LT1394C View Datasheet(PDF) - Linear Technology

Part Name

Description

MFG CO.

LT1394C

7ns, Low Power, Single Supply, Ground-Sensing Comparator

Linear Technology 

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LT1394

TYPICAL APPLICATION

Voltage-Controlled Crystal Oscillator (VCXO)

Figure 20, a variant of the basic crystal oscillator, permits

voltage tuning the output frequency. Such voltage-con-

trolled crystal oscillators (VCXO) are often employed

where slight variation of a stable carrier is required. This

example is specifically intended to provide a 4 × NTSC

sub-carrier tunable oscillator suitable for phase locking.

The LT1394 is set up as a crystal oscillator, operating

similarly to Figure 3 (a). The varactor diode is biased from

the tuning input. The tuning network is arranged so a 0V

to 5V drive provides a reasonably symmetric, broad tuning

range around the 14.31818MHz center frequency. The

indicated selected capacitor sets tuning bandwidth. It

should be picked to complement loop response in phase

locking applications. Figure 21 is a plot of tuning input

voltage versus frequency deviation. Tuning deviation from

the 4 × NTSC 14.31818MHz center frequency exceeds

±240ppm for a 0V to 5V input.

9

14.3217MHz

8

7

6

5 14.31818MHz

4

3

2

1

14.314.0MHz

0

0

1

2

3

4

5

INPUT VOLTAGE (V)

1394 F21

Figure 21. Control Voltage vs Output Frequency for Figure 15.

Tuning Deviation from Center Frequency Exceeds ±240ppm

5V

1N4148 47k*

3.9k* VIN

1M

C SELECT***

0.047µF

1M*

LT1004-2.5 1k*

0V TO 5V

5V

1M MV-209†

1M

2k 100pF

390Ω

+

Y1** 15pF

LT1394

–

2k

200pF

100pF

FREQUENCY

* 1% FILM RESISTOR

OUTPUT

** NORTHERN ENGINEERING LABS C-2350N-14.31818MHz

*** C SELECT SETS TUNING BANDWIDTH. SET TO COMPLEMENT

LOOP RESPONSE IN PHASE LOCKING APPLICATIONS

† VARACTOR DIODE

1394 F20

Figure 20. A 4× NTSC Sub-Carrier Voltage-Tunable Crystal Oscillator. Tuning Range

and Bandwidth Accommodate Variety of Phase Locked Loops

RELATED PARTS

PART NUMBER

LT1016

LT1116

LT1671

LT1720

DESCRIPTION

UltraFast Precision Comparator

12ns Single Supply Ground-Sensing Comparator

Fast Single Supply Comparator

UltraFast Dual Single Supply Comparator

16 Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408)432-1900 q FAX:(408)434-0507 q www.linear-tech.com

COMMENTS

Industry Standard 10ns Comparator

Single Supply Version of LT1016

60ns, 450µA Single Supply Comparator

Dual 4.5ns, 4mA Single Supply Comparator

1394f LT/TP 0499 4K • PRINTED IN USA

© LINEAR TECHNOLOGY CORPORATION 1998

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