Datasheet

16
LTC1744
1744f
Input Range
The input range can be set based on the application. For
oversampled signal processing in which the input fre-
quency is low (<10MHz), the largest input range will
provide the best signal-to-noise performance while main-
taining excellent SFDR. For high input frequencies
(>10MHz), the 2V range will have the best SFDR perfor-
mance but the SNR will degrade by 3.5dB. See the Typical
Performance Characteristics section.
APPLICATIO S I FOR ATIO
WUU
U
Figure 7. Transformer Driven ENC/ENC
V
DD
LTC1744
1744 F07
BIAS
V
DD
5V
ENC
ENC
ANALOG INPUT
2V BIAS
2V BIAS
1:4
0.1µF
CLOCK
INPUT
50Ω
6k
6k
TO INTERNAL
ADC CIRCUITS
Driving the Encode Inputs
The noise performance of the LTC1744 can depend on the
encode signal quality as much as on the analog input. The
ENC/ENC inputs are intended to be driven differentially,
primarily for noise immunity from common mode noise
sources. Each input is biased through a 6k resistor to a 2V
bias. The bias resistors set the DC operating point for
transformer coupled drive circuits and can set the logic
threshold for single-ended drive circuits.