFN Package
Gain and phase are well matched between the two channels. Gain for each channel is independently programmed
using two external resistors. The LT6604-2.5 enables level
shifting by providing an adjustable output common mode
voltage, making it ideal for directly interfacing to ADCs.
The LT6604-2.5 is fully specified for 3V operation. The
differential design enables outstanding performance up
to a 4VP-P signal level for a single 3V supply.
APPLICATIONS
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Dual Differential ADC Driver and Filter
Single-Ended to Differential Converter
Matched, Dual, Differential Gain or Filter Stage
Common Mode Translation of Differential Signals
High Speed ADC Antialiasing and DAC Smoothing in
Wireless Infrastructure or Networking Applications
High Speed Test and Measurement Equipment
Medical Imaging
See the back page of this datasheet for a complete list of
related single and dual differential amplifiers with integrated
2.5MHz to 20MHz lowpass filters.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.v
TYPICAL APPLICATION
Channel to Channel Gain Matching
3V
18
+
1580Ω
+INA
VMIDA
0.01μF
–
+
V+A
–
VOCMA
–INA
–
+
1580Ω
+
1580Ω
0.01μF
1580Ω
+OUTA
V+B
+INB
VMIDB
–
–OUTA
+
–
VOCMB
–INB
–
+
LTC22xx
3V
50Ω
50Ω
+
18pF
AIN
DOUT
–
3V
–OUTB
50Ω
+OUTB
50Ω
+
18pF
AIN
50 TYPICAL UNITS
16 TA = 25°C
GAIN = 1
14 fIN = 2.5MHz
DUAL ADC
NUMBER OF UNITS
LT6604-2.5
12
10
8
6
4
DOUT
2
–
0
V–
–0.25
660425 TA01
–0.15
–0.05 0 0.05
0.15
GAIN MATCH (dB)
0.25
660425 TA01b
660425f
1
LT6604-2.5
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
31 V–
32 V–
33 NC
TOP VIEW
34 VMIDA
Total Supply Voltage .................................................11V
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
Input Voltage
+IN, –IN, VOCM, VMID (Note 8) ..............................±VS
Input Current
+IN, –IN, VOCM, VMID (Note 8) ........................±10mA
NC 1
30 NC
+INA 2
29 –OUTA
NC 3
28 NC
–INA 4
27 +OUTA
NC 5
26 NC
25 V+A
VOCMA 6
V– 7
24 V–
35
VMIDB 8
23 NC
NC 9
22 NC
+INB 10
21 –OUTB
NC 11
20 NC
–INB 12
19 +OUTB
V+B 17
NC 16
NC 15
18 NC
VOCMB 14
NC 13
UFF PACKAGE
34-LEAD (4mm s 7mm) PLASTIC QFN
TJMAX = 150°C, θJA = 43°C/W, θJC = 4°C/W
EXPOSED PAD (PIN 35) IS V–, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
SPECIFIED TEMPERATURE RANGE
LT6604CUFF-2.5#PBF
LT6604CUFF-2.5#TRPBF
60425
34-Lead (4mm × 7mm) Plastic QFN
0°C to 70°C
LT6604IUFF-2.5#PBF
LT6604IUFF-2.5#TRPBF
60425
34-Lead (4mm × 7mm) Plastic QFN
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
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/
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. Unless otherwise specified VS = 5V (V+ = 5V, V– = 0V), RIN = 1580Ω, and
RLOAD = 1k.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Filter Gain Either Channel, VS = 3V
VIN = 2VP-P, fIN = DC to 260kHz
VIN = 2VP-P, fIN = 700kHz (Gain Relative to 260kHz)
VIN = 2VP-P, fIN = 1.9MHz (Gain Relative to 260kHz)
VIN = 2VP-P, fIN = 2.2MHz (Gain Relative to 260kHz)
VIN = 2VP-P, fIN = 2.5MHz (Gain Relative to 260kHz)
VIN = 2VP-P, fIN = 7.5MHz (Gain Relative to 260kHz)
VIN = 2VP-P, fIN = 12.5MHz (Gain Relative to 260kHz)
–0.5
–0.15
–0.2
–0.6
–2.1
0.1
0
0.2
0.1
–0.9
–34
–51
0.4
0.1
0.6
0.5
0
– 31
dB
dB
dB
dB
dB
dB
dB
l
l
l
l
l
l
660425f
2
LT6604-2.5
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. Unless otherwise specified VS = 5V (V+ = 5V, V– = 0V), RIN = 1580Ω, and
RLOAD = 1k.
