LTC6255 datasheet(23/30 Pages) LINER

23 / 30 page

LTC6752/LTC6752-1/

LTC6752-2/LTC6752-3/

LTC6752-4

6752fc

For more information www.linear.com/LTC6752

Typical applicaTions

COMPARATOR U2

TIMING

RESISTOR R

TIMING

CAPACITOR C

3.3V

100pF

22k

–

6.65k

22k

VCC

3.3V

COMPARATOR U1

3.3V

15k

OUTPUT 3.3V 100ns PULSE

–

VCC

LTC6752-2

INPUT 15mV TO 3.3V PULSE

MINIMUM PULSE WIDTH 5ns

VDD

VEE

LE/HYST

SHDN

OUT

49.9

1000pF

SOD-123

OSA

49.9

ZOUT = 50

LTC6752-2

VDD

VEE

LE/HYST

SHDN

OUT

Figure 11

Figure 12

Figure 13

500mV/DIV

IN–

IN+

OUT

0.5

1.0

1.5

2.0

2.5

4.0

3.5

3.0

4.5

5.0

10ns/DIV

6752 F11

OUTPUT, 2V/DIV

INPUT, 20mV/DIV

20ns/DIV

6752 F13

Pulse Stretcher Circuit/Monostable Multivibrator

For detecting short pulses from a single sensor, a pulse

stretcher is often required. The circuit of Figure 12 acts as

a one-shot, stretching the width of an incoming pulse to a

consistent~100ns.Thecircuitworksasfollows:Compara-

tor U1 functions as a threshold detector, and Comparator

U2 functions as a one-shot. Comparator U1 is biased with

a threshold of 11mV to overcome comparator and system

offsets, and establish a low output in the absence of an

input signal. An input pulse causes the output of U1 to go

high, which then causes the output of U2 to go high. The

output of U2 is fed back to the input of the 1st compara-

tor, Timing Capacitor C now begins charging through R.

After 100ns, U2 goes low, allowing U1 also to go low. A

new pulse at the input of U2 can now restart the process.

Timing capacitor C can be increased without limit for

longer output pulses.

Figure 13 shows input and output waveforms for the pulse

stretcher circuit.

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