LTC6406
3GHz, Low Noise,
Rail-to-Rail Input Differential
Amplifier/Driver
FEATURES
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DESCRIPTION
The LTC
®
6406 is a very low noise, low distortion, fully
differential input/output amplifier optimized for 3V, single
supply operation. The LTC6406 input common mode range
is rail-to-rail, while the output common mode voltage is
independently adjustable by applying a voltage on the
V
OCM
pin. This makes the LTC6406 ideal for level-shifting
signals with a wide common mode range for driving 12-bit
to 16-bit single supply, differential input ADCs.
A 3GHz gain-bandwidth product results in 70dB linearity for
50MHz input signals. The LTC6406 is unity-gain stable and
the closed-loop bandwidth extends from DC to 800MHz.
The output voltage swing extends from near ground to
2V, to be compatible with a wide range of ADC converter
input requirements. The LTC6406 draws only 18mA, and
has a hardware shutdown feature which reduces current
consumption to 300μA.
The LTC6406 is available in a compact 3mm
×
3mm 16-pin
leadless QFN package as well as an 8-lead MSOP package,
and operates over a –40°C to 85°C temperature range.
L,
LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
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Low Noise: 1.6nV/√Hz RTI
Low Power: 18mA at 3V
Low Distortion (HD2/HD3):
–80dBc/–69dBc at 50MHz, 2V
P-P
–104dBc/–90dBc at 20MHz, 2V
P-P
Rail-to-Rail Differential Input
2.7V to 3.5V Supply Voltage Range
Fully Differential Input and Output
Adjustable Output Common Mode Voltage
800MHz –3dB Bandwidth with A
V
= 1
Gain-Bandwidth Product: 3GHz
Low Power Shutdown
Available in 8-Lead MSOP and Tiny 16-Lead
3mm
×
3mm
×
0.75mm QFN Packages
APPLICATIONS
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Differential Input ADC Driver
Single-Ended to Differential Conversion
Level-Shifting Ground-Referenced Signals
Level-Shifting V
CC
-Referenced Signals
High Linearity Direct Conversion Receivers
TYPICAL APPLICATION
ADC Driver: Single-Ended Input to Differential Output with
Common Mode Level Shifting
1.8pF
V
IN
Harmonic Distortion vs Frequency
–30
V
S
= 3V
V
OCM
= V
ICM
= 1.25V
–40
R
LOAD
= 800Ω
= 2V
P-P
V
–50
OUTDIFF
DIFFERENTIAL INPUTS
–60
–70
–80
–90
–100
2ND, R
I
= R
F
= 150Ω
2ND, R
I
= R
F
= 500Ω
3RD, R
I
= R
F
= 150Ω
3RD, R
I
= R
F
= 500Ω
150Ω
150Ω
3V
DISTORTION (dBc)
3V
V
DD
– +
V
OCM
1.25V
LTC6406
+INA
LTC22xx ADC
–INA
GND
+ –
150Ω
150Ω
6406 TA01
–110
1
10
FREQUENCY (MHz)
100
6406 TA01b
1.8pF
6406fb
1
LTC6406
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Total Supply Voltage (V
+
to V
–
) ................................3.5V