PARAMETER
CONDITIONS
Matching of Filter Gain, VS = 3V
VIN = 2VP-P, fIN = DC to 260kHz
VIN = 2VP-P, fIN = 700kHz (Gain Relative to 260kHz)
VIN = 2VP-P, fIN = 1.9MHz (Gain Relative to 260kHz)
VIN = 2VP-P, fIN = 2.2MHz (Gain Relative to 260kHz)
VIN = 2VP-P, fIN = 2.5MHz (Gain Relative to 260kHz)
VIN = 2VP-P, fIN = 7.5MHz (Gain Relative to 260kHz)
VIN = 2VP-P, fIN = 12.5MHz (Gain Relative to 260kHz)
Matching of Filter Phase, VS = 3V
MIN
TYP
MAX
l
l
l
l
l
l
0.04
0.005
0.02
0.03
0.05
0.15
0.05
0.4
0.1
0.3
0.4
0.6
1.1
2.8
dB
dB
dB
dB
dB
dB
dB
VIN = 2VP-P, fIN = 700kHz
VIN = 2VP-P, fIN = 1.9MHz
VIN = 2VP-P, fIN = 2.2MHz
l
l
l
0.2
0.6
0.8
1.5
3.5
4.5
deg
deg
deg
Filter Gain Either Channel, VS = 5V
VIN = 2VP-P, fIN = DC to 260kHz
VIN = 2VP-P, fIN = 700kHz (Gain Relative to 260kHz)
VIN = 2VP-P, fIN = 1.9MHz (Gain Relative to 260kHz)
VIN = 2VP-P, fIN = 2.2MHz (Gain Relative to 260kHz)
VIN = 2VP-P, fIN = 2.5MHz (Gain Relative to 260kHz)
VIN = 2VP-P, fIN = 7.5MHz (Gain Relative to 260kHz)
VIN = 2VP-P, fIN = 12.5MHz (Gain Relative to 260kHz)
l
l
l
l
l
l
–0.1
0
0.2
0.1
–0.9
–34
–51
0.4
0.1
0.6
0.5
0
– 31
dB
dB
dB
dB
dB
dB
dB
Matching of Filter Gain, VS = 5V
VIN = 2VP-P, fIN = DC to 260kHz
VIN = 2VP-P, fIN = 700kHz (Gain Relative to 260kHz)
VIN = 2VP-P, fIN = 1.9MHz (Gain Relative to 260kHz)
VIN = 2VP-P, fIN = 2.2MHz (Gain Relative to 260kHz)
VIN = 2VP-P, fIN = 2.5MHz (Gain Relative to 260kHz)
VIN = 2VP-P, fIN = 7.5MHz (Gain Relative to 260kHz)
VIN = 2VP-P, fIN = 12.5MHz (Gain Relative to 260kHz)
l
l
l
l
l
l
0.04
0.005
0.02
0.03
0.05
0.15
0.05
0.4
0.1
0.3
0.4
0.6
1.1
2.8
dB
dB
dB
dB
dB
dB
dB
Matching of Filter Phase, VS = 5V
VIN = 2VP-P, fIN = 700kHz
VIN = 2VP-P, fIN = 1.9MHz
VIN = 2VP-P, fIN = 2.2MHz
l
l
l
0.2
0.6
0.8
1.5
3.5
4.5
deg
deg
deg
dB
–0.5
–0.15
–0.2
–0.6
–2.1
UNITS
Filter Gain Either Channel, VS = ±5V
VIN = 2VP-P, fIN = DC to 260kHz
–0.6
–0.1
0.4
Filter Gain, RIN = 402Ω
VOUT = 2VP-P, fIN = DC to 260kHz
VS = 3V
VS = 5V
VS = ±5V
11.3
11.3
11.2
11.8
11.8
11.7
12.3
12.3
12.2
Filter Gain Temperature Coefficient (Note 2)
fIN = 260kHz, VIN = 2VP-P
780
ppm/°C
Noise
Noise BW = 10kHz to 2.5MHz, RIN = 1580Ω
51
μVRMS
Distortion (Note 4)
VIN = 1VRMS, fIN = 1MHz, RL = 800Ω
2nd Harmonic
3rd Harmonic
92
88
dBc
dBc
–119
dB
Channel Separation (Note 9)
VIN = 2VP-P, fIN = 1MHz
Differential Output Swing
Measured Between OUT+ and OUT–, VOCM Shorted to VMID
VS = 5V
VS = 3V
l
l
8.8
5.1
9.3
5.5
dB
dB
dB
VP-P_DIFF
VP-P_DIFF
660425f
3
LT6604-2.5
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. Unless otherwise specified VS = 5V (V+ = 5V, V– = 0V), RIN = 1580Ω, and
RLOAD = 1k.
PARAMETER
CONDITIONS
Input Bias Current
Average of IN+ and IN–
l
Input Referred Differential Offset
RIN = 1580Ω, Differential Gain = 1V/V
VS = 3V
VS = 5V
VS = ±5V
l
l
l
5
5
5
25
30
35
mV
mV
mV
RIN = 402Ω, Differential Gain = 4V/V
VS = 3V
VS = 5V
VS = ±5V
l
l
l
3
3
3
13
16
20
mV
mV
mV
MIN
TYP
–35
–15
Differential Offset Drift
Input Common Mode Voltage (Note 3)
Output Common Mode Voltage (Note 5)
Output Common Mode Offset
(with Respect to VOCM)
Power Supply Current
(Per Channel)
μV/°C
Differential Input = 500mVP-P, RIN ≥402Ω
VS = 3V
VS = 5V
VS = ±5V
l
l
l
0
0
–2.5
1.5
3
1
V
V
V
Differential Output = 2VP-P, VMID at Mid Supply
VS = 3V
VS = 5V
VS = ±5V
l
l
l
1
1.5
–1
1.5
3
2
V
V
V
VS = 3V
VS = 5V
VS = ±5V
l
l
l
–25
–30
–55
45
45
35
mV
mV
mV
10
5
–10
63
VS = 5V
VS = 3V
2.45
2.51
1.5
2.56
V
V
7.7
kΩ
l
4.3
5.7
l
l
–15
–10
–3
–3
VS = 3V, VS = 5V
VS = 3V, VS = 5V
VS = ±5V
l
l
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 (RIN).
Note 3: The input common mode voltage is the average of the voltages
applied to the external resistors (RIN).
Note 4: Distortion is measured differentially using a differential stimulus.
The input common mode voltage, the voltage at VOCM, and the voltage at
VMID are equal to one half of the total power supply voltage.
Note 5: Output common mode voltage is the average of the +OUT and
–OUT voltages. The output common mode voltage is equal to VOCM.
Note 6: The LT6604C-2.5 is guaranteed functional over the operating
temperature range –40°C to 85°C.
dB
l
VOCM = VMID = VS/2
VS = 5V
VS = 3V
VMID Input Resistance
VOCM Bias Current
UNITS
μA
10
Common Mode Rejection Ratio
Voltage at VMID
MAX
26
28
μA
μA
30
33
36
mA
mA
mA
Note 7: The LT6604C-2.5 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 to 85°C. The LT6604I-2.5 is
guaranteed to meet specified performance from –40°C to 85°C.
