82540EP/82541(PI/GI/EI) & 82562EZ(EX) Dual Footprint Design Guide
58
where
x = Average measured frequency in Hertz and
y = Ideal reference frequency in Hertz
Example 3.
Given: The measured averaged center frequency is 24.99963 MHz (or 24,999,630 Hertz).
Example 4.
Given: The measured averaged center frequency is 25.00027 MHz (or 25,000,270 Hertz).
Note:
The following items should be noted for an ideal reference crystal on a typical printed circuit
board.
•
If the transmitter reference frequency is more than 8 ppm below the target frequency, then the
values for C1 and C2 are too big and they should be decreased. When tests are performed
across temperature, it may be acceptable for the center frequency deviation to be a little greater
than 8 ppm.
•
If the transmitter reference frequency is more than 8 ppm above the target frequency, then the
values for C1 and C2 are too small and they should be increased. When tests are performed
across temperature, it may be acceptable for the center frequency deviation to be a little greater
than 8 ppm.
FrequencyAccuracy ppm
(
)
x
y
–
(
)
y 1000000
⁄
(
)
--------------------------------
=
FrequencyAccuracy ppm
(
)
24999630
25000000
–
(
)
25000000 1000000
⁄
(
)
----------------------------------------------------------
14.8ppm
–
=
=
FrequencyAccuracy ppm
(
)
25000270
25000000
–
(
)
25000000 1000000
⁄
(
)
----------------------------------------------------------
10.8ppm
=
=
Содержание 82562EX
Страница 42: ...82540EP 82541 PI GI EI 82562EZ EX Dual Footprint Design Guide 34 Note This page intentionally left blank...
Страница 44: ...82540EP 82541 PI GI EI 82562EZ EX Dual Footprint Design Guide 36 Note This page intentionally left blank...
Страница 68: ...82540EP 82541 PI GI EI 82562EZ EX Dual Footprint Design Guide 60 Note This page intentionally left blank...