Input Current
+IN, –IN, V
OCM
,
SHDN,
V
TIP
(Note 2) ...............±10mA
Output Short-Circuit Duration (Note 3) ............ Indefinite
Operating Temperature Range
(Note 4) ............................................... –40°C to 85°C
Specified Temperature Range (Note 5)
LTC6406C ................................................ 0°C to 70°C
LTC6406I.............................................. –40°C to 85°C
Junction Temperature ........................................... 150°C
Storage Temperature Range................... –65°C to 150°C
PIN CONFIGURATION
TOP VIEW
–OUTF
–OUT
+IN
NC
16 15 14 13
SHDN
V
+
V
–
V
OCM
1
2
3
4
5
V
TIP
6
–IN
7
+OUT
8
+OUTF
17
12 V
–
11 V
+
10 V
+
9
V
–
–IN
V
OCM
V
+
+OUT
1
2
3
4
TOP VIEW
9
8
7
6
5
+IN
SHDN
V
–
–OUT
MS8E PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 150°C,
θ
JA
= 40°C/W,
θ
JC
= 10°C/W
EXPOSED PAD (PIN 9) IS V
–
, MUST BE SOLDERED TO PCB
UD PACKAGE
16-LEAD (3mm
×
3mm) PLASTIC QFN
T
JMAX
= 150°C,
θ
JA
= 68°C/W,
θ
JC
= 4.2°C/W
EXPOSED PAD (PIN 17) IS V
–
, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC6406CUD#PBF
LTC6406IUD#PBF
LTC6406CMS8E#PBF
LTC6406IMS8E#PBF
TAPE AND REEL
LTC6406CUD#TRPBF
LTC6406IUD#TRPBF
LTC6406CMS8E#TRPBF
LTC6406IMS8E#TRPBF
PART MARKING*
LCTC
LCTC
LTCTB
LTCTB
PACKAGE DESCRIPTION
16-Lead (3mm
×
3mm) Plastic QFN
16-Lead (3mm
×
3mm) Plastic QFN
8-Lead Plastic MSOP
8-Lead Plastic MSOP
SPECIFIED
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–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/
6406fb
2
LTC6406
DC ELECTRICAL CHARACTERISTICS
SYMBOL
V
OSDIFF
ΔV
OSDIFF
/ΔT
PARAMETER
Differential Offset Voltage (Input Referred)
The
l
denotes the specifications which apply over the full
operating temperature range, otherwise specifications are at T
A
= 25°C. V
+
= 3V, V
–
= 0V, V
CM
= V
OCM
= V
ICM
= 1.25V, V
SHDN
= open,
R
BAL
= 100kΩ, R
I
= 150Ω, R
F
= 150Ω (0.1% Resistors), C
F
= 1.8pF (See Figure 1) unless otherwise noted. V
S
is defined as (V
+
– V
–
).
V
OUTCM
is defined as (V
+OUT
+ V
–OUT
)/2. V
ICM
is defined as (V
+IN
+ V
–IN
)/2. V
OUTDIFF
is defined as (V
+OUT
– V
–OUT
).
CONDITIONS
V
ICM
= 3V (Note 12)
V
ICM
= 1.25V
V
ICM
= 0V (Note 12)
V
ICM
= 3V (Note 12)
V
ICM
= 1.25V
V
ICM
= 0V (Note 12)
V
ICM
= 3V
V
ICM
= 1.25V
V
ICM
= 0V
V
ICM
= 3V
V
ICM
= 1.25V
V
ICM
= 0V
Common Mode
Differential Mode
Differential
l
l
l
l
l
l
l
MIN
TYP
±1
±0.25
±1
12
1
7
6
–9
–17
±1
±1
±1
130
3
1
1.6
2.5
9
MAX
±5
±3.5
±5
UNITS
mV
mV
mV
μV/°C
μV/°C
μV/°C
μA
μA
μA
μA
μA
μA
kΩ
kΩ
pF
nV/√Hz
pA/√Hz
nV/√Hz
Differential Offset Voltage Drift (Input Referred)
I
B
Input Bias Current (Note 6)
–24
–1
I
OS
Input Offset Current (Note 6)
