LTC6405 Linear Technology, LTC6405 Datasheet - Page 13

• Manufacturer Part Number: LTC6405
• Description: Rail-to-Rail Input Differential Amplifier/Driver
• Manufacturer: Linear Technology

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APPLICATIONS INFORMATION
Functional Description
The LTC6405 is a small outline, wideband, low noise, and
low distortion fully-differential amplifi er with accurate
output phase balancing. The LTC6405 is optimized to
drive low voltage, single-supply, differential input analog-
to-digital converters (ADCs). The LTC6405 input common
mode range is rail-to-rail, while the output common mode
voltage is independently adjustable by applying a voltage
on the V
near-ground to 4V, to be compatible with a wide range of
ADC converter input requirements. This makes the LTC6405
ideal for level shifting signals with a wide common mode
range for driving 12-bit to 16-bit single supply, differential
input ADCs. The differential output allows for twice the
signal swing in low voltage systems when compared to
single-ended output amplifi ers. The balanced differential
nature of the amplifi er also provides even-order harmonic
distortion cancellation, and less susceptibility to common
OCM
V
DEFAULT VALUES
(R
*TO OPTIMIZE THE HIGH FREQUENCY PERFORMANCE FOR THE PIN CONFIGURATION OF THE LTC6405
pin. The output voltage swing extends from
IN THE SMALL MSOP PACKAGE, A FEEDBACK RESISTANCE OF AT LEAST 300Ω IS RECOMMENDED.
CM
PACKAGE
I
, R
MSOP*
V
QFN
V
F
INM
INP
: 0.1% RESISTORS)
+
–
+
–
300Ω
200Ω
V
R
V
VOCM
0.01μF
I
SHDN
0.1μF
V
V
+
–
R
R
I
I
300Ω
200Ω
R
F
0.01μF
1
2
3
4
SHDN
V
V
V
+
OCM
–
1.0pF
1.8pF
16
V
5
C
SHDN
–
F
NC
V
TIP
V
V
+IN
–IN
15
6
+IN
–IN
Figure 1. DC Test Circuit
+
–
V
OCM
C
R
R
C
F
F
F
F
14
7
–OUT
+OUT
50Ω
1.25pF
50Ω
mode noise (like power supply noise). The LTC6405 can be
used as a single ended input to differential output amplifi er,
or as a differential input to differential output amplifi er.
The LTC6405 output common mode voltage, defi ned as the
average of the two output voltages, is independent of the
input common mode voltage, and is adjusted by applying
a voltage on the V
is an internal resistive voltage divider, which develops a
potential of 2.5V (if the supply is 5V). It is recommended
that a high quality ceramic cap is used to bypass the V
pin to a low impedance ground plane. The LTC6405’s
internal common mode feedback path forces accurate
output phase balancing to reduce even order harmonics,
and centers each individual output about the potential set
by the V
V
+OUTF
V
13
8
OUTCM
V
1.25pF
1.25pF
–OUTF
–OUTF
+OUTF
V
+
LTC6405
OCM
V
V
–
–
6405 F01
= V
V
V
V
V
pin.
–
+
+
–
12
11
10
9
OCM
V
V
–
–
OCM
=
0.1μF
0.1μF
0.1μF
V
+OUT
pin. If the pin is left open, there
V
V
–
–
0.1μF
+ V
2
–OUT
0.1μF
V
+
R
100k
R
100k
LTC6405
BAL
BAL
V
V
V
OUTCM
–OUT
+OUT
13
6405fa
OCM