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參數(shù)資料
| 型號： | MC12439FN |
| 廠商： | FREESCALE SEMICONDUCTOR INC |
| 元件分類： | 時鐘產(chǎn)生/分配 |
| 英文描述： | 800 MHz, OTHER CLOCK GENERATOR, PQCC28 |
| 封裝： | PLASTIC, LCC-28 |
| 文件頁數(shù)： | 5/10頁 |
| 文件大小： | 155K |
| 代理商： | MC12439FN |
MC12439
FREESCALE SEMICONDUCTOR ADVANCED CLOCK DRIVERS DEVICE DATA
373
Figure 2. MC12439 Block Diagram
PROGRAMMING INTERFACE
Programming the device amounts to properly configuring the
internal dividers to produce the desired frequency at the
outputs. The output frequency can by represented by this
formula:
FOUT = FXTAL x M ÷ N(1)
Where FXTAL is the crystal frequency, M is the loop divider
modulus, and N is the output divider modulus. Note that it is
possible to select values of M such that the PLL is unable to
achieve loop lock. To avoid this, always make sure that M is
selected to be 25
≤ M ≤ 50 for a 16MHz input reference.
For input references other than 16MHz, the valid M values
can be calculated from the valid VCO range of 400–800MHz.
Assuming that a 16MHz reference frequency is used, the
above equation reduces to:
FOUT = 16 x M
÷ N
Substituting the four values for N (1, 2, 4, 8) yields:
From these ranges, the user will establish the value of N
required, then the value of M can be calculated based on the
appropriate equation above. For example, if an output
frequency of 384MHz was desired, the following steps would be
taken to identify the appropriate M and N values. 384 MHz falls
within the frequency range set by an N value of 2,
so N [1:0] = 00. For N = 2, FOUT = 8M and M = FOUT ÷ 8.
Therefore, M = 384
÷ 8 = 48, so M[8:0] = 0110000.
16.66MHz
S_LOAD
P_LOAD
S_DATA
S_CLOCK
XTAL1
XTAL2
OSC
4
5
PHASE
DETECTOR
28
7
7-BIT DIV M
COUNTER
LATCH
VCO
DIV N
(1, 2, 4, 8)
LATCH
400–800
MHz
FOUT
+3.3 or 5.0V
25
24
23
VCC0
LATCH
TEST
20
+3.3 or 5.0V
PLL_VCC
0
1
7-BIT SR
27
26
0
1
2-BIT SR
3-BIT SR
VCC1
+3.3 or 5.0V
M[6:0]
7
8
→ 14
N[1:0]
2
17, 18
21
22, 19
OE
6
FREF_EXT
3
0
1
XTAL_SEL
15
PWR_DOWN
2
POWER DOWN
DIV 2
Table 2. Output Frequency Range
N
FOUT
Output Frequency Range
1
2
4
8
16 x M
8 x M
4 x M
2 x M
400 – 800 MHZ
200 – 400 MHZ
100 – 200 MHZ
50 – 100 MHZ
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