7

LTC1520

Alternate Uses

The tightly controlled propagation delay of the LTC1520

allows the part to serve as a fixed delay element. Figure 9

shows the LTC1520 used as a tapped delay line with 18ns

±3ns steps. Several LTC1520s may be connected in series

to form longer delay lines. Each tap in the delay line is

accurate to within

±17% over temperature.

As shown in Figure 10, the LTC1520 can be used to create

a temperature stable ring oscillator with period increments

of 36ns. Low skew and good channel-to-channel match-

ing enable this oscillator to achieve better than a 45/55

duty cycle (the duty cycle approaches 50/50 as more

LTC1520s are used for lower frequencies). Note that the

fixed voltage bias may either be created externally with a

resistor divider or generated internally using a bypass

capacitor and the internal open circuit bias point (approxi-

mately 3.3V). The use of the internal bias point will result

in a 1% to 2% distortion of the duty cycle.

–

+

0ns DELAY

INPUT

1/4 LTC1520

–

+

18ns DELAY

1/4 LTC1520

–

+

36ns DELAY

1/4 LTC1520

–

+

54ns DELAY

72ns DELAY

1/4 LTC1520

3.3k

5V

0.01

µF

3.3k

1520 F09

Figure 9. Tapped Delay Line with 18ns Steps

Figure 10. Temperature Stable Ring Oscillators

–

+

–

+

1/4 LTC1520

–

+

1/4 LTC1520

9.3MHz OSCILLATOR

WITH BETTER THAN

45/55 DUTY CYCLE

TYPICAL STABILITY

±5% OVER TEMPERATURE

1/4 LTC1520

3.3k

5V

0.01

µF

3.3k

–

+

–

+

1/4 LTC1520

–

+

1/4 LTC1520

–

+

1/4 LTC1520

6.9MHz

OSCILLATOR OUTPUT

1/4 LTC1520

0.01

µF

1520 F10