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参数资料
| 型号： | ICD2053BSC-1 |
| 厂商： | CYPRESS SEMICONDUCTOR CORP |
| 元件分类： | XO, clock |
| 英文描述： | 100 MHz, OTHER CLOCK GENERATOR, PDSO8 |
| 封装： | 0.150 INCH, SOIC-8 |
| 文件页数： | 4/9页 |
| 文件大小： | 138K |
| 代理商： | ICD2053BSC-1 |
ICD2053B
Document #: 38-07134 Rev. **
Page 4 of 9
VCO Programming Constraints
There are seven primary programming constraints the user
must be aware of:
.
The constraints have to do with trade-offs between optimum
speed with lowest noise, VCO stability and factors affecting
the loop equation. The factors are listed for completeness
sake; however, by using the above-mentioned BITCALC pro-
gram, these constraints become transparent.
PROGRAM Register Example
The following is an example of the calculations BITCALC per-
forms:
Derive the proper programming word for a 39.5 MHz output
frequency, using 14.31818 MHz as the reference frequency:
Since 39.5 MHz < 50 MHz, double it to 79.0 MHz. Set M to 001
to post divide by 2. Set I to 0000. The result:
f(VCO) = 79.0 = (2 * 14.31818 *
P/
Q)
P/
Q = 2.7587
Several choices of P and Q are available for this example:
Normally, one would choose (P,Q) = (80,29) for the best accu-
racy (40 PPM). However, we will choose (P,Q) = (91,33) as it
illustrates bit stuffing.
Therefore:
P’ = P
3 = 91 3 = 88 = 1011000
Q’ = Q
2 = 33 2 = 31 = 0011111
The programming word, W, is generated by first creating the
non-bit-stuffed word W’ by concatenating P’=1011000, D=1,
M=001, Q’=0011111, I=0000, and then bit-stuffing.
W’ = 1011000 1 001 0011111 0000
W = 10110001001001101110000
Zeros were stuffed in one place in this example.
Output Frequency Accuracy
The accuracy of the ICD2053B output frequency depends on
the target output frequency and reference frequency. As stated
previously, the output frequency of the ICD2053B is mathe-
matically related to the input reference frequency:
f(OUT) = (2 * f(REF) *
P/
Q) ÷ 2
n, n = 0...7.
Only certain output frequencies are possible for a particular
reference frequency. However, the ICD2053B generally pro-
duces an output frequency within 0.1% of the desired output
frequency. Specifics regarding accuracy (in ppm) are given for
any desired output frequency in the BITCALC program output.
Frequency Modification Procedure
When changing to a new frequency, there is a period of time
during which the output signal will jump in frequency, or glitch
due to changes in the serial word. For applications in which it
is critical that the output clock not glitch and always maintain
some known value, the MUXREF feature in the Control regis-
ter should be used. MUXREF causes the reference clock to be
multiplexed, glitch-free, to the output clock. The output will re-
main at this fixed frequency while the VCO seeks its new pro-
grammed value.
The procedure for programming the ICD2053B to an initial or
new frequency is as follows:
1. Load the Control register to enable MUXREF and enable
loading of the Program register. This will set the output to
the reference frequency. The transition is guaranteed to be
glitch-free. (See timing specifications.) Note that the Proto-
col Word must follow the Control register data. Also note
that all data is shifted in LSB (Least Significant Bit) first.
Control word = 0 1 1 1 1 0
0 0 0 0 X 1 0 1
← LSB
Protocol Word
Control Reg. Data
The state of the Pin 7 Usage bit is defined by the user, and
so is denoted as X.
2. Shift in the desired output frequency value computed via a
22-bit data word (as defined above), plus any bit-stuffs (as
defined above). Remember to bit-stuff a 0 after any three
sequential 1s.
3. Load the Control register to enable MUXREF and disable
loading of the Program register. This loads the Program
word bits into the Program register and keeps the output
set to the reference frequency while the new frequency set-
tles
Control word = 0 1 1 1 1 0
0 0 0 0 X 1 0 0
Protocol Word
Control Reg. Data
4. Wait for VCO to settle in the new state (10 ms to within 0.1%
of the new frequency).
Load the Control register to enable new frequency output.
The transition is guaranteed to be glitch-free. (See the tim-
ing specifications.)
Control word = 0 1 1 1 1 0
0 0 0 0 X 0 0 0
Protocol Word
Control Reg. Data
Table 3. Programming Constraints
Parameter
Minimum
Maximum
f(REF)
1 MHz
25 MHz
f(REF)/Q
200 kHz
1 MHz
f(VCO)
50 MHz
150 MHz
divisor
1
128
fOUT
50 MHz/128
100 MHz
Q
3
129
P
4
130
P
Q
f(VCO)
Error (PPM)
69
25
79.0363
460
80
29
78.9969
40
91
33
78.9969
419
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ICD2061A | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Video/Graphics Clock Generator |
| ICD2061ASC | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Video/Graphics Clock Generator |
| ICD2061ASC1 | 制造商:ICD 功能描述:2061 CDESIGN S8G1B |
| ICD2061ASC-1 | 制造商:ICD 功能描述:2061 CDESIGN S8G1B |
| ICD2061CC-1 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Video/Graphics Clock Generator |
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