LTC1407 LINER [Linear Technology], LTC1407 Datasheet - Page 12

• Manufacturer Part Number: LTC1407
• Description: Serial 12-Bit/14-Bit, 3Msps Simultaneous Sampling Simultaneous Sampling
• Manufacturer: LINER [Linear Technology]

APPLICATIO S I FOR ATIO
LTC1407/LTC1407A
LT1818/LT1819: 400MHz, 2500V/ s, 9mA, Single/Dual
Voltage Mode Operational Amplifier.
LT6200: 165MHz GBWP, –85dBc distortion at 1MHz,
unity gain stable, rail-to-rail in and out, 15mA/amplifier,
0.95nV/ Hz.
LT6203: 100MHz GBWP, –80dBc distortion at 1MHz,
unity gain stable, rail-to-rail in and out, 3mA/amplifier,
1.9nV/ Hz.
LT6600: Amplifier/Filter Differential In/Out with 10MHz
Cutoff.
INPUT FILTERING AND SOURCE IMPEDANCE
The noise and the distortion of the input amplifier and
other circuitry must be considered since they will add to
the LTC1407/LTC1407A noise and distortion. The small-
signal bandwidth of the sample-and-hold circuit is 50MHz.
Any noise or distortion products that are present at the
analog inputs will be summed over this entire bandwidth.
Noisy input circuitry should be filtered prior to the analog
12
U
U
W
ANALOG
ANALOG
INPUT
INPUT
U
Figure 1. RC Input Filter
*TIGHT TOLERANCE REQUIRED TO AVOID
APERTURE SKEW DEGRADATION
51 *
51 *
10 F
47pF*
47pF*
inputs to minimize noise. A simple 1-pole RC filter is suf-
ficient for many applications. For example, Figure 1 shows
a 47pF capacitor from CHO
resistor to limit the net input bandwidth to 30MHz. The
47pF capacitor also acts as a charge reservoir for the input
sample-and-hold and isolates the ADC input from sam-
pling-glitch sensitive circuitry. High quality capacitors and
resistors should be used since these components can add
distortion. NPO and silvermica type dielectric capacitors
have excellent linearity. Carbon surface mount resistors
can generate distortion from self heating and from dam-
age that may occur during soldering. Metal film surface
mount resistors are much less susceptible to both prob-
lems. When high amplitude unwanted signals are close in
frequency to the desired signal frequency a multiple pole
filter is required.
High external source resistance, combined with 13pF of
input capacitance, will reduce the rated 50MHz input band-
width and increase acquisition time beyond 39ns.
11
1
2
3
4
5
CH0
CH0
V
GND
CH1
CH1
REF
LTC1407A
LTC1407/
+
–
+
–
1407 F01
+
to ground and a 51 source
1407f