l
±3
R
IN
C
IN
e
n
i
n
e
nVOCM
V
ICMR
(Note 7)
CMRRI
(Note 8)
CMRRIO
(Note 8)
PSRR
(Note 9)
PSRRCM
(Note 9)
G
CM
ΔG
CM
BAL
Input Resistance
Input Capacitance
Differential Input Referred Noise Voltage Density
f = 1MHz, Not Including
R
I
/R
F
Noise
Input Noise Current Density
f = 1MHz, Not Including
R
I
/R
F
Noise
Input Referred Common Mode Output Noise Voltage Density f = 1MHz
Input Signal Common Mode Range
Input Common Mode Rejection Ratio
(Input Referred)
ΔV
ICM
/ΔV
OSDIFF
Output Common Mode Rejection Ratio (Input Referred)
ΔV
OCM
/ΔV
OSDIFF
Differential Power Supply Rejection
(ΔV
S
/ΔV
OSDIFF
)
Output Common Mode Power Supply Rejection
(ΔV
S
/ΔV
OSCM
)
Common Mode Gain (ΔV
OUTCM
/ΔV
OCM
)
Common Mode Gain Error 100 • (G
CM
– 1)
Output Balance (ΔV
OUTCM
/ΔV
OUTDIFF
)
Op-Amp Inputs
V
ICM
from 0V to 3V
V
OCM
from 0.5V to 2V
V
S
= 2.7V to 3.5V
V
S
= 2.7V to 3.5V
V
OCM
from 0.5V to 2V
V
OCM
from 0.5V to 2V
ΔV
OUTDIFF
= 2V
Single-Ended Input
Differential Input
l
l
l
l
l
l
l
l
l
l
l
l
l
V
–
50
50
55
55
65
70
75
65
1
±0.4
–57
–65
±6
15
0.5
12
1.15
2.2
2
2
1.95
1.7
18
1.25
2.35
2.15
2.05
2
1.85
0.23
0.34
0.75
V
+
V
dB
dB
dB
dB
V/V
±0.8
–45
–45
±15
2
24
1.35
%
dB
dB
mV
μV/°C
V
kΩ
V
V
V
V
V
V
V
V
V
6406fb
V
OSCM
ΔV
OSCM
/ΔT
V
OUTCMR
(Note 7)
R
INVOCM
V
OCM
V
OUT
Common Mode Offset Voltage (V
OUTCM
– V
OCM
)
Common Mode Offset Voltage Drift
Output Signal Common Mode Range
(Voltage Range for the V
OCM
Pin)
Input Resistance, V
OCM
Pin
Self-Biased Voltage at the V
OCM
Pin
Output Voltage, High, +OUT/–OUT Pins
V
OCM
= Open
V
S
= 3.3V, I
L
= 0
V
S
= 3.3V, I
L
= –20mA
V
S
= 3V, I
L
= 0
V
S
= 3V, I
L
= –5mA
V
S
= 3V, I
L
= –20mA
V
S
= 3V, I
L
= 0
V
S
= 3V, I
L
= 5mA
V
S
= 3V, I
L
= 20mA
l
l
l
l
l
l
l
l
l
Output Voltage, Low, +OUT/–OUT Pins
0.33
0.4
0.85
3
LTC6406
DC ELECTRICAL CHARACTERISTICS
SYMBOL
I
SC
A
VOL
V
S
I
S
I
SHDN
R
SHDN
V
IL
V
IH
t
ON
t
OFF
PARAMETER
Output Short-Circuit Current, +OUT/–OUT Pins (Note 10)
Large-Signal Open Loop Voltage Gain
Supply Voltage Range
Supply Current
Supply Current in Shutdown
SHDN
Pull-Up Resistor
SHDN
Input Logic Low
SHDN
Input Logic High
Turn-On Time
Turn-Off Time
V
SHDN
= 0V
V
SHDN
= 0V to 0.5V
l
l
l
l
l
l
The
l
denotes the specifications which apply over the full
operating temperature range, otherwise specifications are at T
A
= 25°C. V
+
= 3V, V
–
= 0V, V
CM
= V
OCM
= V
ICM
= 1.25V, V
SHDN
= open,
R
BAL
= 100kΩ, R
I
= 150Ω, R
F
= 150Ω (0.1% Resistors), C
F
= 1.8pF (See Figure 1) unless otherwise noted. V
S
is defined as (V
+
– V
–
).
V
OUTCM
is defined as (V
+OUT
+ V
–OUT
)/2. V
ICM
is defined as (V
+IN
+ V
–IN
)/2. V
OUTDIFF
is defined as (V
+OUT
– V
–OUT
).
