Datasheet LTC6930-X.XX (Analog Devices) - 10

LTC6930-X.XX
applicaTions inForMaTion
5 years is not 5 times the drift for one year. A sample cal-
Setting the Frequency
culation for drift over 5 years at 30ppm/√kHr is as follows: The output frequency of the LTC6930 is chosen from the 5 years • 365.25 days/year • 24 hours/day = 43,830 values in Table 1 and set using the DIV pins, as noted hours = 43.830kHr in the table. Master oscillator frequency is preset in the √43.830kHr = 6.62√kHr factory, and the DIV pins select an internal binary divider of up to 128. 6.62√kHr • 30ppm/√kHr = 0.0198% over 5 years. For example, if the desired oscillator output frequency Drift calculations assume that the part is in continuous is 2.5MHz, finding 2.5MHz in Table 1 shows that the operation during the entire time period of the calculation. LTC6930-5.00 should be ordered, having a master The movement of ions which results in drift is usually aided oscillator frequency of 5MHz, and a DIV value of [001] by electric fields in the operating parts, and the typical drift should be used. This would equate to grounding DIVC spec applies while the part is powered up. Conservative and DIVB, while connecting DIVA to the positive supply. calculations would use a tenth of the drift specification for Frequencies other than those shown in Table 1 may time when power is not applied to the part. be requested.
Table 1. Frequency Setting and Available Frequencies ÷1 ÷2 ÷4 ÷8 ÷16 ÷32 ÷64 ÷128 DIV Pin Settings [DIVC][DIVB][DIVA] 000 001 010 011 100 101 110 111
LTC6930-4.19 4.194304MHz 2.097152MHz 1.048576MHz 524.288kHz 262.144kHz 131.072kHz 65.536kHz 32.768kHz LTC6930-5.00 5.000MHz 2.500MHz 1.250MHz 625.0kHz 312.5kHz 156.25kHz 78.125kHz 39.0625kHz LTC6930-7.37 7.3728MHz 3.6864MHz 1.8432MHz 921.6kHz 460.8kHz 230.4kHz 115.2kHz 57.6kHz LTC6930-8.00 8.000MHz 4.000MHz 2.000MHz 1000kHz 500.0kHz 250.0kHz 125.0kHz 62.5kHz LTC6930-8.19 8.192MHz 4.096MHz 2.048MHz 1024kHz 512.0kHz 256.0kHz 128.0kHz 64.0kHz 6930fe 10 For more information www.linear.com/LTC6930 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information AC Electrical Characteristics DC Electrical Characteristics Timing Characteristics Pin Functions Applications Information Package Description Revision History Related Parts