Note 8: Input pins (+IN, –IN, VOCM and VMID) are protected by steering
diodes to either supply. If the inputs should exceed either supply voltage,
the input current should be limited to less than 10mA. In addition, the
inputs +IN, –IN are protected by a pair of back-to-back diodes. If the
differential input voltage exceeds 1.4V, the input current should be limited
to less than 10mA
Note 9: Channel separation (the inverse of crosstalk) is measured by
driving a signal into one input while terminating the other input. Channel
separation is the ratio of the resulting output signal at the driven channel
to the output at the channel that is not driven.
660425f
4
LT6604-2.5
TYPICAL PERFORMANCE CHARACTERISTICS
Frequency Response
12
VS = p2.5V
RIN = 1580Ω
GAIN = 1
0
0
GAIN
Passband Gain and Group Delay
320
12
300
11
320
GAIN
300
10
280
–24
260
9
260
–3
240
8
240
–4
220
–5
200
–36
–48
–60
GROUP DELAY
–6
–72
–84
–96
100k
1M
10M
FREQUENCY (Hz)
50M
180
VS = 5V
–7
RIN = 1580Ω 160
GAIN = 1
–8
140
TA = 25oC
–9
120
0.5 0.75 1.0 1.25 1.5 1.75 2.0 2.25 2.5 2.75 3.0
FREQUENCY (MHz)
660425 G01
7
220
GROUP DELAY
6
200
180
VS = 5V
RIN = 402Ω 160
GAIN = 4
140
3
TA = 25oC
120
2
0.5 0.75 1.0 1.25 1.5 1.75 2.0 2.25 2.5 2.75 3.0
FREQUENCY (MHz)
5
4
660425 G03
660425 G02
Output Impedance vs Frequency
(OUT+ or OUT–)
Common Mode Rejection Ratio
100
Power Supply Rejection Ratio
110
90
VIN = 1VP-P
VS = 5V
100 R = 1580Ω
IN
GAIN = 1
90
CMRR (dB)
10
1
V+ TO
DIFFERENTIAL OUT
VS = 3V
80
70
60
PSRR (dB)
OUTPUT IMPEDANCE (Ω)
GAIN (dB)
280
–2
GAIN (dB)
–1
GROUP DELAY (ns)
–12
GROUP DELAY (ns)
GAIN (dB)
Passband Gain and Group Delay
1
80
70
50
40
30
60
20
50
0.1
100k
10
40
1M
10M
FREQUENCY (Hz)
0
1k
100M
10k
100k
1M
FREQUENCY (Hz)
10M
100M
1k
10k
100k
1M
FREQUENCY (Hz)
10M
100M
660425 G05
660425 G04
660425 G06
DIFFERENTIAL INPUT,
2ND HARMONIC
DIFFERENTIAL INPUT,
3RD HARMONIC
SINGLE-ENDED INPUT,
2ND HARMONIC
SINGLE-ENDED INPUT,
3RD HARMONIC
–80
–90
VIN = 2VP-P
VS = 3V
RL = 800Ω AT
EACH OUTPUT
GAIN = 1
–100
–110
0.1
1
FREQUENCY (MHz)
10
660425 G07
Distortion vs Frequency
–60
DIFFERENTIAL INPUT,
2ND HARMONIC
DIFFERENTIAL INPUT,
3RD HARMONIC
SINGLE-ENDED INPUT,
2ND HARMONIC
SINGLE-ENDED INPUT,
3RD HARMONIC
–70
DISTORTION (dBc)
–70
DISTORTION (dBc)
Distortion vs Frequency
–60
–80
–90
VIN = 2VP-P
VS = 5V
RL = 800Ω AT
EACH OUTPUT
GAIN = 1
–100
–110
0.1
DIFFERENTIAL INPUT,
2ND HARMONIC
DIFFERENTIAL INPUT,
3RD HARMONIC
SINGLE-ENDED INPUT,
2ND HARMONIC
SINGLE-ENDED INPUT,
3RD HARMONIC
–70
DISTORTION (dBc)
Distortion vs Frequency
–60
1
FREQUENCY (MHz)
10
–80
–90
VIN = 2VP-P
VS = p5V
RL = 800Ω AT
EACH OUTPUT
GAIN = 1
–100
–110
0.1
1
FREQUENCY (MHz)
10
660425 G08
660425 G09
660425f
5
LT6604-2.5
TYPICAL PERFORMANCE CHARACTERISTICS
2ND HARMONIC,
DIFFERENTIAL INPUT
3RD HARMONIC,
DIFFERENTIAL INPUT
2ND HARMONIC,
SINGLE-ENDED INPUT
3RD HARMONIC,
SINGLE-ENDED INPUT
–60
–70
–80
–90
VS = 3V
F = 1MHz
RL = 800Ω AT
EACH OUTPUT
GAIN = 1
–100
–110
0
1
2
3
4
INPUT LEVEL (VP-P)
5
Distortion vs Signal Level
–40
2ND HARMONIC,
DIFFERENTIAL INPUT
3RD HARMONIC,
DIFFERENTIAL INPUT
2ND HARMONIC,
SINGLE-ENDED INPUT
3RD HARMONIC,
SINGLE-ENDED INPUT
–50
DISTORTION (dBc)
–50
DISTORTION (dBc)
Distortion vs Signal Level
–40
–60
–70
–80
–90
VS = 5V
F = 1MHz
RL = 800Ω AT
EACH OUTPUT
GAIN = 1
–100
–110
0
6
1
660425 G10
2
3
4
5
6
7
INPUT LEVEL (VP-P)
8
–60
–70
–70
–80
–90
VS = p5V
F = 1MHz
RL = 800Ω AT
EACH OUTPUT
GAIN = 1
–110
0
1
2
660425 G11
–40
2VP-P 1MHz INPUT
RIN = 1580Ω
GAIN = 1
–80
–90
–100
8
9
660425 G12
2ND HARMONIC,
VS = 3V
3RD HARMONIC,
VS = 3V
2ND HARMONIC,
VS = 5V
3RD HARMONIC,
VS = 5V
–50
–60
–70
–80
–90
–100
–110
2VP-P 1MHz INPUT, RIN = 402Ω, GAIN = 4
–110
–2
–1
0
1
2
–3
3
INPUT COMMON MODE VOLTAGE RELATIVE TO VMID (V)
–2
–1
0
1
2
–3
3
INPUT COMMON MODE VOLTAGE RELATIVE TO VMID (V)
660425 G13
660425 G14
Single Channel Supply Current vs
Total Supply Voltage
