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參數(shù)資料
| 型號： | NBC12439A |
| 廠商： | ON SEMICONDUCTOR |
| 英文描述： | 3.3V/5V Programmable PLL Synthesized Clock Generator(3.3V/5V可編程PLL合成時鐘發(fā)生器) |
| 中文描述： | 3.3V/5V的可編程鎖相環(huán)路合成時鐘發(fā)生器（3.3V/5V的可編程PLL頻率合成時鐘發(fā)生器） |
| 文件頁數(shù)： | 9/20頁 |
| 文件大?。?/td> | 208K |
| 代理商： | NBC12439A |
NBC12439, NBC12439A
http://onsemi.com
9
PROGRAMMING INTERFACE
Programming the NBC12439 and NBC12439A is
accomplished by properly configuring the internal dividers
to produce the desired frequency at the outputs. The output
frequency can by represented by this formula:
F
OUT
(F
XTAL
orFREF_EXT
2)
2M
N
(eq. 1)
This can be simplified to:
F
OUT
(F
XTAL
orFREF_EXT)
M
N
(eq. 2)
where F
XTAL
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 16 MHz input reference.
See Table 11.
Assuming that a 16 MHz reference frequency is used the
above equation reduces to:
FOUT
16M
N
(eq. 3)
Substituting the four values for N (1, 2, 4, 8) yields:
Table 10. Programmable Output Divider Function
Table
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OUT
Output
Frequency
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F
OUT
The user can identify the proper M and N values for the
desired frequency from the above equations. The four output
frequency ranges established by N are 400-800 MHz,
200 - 400 MHz,
100 - 200 MHz and
respectively. From these ranges, the user will establish the
value of N required. The value of M can then be calculated
based on Equation 1. For example, if an output frequency of
384 MHz 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; thus, N
[1:0]
For N = 2, F
OUT
= 8M and M = F
OUT
M = 384
8 = 48, so M[6:0] = 0110000. Following this same
procedure, a user can generate a selected frequency. The size
of the programmable frequency steps of F
OUT
will be equal
to F
XTAL
÷
N.
For input reference frequencies other than 16 MHz, see
Table 11, which shows the usable VCO frequency and M
divider range.
50 - 100 MHz,
=
00.
8. Therefore,
The input frequency and the selection of the feedback
divider M is limited by the VCO frequency range and
fXTAL. M must be configured to match the VCO frequency
range of 400 to 800 MHz in order to achieve stable PLL
operation.
Mmin
Mmax
fVCOmin
fVCOmax
FXTALand
FXTAL
(eq. 4)
(eq. 5)
The value for M falls within the constraints set for PLL
stability. If the value for M fell outside of the valid range, a
different N value would be selected to move M in the
appropriate direction.
The M and N counters can be loaded either through a
parallel or serial interface. The parallel interface is
controlled via the P_LOAD signal such that a LOW to HIGH
transition will latch the information present on the M[6:0]
and N[1:0] inputs into the M and N counters. When the
P_LOAD signal is LOW, the input latches will be
transparent and any changes on the M[6:0] and N[1:0] inputs
will affect the FOUT output pair. To use the serial port, the
S_CLOCK signal samples the information on the S_DATA
line and loads it into a 12 bit shift register. Note that the
P_LOAD signal must be HIGH for the serial load operation
to function. The Test register is loaded with the first three
bits, the N register with the next two, and the M register with
the final nine bits of the data stream on the S_DATA input.
For each register, the most significant bit is loaded first (T2,
N1, and M6). The HIGH to LOW transition on the S_LOAD
input will latch the new divide values into the counters. A
pulse on the S_LOAD pin after the shift register is fully
loaded will transfer the divide values into the counters.
Figures 5 and 6 illustrate the timing diagram for both a
parallel and a serial load of the device synthesizer.
M[6:0] and N[1:0] are normally specified after power-up
through the parallel interface, and then possibly, fine tuned
again through the serial interface. This approach allows the
application to ramp up at one frequency and then change or
fine-tune the clock as the ability to control the serial
interface becomes available.
The TEST output provides visibility for one of the several
internal nodes as determined by the T[2:0] bits in the serial
configuration stream. It is not configurable through the
parallel interface. The T2, T1, and T0 control bits are preset
to `000' when P_LOAD is LOW so that the PECL FOUT
outputs are as jitter-free as possible. Any active signal on the
TEST output pin will have detrimental affects on the jitter
of the PECL output pair. In normal operations, jitter
specifications are only guaranteed if the TEST output is
static. The serial configuration port can be used to select one
of the alternate functions for this pin.
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相關代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| NBC12439AFA | 功能描述:時鐘發(fā)生器及支持產(chǎn)品 3.3V/5V Programmable RoHS:否 制造商:Silicon Labs 類型:Clock Generators 最大輸入頻率:14.318 MHz 最大輸出頻率:166 MHz 輸出端數(shù)量:16 占空比 - 最大:55 % 工作電源電壓:3.3 V 工作電源電流:1 mA 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:QFN-56 |
| NBC12439AFAG | 功能描述:鎖相環(huán) - PLL 3.3V/5V Programmable PLL Clock Generator RoHS:否 制造商:Silicon Labs 類型:PLL Clock Multiplier 電路數(shù)量:1 最大輸入頻率:710 MHz 最小輸入頻率:0.002 MHz 輸出頻率范圍:0.002 MHz to 808 MHz 電源電壓-最大:3.63 V 電源電壓-最小:1.71 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:QFN-36 封裝:Tray |
| NBC12439AFAR2 | 功能描述:時鐘發(fā)生器及支持產(chǎn)品 3.3V/5V Programmable RoHS:否 制造商:Silicon Labs 類型:Clock Generators 最大輸入頻率:14.318 MHz 最大輸出頻率:166 MHz 輸出端數(shù)量:16 占空比 - 最大:55 % 工作電源電壓:3.3 V 工作電源電流:1 mA 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:QFN-56 |
| NBC12439AFAR2G | 功能描述:鎖相環(huán) - PLL 3.3V/5V Programmable PLL Clock Generator RoHS:否 制造商:Silicon Labs 類型:PLL Clock Multiplier 電路數(shù)量:1 最大輸入頻率:710 MHz 最小輸入頻率:0.002 MHz 輸出頻率范圍:0.002 MHz to 808 MHz 電源電壓-最大:3.63 V 電源電壓-最小:1.71 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:QFN-36 封裝:Tray |
| NBC12439AFN | 功能描述:時鐘發(fā)生器及支持產(chǎn)品 3.3V/5V Programmable RoHS:否 制造商:Silicon Labs 類型:Clock Generators 最大輸入頻率:14.318 MHz 最大輸出頻率:166 MHz 輸出端數(shù)量:16 占空比 - 最大:55 % 工作電源電壓:3.3 V 工作電源電流:1 mA 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:QFN-56 |
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