LTC6400CUD-8#TRPBF Linear Technology, LTC6400CUD-8#TRPBF Datasheet - Page 10

• Manufacturer Part Number: LTC6400CUD-8#TRPBF
• Description: IC ADC DRIVER DIFF 2.2GHZ 16QFN
• Manufacturer: Linear Technology
• Type: ADC Driverr

Specifications of LTC6400CUD-8#TRPBF

• Applications: Data Acquisition
• Mounting Type: Surface Mount
• Package / Case: 16-WQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
LTC6400-8
Figure 1. Input Termination for Differential 50Ω Input Impedance
Using Shunt Resistor
Figure 2. Input Termination for Differential 50Ω Input Impedance
Using a Balun
order to minimize the refl ection due to input mismatch.
Alternatively, one could apply a narrowband impedance
match at the inputs of the LTC6400-8 for frequency selec-
tion and/or noise reduction.
Referring to Figure 3, LTC6400-8 can be easily confi gured
for single-ended input and differential output without a
balun. The signal is fed to one of the inputs through a
matching network while the other input is connected to
the same matching network and a source resistor. Because
the return ratios of the two feedback paths are equal, the
two outputs have the same gain and thus symmetrical
swing. In general, the single-ended input impedance and
termination resistor R
of R
that the single-ended input impedance is 322Ω and R
59Ω in order to match to a 50Ω source impedance.
10
+
–
V
25Ω
25Ω
IN
MINI CIRCUITS
TCM4-19
S
+
–
, R
V
25Ω
25Ω
•
IN
1:4
G
•
and R
57.6Ω
402Ω
13
14
15
16
13
14
15
16
F
. For example, when R
+IN
+IN
–IN
–IN
+IN
+IN
–IN
–IN
200Ω
200Ω
200Ω
200Ω
T
are determined by the combination
IN+
IN–
IN+
IN–
500Ω
500Ω
500Ω
500Ω
OUT–
OUT+
OUT–
OUT+
S
is 50Ω, it is found
12.5Ω
12.5Ω
12.5Ω
12.5Ω
50Ω
50Ω
50Ω
50Ω
LTC6400-8
LTC6400-8
2.7pF
2.7pF
+OUTF
–OUTF
+OUTF
–OUTF
+OUT
–OUT
+OUT
–OUT
64008 F01
64008 F02
T
8
7
6
5
8
7
6
5
is
The LTC6400-8 is unconditionally stable, i.e. differential
stability factor Kf>1 and stability measure B1>0. However,
the overall differential gain is affected by both source
impedance and load impedance as shown in Figure 4:
The noise performance of the LTC6400-8 also depends upon
the source impedance and termination. For example, an
input 1:4 transformer in Figure 2 improves SNR by adding
6dB gain at the inputs. A trade-off between gain and noise
is obvious when constant noise fi gure circle and constant
gain circle are plotted within the input Smith Chart, based
on which users can choose the optimal source impedance
for a given gain and noise requirement.
+
–
–
+
A
0.1μF
1/2 R
1/2 R
59.0Ω
V
27.4Ω
V
50Ω
Figure 3. Input Termination for Single-Ended 50Ω Input
Impedance
IN
R
V
IN
S
R
S
S
=
T
0.1μF
0.1μF
V
13
14
15
16
V
OUT
IN
+IN
+IN
–IN
–IN
Figure 4. Calculate Differential Gain
13
14
15
16
=
+IN
+IN
–IN
–IN
200Ω
200Ω
R
S
1000
200Ω
200Ω
+
IN+
IN–
400 25
IN+
IN–
500Ω
500Ω
•
OUT–
OUT+
500Ω
500Ω
R
+
OUT–
OUT+
L
R
L
12.5Ω
12.5Ω
50Ω
50Ω
12.5Ω
12.5Ω
50Ω
50Ω
LTC6400-8
2.7pF
+OUTF
–OUTF
+OUT
–OUT
64008 F04
LTC6400-8
2.7pF
+OUTF
–OUTF
+OUT
–OUT
64008 F03
8
7
6
5
1/2 R
1/2 R
V
OUT
64008f
8
7
6
5
L
L