CONDITIONS
l
MIN
±35
2.7
TYP
±55
90
MAX
UNITS
mA
dB
3.5
18
300
22
500
140
2.55
V
mA
μA
kΩ
V
V
ns
ns
60
0.4
100
0.7
2.25
200
50
AC ELECTRICAL CHARACTERISTICS
SYMBOL
SR
GBW
f
–3dB
PARAMETER
Slew Rate
Gain-Bandwidth Product
–3dB Frequency (See Figure 2)
50MHz Distortion
Differential Input, V
OUTDIFF
= 2V
P-P
(Note 13)
The
l
denotes the specifications which apply over the full
operating temperature range, otherwise specifications are at T
A
= 25°C. V
+
= 3V, V
–
= 0V, V
CM
= V
OCM
= V
ICM
= 1.25V, V
SHDN
= open,
R
I
= 150Ω, R
F
= 150Ω (0.1% Resistors), C
F
= 1.8pF R
LOAD
= 400Ω (See Figure 2) unless otherwise noted. V
S
is defined as (V
+
– V
–
).
,
V
ICM
is defined as (V
+IN
+ V
–IN
)/2. V
OUTDIFF
is defined as (V
+OUT
– V
–OUT
).
CONDITIONS
Differential Output
f
TEST
= 30MHz
l
MIN
TYP
630
3
MAX
UNITS
V/μS
GHz
MHz
dBc
dBc
dBc
dBc
500
800
–77
–65
–85
–72
V
OCM
= 1.25V, V
S
= 3V
2nd Harmonic
3rd Harmonic
V
OCM
= 1.25V, V
S
= 3V, R
LOAD
= 800Ω
2nd Harmonic
3rd Harmonic
V
OCM
= 1.25V, V
S
= 3V, R
LOAD
= 800Ω,
R
I
= R
F
= 500Ω
2nd Harmonic
3rd Harmonic
l
–55
–80
–69
dBc
dBc
50MHz Distortion
Single-Ended Input, V
OUTDIFF
= 2V
P-P
(Note 13)
3rd-Order IMD at 49.5MHz, 50.5MHz
OIP3 at 50MHz (Note 11)
t
S
Settling Time
V
OCM
= 1.25V, V
S
= 3V, R
LOAD
= 800Ω,
R
I
= R
F
= 500Ω
2nd Harmonic
3rd Harmonic
V
OUTDIFF
= 2V
P-P
Envelope,
R
LOAD
= 800Ω
R
LOAD
= 800Ω
V
OUTDIFF
= 2V Step
1% Settling
0.1% Settling
Shunt-Terminated to 50Ω, R
S
= 50Ω
Z
IN
= 200Ω (R
I
= 100Ω, R
F
= 300Ω)
–69
–73
–65
36.5
7
11
14.1
7.5
dBc
dBc
dBc
dBm
ns
ns
dB
dB
NF
Noise Figure at 50MHz
6406fb
4
LTC6406
ELECTRICAL CHARACTERISTICS
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:
Input pins (+IN, –IN, V
OCM
,
SHDN
and V
TIP
) 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 3:
A heat sink may be required to keep the junction temperature
below the Absolute Maximum Rating when the output is shorted
indefinitely. Long-term application of output currents in excess of the
absolute maximum ratings may impair the life of the device.
Note 4:
The LTC6406C/LTC6406I are guaranteed functional over the
operating temperature range –40°C to 85°C.
Note 5:
The LTC6406C is guaranteed to meet specified performance from
0°C to 70°C. The LTC6406C is designed, characterized, and expected
to meet specified performance from –40°C to 85°C but is not tested or
QA sampled at these temperatures. The LTC6406I is guaranteed to meet
specified performance from –40°C to 85°C.
Note 6:
Input bias current is defined as the average of the input currents
flowing into the inputs (–IN, and +IN). Input offset current is defined as the
difference between the input currents (I
OS
= I
B+
– I
B–
).