Distortion vs Output
Common Mode Level
2ND HARMONIC,
VS = 3V
3RD HARMONIC,
VS = 3V
2ND HARMONIC,
VS = 5V
3RD HARMONIC,
VS = 5V
2ND HARMONIC,
VS = p5V
3RD HARMONIC,
VS = p5V
–50
–60
–70
–80
–90
–100
32
30
SUPPLY CURRENT (mA)
–40
DISTORTION COMPONENT (dBc)
3
4
5
6
7
INPUT LEVEL (VP-P)
Distortion vs Input Common
Mode Level
DISTORTION COMPONENT (dBc)
DISTORTION COMPONENT (dBc)
–50
2ND HARMONIC,
VS = 3V
3RD HARMONIC,
VS = 3V
2ND HARMONIC,
VS = 5V
3RD HARMONIC,
VS = 5V
–60
–100
9
Distortion vs Input Common
Mode Level
–40
2ND HARMONIC,
DIFFERENTIAL INPUT
3RD HARMONIC,
DIFFERENTIAL INPUT
2ND HARMONIC,
SINGLE-ENDED INPUT
3RD HARMONIC,
SINGLE-ENDED INPUT
–50
DISTORTION (dBc)
Distortion vs Signal Level
–40
TA = 85°C
28
TA = 25°C
26
24
22
TA = –40°C
20
18
2VP-P 1MHz INPUT, RIN = 1580Ω, GAIN = 1
–110
–1.5 –1.0 –0.5
0
1.0 1.5 2.0
VOLTAGE VOCM TO VMID (V)
0.5
2.5
16
2
3
4
6
8
5
7
9
TOTAL SUPPLY VOLTAGE (V)
10
660425 G15
660425 G16
660425f
6
LT6604-2.5
TYPICAL PERFORMANCE CHARACTERISTICS
Channel Separation vs Frequency
(Note 9)
Transient Response Gain = 1
–10
VOUT+
50mV/DIV
CHANNEL SEPARATION (dB)
–30
DIFFERENTIAL
INPUT
200mV/DIV
500ns/DIV
660425 G17
–50
–70
–90
–110
–130
100k
VIN = 2VP-P
VS = 5V
RL = 800Ω AT
EACH OUTPUT
GAIN = 1
1M
10M
FREQUENCY (Hz)
100M
660425 G18
PIN FUNCTIONS
+INA, –INA (Pins 2, 4): Channel A Input Pins. Signals can
be applied to either or both input pins through identical
external resistors, RIN. The DC gain from the differential
inputs to the differential outputs is 1580Ω/RIN.
+INB, –INB (Pins 10, 12): Channel B Input Pins. Signals
can be applied to either or both input pins through identical external resistors, RIN. The DC gain from differential
inputs to the differential outputs is 1580Ω/RIN.
VOCMA (Pin 6): DC Common Mode Reference Voltage
for the 2nd Filter Stage in channel A. Its value programs
the common mode voltage of the differential output of
the filter. Pin 6 is a high impedance input, which can be
driven from an external voltage reference, or Pin 6 can be
tied to Pin 34 on the PC board. Pin 6 should be bypassed
with a 0.01μF ceramic capacitor unless it is connected to
a ground plane.
VOCMB (Pin 14): DC Common Mode Reference Voltage
for the 2nd Filter Stage in Channel B. Its value programs
the common mode voltage of the differential output of
the filter. Pin 14 is a high impedance input, which can be
driven from an external voltage reference, or Pin 14 can be
tied to Pin 8 on the PC board. Pin 14 should be bypassed
with a 0.01μF ceramic capacitor unless it is connected to
a ground plane.
V– (Pins 7, 24, 31, 32, 35): Negative Power Supply Pin
(can be ground).
V+A, V+B (Pins 25, 17): Positive Power Supply Pins
for Channels A and B. For a single 3.3V or 5V supply
(V– grounded) a quality 0.1μF ceramic bypass capacitor
is required from each positive supply pin (V+A, V+B) to
the negative supply pin (V–). The bypass should be as
close as possible to the IC. For dual supply applications,
bypass the negative supply pins to ground and each of the
positive supply pins (V+A, V+B) to ground with a quality
0.1μF ceramic capacitor.
VMIDB (Pin 8): The VMIDB pin is internally biased at midsupply, see Block Diagram. For single supply operation
the VMIDB pin should be bypassed with a quality 0.01μF
ceramic capacitor to V–. For dual supply operation, Pin 8
can be bypassed or connected to a high quality DC ground.
A ground plane should be used. A poor ground will increase
noise and distortion. Pin 8 sets the output common mode
voltage of the 1st stage of the filter in channel B. It has a
5.5kΩ impedance, and it can be overridden with an external
low impedance voltage source.
+OUTB, –OUTB (Pins 19, 21): Output Pins. Pins 19 and
21 are the filter differential outputs for channel B. With a
typical short-circuit current limit greater than ±40mA, each
pin can drive a 100Ω and/or 50pF load to AC ground.
