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參數資料
| 型號： | ADF4218BRU |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | XO, clock |
| 英文描述： | Dual RF PLL Frequency Synthesizers |
| 中文描述： | PLL FREQUENCY SYNTHESIZER, 2500 MHz, PDSO20 |
| 封裝： | TSSOP-20 |
| 文件頁數： | 10/20頁 |
| 文件大小： | 227K |
| 代理商： | ADF4218BRU |
REV. 0
ADF4216/ADF4217/ADF4218
–10–
CIRCUIT DESCRIPTION
REFERENCE INPUT SECTION
The reference input stage is shown below in Figure 2. SW1 and
SW2 are normally closed switches. SW3 is normally open. When
power-down is initiated, SW3 is closed and SW1 and SW2 are
opened. This ensures that there is no loading of the REF
IN
pin
on power-down.
BUFFER
100k
SW2
NC
NC
SW1
REF
IN
SW3
NO
TO
R COUNTER
POWER-DOWN
CONTROL
Figure 2. Reference Input Stage
IF/RF INPUT STAGE
The IF/RF input stage is shown in Figure 3. It is followed by a
2-stage limiting amplifier to generate the CML clock levels
needed for the prescaler.
2k
RF
IN
A
AV
DD
BIAS
GENERATOR
2k
RF
IN
B
AGND
Figure 3. IF/RF Input Stage
PRESCALER
The dual modulus prescaler (P/P+1), along with the A and B
counters, enables the large division ratio, N, to be realized
(N = BP + A). This prescaler, operating at CML levels, takes
the clock from the IF/RF input stage and divides it down to a
manageable frequency for the CMOS A and B counters. It is
based on a synchronous 4/5 core.
The prescaler is selectable. On the IF side it can be set to
either 8/9 (DB20 of the IF AB Counter Latch set to 0) or 16/17
(DB20 set to 1). On the RF side it can be set to 64/65 (DB20 of
the RF AB Counter Latch set to 0) or 32/33 (DB20 set to 1).
See Tables IV and VI.
A AND B COUNTERS
The A and B CMOS counters combine with the dual modulus
prescaler to allow a wide ranging division ratio in the PLL feed-
back counter. The devices are guaranteed to work when the
prescaler output is 165 MHz or less. Typically they will work
with 200 MHz output from the prescaler.
Pulse Swallow Function
The A and B counters, in conjunction with the dual modulus
prescaler make it possible to generate output frequencies which
are spaced only by the Reference Frequency divided by R. The
equation for the VCO frequency is as follows:
f
VCO
= [(
P
×
B
) +
A
]
×
f
REFIN
/
R
f
VCO
= Output frequency of external voltage controlled oscilla-
tor (VCO).
P
= Preset modulus of dual modulus prescaler (8/9, 16/17,
etc.).
B
= Preset Divide Ratio of binary 11-bit counter (1 to
2047).
A
= Preset Divide Ratio of binary 6-bit A counter (0 to
63).
f
REFIN
= Output frequency of the external reference frequency
oscillator.
R
= Preset divide ratio of binary 14-bit programmable
reference counter (1 to 16383).
R COUNTER
The 14-bit R counter allows the input reference frequency to be
divided down to produce the reference clock to the phase fre-
quency detector (PFD). Division ratios from 1 to 16,383 are
allowed.
N = BP+A
PRESCALER
P/P+1
MODULUS
CONTROL
LOAD
LOAD
11-BIT B
COUNTER
6-BIT A
COUNTER
N
DIVIDER
FROM IF/RF
INPUT STAGE
TO PFD
Figure 4. A and B Counters
PHASE FREQUENCY DETECTOR (PFD) AND CHARGE
PUMP
The PFD takes inputs from the R counter and N counter and
produces an output proportional to the phase and frequency
difference between them. Figure 5 is a simplified schematic.
CHARGE
PUMP
U3
CP
DELAY
ELEMENT
D1
Q1
U1
CLR1
UP
HI
IN
D1
Q1
U1
CLR2
DOWN
HI
–
IN
Figure 5. PFD Simplified Schematic
相關PDF資料 |
PDF描述 |
|---|---|
| ADF4251 | Dual Fractional-N/Integer-N Frequency Synthesizer |
| ADF4251BCP | Dual Fractional-N/Integer-N Frequency Synthesizer |
| ADF4251BCP-REEL | Dual Fractional-N/Integer-N Frequency Synthesizer |
| ADF4251BCP-REEL7 | Dual Fractional-N/Integer-N Frequency Synthesizer |
| ADF4252BCP | Dual Fractional-N/Integer-N Frequency Synthesizer |
相關代理商/技術參數 |
參數描述 |
|---|---|
| ADF4218BRU-REEL | 制造商:Analog Devices 功能描述:PLL Frequency Synthesizer Dual 20-Pin TSSOP T/R |
| ADF4218L | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:ADF4217L/18L/19L: Dual Low Power Frequency Synthesizers Data Sheet (Rev. B. 7/02) |
| ADF4218LBCC | 制造商:Analog Devices 功能描述:PLL Frequency Synthesizer Dual Up to 188MHz 24-Pin LGA |
| ADF4218LBCC-REEL | 制造商:Analog Devices 功能描述:PLL Frequency Synthesizer Dual Up to 188MHz 24-Pin LGA T/R |
| ADF4218LBCC-REEL7 | 制造商:Analog Devices 功能描述:PLL Frequency Synthesizer Dual Up to 188MHz 24-Pin LGA T/R |
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