LTC6930C データシートの表示（PDF） - Linear Technology

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LTC6930C

32.768kHz to 8.192MHz Precision µPower Oscillators

Linear Technology 

LTC6930-X.XX

Applications Information

5 years is not 5 times the drift for one year. A sample cal-

culation for drift over 5 years at 30ppm/√kHr is as follows:

5 years • 365.25 days/year • 24 hours/day = 43,830

hours = 43.830kHr

√43.830kHr = 6.62√kHr

6.62√kHr • 30ppm/√kHr = 0.0198% over 5 years.

Drift calculations assume that the part is in continuous

operation during the entire time period of the calculation.

The movement of ions which results in drift is usually aided

by electric fields in the operating parts, and the typical drift

spec applies while the part is powered up. Conservative

calculations would use a tenth of the drift specification for

time when power is not applied to the part.

Setting the Frequency

The output frequency of the LTC6930 is chosen from the

values in Table 1 and set using the DIV pins, as noted

in the table. Master oscillator frequency is preset in the

factory, and the DIV pins select an internal binary divider

of up to 128.

For example, if the desired oscillator output frequency

is 2.5MHz, finding 2.5MHz in Table 1 shows that the

LTC6930-5.00 should be ordered, having a master

oscillator frequency of 5MHz, and a DIV value of [001]

should be used. This would equate to grounding DIVC

and DIVB, while connecting DIVA to the positive supply.

Frequencies other than those shown in Table 1 may

be requested.

Table 1. Frequency Setting and Available Frequencies

÷1

÷2

÷4

DIV Pin Settings

[DIVC][DIVB][DIVA]

000

001

010

LTC6930-4.19

4.194304MHz 2.097152MHz 1.048576MHz

LTC6930-5.00

5.000MHz 2.500MHz 1.250MHz

LTC6930-7.37

7.3728MHz 3.6864MHz 1.8432MHz

LTC6930-8.00

8.000MHz 4.000MHz 2.000MHz

LTC6930-8.19

8.192MHz 4.096MHz 2.048MHz

÷8

011

524.288kHz

625.0kHz

921.6kHz

1000kHz

1024kHz

÷16

100

262.144kHz

312.5kHz

460.8kHz

500.0kHz

512.0kHz

÷32

101

131.072kHz

156.25kHz

230.4kHz

250.0kHz

256.0kHz

÷64

110

65.536kHz

78.125kHz

115.2kHz

125.0kHz

128.0kHz

÷128

111

32.768kHz

39.0625kHz

57.6kHz

62.5kHz

64.0kHz

6930fe

10

For more information www.linear.com/LTC6930

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