660425f
7
LT6604-2.5
PIN FUNCTIONS
+OUTA, – OUTA (Pins 27, 29): Output Pins. Pins 27 and
29 are the filter differential outputs for channel A. With a
typical short-circuit current greater than ±40mA, each pin
can drive a 100Ω and/or 50pF load to AC ground.
VMIDA (Pin 34): The VMIDA pin is internally biased at midsupply, see Block Diagram. For single supply operation
the VMIDA pin should be bypassed with a quality 0.01μF
ceramic capacitor to V–. For dual supply operation, Pin
34 can be bypassed or connected to a high quality DC
ground. A ground plane should be used. A poor ground
will increase noise and distortion. Pin 34 sets the output
common mode voltage of the 1st stage of the filter in channel A. It has a 5.5kΩ impedance, and it can be overridden
with an external low impedance voltage source.
Exposed Pad (Pin 35): V–. The Exposed Pad must be
soldered to the PCB. If V– is separate from ground, tie
the Exposed Pad to V–.
BLOCK DIAGRAM
VMIDA
V–
NC
V+A
NC
RIN
NC
11k
+INA
VIN+A
V–
LOWPASS
FILTER STAGE
1580Ω
–OUTA
11k
800Ω
V–
NC
OP AMP
+
–INA
VIN–A
+ –
–
VOCM
VOCM
+
–
RIN
NC
800Ω
– +
800Ω
NC
+OUTA
NC
800Ω
1580Ω
VOCMA
V–
VMIDB
V+A
V+B
V–
11k
LOWPASS
FILTER STAGE
1580Ω
NC
11k
800Ω
V–
NC
OP AMP
+INB
+
VIN+B
RIN
NC
800Ω
+ –
–
VOCM
NC
–
–OUTB
VOCM
+
– +
800Ω
NC
–INB
VIN–B
+OUTB
RIN
800Ω
1580Ω
NC
NC
660025 BD
VOCMB
NC
NC
V+B
660425f
8
LT6604-2.5
APPLICATIONS INFORMATION
Interfacing to the LT6604-2.5
operating with a single 3.3V supply and unity passband
gain; the input signal is DC-coupled. The common mode
input voltage is 0.5V, and the differential input voltage is
2VP-P. The common mode output voltage is 1.65V, and the
differential output voltage is 2VP-P for frequencies below
2.5MHz. The common mode output voltage is determined
by the voltage at VOCM. Since VOCM is shorted to VMID,
the output common mode is the mid-supply voltage. In
addition, the common mode input voltage can be equal
to the mid-supply voltage of VMID.
Note: The LT6604-2.5 contains two identical lowpass
filters. The following applications information only refers
to one filter. The two filters are independent except that
they share the same negative supply voltage V–. The two
filters can be used simultaneously by replicating the example circuits. The referenced pin numbers correspond
to the A channel filter.
Each LT6604-2.5 channel requires two equal external resistors, RIN, to set the differential gain to 1580Ω/RIN. The
inputs to the filter are the voltages VIN+ and VIN– presented
to these external components, Figure 1. The difference
between VIN+ and VIN– is the differential input voltage. The
average of VIN+ and VIN– is the common mode input voltage.
Similarly, the voltages VOUT+ and VOUT– appearing at pins
27 and 29 of the LT6604-2.5 are the filter outputs. The difference between VOUT+ and VOUT– is the differential output
voltage. The average of VOUT+ and VOUT– is the common
mode output voltage. Figure 1 illustrates the LT6604-2.5
Figure 2 shows how to AC couple signals into the LT66042.5. In this instance, the input is a single-ended signal.
AC-coupling allows the processing of single-ended or
differential signals with arbitrary common mode levels.
The 0.1μF coupling capacitor and the 1580Ω gain setting
resistor form a high pass filter, attenuating signals below
1kHz. Larger values of coupling capacitors will proportionally reduce this highpass 3dB frequency.
In Figure 3 the LT6604-2.5 channel is providing 12dB of
gain. The common mode output voltage is set to 2V.
3.3V
0.1μF
V
3
–
VIN
2
VIN+
1
0.01μF
+
VIN
0
t
VIN–
V
25
1580Ω
3
4
–
27
34 1/2 +
LT6604-2.5
6
VOUT+
– 29
VOUT–
2
+
1580Ω
7
2
VOUT+
1
VOUT–
t
0
660425 F01
Figure 1
3.3V
0.1μF
V
0.1μF
2
1580Ω
4
–
27
34 1/2 +
LT6604-2.5
6
1
VIN
0
+
0.1μF
t
VIN
0.01μF
2
+
–1
V
25
–
+
1580Ω
29
3
VOUT+
2
VOUT–
1
7
VOUT+
VOUT–
0
660425 F02
t
Figure 2
5V
0.1μF
V
3
VIN
–
4
–
27
34 1/2 +
LT6604-2.5
6
2
1
0
0.01μF
500mVP-P (DIFF)
VIN+
VIN–
VIN
t
V
25
402Ω
2
+
402Ω
+
–
–
+
7
2V
29
3
VOUT+
VOUT+
2
VOUT–
1
0
VOUT–
660425 F03
t
Figure 3
660425f
9
LT6604-2.5
APPLICATIONS INFORMATION
Use Figure 4 to determine the interface between the
LT6604-2.5 and a current output DAC. The gain, or “transimpedance,” is defined as A = VOUT/IIN. To compute the
transimpedance, use the following equation:
A=
CURRENT
OUTPUT
DAC
34
0.01μF
6
660425 F04
R1
2
R2
LT6604-2.5
–
+
7
29
29
402Ω
0.1μF
660425 F05
–2.5V
Figure 5
Differential and Common Mode Voltage Ranges
25
27
7
50Ω
VOUT–
0.1μF
–
1/2 +
+
NETWORK
ANALYZER
INPUT
VOUT+
3.3V
4
–
COILCRAFT
TTWB-16A
4:1
402Ω
53.6Ω and 392Ω resistors satisfy the two constraints
above. The transformer converts the single-ended source
into a differential stimulus. Similarly, the output of the
LT6604-2.5 will have lower distortion with larger load
resistance yet the analyzer input is typically 50Ω. The 4:1
turns (16:1 impedance) transformer and the two 402Ω
resistors of Figure 5, present the output of the LT6604-2.5
with a 1600Ω differential load, or the equivalent of 800Ω
to ground at each output. The impedance seen by the
network analyzer input is still 50Ω, reducing reflections in
the cabling between the transformer and analyzer input.
