LTC6752-4_15 Datasheet, PDF (24/30 Pages) Linear Technology – 280MHz, 2.9ns Comparator Family with Rail-to-Rail Inputs and CMOS Outputs

LTC6752/LTC6752-1/
LTC6752-2/LTC6752-3/LTC6752-4
Typical Applications
Common Mode Rejecting Line Receiver
Differential electrical signals being transmitted over long
cables are often attenuated. Electrical noise on the cables
can take the form of common mode signals.
The LTC6752 comparators can be used to retrieve attenu-
ated differential signals that have been corrupted by high
frequency common mode noise, as shown in Figure 14.
Figure 15 shows an LTC6752-2 retrieving a 200MHz,
200mV_P-P differential input signal that has 2.5V of random,
common mode noise superimposed on it. The input supply
(V_CC) used was 5V and the output supply used was 2.7V.
A small amount of modulation is seen at the output due
to a small amount of differential modulation at the inputs,
which causes cycle to cycle variations in propagation delay.
Fast Event Capture
The circuit shown in Figure 16 can be used to capture
small and fast events. The comparator output is used to
signal the latch pin and hold the output in the HIGH state.
The circuit will reset when the RESET line is low. An open
drain 1.5ns NAND gate is used to both invert the output
signal and is used to MUX in the RESET line from the
supervising circuit. One important feature of the NAND is
that it is open drain which allows the comparator to use
either its default 5mV of hysteresis or a user programmed
hysteresis. The latch recovery time of this circuit is roughly
210ns and is dominated by the time constant created by the
capacitance seen at the output of the NAND gate and the
20k series resistance of the LE/HYST pin. The waveforms
are shown in Figure 17.
3.3V
SMALL DIFFERENTIAL SIGNAL WITH
LARGE COMMON MODE COMPONENT
V_CC = 5V
+IN ₊
V_DD = 2.7V
LTC6752-2
Q
–IN _–
V_EE
6752 F14
Figure 14
EVENT IN INPUT
50mV, 10ns
3.3V
182k
REF
200Ω
0.1μF
+ ^VCC
V_DD
2.2μF
LTC6752-2 _VEE Q
LE/HYST
–
SHDN
0.1μF
OUT
RESET
NXP 74LVC1G38
6752 F16
Figure 16
500mV/DIV
Q
–IN +IN
OUT
500mV/DIV
INPUT
RESET
REF
24
50ns/DIV
Figure 15
6752 F15
50ns/DIV
Figure 17
For more information www.linear.com/LTC6752
6752 F17
6752fb