LTC6605-10 Linear Technology, LTC6605-10 Datasheet - Page 17

• Manufacturer Part Number: LTC6605-10
• Description: Dual Matched 10MHz Filter
• Manufacturer: Linear Technology

APPLICATIONS INFORMATION
sampling transient of the ADC (see Figure 8). The capaci-
tance serves to provide the bulk of the charge during the
sampling process, while the two resistors at the outputs
of the LTC6605-10 are used to dampen and attenuate
any charge injected by the ADC. The RC fi lter gives the
additional benefi t of band limiting broadband output noise.
The selection of the RC time constant is trial and error
for a given ADC, but the following guidelines are recom-
mended. Choose an RC time constant that is smaller than
the reciprocal of the fi lter cutoff frequency confi gured by the
LTC6605-10. Time constants on the order of 2ns do a good
job of fi ltering broadband noise. Longer time constants
V
IN
+
–
BIAS
1
2
3
4
5
1/2 LTC6605-10
+
–
CHANNEL A
22
21
20
19
18
0.1μF
10nF
Figure 8. Driving an ADC
1μF
3V
V
OCM
τ = R • (C1 + 2 • C2)
R
R
improve SNR at the expense of settling time. The resistors
in the decoupling network should be at least 25Ω. Too large
of a resistor will leave insuffi cient settling time. Too small
of a resistor will not properly dampen the load transient
of the sampling process, prolonging the time required for
settling. In 16-bit applications, this will typically require a
minimum of eleven RC time constants. The 10Ω resistors
at the inputs to the ADC minimize the sampling transients
that charge the RC fi lter capacitors. For lowest distortion,
choose capacitors with low dielectric absorption, such as
a C0G multilayer ceramic capacitor.
C2
C1
C1
10Ω
10Ω
A
A
IN
IN
+
–
V
CM
ADC
2.2μF
CONTROL
GND
LTC6605-10
www.DataSheet4U.com
D15
D0
•
•
1μF
660510 F08
3.3V
17
660510f