R1
R1• R2
+ IIN •
R1+ R2 + 1580
R1+ R2
= 26mV + IIN • 48.3Ω
IIN+
53.6Ω
25
–
27
34 1/2 +
LT6604-2.5
6
392Ω
VDAC = VMID •
R1
NETWORK
ANALYZER
SOURCE
COILCRAFT
TTWB-1010
1:1 392Ω 4
2
By setting R1 + R2 = 1580Ω, the gain equation reduces to
A = R1(Ω). The voltage at the pins of the DAC is determined
by R1, R2, the voltage on VMID and the DAC output current.
Consider Figure 4 with R1 = 49.9Ω and R2 = 1540Ω. The
voltage at VMID, for VS = 3.3V, is 1.65V. The voltage at the
DAC pins is given by:
R2
0.1μF
50Ω
1580 • R1
(Ω)
(R1+ R2)
IIN–
2.5V
VOUT+ – VOUT–
IIN+ – IIN–
=
1580 • R1
R1 + R2
Figure 4
Evaluating the LT6604-2.5
The low impedance levels and high frequency operation
of the LT6604-2.5 require some attention to the impedance matching networks between the LT6604-2.5 and
other devices. The previous examples assume an ideal
(0Ω) source impedance and a large (1k) load resistance.
Among practical examples where impedance must be
considered is the evaluation of the LT6604-2.5 with a
network analyzer.
Figure 5 is a laboratory setup that can be used to characterize the LT6604-2.5 using single-ended instruments
with 50Ω source impedance and 50Ω input impedance.
For a 12dB gain configuration the LT6604-2.5 requires a
402Ω source resistance yet the network analyzer output is
calibrated for a 50Ω load resistance. The 1:1 transformer,
The rail-to-rail output stage of the LT6604-2.5 can process
large differential signal levels. On a 3V supply, the output
signal can be 5.1VP-P. Similarly, a 5V supply can support
signals as large as 8.8VP-P. To prevent excessive power
dissipation in the internal circuitry, the user must limit
differential signal levels to 9VP-P.
The two amplifiers inside the LT6604-2.5 channel have
independent control of their output common mode voltage
(see the “Block Diagram” section). The following guidelines
will optimize the performance of the filter.
VMID can be allowed to float, but it must be bypassed to
an AC ground with a 0.01μF capacitor or instability may
be observed. VMID can be driven from a low impedance
source, provided it remains at least 1.5V above V– and at
least 1.5V below V+. An internal resistor divider sets the
voltage of VMID. While the internal 11k resistors are well
matched, their absolute value can vary by ±20%. This
should be taken into consideration when connecting an
external resistor network to alter the voltage of VMID.
660425f
10
LT6604-2.5
APPLICATIONS INFORMATION
VOCM can be shorted to VMID for simplicity. If a different
common mode output voltage is required, connect VOCM
to a voltage source or resistor network. For 3V and 3.3V
supplies the voltage at VOCM must be less than or equal
to the mid supply level. For example, voltage (VOCM) ≤
1.65V on a single 3.3V supply. For power supply voltages
higher than 3.3V the voltage at VOCM can be set above mid
supply, as shown in Table 1. The voltage on VOCM should
not be more than 1V below the voltage on VMID. VOCM is
a high impedance input.
Table 1. Output Common Mode Range for Various Supplies
SUPPLY
VOLTAGE
DIFFERENTIAL OUT
VOLTAGE SWING
OUTPUT COMMON MODE RANGE
FOR LOW DISTORTION
3V
4VP-P
2VP-P
1VP-P
1.4V ≤ VOCM ≤ 1.6V
1V ≤ VOCM ≤ 1.6V
0.75V ≤ VOCM ≤ 1.6V
5V
8VP-P
4VP-P
2VP-P
1VP-P
2.4V ≤ VOCM ≤ 2.6V
1.5V ≤ VOCM ≤ 3.5V
1V ≤ VOCM ≤ 3.75V
0.75V ≤ VOCM ≤ 3.75V
±5V
9VP-P
4VP-P
2VP-P
1VP-P
–2V ≤ VOCM ≤ 2V
–3.5V ≤ VOCM ≤ 3.5V
–3.75V ≤ VOCM ≤ 3.75V
–4.25V ≤ VOCM ≤ 3.75V
NOTE: The voltage at VOCM should not be more than 1V below the voltage
at VMID. To achieve some of the output common mode ranges shown in the
table, the voltage at VMID must be set externally to a value below mid supply.
The LT6604-2.5 was designed to process a variety of
input signals including signals centered on the mid-supply voltage and signals that swing between ground and
a positive voltage in a single supply system (Figure 1).
The allowable range of the input common mode voltage
(the average of VIN+ and VIN– in Figure 1) is determined
by the power supply level and gain setting (see “Electrical
Characteristics”).
at 2.5V. Since the input common mode voltage is near 0V,
there will be approximately a total of 2.5V drop across
the series combination of the internal 1580Ω feedback
resistor and the external 402Ω input resistor. The resulting 1.25mA common mode DC current in each input path,
must be absorbed by the sources VIN+ and VIN–. VOCM sets
the common mode output voltage of the 2nd differential
amplifier inside the LT6604-2.5 channel, and therefore sets
the common mode output voltage of the filter. Since, in
the example of Figure 3, VOCM differs from VMID by 0.5V,
an additional 625μA (312μA per side) of DC current will
flow in the resistors coupling the 1st differential amplifier
output stage to the filter output. Thus, a total of 3.125mA
is used to translate the common mode voltages.
