LT1720IS8 Linear Technology, LT1720IS8 Datasheet - Page 28

• Manufacturer Part Number: LT1720IS8
• Description: IC COMP R-RINOUT DUAL 8-SOIC
• Manufacturer: Linear Technology
• Series: UltraFast™r
• Type: General Purposer

Specifications of LT1720IS8

• 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

LT1720/LT1721
TYPICAL APPLICATION
Pulse Stretcher
For detecting short pulses from a single sensor, a pulse
stretcher is often required. The circuit of Figure 20 acts as
a one-shot, stretching the width of an incoming pulse to a
consistent 100ns. Unlike a logic one-shot, this LT1720-based
circuit requires only 100pV-s of stimulus to trigger.
The circuit works as follows: Comparator C1 functions as
a threshold detector, whereas comparator C2 is configured
as a one-shot. The first comparator is prebiased with a
threshold of 8mV to overcome comparator and system
offsets and establish a low output in the absence of an
input signal. An input pulse sends the output of C1 high,
which in turn latches C2’s output high. The output of C2
is fed back to the input of the first comparator, causing
regeneration and latching both outputs high. Timing
RELATED PARTS
PART NUMBER
LT1016
LT1116
LT1394
LT1671
LT1715
LT1719
28
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone]
DESCRIPTION
UltraFast Precision Comparator
12ns Single Supply Ground-Sensing Comparator
7ns, UltraFast, Single Supply Comparator
60ns, Low Power, Single Supply Comparator
4ns, 150MHz Dual Comparator
4.5ns Single Supply 3V/5V Comparator
●
FAX: [phone]
PULSE SOURCE
50Ω
51Ω
●
www.linear.com
Figure 20. A 1ns Pulse Stretcher
6.8k
1N5711
24Ω
15k
–
1/2 LT1720
+
C1
5V
1/2 LT1720
1k
R
2k
C2
capacitor C now begins charging through R and, at the
end of 100ns, C2 resets low. The output of C1 also goes
low, latching both outputs low. A new pulse at the input
of C1 can now restart the process. Timing capacitor C can
be increased without limit for longer output pulses.
This circuit has an ultimate sensitivity of better than
14mV with 5ns to 10ns input pulses. It can even detect
an avalanche generated test pulse of just 1ns duration
with sensitivity better than 100mV.
events better than the coincidence detector of Figure 14
because the one-shot is configured to catch just 100mV of
upward movement from C1’s V
detector’s 3ns specification is based on a full, legitimate
logic high, without the help of a regenerative one-shot.
6
See Linear Technology Application Note 47, Appendix B. This circuit can detect the output of the
pulse generator described after 40dB attenuation.
COMMENTS
Industry Standard 10ns Comparator
Single Supply Version of LT1016
6mA Single Supply Comparator
450μA Single Supply Comparator
Similar to the LT1720 with Independent Input/Output Supplies
Single Comparator Similar to the LT1720/LT1721
–
+
0.01μF
2k
2k
C
100pF
17201 F20
OUTPUT
100ns
© LINEAR TECHNOLOGY CORPORATION 1998
OL
, whereas the coincidence
LT 0908 REV C • PRINTED IN USA
6
It can detect short
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