LTC1743 Linear Technology, LTC1743 Datasheet - Page 17

• Manufacturer Part Number: LTC1743
• Description: 12-Bit 50Msps ADC
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
Any noise present on the encode signal will result in
additional aperture jitter that will be RMS summed with the
inherent ADC aperture jitter.
In applications where jitter is critical (high input frequen-
cies) take the following into consideration:
1. Differential drive should be used.
2. Use as large an amplitude as possible; if transformer
coupled use a higher turns ratio to increase the
amplitude.
V
THRESHOLD
Figure 8a. Single-Ended ENC Drive,
Not Recommended for Low Jitter
CLOCK
U
INPUT
= 2V
0.1 F
Figure 7. Transformer Driven ENC/ENC with Equivalent Encode Input Circuit
U
0.1 F
ANALOG INPUT
50
2V
ENC
ENC
W
1:4
LTC1743
1743 F08a
ENC
ENC
U
LTC1743
V
V
DD
DD
2V BIAS
2V BIAS
6k
6k
3. If the ADC is clocked with a sinusoidal signal, filter the
4. Balance the capacitance and series resistance at both
The encode inputs have a common mode range of 1.8V to
V
single-ended drive.
DD
5V
encode signal to reduce wideband noise.
encode inputs so that any coupled noise will appear at
both inputs as common mode noise.
. Each input may be driven from ground to V
Figure 8b. ENC Drive Using a CMOS-to-PECL Translator
MC100LVELT22
D0
BIAS
3.3V
Q0
Q0
130
83
TO INTERNAL
ADC CIRCUITS
3.3V
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1743 F07
130
83
ENC
ENC
LTC1743
LTC1743
1743 F08b
17
DD
1743f
for