A simple modification to Figure 3 will reduce the DC common mode currents by 36%. If VMID is shorted to VOCM
the common mode output voltage of both op amp stages
will be 2V and the resulting DC current will be 2mA. Of
course, by AC-coupling the inputs of Figure 3, the common
mode DC current can be reduced to 625μA.
Noise
The noise performance of the LT6604-2.5 channel can be
evaluated with the circuit of Figure 6. Given the low noise
output of the LT6604-2.5 and the 6dB attenuation of the
transformer coupling network, it is necessary to measure
the noise floor of the spectrum analyzer and subtract the
instrument noise from the filter noise measurement.
Example: With the IC removed and the 25Ω resistors
grounded, Figure 6, measure the total integrated noise (eS)
of the spectrum analyzer from 10kHz to 2.5MHz. With the
IC inserted, the signal source (VIN) disconnected, and the
Common Mode DC Currents
In applications like Figure 1 and Figure 3 where the LT66042.5 not only provides lowpass filtering but also level shifts
the common mode voltage of the input signal, DC currents
will be generated through the DC path between input and
output terminals. Minimize these currents to decrease
power dissipation and distortion.
2.5V
0.1μF
VIN
RIN
25
4
–
27
34 1/2 +
LT6604-2.5
6
2
RIN
–
+
29
7
COILCRAFT
TTWB-1010
25Ω
1:1
SPECTRUM
ANALYZER
INPUT
50Ω
25Ω
660425 F06
Consider the application in Figure 3. VMID sets the output
common mode voltage of the 1st differential amplifier inside
the LT6604-2.5 channel (see the “Block Diagram” section)
0.1μF
–2.5V
Figure 6
660425f
11
LT6604-2.5
APPLICATIONS INFORMATION
input resistors grounded, measure the total integrated noise
out of the filter (eO). With the signal source connected, set
the frequency to 100kHz and adjust the amplitude until
VIN measures 100mVP-P. Measure the output amplitude,
VOUT, and compute the passband gain A = VOUT/VIN. Now
compute the input referred integrated noise (eIN) as:
(eO )2 – (eS )2
eIN =
A
Table 2 lists the typical input referred integrated noise for
various values of RIN.
Table 2. Noise Performance
RIN
INPUT REFERRED
INTEGRATED NOISE
10kHz TO 2.5MHz
INPUT REFERRED
INTEGRATED NOISE
10kHz TO 5MHz
4
402Ω
18μVRMS
23μVRMS
2
806Ω
29μVRMS
39μVRMS
1
1580Ω
51μVRMS
73μVRMS
PASSBAND
GAIN
Figure 7 is plot of the noise spectral density as a function
of frequency for an LT6604-2.5 channel with RIN = 1580Ω
using the fixture of Figure 6 (the instrument noise has
been subtracted from the results).
The noise at each output is comprised of a differential
component and a common mode component. Using a
transformer or combiner to convert the differential outputs
to single-ended signal rejects the common mode noise and
gives a true measure of the S/N achievable in the system.
100
80
40
SPECTRAL DENSITY
30
60
20
40
10
20
INTEGRATED
0
0.01
0
0.1
1
10
FREQUENCY (MHz)
660425 F07
INTEGRATED NOISE (μVRMS)
NOISE SPECTRAL DENSITY (nVRMS/√Hz)
50
Conversely, if each output is measured individually and the
noise power added together, the resulting calculated noise
level will be higher than the true differential noise.
Power Dissipation
The LT6604-2.5 amplifiers combine high speed with large
signal currents in a small package. There is a need to ensure that the die’s junction temperature does not exceed
150°C. The LT6604-2.5 has an exposed pad (pin 35) which
is connected to the negative supply (V–). Connecting the
pad to a ground plane helps to dissipate the heat generated
by the chip. Metal trace and plated through-holes can be
used to spread the heat generated by the device to the
backside of the PC board.
Junction temperature, TJ, is calculated from the ambient
temperature, TA, and power dissipation, PD. The power
dissipation is the product of supply voltage, VS, and total
supply current, IS. Therefore, the junction temperature is
given by:
TJ = TA + (PD • θJA) = TA + (VS • IS • θJA)
where the supply current, IS, is a function of signal level,
load impedance, temperature and common mode voltages.
For a given supply voltage, the worst-case power dissipation
occurs when the differential input signal is maximum, the
common mode currents are maximum (see Applications
Information regarding Common Mode DC Currents), the
load impedance is small and the ambient temperature is
maximum. To compute the junction temperature, measure
the supply current under these worst-case conditions, use
43°C/W as the package thermal resistance, then apply the
equation for TJ. For example, using the circuit in Figure 3
with DC differential input voltage of 1V, a differential
output voltage of 4V, no load resistance and an ambient
temperature of 85°C, the supply current (current into V+)
measures 37.6mA per channel. The resulting junction
temperature is: TJ = TA + (PD • θJA) = 85 + (5 • 2 • 0.0376
• 43) = 101°C. The thermal resistance can be affected by
the amount of copper on the PCB that is connected to V–.
The thermal resistance of the circuit can increase if the
Exposed Pad is not connected to a large ground plane
with a number of vias.
