LTC6752ISC6-4 datasheet(24/30 Pages) AD

24 / 30 page

LTC6752/LTC6752-1/

LTC6752-2/LTC6752-3/

LTC6752-4

6752fc

For more information www.linear.com/LTC6752

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,

200mVP-Pdifferentialinputsignalthathas2.5Vofrandom,

commonmodenoisesuperimposedonit. Theinputsupply

(VCC) 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,

whichcausescycletocyclevariationsinpropagationdelay.

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.Thelatchrecoverytimeofthiscircuitisroughly

210nsandisdominatedbythetimeconstantcreatedbythe

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.

Figure 14

Figure 15

–

VCC = 5V

VDD = 2.7V

6752 F14

SMALL DIFFERENTIAL SIGNAL WITH

LARGE COMMON MODE COMPONENT

VEE

+IN

–IN

LTC6752-2

500mV/DIV

–IN +IN

50ns/DIV

6752 F15

Figure 16

Figure 17

500mV/DIV

50ns/DIV

6752 F17

RESET

INPUT

REF

OUT

3.3V

6752 F16

–

VCC

LTC6752-2

VDD

VEE

LE/HYST

SHDN

2.2F

0.1F

200

182k

EVENT IN

50mV, 10ns

INPUT

RESET

3.3V

REF

NXP 74LVC1G38

OUT

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