LTC6905

5

6905fd

PIN FUNCTIONS

ply must be kept free from noise and ripple. It should be

bypassed directly to the GND (Pin 2) with a 0.1μF capaci-

tor or higher.

GND (Pin 2): Ground. Should be tied to a ground plane

for best performance.

SET (Pin 3): Frequency-Setting Resistor Input. The value

mines the oscillator frequency. The voltage on this pin is

voltage. For best performance, use a precision metal film

resistor with a value between 10k and 25k and limit the

capacitance on this pin to less than 10pF.

DIV (Pin 4): Divider-Setting Input. This three-state input

selects among three divider settings, determining the value

for the ÷1 setting, the highest frequency range. Floating

Pin 4 divides the master oscillator by 2. Pin 4 should

be tied to GND for the ÷4 setting, the lowest frequency

range. To detect a floating DIV pin, the LTC6905 attempts

to pull the pin toward midsupply. This is realized with two

other one tied to ground and Pin 4. Therefore, driving

the DIV pin high requires sourcing approximately 15μA.

Likewise, driving DIV low requires sinking 11μA. When

Pin 4 is floated, it should be bypassed by a 1nF capacitor

to ground or it should be surrounded by a ground shield

to prevent excessive coupling from other PCB traces.

OUT (Pin 5): Oscillator Output. This pin can drive 5kΩ

and/or 5pF loads. For larger loads, refer to the Applications

Information section.

TYPICAL PERFORMANCE CHARACTERISTICS

Jitter vs Frequency

Frequency vs Temperature

LTC6905 Output Operating at

LTC6905 Output Operating at

SUPPLY VOLTAGE (V)

2.5

0

5

15

20

25

4.5

45

6905 G04

10

3.5

3

5

4

5.5

30

35

40

FREQUENCY (MHz)

0

0

0.20

0.60

÷4

÷2

÷1

0.80

1.00

40

80 100

180

6905 G05

0.40

20

60

120 140 160

1.20

TEMPERATURE (°C)

–40

–1.0

–0.8

–0.4

–0.2

0

1.0

0.4

0

40

60

6905 G08

–0.6

0.6

0.8

0.2

–20

20

80 100 120

1V/DIV

12.5ns/DIV

6905 G06

1V/DIV

1ns/DIV

6905 G07