Figure 7. Input Referred Noise, Gain = 1
660425f
12
LT6604-2.5
TYPICAL APPLICATIONS
IQ DAC Output Filter
5V
0.1μF
5V
1580Ω
52.3Ω
16 BIT 4kHz to 2.5MHz
DISCRETE MULTI-TONE
SIGNAL @ 50MSPS
LADCOM
IOUT A
52.3Ω
LTC1668
56pF
IOUT B
25
4
–
27
34 1/2 +
LT6604-2.5
6
2
CLK
+
1580Ω
QOUT
– 29
7
0.1μF
–5V 50MHz
–5V
5V
0.1μF
5V
1580Ω
52.3Ω
LADCOM
IOUT A
52.3Ω
LTC1668
56pF
IOUT B
17
–
19
8 1/2 +
LT6604-2.5
14
12
10
CLK
1580Ω
+
IOUT
– 21
24
0.1μF
–5V 50MHz
–5V
DAC Output Spectrum
LT6604-2.5 Output Spectrum
0
0
–10
–10
–20
–20
BASEBAND SIGNAL
–30
–30
–40
DAC OUTPUT IMAGE
–50
(dBm)
(dBm)
660425 TA02a
–40
–50
–60
–60
–70
–70
–80
–80
–90
0
12 24 36 48 60 72 84 96 108 120
FREQUENCY (MHz)
–90
0
12 24 36 48 60 72 84 96 108 120
FREQUENCY (MHz)
660425 TA02b
660025 TA02c
660425f
13
LT6604-2.5
TYPICAL APPLICATIONS
Dual, Matched 5th Order, 2.5MHz Lowpass Filter, Gain = 1
V+
0.1μF
VIN–
R
787Ω
R
787Ω
C
82pF
VIN+
25
–
27
1/2
34
+
LT6604-2.5
6
4
2
R
787Ω
+
R
787Ω
QOUT
– 29
7
0.1μF
1
C=
2π • R • 2.5MHz
GAIN =
VIN–
V–
1580Ω
2R
R
787Ω
V+
0.1μF
R
787Ω
C
82pF
VIN+
17
–
19
8 1/2 +
LT6604-2.5
14
12
10
R
787Ω
R
787Ω
+
QOUT
– 21
24
0.1μF
V–
660425 TA03a
Frequency Response
10
Transient Response Gain = 1
VS = ±2.5V
GAIN = 1
R = 787Ω
TA = 25°C
0
–10
VOUT+
50mV/DIV
GAIN (dB)
–20
–30
DIFFERENTIAL
INPUT
200mV/DIV
–40
–50
–60
–70
500ns/DIV
–80
–90
100k
1M
FREQUENCY (Hz)
660425 TA03c
10M 20M
660425 TA03b
660425f
14
LT6604-2.5
PACKAGE DESCRIPTION
UFF Package
34-Lead Plastic QFN (4mm × 7mm)
(Reference LTC DWG # 05-08-1758 Rev Ø)
0.70 ± 0.05
1.90 ± 0.05
4.50 ± 0.05
PACKAGE OUTLINE
1.83 ± 0.05
3.10 ± 0.05
1.50 REF
1.90 ± 0.05
1.47 ± 0.05
2.64 ± 0.05
1.29 ± 0.05
0.25 ± 0.05
0.50 BSC
6.00 REF
6.10 ± 0.05
7.50 ± 0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
4.00 ± 0.10
PIN 1 NOTCH
R = 0.30 OR
0.25 × 45°
CHAMFER
R = 0.10
TYP
0.75 ± 0.05
1.50 REF
33
34
0.40 ± 0.10
1
PIN 1
TOP MARK
(NOTE 6)
1.90 ± 0.10
2
1.47 ± 0.10
7.00 ± 0.10
6.00 REF
1.83 ± 0.10
1.90 ± 0.10
2.64 ± 0.10
(UFF34) QFN 0807 REV Ø
0.200 REF
R = 0.125
TYP
0.00 – 0.05
0.25 ± 0.05
0.50 BSC
0.99 ± 0.10
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE
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 0.20mm 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
660425f
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
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.
15
LT6604-2.5
RELATED PARTS
PART NUMBER DESCRIPTION
COMMENTS
Integrated Filters
LTC1562-2
Very Low Noise, 8th Order Filter Building Block
Lowpass and Bandpass Filters up to 300kHz
LTC1565-31
650kHz Linear Phase Lowpass Filter
Continuous Time, 7th Order, Differential
LTC1566-1
Low Noise, 2.3MHz Lowpass Filter
Continuous Time, 7th Order, Differential
LT1568
Very Low Noise, 4th Order Filter Building Block
Lowpass and Bandpass Filters up to 10MHz
LTC1569-7
Linear Phase, Tunable 10th Order Lowpass Filter
Single-Resistor Programmable Cut-Off to 300kHz
LT6600-2.5
Very Low Noise Differential 2.5MHz Lowpass Filter
SNR = 86dB at 3V Supply, 4th Order Filter
LT6600-5
Very Low Noise Differential 5MHz Lowpass Filter
SNR = 82dB at 3V Supply, 4th Order Filter
LT6600-10
Very Low Noise Differential 10MHz Lowpass Filter
SNR = 82dB at 3V Supply, 4th Order Filter
LT6600-15
Very Low Noise Differential 15MHz Lowpass Filter
SNR = 76dB at 3V Supply, 4th Order Filter
LT6600-20
Very Low Noise Differential 20MHz Lowpass Filter
SNR = 76dB at 3V Supply, 4th Order Filter
LTC6601
Low Noise, Fully Differential, Pin Configurable Amplifier/Driver/2nd Order
Filter Building Block
LTC6602
Dual Adjustable Lowpass Filter for RFID
LTC6603
Dual Adjustable Lowpass Filter for Communications
LT6604-5
Dual Very Low Noise, Differential Amplifier and 5MHz Lowpass Filter
SNR = 82dB at 3V Supply, 4th Order Filter
LT6604-10
Dual Very Low Noise, Differential Amplifier and 10MHz Lowpass Filter
SNR = 82dB at 3V Supply, 4th Order Filter
LT6604-15
Dual Very Low Noise, Differential Amplifier and 15MHz Lowpass Filter
SNR = 76dB at 3V Supply, 4th Order Filter
660425f
16 Linear Technology Corporation
LT 0708 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
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www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2008