Note 7:
Input common mode range is tested using the test circuit of
Figure 1 by taking three measurements of differential gain with a ±1V DC
differential output with V
ICM
= 0V; V
ICM
= 1.25V; V
ICM
= 3V, verifying that
the differential gain has not deviated from the V
ICM
= 1.25V case by more
than 0.5%, and that the common mode offset (V
OSCM
) has not deviated
from the common mode offset at V
ICM
= 1.25V by more than ±20mV.
The voltage range for the output common mode range is tested using the
test circuit of Figure 1 by applying a voltage on the V
OCM
pin and testing at
both V
OCM
= 1.25V and at the Electrical Characteristics table limits to verify
that the common mode offset (V
OSCM
) has not deviated by more than
±10mV from the V
OCM
= 1.25V case.
Note 8:
Input CMRR is defined as the ratio of the change in the input
common mode voltage at the pins +IN or –IN to the change in differential
input referred voltage offset. Output CMRR is defined as the ratio of
the change in the voltage at the V
OCM
pin to the change in differential
input referred voltage offset. This specification is strongly dependent on
feedback ratio matching between the two outputs and their respective
inputs, and it is difficult to measure actual amplifier performance (see the
“Effects of Resistor Pair Mismatch” in the Applications Information section
of this data sheet). For a better indicator of actual amplifier performance
independent of feedback component matching, refer to the PSRR
specification.
Note 9:
Differential power supply rejection (PSRR) is defined as the ratio
of the change in supply voltage to the change in differential input referred
voltage offset. Common mode power supply rejection (PSRRCM) is
defined as the ratio of the change in supply voltage to the change in the
common mode offset, V
OUTCM
– V
OCM
.
Note 10:
Extended operation with the output shorted may cause the
junction temperature to exceed the 150°C limit.
Note 11:
Because the LTC6406 is a feedback amplifier with low output
impedance, a resistive load is not required when driving an ADC.
Therefore, typical output power can be very small in many applications. In
order to compare the LTC6406 with “RF style” amplifiers that require 50Ω
load, the output voltage swing is converted to dBm as if the outputs were
driving a 50Ω load. For example, 2V
P-P
output swing is equal to 10dBm
using this convention.
Note 12:
Includes offset/drift induced by feedback resistors mismatch. See
the Applications Information section for more details.
Note 13:
QFN package only. Refer to data sheet curves for MSOP package
numbers.
TYPICAL PERFORMANCE CHARACTERISTICS
Differential Input Referred Offset
Voltage vs Temperature
1.2
1.0
DIFFERENTIAL V
OS
(mV)
0.8
0.6
0.4
0.2
0
–0.2
–50
DIFFERENTIAL V
OS
(mV)
V
S
= 3V
V
OCM
= 1.25V
V
ICM
= 1.25V
R
I
= R
F
= 150Ω
FIVE TYPICAL UNITS
2.0
1.5
1.0
0.5
0
–0.5
V = 3V
–1.0 V
S
= 1.25V
OCM
R
I
= R
F
= 150Ω
–1.5 0.1% FEEDBACK NETWORK RESISTORS
TYPICAL UNIT
–2.0
0
0.5
1.0
1.5
2.0
2.5
INPUT COMMON MODE VOLTAGE (V)
Differential Input Referred
Offset Voltage vs Input Common
Mode Voltage
COMMON MODE OFFSET VOLTAGE (mV)
T
A
= –40°C
T
A
= 0°C
T
A
= 25°C
T
A
= 70°C
T
A
= 85°C
7
6
5
4
3
2
Common Mode Offset Voltage
vs Temperature
–25
0
25
50
TEMPERATURE (°C)
75
100
6406 G01
3.0
V
S
= 3V
V
OCM
= 1.25V
1
V
ICM
= 1.25V
FIVE TYPICAL UNITS
0
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
6406 G03
6406 G02
6406fb
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