LT1720CS8#TR Linear Technology, LT1720CS8#TR Datasheet - Page 22

• Manufacturer Part Number: LT1720CS8#TR
• Description: IC COMP DUAL R-R 4MA 4.5NS 8SOIC
• Manufacturer: Linear Technology
• Series: UltraFast™r
• Type: General Purposer

Specifications of LT1720CS8#TR

• Number Of Elements: 2
• Output Type: CMOS, Rail-to-Rail, TTL
• Voltage - Supply: 2.7 V ~ 6 V
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIONS INFORMATION
LT1720/LT1721
The input waveform is presented to the diode bridge switch,
the output of which feeds the LT1227 wideband amplifier.
The LT1720 comparators, triggered by the sample com-
mand, generate phase-opposed outputs. These signals are
level shifted by the transistors, providing complementary
bipolar drive to switch the bridge. A skew compensation
trim ensures bridge-drive signal simultaneity within 1ns.
The AC balance corrects for parasitic capacitive bridge im-
balances. A DC balance adjustment trims bridge offset.
The trim sequence involves grounding the input via
50Ω and applying a 100kHz sample command. The
DC balance is adjusted for minimal bridge ON vs OFF
variation at the output. The skew compensation and AC
22
CLOCK
INPUT
** SUMIDA CD43-100
* 1% FILM RESISTOR
†
POLYSTYRENE, 5%
= 1N4148
= 74HC04
“FIXED”
TRIM
10ns
0V TO 2V ≈
2k*
2k
INPUT
SKEW
12pF
10ns
Figure 18. Voltage-Controlled Clock Skew
“SKEWED”
VARACTOR
†
MV-209
DIODE
14k
–
+
LT1077
0.005μF
A1
2.5k*
36pF
†
balance adjustments are then optimized for minimum AC
disturbance in the output. Finally, unground the input and
the circuit is ready for use.
Voltage-Controlled Clock Skew Generator
It is sometimes necessary to generate pairs of identical
clock signals that are phase skewed in time. Further, it is
desirable to be able to set the amount of time skew via a
tuning voltage. Figure 18’s circuit does this by utilizing the
LT1720 to digitize phase information from a varactor-tuned
time domain bridge. A 0V to 2V control signal provides
≈±10ns of output skew. This circuit operates from a 2.7V
to 6V supply.
1M
6.2M*
1.82M*
1M
2.2μF
V
CC
0.1μF
–
+
–
+
+
1/2 LT1720
1/2 LT1720
2.7V TO 6V
C2
C1
V
CC
V
V
IN
C
V
200pF
LT1317
CC
L1**
2.5k
2.5k
GND
SW
FB
Q
Q
FIXED
OUTPUT
SKEWED
OUTPUT
47μF
17201 F18
1.1M
100k
17201fc